Demolition and reuse of concrete and masonry: guidelines for demolition and reuse of concrete and masonry: proceedings of the Third international RILEM symposium on demolition and reuse of concrete and masonry held in Odense, Denmark, 24-27 October 1993

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Demolition and Reuse of Concrete and Masonry

Related books on recycling and demolition Demolition and Reuse of Concrete and Masonry Edited by Y.Kasai With the increase in demolition on congested urban sites, the construction industry has been obliged to develop more efficient demolition techniques which are quieter and less intrusive: This book deals with the theoretical and pracitcal aspects of demolition of concrete and masonry buildings and the recycling of demolished materials. It forms the Proceedings of the Second International RILEM Symposium held in 1988 in Tokyo. Hardback (0 412 32110 6), 2 volumes, 814 pages Recycling of Demolished Concrete and Masonry Edited by T.C.Hansen This RILEM Report contains state of the art reviews on three topics: recycling of demolished concrete, recycling of masonry rubble, and localized cutting by blasting of conrete. It has been compiled by RILEM Technical Committee 37-DRC, and draws on research and practical experience worldwide. Hardback (0 419 15820 0), 316 pages For information on these and other titles, contact The Promotion Department, E & FN Spon, 2–6 Boundary Row, London SE1 8HN, Tel: 071–865 0066.

Demolition and Reuse of Concrete and Masonry Guidelines for Demolition and Reuse of Concrete and Masonry Proceedings of the Third International RILEM Symposium on Demolition and Reuse of Concrete and Masonry held in Odense, Denmark. Organized by RILEM TC 121-DRG and the Danish Building Research Institute. Odense, Denmark 24–27 October 1993 EDITED BY

Erik K.Lauritzen DEMEX Consulting Engineers, Frederiksberg, Denmark

E & EN SPON An Imprint of Chapman & Hall London • Glasgow • New York • Tokyo • Melbourne • Madras

Published by E & FN Spon, an imprint of Chapman & Hall, 2–6 Boundary Row, London SE1 8HN, UK This edition published in the Taylor & Francis e-Library, 2005. “To purchase your own copy of this or any of Taylor & Francis or Routledge's collection of thousands of eBooks please go to www.eBookstore.tandf.co.uk.” Chapman & Hall, 2–6 Boundary Row, London SE1 8HN, UK Blackie Academic & Professional, Wester Cleddens Road, Bishopbriggs, Glasgow G64 2NZ, UK Chapman & Hall Inc., One Penn Plaza, 41st Floor, New York NY10119, USA Chapman & Hall Japan, Thomson Publishing Japan, Hirakawacho Nemoto Building, 6F, 1–7–11 Hirakawa-cho, Chiyoda-ku, Tokyo 102, Japan Chapman & Hall Australia, Thomas Nelson Australia, 102 Dodds Street, South Melbourne, Victoria 3205, Australia Chapman & Hall India, R.Seshadri, 32 Second Main Road, CIT East, Madras 600 035, India First edition 1994 © 1994 RILEM ISBN 0-203-62687-7 Master e-book ISBN

ISBN 0-203-63071-8 (Adobe e-Reader Format) ISBN 0 419 18400 7 (Print Edition) Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the UK Copyright Designs and Patents Act, 1988, this publication may not be reproduced, stored, or transmitted, in any form or by any means, without the prior permission in writing of the publishers, or in the case of reprographic reproduction only in accordance with the terms of the licences issued by the Copyright Licensing Agency in the UK, or in accordance with the terms of licences issued by the appropriate Reproduction Rights Organization outside the UK. Enquiries concerning reproduction outside the terms stated here should be sent to the publishers at the London address printed on this page. The publisher makes no representation, express or implied, with regard to the accuracy of the information contained in this book and cannot accept any legal responsibility or liability for any errors or omissions that may be made. A catalogue record for this book is available from the British Library Library of Congress Cataloging-in-Publication data available Publisher’s Note This book has been produced from camera ready copy provided by the individual contributors in order to make the book available for the symposium.

Contents

Preface

xii

Introduction

xiv

Organizing Committee

xvi

Scientific Committee

xvi

RILEM Technical Committee 121-DRG

xvii

Sponsors and Cooperating Organizations

xviii

Reports issued by RILEM Technical Committees 37-DRC and 121-DRG

xix

KEYNOTE PAPERS

1 Financial, economical and political aspects of the reuse of construction and demolition waste H.P BARTH

3

2 Guidelines for seismic capacity evaluation of reinforced concrete buildings T.OKADA

9

PART ONE GUIDELINES FOR DEMOLITION WITH RESPECT TO REUSE OF BUILDING MATERIALS

3 Guidelines for demolition with respect to the reuse of building materials: guidelines and experiences in Belgium B.P.SIMONS and F.HENDERIECKX

26

4 Guidelines and experience from the demolition of houses in connection with the Øresund Link between Denmark and Sweden E.K.LAURITZEN and M.JANNERUP

37

PART TWO GUIDELINES FOR THE REUSE OF CONCRETE AND MASONRY AS AGGREGATES IN CONCRETE IN RELATION TO EXISTING SPECIFICATIONS

5 Reuse of demolition materials in relation to specifications in the UK R.J.COLLINS

51

6 Recycling of construction and demolition waste in Belgium: actual situation and future evolution J.VYNCKE and E.ROUSSEAU

60

7 Practical guideline for the use of recycled aggregates in concrete in France and Spain A.MOREL, J.L.GALLIAS, M.BAUCHARD, F.MANA and E.ROUSSEAU

76

8 Concrete/masonry recycling progress in the USA C.J.KIBERT

88

9 Guidelines and the present state of the reuse of demolished concrete in Japan Y.KASAI

97

10 The processing of building rubble as concrete aggregate in Germany R.-R.SCHULZ

114

PART THREE PRESENTATION OF THE WORK DONE BY RILEM TC 121-DRG

11 Report on unified specifications for recycled coarse aggregates for concrete A.HENRICHSEN

129

12 Demolition and reuse following disasters C.DE PAUW

131

PART FOUR RECENT DEVELOPMENTS IN DEMOLITION TECHNIQUES

13 Experience gained in dismantling of the Japan Power Demonstration Reactor (JPDR) M.YOKOTA, Y.SEIKI and H.ISHIKAWA

146

14 Blasting demolition of six-storey reinforced concrete building (Part 1: Experimental blasting of reinforced concrete components) * K.KUROKAWA, T.YOSHIDA, T.SAITO, M.YAMAMOTO and S.NAKAMURA

162

15 Blasting demolition of six-storey reinforced concrete apartment buildings (Part 2: Demolition plan, pre-work measures, collapse conditions) * Y.KASAI, T.SAITO, Y.SEKI, K.TOMITA and J.ISHIBASHI

181

16 Blasting demolition of six-storey reinforced concrete apartment building (Part 3: Blast design, noise and vibration) * I.SAWADA, U.YAMAGUCHI, N.KOBAYASHI, M.NAKAJIKU, H.SHIBATA and T.SHINDO

194

17 Progress of blasting demolition techniques for reinforced concrete constructions in Japan * Y.KASAI, K.HASHIZUME and T.SHINDO

208

18 Fracture control techniques for partial demolition of concrete by blasting * Y.NAKAMURA, S.KUBOTA, J.MUKUGI, T.OHHARA, H.MATSUNAGA and M.YAMAMOTO

221

19 Protection methods from fragmentation in blasting demolition (Part 1: Evaluation of cover materials and protection methods) * K.SUEYOSHI, Y.KASAI, T.SAITOU, K.TOMITA and S.KOBAYASI

235

20 Protection methods from fragmentation in blasting demolition (Part 2: Dynamic movement of fragments) * Y.OGATA, K.KATSUYAMA, Y.WADA, U.YAMAGUCHI, K.HASHIZUME, T.SATO and S.OHTSUBO

251

21 Non-explosive demolition agent in Japan H.HAYASHI, K.SOEDA, T.HIDA and M.KANBAYASHI

267

22 Fast-acting non-explosive demolition agent * K.SOEDA, H.HAYASHI, T.HIDA and K.TSUCHIYA

281

23 Expansive energies of non-explosive demolition agent * H.HANEDA, Y.TSUJI and M.HANADA

296

24 Recent demolition techniques using electric power in Japan W.NAKAGAWA

307

25 The explosive demolition of tall buildings G.T.WILLIAMS

324

26 The application of modified water jets as tools for demolition * A.W.MOMBER

336

27 Investigation into the cutting of bonded prestressing bars during demolition * A.BELHADJ and P.WALDRON

347

PART FIVE PROPERTIES OF CONCRETE WITH RECYCLED AGGREGATES

28 Recycling of concrete in aggressive environment F.R.GOTTFREDSEN and F.THØGERSEN

362

29 Modifying the performance of concrete made with coarse and fine recycled concrete aggregates P.J.WAINWRIGHT, A.TREVORROW, Y.YU and Y.WANG

371

30 Behaviour of reinforced concrete beams containing recycled aggregate F.YAGISHITA, M.SANO and M.YAMADA

384

31 Mechanical and physico-chemical properties of concrete produced with coarse and fine recycled concrete aggregates J.D MERLET and P.PIMIENTA

400

32 Siliceous by-products for use in blended cements * H.H.BAHNASAWY and M.A.SHATER

413

33 The total evaluation of recycled aggregate and recycled concrete * M.KIKUCHI, A.YASUNAGA and K.EHARA

425

34 Physical properties of recycled concrete using recycled coarse aggregate made of concrete with finishing materials * K.YANAGI, M.HISAKA and Y.KASAI

438

35 Exploration of concrete and structural concrete elements made of reused masonry * A.PAKVOR, M.MURAVLJOV and T.KOVACEVIC

453

PART SIX REUSE OF CONCRETE AND MASONRY MATERIALS— EXAMPLES

36 A method for total reutilization of masonry by crushing, burning, shaping 473 and autoclaving H.HANSEN

37 Recycling of clay bricks P.KRISTENSEN

478

38 Special techniques for the recycling of concrete base plates (railway “sleepers”) K.KLÖPPER

482

39 Recycling of reinforced concrete structures and buildings using composite 488 construction: approach to an environmental-economic assessment K.RAHLWES 40 Recycling of concrete for the reconstruction of the concrete pavement on the Vienna-Salzburg motorway H.SOMMER

500

41 Inert wastes from ceramics production and construction works: recycling experiences in Sassuolo, Italy G.F.SAETTI, A.COCCONCELLI, G.FINELLI and C.MEDICI

512

42 Recycling powdered concrete waste * M.SANO, F.YAGISHITA and M.YAMADA

523

PART SEVEN BUILDING WASTE MANAGEMENT

536 43 Development of integrated waste management strategies for demolition waste M.NICOLAI, M.RUCH, Th.SPENGLER, S.VALDIVIA, J.HAMIDOVIC and O.RENTZ 44 Buildings as reservoiers of materials—thier reuse and implications for future construction design T.E.LAHNER and P.H.BRUNNER

548

45 Possibilities for implementing economic, fiscal and practical instruments to promote cleaner technology L.SØBORG

557

46 Transition of the technique of reinforced concrete constructions measured 561 to earthquake damage in Japan K.YAMABE, H.KUBOTA and Y.KASAI

PART EIGHT CLOSING SESSION

47 Retrieving materials—the effects of EC health and safety directives B.S.NEALE

575

48 The Great Belt Link project C.E.LOOSEMORE

582

49 The “Recycled House” in Odense E.BITSCH OLSEN

592

Author index

Subject index

* Papers which are not presented at the symposium or papers which are presented together with other papers.

599

602

Preface The first and second international symposia on Demolition and Recycling of Concrete and Masonry were held in Rotterdam in 1985 and in Tokyo in 1988 under the auspices of RILEM Technical Committee 37-DRC These earlier symposia focused primarily on theoretical aspects of demolition and recycling/reuse of building materials. This work has enabled the necessary knowledge to be built up, but owing to inadequate communication, the knowledge was not being translated into practice. It was therefore decided to follow up the work by TC-37-DRC with recommendations and standards for demolition and reuse of concrete and masonry. This has been the task of the new RILEM TC-121-DRG on Guidelines for demolition and reuse of Concrete and Masonry. The need for demolition, repair and renewal of concrete and masonry structures is rising all over the world. Recent years have demonstrated that numerous natural disasters such as earthquakes and also war activities have caused very extensive damage in urban areas. This has led to a need for effective methods for site clearance and reconstruction. For these reasons the third RILEM symposium deals with subjects concerning the integration of demolition and recycling operations in the construction and housing industry. The aim is to bring together specialist from the construction industry, urban development, disaster mitigation, material scientists, civil engineers and planners to discuss further aspects of demolition and recycling of building materials. The conclusions of the third symposium will be brought in a new RILEM report which is scheduled for completion in 1994. Torben C.Hansen President of RILEM

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Introduction The Third International RILEM1 Symposium on Demolition and Reuse of Concrete and Masonry follows the first EDA-RILEM symposium, held in Antwerp in 1985, and the second RILEM symposium held in Tokyo in 1988. The Third Symposium concludes the work carried out by two RILEM Technical Committees: TC 37-DRC on Demolition and Reuse of Concrete, 1981–1988, and TC 121DRG on Guidelines for Demolition and Reuse of Concrete and Masonry, 1989– 1993. The Symposium presents world-wide technical developments in the field of demolition and recycling in the last decade. From the work of the TC 37-DRC it could be concluded that there was a lack of increasing technical information, especially guidelines and standards for demolition and recycling of building wastes, in many countries. Furthermore, the need for demolition and repair of concrete structures in the world is rising. In the last decade numerous natural disasters and war activities have caused major damage to urban areas, and this has led to the need for effective methods of site clearance. Therefore RILEM decided to establish TC DRG-121 in 1989 with the main objective of preparing draft guidelines for demolition and reuse of concrete and masonry with special regard to urban development and clearance of urban areas after major natural disasters and wars. At the first meeting of TC DRG-121 in Copenhagen in 1989, it was decided to form two task forces with the following objectives: To prepare technical recommendations leading to guidelines for the production of concrete from recycled concrete and masonry (Task Force 1). To prepare a state-of-the-art report on site clearing, demolition and recycling of damaged concrete structures with special emphasis on earthquake and war damaged structures (Task Force 2). 1

Réunion Internationale des Laboratoires d’Essais et de recherches sur les Matériaux et les Constructions/International Union of Testing and Research Laboratoires for Materials and Structures

Based on recent projects prepared for the EC, based on work in various countries, and based on an official Danish recommendation on recycled aggregates for new concrete, Task Force 1 has prepared a RILEM recommendation on recycled aggregates. In relation to the cooperation between CEN and RILEM, this recommendation will be very valuable

for further standardization in this field. A final report on this subject will be published in 1994. Task Force 2 has collected information on building waste management after recent major natural disasters: e.g. earthquakes in Algeria 1981, Mexico 1985, Armenia 1989, San Francisco 1989, Luzon 1990 and Erzincan 1992. Disaster management and experiences in Japan have been studied in detail. A state-of-the-art report has been prepared with the aim of improving building waste management after natural disasters and wars. These Proceedings contain papers presented at the Third International RILEM Symposium, and also a number of papers which were not presented orally, due to limitations of time. The papers are arranged in the nine sessions of the symposium programme, starting with a keynote session presenting the issues of the symposium. The next two sessions present the state-of-the-art on guidelines for demolition and recycling in different countries throughout the world. The work of RILEM TC 121-DRG and the two Task Forces is then presented in Session 3. In two parallel sessions, 4 and 5, recent developments in demolition techniques and recycling are covered, followed by a presentation of practical experience and examples in Session 6. Other aspects of demolition and recycling (e.g. management, legal and economic aspects) are dealt with in Session 7, and the symposium concludes with the presentation of two major recycling projects in Denmark. As chairman of RILEM TC 121-DRG I sincerely hope that the symposium will be successful and will contribute to a better understanding and further development of techniques for demolition and recycling of concrete and masonry. I would like to thank everyone who served as members and corresponding members of RILEM TC 121-DRG. Especially, I thank the Secretary Mr Johan Vyncke (B); the Chairman of Task Force 1, Mr Anders Henrichsen (DK): the Chairman of Task Force 2, Mr Carlo de Pauw (B); and all members of the two Task Forces for their enthuiasm and hard work. Moreover, I would also like to express my thanks to the Chairman of the Organizing Committee, Dr Bjarne Chr. Jensen; the Secretary of the Organizing Committee, Mr Jens Chr. Ellum; and the members of the Organizing Committee and the Scientific Committee for all their work in connection with the preparation of this symposium. Very special thanks go to RILEM and the cooperating organizations, and to the Danish Building Research Institute for organizing this symposium. Erik K.Lauritzen

Organizing Committee Dr Bjarne Chr. Jensen, Professor h.c., Chairman, Carl Bro A/S Denmark Mr Erik K.Lauritzen, Coordinator, DEMEX Consulting Engineers A/S, Denmark Mr Jens Chr. Ellum, Secretary, Danish Building Research Institute, Denmark Mr Michel Brusin, General Secretariat, RILEM, France Mr Georg Christensen, Danish Building Research Institute, Denmark Mr Carlo De Pauw, ENBRI, Belgian Building Research Institute, Belgium Mr Niels Jørn Hahn, R98, Copenhagen, Denmark Mr Anders Henrichsen, Professor h.c., Dansk Beton Teknik A/S, Denmark

Scientific Committee Mr Erik K.Lauritzen, Chairman, DEMEX Consulting Engineers A/S, Denmark Dr Susi Buchner, Gifford and Partners, England Mr Carlo de Pauw, Belgian Building Research Institute, Belgium Dr Charles Hendriks, Professor, INTRON B.V., The Netherlands Mr Anders Henrichsen, Professor h.c., Dansk Beton Teknik A/S, Denmark Dr Yoshio Kasai, Professor, Nihon University, Japan Dr Peter Lindsell, Gifford and Partners, England Dr Christer Molin, Tremix, Sweden Dr André Morel, CEBTP, France Mr Torsten Thorsen, Danmarks Ingeniørakademi, Denmark Dr Tony Trevorrow, Nottingham Trent University, England Mr Johan Vyncke, Belgian Building Research Institute, Belgium Dr Peter J.Wainwright, University of Leeds, England

RILEM Technical Committee 121-DRG Mr Erik K.Lauritzen, Chairman, DEMEX Consulting Engineers A/S, Denmark Mr Robert Basart*, European Demolition Association, The Netherlands Dr Susi Buchner, Gifford and Partners, England Mrs Catherine Charlot-Valdieu*, CSTB, France Mr Carlo de Pauw, Belgian Building Research Institute, Belgium Dr Torben C.Hansen, Professor*, Technical University of Denmark Dr Charles Hendriks, Professor, INTRON B.V., The Netherlands Mr Anders Henrichsen, Professor h.c., Dansk Beton Teknik A/S, Denmark Dr Yoshio Kasai, Professor, Nihon University, Japan Mr Joseph F.Lamond, ACI 555, USA Dr Peter Lindsell, Gifford and Partners, England Mr Terence R.Mills*, England Dr Christer Molin, Tremix, Sweden Dr André Morel, CEBTP, France Dr Mike Mulheron*, University of Surrey, England Dr Rolf-Rainer Schulz*, Fachhochschule Frankfurt a.m., Germany Mr Torsten Thorsen, Danmarks Ingeniørakademi, Denmark Dr Tony Trevorrow, Nottingham Trent University, England Mr Johan Vyncke, Secretary, Belgian Building Research Institute, Belgium Dr Peter J.Wainwright, University of Leeds, England Mr Myles Whelan, Whelan the Wrecker Pty Ltd, Australia * Corresponding member

Sponsors and Cooperating Organizations The Symposium has been sponsored by RILEM

Réunion Internationale des Laboratoires d’Essais et de Recherches sur les Matériaux et les Construction, International Union of Testing and Research Laboratories for Materials and Structures in cooperation with

UNESCO United Nations Educational, Scientific and Cultural Organization ACI

American Concrete Institute

ISWA

International Solid Waste Association

DBF

Danish Concrete Association

ENBRI

European Network of Building Research Institutes

CIB

Conseil International du Bâtiment

IDNDR

International Decade of Natural Disaster Reduction

UNCRD

UN Center for Regional Development

DBV

Deutscher Beton-Verein E.V.

Reports issued by RILEM Technical Committees 37-DRC and 121-DRG [1] EDA-RILEM (1985). Demolition Techniques. Proceedings of the First International EDA-RILEM Conference on Demolition and Reuse of Concrete, Rotterdam, 1–3 June, 1985, European Demolition Association, Wassenaarseweg 80, 2596 CZ Den Haag, The Netherlands. [2] EDA-RILEM (1985). Reuse of Concrete and Brick Materials. Proceedings of the First International EDA-RILEM Conference on Demolition and Reuse of Concrete, Rotterdam, 1–3 June, 1985, European Demolition Association, Wassenaarseweg 80, 2596 CZ Den Haag, The Netherlands. [3] Y.Kasai (Editor) (1988). Demolition and Reuse of Concrete and Masonry Volume One: Demolition Methods and Practice Volume Two: Reuse of Demolition Waste Proceedings of the Second International RILEM Conference on Demolition and Reuse of Concrete, Tokyo, 7–11 November 1988, Chapman & Hall, London. [4] Torben C.Hansen (Editor) (1992). Recycling of Demolished Concrete and Masonry, Third state-of-the-art report 1945–1989, RILEM Report No. 6, E. & F.N.Spon, London. [5] Erik K.Lauritzen (Editor) (1993). Demolition and Reuse of Concrete and Masonry. Proceedings of the Third International RILEM Conference on Demolition and Reuse of Concrete and Masonry, Odense, Denmark, 24–27 October 1993, E. & F.N.Spon, Chapman & Hall, London. Planned issues: [6] Anders Henrichsen, Charles Hendriks, Johan Vyncke (1993), Guidelines for Reuse of Concrete and Masonry Rubble as Aggregates in Concrete, RILEM TC-121-DRG, Task Force 1 Report. Draft report will be available at the RILEM Symposium, October 1993. Final report is planned to be published as RILEM Technical Recommendation in RILEM “Materials and Structures” in 1994. [7] Johan Vyncke, Y.Kasai, Carlo De Pauw, Erik K.Lauritzen, Susi Buchner (1993) Demolition of Structures and Reuse of Buildings and Construction Material following Disasters, RILEM TC-121-DRG, Task Force 2 Report, E. & F.N.Spon, Chapman & Hall, London.

KEYNOTE PAPERS

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1 FINANCIAL, ECONOMICAL AND POLITICAL ASPECTS OF THE REUSE OF CONSTRUCTION AND DEMOLITION WASTE H.P BARTH European Construction Industry Federation (FIEC), Brussels, Belgium, Federation of Dutch Contractors Organisations (AVBB), The Hague, The Netherlands Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract Reuse of construction and demolition wastes forms part of a far wider, complex issue, primarily relating to supplies of construction materials. Within this area, environmental requirements demand objectives for optimizing the use of secondary materials. The realisation of these objectives will be feasible only if both legislation and the markets—in which principals play a crucial role—allow scope and/or create the right conditions for this. Only through the combined efforts of all parties in the market can these objectives be attained. An integrated and consistent policy is needed on the use of secondary raw materials, with clear minimum requirements which are binding on all market parties. Standardization plays a crucial role here. Legislation should be clear, unambiguous, workable and feasible. Cost-benefit analyses should be prepared for all policy measures, including consideration of their environmental effectiveness, their impact on industrial competitiveness and the fair distribution of responsibilities and costs. Existing EC-legislation does not satisfy any of these considerations and criteria. Key words: Legislation, regulation, policy, economic feasibility, financial feasibility, principals, construction industry, market, standardization.

1 Introduction The main objective of construction contractors is to create construction products which

Demolition and reuse of concrete and masonry

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offer good quality and price-performance in all respects. A prime requirement for this is the availability of good quality, inexpensive construction materials. Whether these are primary or secondary materials is of lesser importance: the two compete with each other. The construction industry is served by the availability of secondary raw materials of reliable quality, at favourable prices. Firstly, this will allow the construction industry to help reduce the waste problem and so fulfil its social responsibility for a healthy environment. Furthermore, environmental considerations threaten to create shortages of scarce and expensive primary raw materials. Dumping or incineration of construction and demolition wastes (including dredging sludge and soil) also creates environmental problems and is, moreover, very expensive. Finally, secondary materials already play an important role in the public works and civil engineering sector; the unavailability of cheap, good quality secondary materials would force these sectors to resort to costly primary raw materials. The construction industry can itself contribute towards the availability of good quality, inexpensive secondary raw materials by introducing measures which allow segregation and reutilization of construction and demolition waste. The construction industry has its own, independent responsibility in this respect. However, the opportunities for optimising separate collection and removal to reprocessing facilities are largely determined at earlier stages of the construction process, in which principals, architects and suppliers also play a role. Moreover, adequate processing capacity and application possibilities must be available at later stages of the construction process. These can be created only through clear legislation, applying to all parties in the market. In addition to construction and demolition wastes, secondary materials are also produced from industrial residues. The construction industry has no influence on the availability of these residues, but can affect their application. Again, the market and legislation determine the scope for optimizing applications. The various aspects of this subject are closely interrelated, or should be so. If construction companies do not collect construction and demolition waste separately and remove it for reprocessing, a shortage of the necessary secondary raw materials will be created. If the application of secondary materials is hampered by market forces or legislation, a vast quantity of unusable waste materials will result, with all the attendant costs and environmental problems. What does the construction industry want? Construction industry is calling for clear and consistent legislation, with minimum requirements for compulsory application of recycled materials by all market parties, but in particular, by principals and architects. This requires additional, serviceable regulations and requirements, in areas including segregated collection, training and standardization. However, the emphasis should continue to lie on optimizing possibilities for recycling and application. So far, legislation has focused purely on the supply side—on producers/demolition companies, transporters and waste collectors/managers—at the European Community (EC) level, but also in the various Member-States. The demand side (principals and architects) has been ignored. In fact, construction and environmental legislation sets such stringent requirements for the application of construction materials that optimal application of secondary raw materials is being thwarted. This legislation only increases the existing confusion and mistrust among principals and architects with regard to

Financial, economical and political aspects

5

secondary raw materials. 2 Problems for optimal recycling This brings us to the bottlenecks in policy and legislation which stand in the way of optimal application of secondary materials. Policy and legislation on reuse of secondary materials do not consider the recovery and supply of primary materials. As long as primary materials are available in generous quantities at competitive prices, there will be no question of optimal reuse of secondary materials. This will be reinforced by problems relating to market acceptance of secondary materials. There is confusion and prejudice among all parties regarding environmental hygiene and construction technology aspects, as well as the costs of secondary materials. Demand for these materials is consequently far from optimal. Both points are reflected in the position of the construction industry. Construction contractors are wary of distortion of competition. The availability of cheap primary raw materials, coupled with limited market acceptance of secondary materials, means that contractors will think three times before applying the latter. After all, competitors who simply work with primary materials will, in many cases, receive preferential treatment from principals, at the expense of the progressive, environmentally-conscious contractor. If we genuinely want to achieve optimal use of secondary materials, measures must be introduced in the areas of material supply, construction regulations, education and consciousness-raising and in the transportation and processing of construction and demolition waste. 3 Policy and legislation: the ideal situation A sound policy on recycling of construction and demolition wastes, or on secondary raw materials in general, will cover all aspects and all parties in the market. If the European Commission wants to encourage recycling, it will have to draw up regulations relating to recovery and supply of raw materials, the construction process, training and consciousness-raising, (quality) standardization and certification, segregated collection and removal, and treatment capacity (including in licensing procedures). The requirements of sound policy go still further. After all, it is not only construction and demolition waste that is at issue, but also industrial residues. In this respect, government authorities should set requirements for design and manufacturing regulations, in order to realise good quality, environmentally sound materials. Furthermore, international harmonisation of this legislation will be necessary. If one country reduces recovery of raw materials while imports of these materials from another country increase, or if a country announces a ban on dumping of construction and demolition waste when dumping is permitted 5 kilometres away across the national border, policy cannot succeed. Sound policy must therefore be clear, unambiguous, workable and feasible, consistent,

Demolition and reuse of concrete and masonry

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based on reliable data and a thorough cost-benefits analysis, and must apply to all market parties for the longer term. Policies such as those described above are non-existent at present. At both the EC and the national level, policy and legislation focus one-sidedly on segregation and disposal of wastes. 4 Policy and legislation: the present situation The following outline of current policy is based on EC policy. The differences in policy and legislation between the different member states are so great that they cannot be classified under one heading. This brings us to the first problem. The approach chosen by the EC is based purely on environmental hygiene. Construction and demolition waste can give rise to environmental problems. The character and severity of these problems will depend on many different factors (the amount and composition of waste, construction culture, landscape and space, existing disposal structures), and will therefore vary from one country to another. Even the objective need for legislation on environmental aspects of construction and demolition waste is different for each country. This shows that a purely environmental approach will be inadequate. Another angle must therefore the chosen, producing more common points of departure; that of construction regulations and of raw material supply. With regard to construction regulations, it should be noted that the use of secondary raw materials is not prescribed in the Directive on Construction Products. There is no question of a policy on recovery of primary raw materials. All attention focuses on waste management. Waste management is one of the main themes of the European Commission’s environmental policy, as laid down in the Community Strategy for Waste Management (1989), the Council Resolution on Waste Management (1990), the Fifth Environmental Action Programme (1992) and in five Directives. In the first Directives, dating from the 1975–1986 period, the approach was based purely on environmental hygiene, the objective being ‘the protection of human health and the environment against harmful effects caused by the collection, sorting, transport, treatment, storage and disposal of waste and by the transformation operations necessary for its reuse, recovery and recycling.’ The more recent Directives (from 1991) already place more emphasis, at least in words, on recycling and reuse as ends in themselves, and urge the Member-States to take steps to increase market opportunities for sales of recycled materials. This call is often confined to the preambles of the Directives. Real commitments are not mentioned. The most striking example of this one-sided approach is found in the Directive on Civil Liability for Damage caused by Waste. This refers solely to waste removal and collection agencies. Reuse is not mentioned, while it is precisely in this area that clarity is needed on responsibilities and liability. In short, EC legislation focuses one-sidedly on the creation, removal, collection and storage of construction and demolition waste, as an isolated issue. There is no question of an integrated approach to optimal recycling applications.

Financial, economical and political aspects

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5 The EC Construction and Demolition Waste Project Group The construction industry hoped that this situation would change with the formation, at the end of 1992, of the EC Construction and Demolition Waste Project Group, in which all Member-States and all market parties are represented, as well as the European Commission. This EC Project Group must be seen in the light of the new strategy in EC waste policy. Since 1991, the European Commission has adopted an entirely new approach to the field of waste management. Instead of completely independent formulation of policy and legislation, the EC has decided to involve the Member-States and the relevant groups in society, in the hope that this will speed up the legislative process and, more importantly, make legislation more acceptable in the market. The launch document for the project group states that its intention is ‘to turn the waste problem from an environmental problem into a source of raw materials with a positive economic and social value.’ Another principle is ‘to find environmentally-friendly solutions as far as possible ahead of the waste stage.’ These are fine words, but what do they mean in practice? Firstly, the representatives of the principals and architects did not attend the first two meetings. Secondly, these meetings discussed only the classification of waste flows and reduction targets for prevention and reuse. No attention was paid to problems in the market, to standardization or to the recovery of primary raw materials. Furthermore, the EC has just published a European Waste Catalogue. Regrettably, this must once again be described as a one-sided and incomplete document. It gives a rough indication of whether a material is hazardous or non-hazardous, which in itself does not say much and offers no leads for principals or architects—only for managers of tips and incineration plants. In fact, this approach only increases the doubts and confusion among potential appliers, and hampers reuse. However, private sector organisations such as RILEM are taking valuable initiatives in the areas of standardization, certification, increasing application possibilities by including stipulations in standard specifications etc. The EC and other government authorities should focus more closely on this sort of development and adopt or include the results in concrete policy and legislation, in order to optimise reuse. The construction industry, organised at the European level in FIEC, will continue to draw attention to this in its contacts with the European Commission and through its membership of CEN. 6 Conclusion Reuse of construction and demolition waste forms part of a much wider, complex issue— that of raw material supplies in the construction industry—and can only be solved with the effort and conviction of all market parties concerned. It is pointless to pick out one aspect or sector, and to make this the focus of all attention or criticism. Only through an integrated approach, and through the efforts of all market parties

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concerned, can the objectives of reuse be realised. Within this approach, framework legislation must be drawn up, with clear and unambiguous minimum requirements on the use of secondary raw materials, with which all parties in the market must comply. Cost-benefit analyses should be made for all measures, covering their environmental effectiveness, their effects on pubic and private expenditure (market acceptance), their impact on industrial competitiveness and the fair distribution of responsibilities and costs. Finally, government and semi-government agencies should make use of the valuable knowledge and insights being developed in many organisations, including RILEM. If we want companies to contribute to the optimal reuse of construction and demolition waste in an environmentally and economically sound manner, certain conditions much be met: 1. Broad market acceptance, which includes adequate public and private expenditure and investment; 2. Clear, harmonized and feasible regulations; 3. Dialogue and cooperation, both between the construction industry and the authorities, and within each of these sectors; 4. A constructive, forward-looking attitude on the part of the construction industry itself. A general condition, that encompasses all others and which must absolutely be taken into consideration when any environmental measure is contemplated, is that ‘care for the environment and environmental measures should not endanger the continuity of construction activities and the competitiveness of individual companies.’

2 GUIDELINES FOR SEISMIC CAPACITY EVALUATION OF REINFORCED CONCRETE BUILDINGS T.OKADA Institute of Industrial Science, University of Tokyo, Tokyo, Japan Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract For the rehabilitation of existing buildings, it is necessary to evaluate the structural capacity before and after rehabilitation. In this paper, the basic concept of the guideline to evaluate the seismic capacity of existing reinforced concrete buildings, the guideline for seismic strengthening and their application to existing buildings in Japan are described. The decision criteria to screen vulnerable buildings is also described. Keywords: Seismic Capacity Evaluation, Reinforced concrete, Building, Seismic Strength, Ductility, Rehabilitation

1 Introduction A rehabilitation of buildings has been made mostly when buildings, building components, or materials were physically deteriorated with age. However, there is a trend to rehabilitate rather new buildings. For example, the recent development of the earthquake engineering requires that the seismic safety of existing buildings must be reevaluated and increased, if necessary. To increase the seismic safety, the structural rehabilitation; strengthening, is necessary. Another example is the rehabilitation due to the change of the use of the building. The reform of the educational system, which is a recent trend in Japan, is requiring the remodel of existing school buildings associated with structural renovation. These non-physical reasons could be called “deterioration of software”, while the physical reasons “deterioration of hardware”. A large number of reinforced concrete buildings have been designed and constructed in Japan since 1920’s according to the seismic codes requiring rather high level of seismic capacity. However, the recent experience of earthquake damage and the current knowledge in earthquake engineering suggest that some of the existing buildings do not

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have sufficient seismic capacity. Since 1968 Tokachi-Oki Earthquake, the importance to develop the methodology to evaluate seismic capacity of existing buildings, as well as to revise the existing seismic codes, had been strongly recognized, and various methodologies were proposed [(1), (2), (3)]. In order to unify them, the guideline for evaluation of seismic capacity of existing reinforced concrete buildings [(4)] was developed in 1977 by the special committee at the Japan Building Disaster Prevention Association under the sponsorship of the Ministry of Construction, Japanese Government. The author was the chairman of the task committee to draft the guideline. The guideline for strengthening of existing buildings estimated vulnerable by the evaluation guideline was also developed [(5)]. The guidelines have been widely used and applied to many existing buildings. And they have also been used for estimating reserve seismic capacity of earthquake damaged buildings. The purpose of this paper is to describe 1) basic concept of the gruideline to evaluate seismic capacity, 2) seismic capacity of buildings damaged due to past severe earthquakes, 3) seismic capacity of existing buildings, 4) decision criteria to screen sound buildings and to strengthen vulnerable buildings and basic concept to strengthen vulnerable buildings. 2 Basic Concept of The Guideline for Seismic Capacity Evaluation of Existing Reinforced Concrete Buildings The guideline can be used to evaluate the seismic capacity of existing reinforced concrete buildings and consists of three different level procedures; first, second and third level procedures. The first level procedure is the simplest, but most conservative of the three, while the basic concept is common for all three. In the guideline, the unified seismic performance index of structure (Is) up to six stories is evaluated by the following equation at each story and to each direction; Is=Eo·G·SD·T where, Eo = basic structural index calculated by ultimate horizontal strength, ductility, number of stories and story level considered. At the first story, the Eo-index is basically estimated by: Eo=(Ultimate Based Shear Coefficient)×(Ductility) G = local geological index to modify the Eo-index. SD = structural design index to modify the Eo-index due to the grade of the irregularity of the building shape and distribution of stiffness. T

= time index to modify the Eo-index due to the grade of the deterioration of strength and ductility.

The standard values of the G-, SD- and T-indices are 1.0. The Is-index corresponds to the level of response acceleration normalized by the gravity which causes damage to the building. Therefore, the building can be

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approximately judged whether it is safe or not according to the earthquake level expected at the building site and the fundamental period of the building. In order to calculate the Is-index, any of the first, the second and the third level screening procedure may be used. i) The First Level Screening Procedure Eo-index is approximately calculated from the horizontal strength of the building, based on the sum of the horizontal cross sectional areas of columns and walls and on their average unit strength. SD-index is evaluated by the eight items on the shape of the building both in plan and section. T-index is evaluated, based on the age of the building and the visible distortion and cracks in columns and walls. ii) The Second Level Procedure Eo-index is calculated by the ultimate horizontal strength, failure modes and ductility of columns and walls with assumption of rigid and strong beam and floor system. SD-index is evaluated by horizontal stiffness distribution and vertical mass and stiffness distribution in addition to the results in the first level evaluation procedure. T-index is evaluated by the grade of structural cracking, distortion, changes in quality and deterioration of the building. iii) The Third Level Procedure Eo-index is calculated by the ultimate horizontal strength, failure modes and ductility of columns and walls, based on failure mechanism of frames, considering the strength of beams and overturning of walls. SD-index and T-index may be taken as the same values as used in the second level screening procedure. 3 Seismic Capacity of Earthquake Damaged Buildings An example of the damage ratio of low-rise reinforced concrete buildings due to past severe earthquake in Japan is shown in Table 1. Most of them were three to four story buildings. The damage ratio including heavy and medium damage in the intensity VIII– IX zone by the modified Mercalli scale was about 10% in each earthquake and the ratio of heavy damage was less than 5% [(6)]. These ratios were same in other earthquakes[(7), (8)]. In order to estimate their seismic capacity, the Is-indices were calculated by the guideline as shown in Fig. 1. In the Fig. 1, the Is-indices of thirty reinforced concrete buildings subjected to 1968 Tokachi-Oki Earthquake, 1978 Miyagi-ken-Oki Earthquake and 1978 Izuoshima-Kinkai Earthquake are shown [(9)]. The abscissa expresses the Is-indices of the east to west direction of the buildings and the ordinate the Is-indices of the north to south direction. Numerals show ID-numbers of the buildings and a couple of points connected by broken line shows upper and lower bounds of the Is-index of the bullding. The buildings with Is-

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index of more than 0.6 by the second level screening procedure were not damaged and most of the buildings with Is-index of less than 0.4 were damaged. A similar trial was done for the buildings in the city of Mexico which experienced the 1985.9.19–20 Mexico Earthquake as shown in Fig. 2. Seismic capacities of seven types of apartment houses at Tlaltelolco, two college buildings, two secondary school buildings and an office building were evaluated by the evaluation standard [(10)]. According to increase of the Is-indices, the number of damaged buildings decreases and Is-index of about 0.4 is a border between damage and non-damage.

Fig. 1 IS-indices by Second Level Screening Procedure vs. Earthquake Damage In Japan [Ref. (9)]

Guidelines for seismic capacity evaluation of reinforced concrete buildings

Fig. 2 IS-indices by Second Level Screening Procedure vs. Earthquake Damage in Mexico [Ref. (10)]

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Fig. 3 Distribution of IS-indices of Existing-Buildings [Ref. (9)]

Fig. 4 Distribution of IS-indices [Ref. (11)]

14

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Fig. 5 Distribution of ET-indices [Ref. (11)]

4 Seismic Capacity of Existing Buildings Since the guideline was published, much effort to apply it to existing buildings and to find out vulnerable buildings has been done by Japanese engineers. For an example, in Shizuoka Prefecture where a severe earthquake is predicted to occur in near future, the guideline has been applied to more than four thousand public buildings and about four hundreds of them have already been strengthened or demolished. Fig. 3 shows the distribution of seismic capacity of about 700 existing buildings in Shizuoka Prefecture, where the Is-indices to both directions of each building are considered [(11)]. Most of them were designed and constructed before the code revision in 1970. As shown in the figure, the distribution of the Is-indices can be approximated by a log-normal probability density function. By the guideline, the building with enough seismic capacity is screened by the equation (1). Is≥ET

(1)

The ET-index expresses the decision criteria depending upon the level of ground acceleration, soil condition, number of stories and type of failure [(9), (11)]. An example of the ET-index In the lowest seismic zone in Shizuoka Prefecture is shown in Table 2, where the input acceleration to the basement of building on 0.4 sec. ground soil is

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assumed as 23% of the gravity (0.23g). The acceleration in the highest seismic zone is double of that in the lowest zone. The ET-index was determined by the consideration of non-linear earthquake response of the idealized structural models and the damage experience. For the different level of the ground acceleration, the ET-index is considered proportional to the ground acceleration. 5 Decision Criteria for Screening and for Strengthening Vulnerable Buildings The building satisfying the equation (1) may avoid a damage. However, even if the equation (1) is not satisfied, it does not always mean the building must be strengthened. Because, the equation (1) is considered to give an enough condition to judge the safety of the building. Fig. 1 shows such tendency well. If all buildings with Is-indices less than ET-indices were unsafe, the damage ratios In past earthquakes would be greater than the ratios shown in Table 1. Therefore, a different decision criteria should be used for strengthening. Table 3 shows the decision criteria for strengthening proposed for school buildings [(12)]. In order to verify the concept used in the criteria in Table 3, a reliability based analysis on the seismic safety of existing buildings and damaged buildings was done. Fig. 4 is a schematic expression of distribution of the Is-indices of existing and damaged buildings. Fig. 4-(a) is showing the distribution when the ET-index is deterministic, while Fig. 4-(b) is showing the probabilistic characteristics of ET-index. The hatched part in the Fig. 3 shows the histogram of

Table 1 Damage Ratio due to 1978 Miygi-ken-Oki Earthquake [Ref. (6)]

Guidelines for seismic capacity evaluation of reinforced concrete buildings

Table 2 ET-indices for Maximum Ground Acceleration of 0.23g [Ref. (9)]

Table 3 Decision Criteria for Strengthening of School Buildings [Ref. (10)]

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Fig. 6 Concepts of Seismic Strengthening [Ref. (13)]

Fig. 7 Strengthening by Walls or Braces [Ref. (5)]

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Fig. 8 Detail to provide R/C Wall in Existing Frame [Ref. (13)]

Fig. 9 Detail of Connection between Wall and Existing Frame [Ref. (13)]

19

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Fig. 10 Detail of Steel Brace for Strengthening of Existing R/C Frame [Ref. (13)]

the Is-indices of damaged buildings shown in Fig. 1, where a modification is employed so that the number of the damaged buildings becomes 10% of the total number of buildings. The shape of the Fig. 3 is similar to Fig. 4-(b). It suggests the ET-index may be considered to be probabilistic. Defining P1 and PET which represent density functions of Is-index of existing buildings and ET-index, respectively, the damage ratio V is determined by

(2) Setting

(3) The term of Vp2 may be considered to represent the frequency of Isindices of damaged buildings shown in Fig. 3. Substituting the function p1 in Fig. 3 and the density of hatched part In Fig. 3 Into the equation (3), we obtain the probabilistic density of ETindices as shown in Fig. 5. Assuming the normal distribution, we obtain the probabilistic density function of ETindices as shown in Fig. 5 The curve

in Fig. 3 is obtained by the equation (3), where

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p1 function in Fig 3, and pET function in Fig. 5 are used.

Fig. 11 Strengthening of Columns to Increase Ductility [Ref. (5)]

6 Basic Concept for Strengthening of Vulnerable Buildings A building judged that strengthening is necessary should be strengthened as soon as possible to prevent earthquake damage even if it has not experienced severe earthquake. A vulnerable building lacks enough strength or enough ductility or sometimes both of them. Therefore, the purpose of strengthening is to provide (1) additional strength, (2) additional ductility or (3) both additional strength and ductility. These concepts are illustrated in Fig. 6. Most popular method to increase strength is to provide reinforced concrete shear walls or steel braced frames into existing framing system as shown in Fig. 7. As shown in Fig. 8, anchor bolts are provided at the existing beams and columns, wall reinforcing bars provided and then, concrete is cast. In order to prevent a splitting shear failure at the connection of wall and frame, spiral reinforcement is often used. Special grouting is also used at the connection as shown in Fig. 9. When the soil condition is not so good, the steel braced frame is sometimes used to minimize the increase of the building weight and to increase the strength as shown in Fig. 10. In order to increase the ductility of the building, various techniques to enclose existing column by steel plate or by reinforced concrete jacketing have been developed as shown in Fig. 11. Gaps are

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usually provided both at the top and the bottom of the column, to prevent the increase of bending capacity and to increase only the shear capacity, which is expected to increase ductility. 7 Concluding Remarks Evaluation of seismic capacity of existing buildings and the strengthening if necessary are very important to mitigate earthquake hazard. In this paper, recent trends on this problem in Japan are reported. The author wishes the methodologies described here is applied to the existing buildings not only in Japan but also in other countries with a proper modification. 8 References (1) Hirosawa, M. (1973), Proposal on Standard to Judge Seismic Capacity of Existing R/C Buildings, Kenchiku Gijutsu (in Japanese). (2) Architectural Institute of Japan (1975), Method to Evaluate Seismic Safety of R/C School Buildings and Method of Strengthening (in Japanese). (3) Okada, T. and Bresler, B. (1976), Strength and Ductility Evaluation of Low-Rise Reinforced Concrete Buildings-Screening Method-, EERC Report No.76–1, Univ. of California, Berkeley. (4) Japan Building Disaster Prevention Association (1977), Guideline for Evaluation of Seismic Capacity of Existing Reinforced Concrete Buildings (in Japanese). (5) Japan Building Disaster Prevention Association (1977), Guideline for Strengthening of Existing Reinforced Concrete Buildings (in Japanese). (6) Architectural Institute of Japan (1980), Report on Damage due to 1978 Miyagi-kenOki Earthquake (In Japanese). (7) Building Research Institute (1965), Damage on Buildings due to 1964 Niigata Earthquake, Report of Building Research Institute, No.42 (in Japanese). (8) Architectural Institute of Japan (1968), Report on Damage due to 1968 Tokachi-Oki Earthquake (in Japanese). (9) Umemura, H., Okada, T. and Murakami, M. (1980), Seismic Judgment Index Values for Guideline for Evaluation of Seismic Capacity of R/C Buildings, Proceedings of Annual Convention of Architectural Institute of Japan (in Japanese). (10) Okada, T. et al. (1986), Seismic Capacity of Reinforced Concrete Buildings which suffered 1985 Mexico Earthquake in Mexico City, Part 1–part 13, Proceedings of the Annual Convention of Architectural Institute of Japan (in Japanese). (11) Okada, T. (1983), Seismic Capacity and Strengthening of Reinforced Concrete Buildings, Proceedings of Panel Discussion for Strengthening of Existing Reinforced Concrete Buildings, Japan Concrete Institute (in Japanese). (12) Murakami, M. and Okada, T. (1981), Evaluation and Judgment of Seismic Safety of R/C School Buildings, Japan Building Disaster Prevention Association (in Japanese). (13) Japan Concrete Institute (1984), Handbook for Strengthening of Concrete Structures, Editor: T.Okada, Gihodo-Shuppan.

PART ONE GUIDELINES FOR DEMOLITION WITH RESPECT TO REUSE OF BUILDING MATERIALS

3 GUIDELINES FOR DEMOLITION WITH RESPECT TO THE REUSE OF BUILDING MATERIALS: GUIDELINES AND EXPERIENCES IN BELGIUM B.P.SIMONS and F.HENDERIECKX Belgian Building Research Institute, Zarentem, Belgium Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 26 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract Demolition guidelines can constitute a powerful tool to improve the quality of the waste and to raise the quantity of the recyclable fraction. However, demolition guidelines are only effective if they, being one tool in a global concept for the stimulation of the recycling of construction and demolition waste, can act in synergy with other initiatives. Demolition is treated with respect to requirements of the final products, leading to specifications for the waste. In this frame work, concepts for demolition guidelines are presented. Keywords: Construction and demolition waste, Demolition, Incentives, Demolition guidelines.

1 Introduction In Western Europe, the yearly amount of construction and demolition waste, is about 0,7 to 1 ton per inhabitant. This is nearly twice the weight of the municipal solid waste. Far the biggest part of this construction and demolition waste is good recyclable, at least, if it is brought into a recycling installation in a good condition, considering the requirements of the recycled products. This is only possible, if in demolition practice these aspects are sufficiently taken in account. Demolition guidelines can constitute a powerful tool to improve the quality of the waste and to raise the quantity of the recyclable fraction. However, demolition guidelines are only effective if they, being one tool in a global concept for the stimulation of the recycling of construction and demolition waste, can act in synergy with other initiatives. (1)

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2 Demolition guidelines as part of a global concept for the stimulation of the reuse of construction and demolition waste: 2.1 Materials and waste streams A global concept for the stimulation of the reuse of construction and demolition waste starts with a clear insight in the waste streams (scheme 1) and in the mechanisms, who steer these streams. The waste is generated during construction, renovation and demolition of roads, buildings,… It’s transported to recycling installations, on site or centralised (sometimes via a separation installation), or to landfill or, in some cases to an incinerator. The use of recycled aggregates in construction works closes the circle. Scheme 1 material and waste streams

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2.2 Estimated quantities in Belgium Belgium is turning into a federal country, more and more competencies are transferred from the federal level to the three regions: Flanders, Brussels and Wallonia. Environmental as well as infrastructural competencies are regionalised; in other words, the three regions develop their own policy and their own instruments in these issues. Therefore, the 3 regions are treated separately in this article.

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2.2.1 Quantities of wastes in the Flanders region (2) In a recent study, the amount of construction and demolition wastes in Flanders was estimated at ca 4.6 million tons per year (graph 1). Some 40% consists of concrete while some other 40% of masonry; the remaining 20% consists of bituminous materials (12%), ceramics (3.4%) and various wastes.

The sources of the wastes are buildings (residential or not), roads and building material manufacturing companies (graph 2).

2.2.2 Quantities in the Brussels region (3)

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In the Brussels region, a similar study was carried out. The amount was estimated at 850 000 to 1 000 000 tons per year. The sources and the composition are given in graphs 3 and 4

In comparison to Flanders, the non residential buildings take a far bigger share (graph. 4) (51.9 vs 44.5%). On the other hand, the most important difference in average composition is a higher amount of masonry (45% vs 40%).

2.2.3 Quantities in the Walloon region Extrapolation of the figures from Flanders and Brussels, to the Walloon part of the country, would allow to estimate the amount to some 2 million tons.

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Nevertheless, one should be very careful in making such extrapolations, given the important differencesbetween the regions. 2.3 Bottle-necks A lot of bottle-necks for the recycling of construction and demolition waste can be indicated. they occur at the level of the production of the waste, the recycling activities and the use of recycled products. 2.3.1 The production of the wastes A distinction is to be made between road construction and construction of buildings, artworks,... Both sectors are producers of waste; both are potential clients. The rubble of roads is generally homogeneous and very well recyclable. Concrete as well as asphalt can be recycled, in situ as well as in centralised installations. The waste from construction and demolition of buildings is far more mixed up in comparison to the road. A bottle-neck is the separation of the different materials in order to get a reproducible and usable recycling products. More selective techniques of demolition are desired. Another bottle-neck could be the potential incertainity about the source of the wastes. The recycling company has to develop a good controlling system in order to avoid contaminated rubble. Taxes should be an efficient incentive for canalization of wastes to recycling plants. It can be a very effective instrument, but should also be handled with care, in order not to propagate illegal landfilling. 2.3.2 The recycling activity The profitability of recycling depend mainly on - the cost of the process - the (negative) value of the rubble. An important tool to raise in this negative value is the height of the taxes. However, as mentioned above they should be handled with care. - the difference in selling prices between virgin and the recycled materials (cfr. table 1)

Table 1: comparision of average selling prices

Gravel

porphyry

concrete

recycled mix

asphalt

320

310–390

220–240

180–200

230–280

Another bottle-neck is the legal incertainity about the responsibility. In other words: who’s responsible for the evacuation of contaminated batches.

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2.3.3 The use of the recycled products The first market for recycling products is road construction. If the use of these products is admitted; the quality can be certified and the price is interesting, a large market is created. It’s clear that the public market can and has to be extended. Nevertheless, this market isn’t huge enough to absorb all the recycled materials. New applications have to be developed, in the first place for the use of lower qualities (in the first place masonry granulates). 2.4 Potential incentives for the recycling of construction and demolition waste Several tools can be worked out in order to stimulate recycling: 1. The best way to stimulate recycling is to create or at least to enlarge the market. Recycled granulates should be used as much as technically sound in public works. This also has an effect on the private market, as private investors use the public standards. 2. The fear for lower quality puts a break on the use of recycled products. An official label can obviate these drawbacks if it constitutes a guarantee for a specific good quality. Such a label is to be well defined and given by an official body. 3. In order to obtain recyclable products and to canalise the wastes, new specifications for demolition works should be emitted and introduced in ‘demolition permits’. In the first place, this should be done for public works. 4. Creating a recycling industry is a task for the private sector, as it leads to an economical activity. With this new branch, the authorities can come to agreements in order to stimulate separation of the wastes and to enhance the recycling rates. 5. Higher taxes can be a tool for canalization of the wastes to recycling. They also have an effect on the profitability of recycling. 6. There is a need for new applications of recycled materials, especially for the lower qualities (masonry). Priority should be given to applications with high amounts of recycled granulates. 7. More and more precise information is to be reassembled about (among other things): - amounts and composition - comparison between different demolition techniques - .... 8. The authorities can prohibit landfilling. However, one should be very careful with such new prohibitions, because - there should be enough alternatives for the industry - illegal landfilling could be encouraged 9. Better control is necessary 10. Direct subsidisation of recycling doesn't seem to be effective. It will disturb the market and be very expensive.

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These potential incentives can be classified following their cost-effectiveness.

Table 2: Potential incentives for stimulation of the reuse of construction and demolition waste: cost-effectiveness

For more details about initiatives in Belgium in the field of the use of secondary materials in public works, labelling and taxes, we refer to another lecture in this conference.(4) In the next paragraphs, attention will be paid to demolition and demolition guidelines. 3 Demolition 3.1 Requirements of the recycled granulates. Technical requirements Technical requirements of secondary granulates are treated more in detail in other lectures of this conference. They mainly consist of: - density: the quality of the end product is related to the density of the granulates. The higher the density, the better the strength of the concrete and the better the frostresistance.

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- absence of contaminations: some contaminations have a negative influence on the quality of the end products: organic material, iron, gypsum,… - granulometry: It is clear that the granulometry of secondary materials has to meet the same standards as virgin ones. Aggregates are used in different markets. A first important market consists of road construction. In Flanders, several different types of materials are defined: concrete rubble, mixed rubble masonry and asphalt. Each of these products can be used in well defined applications. More and more recyclers not only commercialise the granulates, but also produce concrete. These companies generally guarantee the features of the concrete. Obviously, analogous specifications for the granulates are applied. Environmental requirements As recycled materials are to be brought into the environment, they have to meet sound environmental standards. It is obvious that one has to avoid to bring heavy metals or other hazardous components into the environment. More details about this issue are presented in (4) 3.2 Requirements of the waste The requirements of the aggregates obviously are reflected in specifications for the waste. In the first place, the waste should be clean enough to produce the desired aggregates. However, in the recycling process, some cleaning steps are included; so a lot of contaminations (metals, plastics, wood,…) are removed. The presence of lower quantities (max some 10%) of these materials don’t cause major problems. For different fractions, one can determine the impurities which should be absolutely banned (red light), and those who are to be avoided (yellow light) (table 3)

Table 3: Requirements of the granulates

Fraction

To avoid

To ban

Concrete, porphyry,…

every other material

fibro cement,roofings packagings, insulation

Mixed rubble,… (incl. ceramics,…)

gypsum,wood plastics, wires,…

fibro cement,roofings packagings, insulation

Asphalt,…

gypsum, wood plastics, wires,…

fibro cement, packagings, insulation

Special attention is to be paid to materials, suspected from an environmental point of view. Pollution can originate from different sources, eg. hydrocarbons in gas stations, heavy metals in non ferro factories. Also carelessness can cause important contaminants (paintings, packagings, lamps,…)

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At last, if the material is to be recycled, it has to be presented in a condition, that the recycling process can be applied in optimal conditions: not oversized, clean,… All these elements can be steered by the acceptation policy of recyclers. Different prices are applied for different fractions, and the freights, containing too much pollution or suspect materials are refused. Indicative prices are given in table 4.

Table 4: Prices for delivery of waste in recyling plants, average prices in Flanders

Fraction concrete, (clean, non reinforced<70 cm)

prices 0–30 BEF

concrete, (clean, reinforced<70 cm)

100–120 BEF

concrete, (clean, reinforced>70 cm)

150–180 BEF

masonry, (clean)

150–180 BEF

masonry, (contamination<10%)

230–300 BEF

asphalt

75–150 BEF

landfill

500–1000 BEF

3.3 Consequences for demolition practice and demolition guidelines. A higher recycling rate can be obtained, if the waste is presented in a condition, were a marketable product can be obtained. In order to obtain clean fractions, a minimum degree of selectivity is required. The more selective the demolition practice, the higher the value of the secondary products. On the other hand, more selectivity means generally a higher cost and more time to carry out the work. Exactly on these 2 items, price and speed, the demolition companies compete on the market. Tools to steer the selectivity are: - raising the cost for more contaminated fractions this in Belgium is realised trough the price-policy of recycling companies and ‘environmental taxes’ - emitting guidelines, and in this way determinating the demolition practice, or, which is desirable, determining the condition of the residues. A realistic degree of selectivity, considering the above mentioned ‘requirements of the waste’ is sought. In Belgium, today demolition guidelines are emitted only in separated cases, certainly not systhematicly. However, in Flanders and in Brussels, guidelines for public works are in project. The headlines of the regulations in project are: 1 For public works, demolition is to be carried out in a way, that a maximum of recyclable products is obtained. Buildings must be dismantled before demolition, and the components, which cause a devaluation of the stone fraction (cfr. table 3) must be taken apart.

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2 A checklist of materials, used in buildings, is to be filled in. In this way, the guidelines can be customised. 3 The waste is to be brought to the destination, were the highest value is obtained. On the other hand, if private buildings are to be demolished, or renovated, also today a permit is requested. In the demands, a list of the materials will have to be submitted and the destination of the waste indicated. These elements will be taken in consideration in order to ad the necessary specifications to the permits. 4 Conclusions As mentioned above, demolition guidelines, if part of a global frame work for the stimulation of the recycling of construction and demolition waste can be a powerful tool to improve the quality of the waste and to raise the quantity of the recyclable fraction. However, these guidelines should be realistic and be worked out considering the requirements of the final destinations. 5 References 1. OVAM & WTCB Recymat: Globale aanpak van hergebruik van bouw en sloopafval, voorbereidingsdossier; OVAM, september 1992 (in Dutch) 2 OVAM & WTCB Recymat: Bouw-en Sloopafval, voorbereiding ontwerpplan 1991– 1995; OVAM, june 1990 (in Dutch) 3 B.Simons, E.Rousseau & M.Coucke: Problematiek van bouw-en sloopafval in het Brussels gewest; BIM/IBGE, march 1991 (in Dutch, also available in French) 4 J.Vyncke & E.Rousseau: Recycling of construction and demolition waste in Belgium, actual situation and future evolution; RILEM 3th international conference, Odense 1993 5. C.De Pauw, B.Simons & J.Vyncke: Recycling in the Belgian building industry, actual practise and outlook for the future; Rec’93 international recycling congress, Geneve 1993

4 GUIDELINES AND EXPERIENCE FROM THE DEMOLITION OF HOUSES IN CONNECTION WITH THE ØRESUND LINK BETWEEN DENMARK AND SWEDEN E.K.LAURITZEN and M.JANNERUP DEMEX Consulting Engineers, Copenhagen, Denmark Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract This paper gives a presentation on the demolition of structures and buildings, and the reuse of materials in connection with two major construction works in Denmark: The Storebælt (Great Belt) Link between Seeland and Fuenen, and The Øresund Link between Denmark and Sweden. The performance requirements for demolition work in Denmark are presented. They are based on recent legislation and regulations for cleaner technology and recycling of waste materials in the construction and civil engineering industry. Practical experience from the selective demolition work of approximately 200 houses is also presented. The paper concludes with some general recommendations for selective demolition. Keywords: Selective Demolition, Reuse of Concrete and Masonry, Cleaner Technology, Danish Legislation.

1 Introduction 1.1 The importance of building waste management At present, several outstanding demolition projects are taking place in different parts of the world. In Hong Kong, for example, the demolition of the “The Walled City”, a historically famous part of Kowloon, was begun earlier this year. The project involves approximately 150,000–200,000 t of demolition waste. In Turkey, the demolition of damaged structures, and the resulting management of building waste is taking place, following the 1992 Erzincan earthquake. This US$ 275 million reconstruction project,

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financed by the World Bank [1], includes one million tonnes of building waste. At the same time, the planning for the reconstruction of Beirut has started, financed by the World Bank and others. The related demolition and building waste management will fill up part of the Mediterranean as land reclamation for new the city, has started. In Jugoslavia the destruction of buildings and structures takes place every day due to war activities—the future reconstruction process will require building waste management of enormous dimensions. Even the World Bank employees face another year of demolition noise and vibration in connection with the second part of the reconstruction of their headquarters in Washington. After circling the world we return to Denmark. where many major construction and demolition projects are also taking place. At least two projects in the “Heavy Weight Class” should be mentioned, namely, - The Great Belt Link between Seeland and Fuenen, presently under construction, and - The Øresund Link between Denmark and Sweden which has just started. Both of these projects involve large amounts of demolition and recycling of waste which will be presented in this paper.

Fig. 1 The two giants of civil engineering in Denmark—The Great Belt Link, and at the bottom The Øresund Link. A third project, The Fehmarn Belt Link to Germany, is also discussed

The purpose of this paper is to illustrate and emphasize the importance of environmental, friendly demolition and building waste management. These should be

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considered as integral part of any construction and civil engineering project. All building and construction activities produce certain amounts of building and construction waste materials (construction and demolition waste=C&D-waste), of which nearly all can be reused. The need for proper planning in demolition and waste management can no longer be neglected. The work of RILEM TC-34-DRC and TC-121-DRG and other investigations has demonstrated that the annual production of C&D-waste in most industrialized countries reaches figures very close to 1 ton of waste per inhabitant [2,3,4], and that recycling of the waste can reduce the consumption of natural resources by about 5% [1,2]. It is therefore it is beyond doubt that recycling of C&D-waste material, and related environmental effects must be regarded as key issues of environmental management in the construction industry and civil engineering. 1.2 Danish action plans for recycling and cleaner technology In June 1992, the former Danish Minister of Environment, Per Stig Møller, presented two action plans, “Waste and Recycling 1993–97” and “Cleaner Technology 1993–97”, to the Danish Parliament’s Environmental Planning Committee. The plans included initiatives to be taken in the next five year pericxi in order to reduce the amount of waste and to ensure the development and implementation of cleaner technology. Attention was especially drawn to the increased goal for reuse of building and construction waste. The previous target of 50% of all construction and demolition waste to be reused by the year 2000 was increased to 60%. Furthermore, the disåosal fees for waste were increased from 1 January 1993, the new values being 195 DKK/ton (32 US$/ton) for dumping and 160 DKK/ton (27 US$/ton) for incineration. 1.3 Action plan for cleaner technology in the building and construction industry The two action plans mentioned above have been combined to form one action plan for the construction industry. This is due to the difficulty of separating the concepts recycling and cleaner technology in the field of building and construction. The long term aim of the plan is to promote the initiatives for reducing both the use of resources and also the environmental impact in all stages of building and construction projects: I

Raw material extraction

II

Production of building materials

III

Construction

IV

Operation and maintenance

V

Demolition, recycling and removal.

The basic strategic element of the plan is the consideration of the life-cycle of total resource utilisation and the resulting impact on the environment. Thus, we are able to

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show the possibility of introducing cleaner technology, thereby aiding the decisionmaking process by fixing an order of priority, classification and implementation of the necessary initiatives. The plan strongly emphasises the following areas: - Investigation of materials and building components - Investigation and development of minimal forms of construction - Minimisation of excess and waste, combined with an increase in recycling - Analysis of industry and construction - Development of models for life-cycle evaluation - Environmentally, friendly planning - Economic and administrative control systems. 1.4 Cleaner technology in very large construction projects As examples of actual projects where considerations for cleaner technology are required, we have used the two above mentioned construction projects in Denmark. Due to the size and importance of these projects, the decision-making processes involved have been heavily influenced by the evaluation of the resources required and the resulting impact on the environment. During the project planning of building and construction projects, it is important that a very accurate evaluation is carried out of all the relationships concerning the extraction of raw materials, production of components, actual construction and operation. The immediate requirement for demolition concerns structures which either lie in the way of the project or ones which were specifically built for the purpose of the project. During the construction of The Great Belt Link, considerable resources were used for the construction of concrete mixing plants, foundations, roads and such; these will be removed when the project is completed. The same kind of temporary works are to be built for the Øresund Link. 2 Demolition and recycling, Great Belt Link Project The construction of the Great Belt Link involves the West Bridge, finished in May 1993, the railway tunnel under the Eastern part of the Belt, which is presently under construction, and the recently started East Bridge for vehicles. So far, the following typical demolition and waste handling problems have ocurred: - Demolition of old/superfluous structures - Handling of rejected concrete elements - Demolition of temporary structures - Handling of refuse, spill and waste from packaging etc. The modifications to the roads and structures on both sides of the Link have required the demolition of certain structures. One such project was a newly constructed, heavily reinforced concrete bridge, demolished in 1991 (see figure 2). The demolition of the bridge was carried out as a demonstration project, with an investigation into demolition techniques and recycling of crushed concrete aggregates in new concrete. This was then

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used in the “Recycled House” in Odense, and in foundations for baffles. The experience gained from the testing of different types of demolition methods and techniques (blasting, balling and hydraulic chopping), particulary related to the recycling of concrete, are illustrated in a paper which was presented by Lauritzen at the 2nd International Conference on Fracture and Damage of Concrete and Rock, Vienna, 9–13 November 1992 [5]. Experience from the recycling of the concrete aggregate is reported in the paper “The RECYCLED HOUSE in Odense”, to be presented by Erik B. Olsen later on in this symposium [6]. Due to the strict requirements of concrete quality and to other difficulties, a considerable number of tunnel elements and some bridge elements were rejected in the initial stages of the tunnelling contract and the West Bridge contract. Many of the rejected tunnel elements were reused for other purposes, and the rejected bridge elements were demolished by use of explosives on site. After completion of the West Bridge project, the temporary Lindholm Concrete Prefabrication Yard is to be demolished. This demolition project, involving 35,000 m3 reinforced concrete, 7,000 t of steel and 5,000 t of asphalt, starts in June 1993 and will be finished by the end of 1993. Clive Loosemore will present this demolition project later on in this symposium, [7], and the demolition site can be visited during the technical excursion afterwards. According to Loosemore, the construction of the West Bridge involved the production and placing of some 480,000 m3 of concrete. Approximately 1% of the concrete produced, ie. some 12,000 t, had to be disposed of due to over-ordering of concrete and the rejection mixed concrete. The disposal and management of this type of concrete waste is also described by Loosemore. By the end of the entire Great Belt Link construction work, the temporary tunnel prefabrication yard in Korsør and the construction site in Kalundborg for the East Bridge will also have to be cleared. In considering the total amount of construction and demolition waste, spill, refuse, packaging etc. we are dealing with very large figures—several hundred thousand tonneswhich clearly indicates the need for planning, management and recycling. As a concluding remark concerning the Great Belt Link project we should also mention that the link will close the present ferry line across the Belt. This will make all ferry berths superfluous, and result in several hundred thousand tonnes more of concrete waste! 3 Demolition and Recycling, Øresund Link project 3.1 Demolition of approximately 350 houses in the Copenhagen area In accordance to Law no. 590 of 19th August 1991 concerning the establishment of the land infrastructure for the Øresund Link, expropriation and demolition of a large number of buildings in Copenhagen has begun. This consists of approximately 200 family houses in Tårnby borough and 150 detached houses in the Municipality of Copenhagen. The demolition is being carried out in a number of different contracts, each of 15–30 houses.

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Fig. 2 Photos showing reinforced concrete bridge before and during demolition. The bridge was not suiatable for the Great Belt Link. Different methods of demolition (blasting, balling, hydraulic chopping, chemical non-explosives) were tested, and the effects on the structure and environment were recorded. Finally the concrete rubble was crushed and used in new concrete in the Recycled House, see [4,5].

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Fig. 3 Sketch of the planned land infrastructure of roads and railways on the Danish side of the Øresund Link.

The management and planning body concerned with the land infrastructure in Copenhagen, A/S Øresundsforbindelsen, has sub-contracted the project planning and supervision of the demolition work to DEMEX Consulting Engineers A/S. The separate contracts are carried out as the houses are expropriated and cleared for demolition. As a result, buildings to be demolished under any one contract are spread throughout the area, some of these being adjacent to still inhabited houses. This places considerable demands on the demolition techniques. Consequently, A/S Øresundsforbindelsen has decided that the demolition should be carried out in three steps: 1. Initially buildings are demolished to the foundation, and the cleaned demolition waste is temporarily deposited within the foundation area. This avoids the use of large machinery and thus reduces the environmental impact on the surrounding neighbourhood. 2. The sites are cleared of trees and bushes, concrete and masonry rubble removed, and buried oil tanks dug up. 3. Roads and remaining structures which are not needed for temporary use are removed.

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The initial demolition of the buildings is carried out as selective demolition, according to experience gained during demonstration projects performed with the Danish National Agency of Environment. Since A/S Øresundsforbindelsen emphasises the importance of the demolition not disturbing the surrounding environment, the demolition work is executed as follows: - All demolition products are dismantled and sorted on site with the intention of maximum recycling. - All environmental nuisance is kept to a minimum. - Movement of machinery and vehicles is carried out with great care and the least possible disturbance to neighbours. - Disturbance to gardens surrounding the houses is kept to a minimum. - Demolition and temporary dumping sites are kept in a clean and orderly manner. Before the start of the separate contracts, the previous owners are asked to remove all possessions of personal interest, such as doors and fixed effects. Thereafter, the nearby youth clubs are given the opportunity to remove remaining effects for sale, the profits of which go directly to the operation of the clubs. 3.2 Selective demolition It is the contractor’s duty to demolish the houses in the following order: 1. Removal of remaining furniture and other efects. 2. Removal of all wastes for special treatment: e.g. asbestos, oil tanks, chemical wastes etc. 3. Removal of all indoor installations and building materials, doors, windows, floors for reuse. All plaster, insulation and other dust-producing material must be removed by vacuum in closed containers. 4. Dismantling of roof structure for reuse as roofing materials and timber 5. Demolishing of walls, leaving the rubble in proper heaps. 6. Sorting of the rubble for all impurities such as paper, wood, plastics etc. All materials except foundation and the rubble must be removed without any noise or inconvenience to neighbours. Most of the materials are kept for reuse, and only very little has been deposited in controlled landfills. Fig. 4 shows a cross section of a typical Danish family house with some 100–150 m2 floorage. It produces approximately 1.0–1.5 t building waste per square meter. 3.3 Special considerations Because situation concerning the acquisition of property under compulsory powers is politically sensitive, special consideration must be paid to the remaining inhabitants in the area. Demolition must be carried out with wheeled machinery under 12 tonnes net weight. Noisy tools are not permitted, and emission of dust is not accepted. The provision supply of electricity, heat, water, and sewage etc. must not be interrupted, and the roads must be kept clean and free of any obstructions.

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Fig.4 Cross section of a typical Danish family house with indication of the different kinds of building materials and classes of waste.

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Fig. 5 Photo showing demolition of the first house using hand held equipment. To avoid dust and mixing of materials, a large industrial vacuum cleaner (STORSUG) was used for removing plaster, insulation, paper and dust. Attention is drawn to the clean working conditions in the house during demolition, photo to the right. Careful asbestos removal was carried out in the house before the start of demolition and vacuuming. When all other materials had been removed and only the bricks remained. then the house was demolished. The photograph below shows the timber and wooden boards along with bricks from a demolished house. The wood is removed for reuse, as are the windows and doors. Here the materials are ready for collection.

3.4 Waste management and recycling In fig. 4 the different classes of wastes are shown. Class A contains recyclable materials of which concrete and masonry rubble should be left on site, whereas Class B and C should be removed for special treatment, incineration or tipping. The figure shows the distribution of the different fractions of waste materials, also. The philosophy of leaving the concrete and masonry rubble was that it would be easier, and hence cheaper, to remove of all the rubble when the greater part of the houses has been demolished and no special considerations were needed any longer.

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Initially, it was planned to crush the concrete and masonry rubble into aggregate for temporary roads used in the project. Later, however, it was discovered that Copenhagen Harbour needed material for construction of new dams for a planned land reclamation project. Therefore, it was necessary to calculate the most feasible economic solution. 3.5 Contracts and economy The project comprising approximately 200 family houses in Tårnby borough was divided into contracts of 15–30 houses per contract, depending on the release of the single houses for demolition. For each contract 6 demolition contractors were invited to tender. Due to the special requirements the bids on the first contract were rather high, but in the following contracts the bids were considerably lower, as shown in fig. 6.

Fig. 6 Prices (Danish kr. per squaremeter) of the first 5 contracts for the demolition of 110 houses

4 Final remarks Thus, with beginning of the Øresund Link project, much care has been taken in the conservation of natural resources and the impact on the environment. At the same time it has become clar that the terms Recycling and Cleaner technology are gaining more and more recognition and importance in the building and construction industry. Recycling and cleaner technology are no longer idealistic concepts which never reach the reality of the construction site. In this project 90% of alla C&D Waste has been reused. Cleaner technology concerns the rational principles and attitudes which aim to continuously reduce the use of resources and the load on the environment for the benefit

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of society as a whole. References [1] Lauritzen E.K. & Saatcioglu T.Fikret: Demolition and reuse of building and construction waste materials in the rehabilitation and reconstruction project after the 13. March 1992 Earthquake in Erzincan. 2nd National Earthquake Engineering Conference 10–13 March 1993, Istanbul [2] Lauritzen, E.K.: Goals and barriers, recycling of concrete and masonry, 2nd Int. Conf. on Fracture and Damage of Concrete and Rock, Vienna, Austria, November 9–13, 1992. E & FN SPON, London [3] Dansk Vejbeton A/S et al.: Recyclability in concrete of demolition refuses containing materials non-compatible to the traditional cement matrix. EC Research Action Programme on materials Secondary Raw materials. EC-Contract No. MA1D-0022-C, October 1991. [4] Hansen T.C.: Recycling of demolished concrete and masonry. E & FN SPON, London 1992 [5] Lauritzen, E.K.: Demolition and recycling of reinforced concrete bridge during construction of The Great Belt Link in Denmark, Conf. on Fracture and Damage of Concrete and Rock, Vienna, Austria, November 9–13, 1992. E & FN SPON, London [6] Olsen, E.B.: The “Recycled House” in Odense, 3rd RILEM Int. Symposium on Demolition and Recycling of Concrete and Masonry 24–27 October 1993. E & FN SPON, London [7] Loosemore, C.E.: The Great Belt Link project, 3rd RILEM Int. Symposium on Demolition and Recycling of Concrete and Masonry 24–27 October 1993. E & FN SPON, London

PART TWO GUIDELINES FOR THE REUSE OF CONCRETE AND MASONRY AS AGGREGATES IN CONCRETE IN RELATION TO EXISTING SPECIFICATIONS

5 REUSE OF DEMOLITION MATERIALS IN RELATION TO SPECIFICATIONS IN THE UK R.J.COLLINS Building Research Establishment, Watford, UK Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract Although 40% of demolition waste in the UK is recycled it is mainly for low grade applications such as fill and hardcore. Higher grade utilisation such as in concrete has been discouraged by a lack of suitable specifications. The main UK Standard for aggregate in concrete is for natural aggregates, and the only other Standards quoted in job specifications are for lightweight aggregates and blastfurnace slag. Nevertheless, there are ways in which recycled aggregate could be used within the context of British Standards. Firstly, in the Standard for concrete, specific allowance is made for aggregates not conforming to British Standard provided the properties of the concrete are satisfactory, but this places an extra duty of care on the specifier. Secondly, there is a British Standard Guide on the use of industrial by-products and waste materials in building and civil engineering which gives specific guidance on the use of demolition waste in construction, but there is little knowledge and virtually no use of this Standard. The UK Department of Transport has recently revised its specification for highway works and this now permits the use of crushed concrete complying with the quality and grading requirements of BS882 as an aggregate for pavement concrete.

1 Introduction Waste and recycled materials already account for about 10% of the aggregates used in the UK, and it is Government policy to increase this level of usage where this furthers aims of materials conservation and environmental protection. The UK Department of the Environment (DoE) in its Geological and Minerals Planning Research Programme has recently commissioned several research studies to follow up these issues and make recommendations for consideration by Government. Some of the findings are now being

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used in the revision of Government minerals planning guidance for England and Wales which advises the regional authorities and aggregates industry on what needs to be done to ensure an adequate and steady supply of minerals at the best balance of social, environmental and economic costs, compatible with the objectives of sustainable development. The initial project in this series was a new survey of the current situation in the UK with regard to the occurrence and utilisation of mineral and construction wastes. The research, carried out for DoE by Arup Economics and Planning (1991), makes a number of recommendations on how an increased utilisation of wastes could be promoted, and this includes a recommendation that further development is required of specifications for the use of recycled aggregates from demolition and construction wastes. The use of demolition wastes is in fact covered by the British Standard BS6543:1985 “Guide to the use industrial by-products and waste materials in building and civil engineering”, however in a survey of specifications recently prepared by the Building Research Establishment (1993) it was found that this British Standard was little known within the construction industry and virtually never used. A major reason why BS6543 is not much used could be that it does not develop systems for quality. This is necessary for higher quality uses of demolition materials particularly in building construction. The BRE Report on specifications (1993), also commissioned by DoE in the run-up to the preparation of new minerals planning guidance, arises from a concern that the most efficient use of all aggregates materials, including waste and recycled ones, is inhibited by standards and specifications. The report has found that wastage through overspecification occurs quite frequently, major causes being an avoidance of any risk, however small, and the economic pressure of fiercely competitive fee bidding. These factors are particularly effective for excluding recycled aggregates from all but the lowest grades of application such as fill and hardcore. The report includes recommendations on how to increase utilisation of waste materials as well as improve overall aggregates efficiency. Further DoE projects on this theme are an investigation of the end use of aggregates and scope for substitution of aggregates by other materials, and a detailed survey of the recycling of demolition and construction materials, both of which should be completed in 1993. 2 Details of specifications 2.1 Unbound applications The annual reuse of demolition waste in the UK of about 11 million tonnes (Arup 1991) is the highest in Europe but most is for fill and hardcore. There are no British Standards specifically covering such use but if a general recommendation is to be followed, then reference is made to BRE Digest 276 “Hardcore” (1983). An increasing amount of crushed concrete is being used as an unbound sub-base for road construction to the “Type 1” specification in the UK national “Specification for Highway Works” which is now in its seventh edition (Department of Transport et al.

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1991) “Type 1” has a fairly low strength requirement of 50kN as measured by the wet 10% fines test in BS812: Part 111:1990, moderately wide grading limits and a requirement that material finer than 425µm is non-plastic. All of these can easily be satisfied by recycled aggregate. There is also a “Type 2” specification with less onerous requirements. The naming of crushed concrete in these specifications excludes other demolition waste and probably arises from a time when there were plentiful supplies of the material from old airfield runways but little recycling of general demolition debris. With the 7th edition of the Specification for Highway Works (1991) a clause has been introduced giving the option to test the quality of aggregate by the magnesium sulphate soundness test, and this is considered in section 2.8 below with specifications for concrete. 2.2 Aggregates for concrete The main UK specification for aggregates in concrete is BS882:1992, now in its 7th revision since original appearance in 1940. This in its title refers to natural aggregates and so necessarily excludes all types of demolition waste. Lightweight aggregates (including those made from waste materials) are covered by the British Standard BS3797:1990. This excludes most demolition wastes (apart from those derived from lightweight concrete and a minority of masonry material) on the grounds of density. The only other British Standard specifications for aggregate covering use in concrete are BS1047:1983 for air-cooled blastfurnace slag, which is obviously irrelevant to the use of demolition waste, and BS6543:1985 which although relevant has been found to be largely ignored. BS882, BS1047 and BS3797 are referred to by the British Standard for concrete, BS5328:1991, but the use of aggregates to these Standard specifications is not mandatory in all circumstances. For “designed” and “prescribed” mixes it is possible to select aggregates outside British Standards as long as the properties of the concrete are satisfactory. This is rather too open-ended for producing job specifications because it places a responsibility on the specifier to guarantee long term durability. Crushed concrete has recently been introduced in the new (7th) edition of the Specification for Highway Works (1991) as permissible aggregate for use in concrete road pavements, provided it complies with the quality and grading requirements of BS882. It is assumed that “quality” in this context refers to: * Compliance with limits for strength, flakiness and fines content * Chloride and sulphate contents low enough to ensure compliance with the British Standard for concrete (BS5328) * General requirements for cleanliness and lack of deleterious matter that could affect setting or durability. All these quality requirements are of course needed for natural aggregates, but there may be more difficulty in demonstrating compliance for recycled aggregate.

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2.3 Strength, flakiness and fines Compliance with the strength requirement for coarse aggregate in BS882 is relatively straightforward. A minimum 10% fines value of 50kN for dry aggregate is required, or 100kN for wearing courses. The data in table 1 indicate that the strength of demolition debris (ie containing masonry) is adequate for the overall specification of 50kN but that good quality crushed concrete would be required for wearing courses. In BS882 the maximum proportion of flaky particles permitted in

Table 1. British Standard strength tests on UK recycled aggregates

Aggregate type Crushed concrete Crushed concrete Demolition debris Demolition debris

10% fines value

Reference

100–108kN Mulheron and O’Mahoney (1987) 150kN O’Mahony (1990) 80kN Mulheron and O’Mahoney (1987) 72–105kN O’Mahony (1990)

coarse aggregate (determined by the procedure in BS812: Section 105.1:1989) is 40%. This is not generally a problem with demolition materials eg flakiness values of about 10 were obtained for crushed concrete sampled in 1992 from the Warren Farm recycling plant near Portsmouth, UK. The fines content in crushed demolition wastes can be quite high but can be controlled within British Standard limits by sieving. 2.4 Chloride The chloride content of concrete with embedded metal (reinforcement) is controlled to strict limits by British Standards (BS8110:1985 and BS5328:1991). Although plain concrete is not subject to any such limits, there can be very little concrete cast within recent years that at the outset contains enough chloride to cause problems if recycled. Problems could arise, however, for concretes saturated with deicing salts, sea salt or some other form of contamination. Also, before 1977, the limits on maximum chloride content were higher and calcium chloride allowed as an accelerator. A significant number of buildings in which calcium chloride was used are now being demolished, particularly in cases where overdoses of calcium chloride were made. In principle the chloride level could be controlled, as is the case for marine aggregates (Gutt and Collins 1987), but there is no experience in the UK for achieving this for recycled aggregate. There is no information on the most appropriate test method, the variability of chloride in recycled aggregate (which would control the frequency and method of sampling), or whether or not chloride contents expressed as a percentage of cement in BS5328 and BS8110 should include cement within the recycled aggregate. Marine aggregates are tested by a water-extract method (BS812: Part 117:1988). This

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does not account for all chloride in the aggregate; small amounts remaining occluded within the aggregate particles are assumed not to pass into the concrete. This may also be true for recycled aggregates, including crushed concrete which has the potential to retain a considerable quantity of chloride as chloroaluminates. In this case the cement content with respect to which the chloride is expressed as a percentage should probably not include the cement content of the aggregate. If chloride is expressed with respect to the total cement content (ie including that in the aggregate) then the total chloride content of the recycled aggregate (determined by the concrete test method BS1881: Part 124: 1988) is probably more appropriate, however this will include chloride occluded in the aggregate which is assumed not to contribute to the potential for corrosion of reinforcement. 2.5 Sulphate Disruptive expansion of concrete due to excess sulphate content is more of a concern of crushed masonry rather than crushed concrete. This is due to plaster adhering to masonry or to high sulphate contents in bricks, either from the outset or due to contamination, especially in chimneys. The sulphate content of concrete is limited to 4.0% SO3 with respect to cement in BS8110:1985 but this is now recognised to be rather restrictive since cements with up to 4.5% SO3 may be allowed for some cements in the new European Standard EN197. BS5328:1991 does not set a limit and takes a more informative approach. It points out that no problems have been experienced with blastfurnace slags with an SO3 limit of 0.7% in BS1047 and lightweight aggregates with an SO3 limit of 1.0% in BS3797. Resistance to expansion also depends on temperature and the type of cement used (Crammond 1984). 2.6 Alkali silica reaction British Standards refer to Concrete Society Technical Report no. 30 (1987) and BRE Digest 330 (1988) for guidance to minimise the risk of alkali silica reaction (ASR). This usually takes the form of limitations on the alkali content of the concrete, but can be achieved by specifying non-reactive aggregate combinations. It is possible for a recycled aggregate to introduce to new concrete alkalis in excess of these requirements. Recycled aggregates are also likely to contain some window glass which is generally regarded to be in the small group of highly reactive aggregates like opal. The guidance documents indicate that non-reactive aggregates should not contain any opal; no limiting value is given either for opal or for glass. Limiting the alkali content of the concrete normally requires a value for the “alkali equivalent” available from the aggregate, but there is no guidance on how this should be determined for recycled aggregate. Total alkali content is likely to be a considerable overestimate. No account is taken of aggregate porosity in reducing susceptibility to ASR expansion. Aggregates with absorption values above 5% replacing inert aggregate in a “typically” reactive concrete mix have been found to reduce expansions due to ASR to a relatively safe 0.05% (Collins et al 1986).

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2.7 Other requirements No other specific limits on impurities are made within British Standards (apart from some limits with relevance only to blastfurnace slag or lightweight aggregate). The only other limit is on the drying shrinkage of aggregate to the test method and limiting values given in BS812: Part 120:1989. This restricts the use of aggregates giving test results of 0.075% and above to “positions where complete drying out never occurs”, “mass concrete surfaced by air entrained concrete” and “members symmetrically and heavily reinforced not exposed to the weather.” The test method however is only applicable to aggregates with absorption values of 3.5% or less. Thus for recycled aggregate resort would have to be made to the modified method in BRE Digest 357 (1991) or to a shrinkage test on the concrete to be used. There is an implication that aggregates should be “clean, hard and durable” with some help in defining what is required only for natural aggregate. This is clearly inadequate for recycled aggregate. The user of recycled aggregate in the UK must currently accept extra risks unless the recycled aggregate comes from a carefully controlled source. A controlled source could be an old road pavement, and thus highway works may offer the best prospects for the use of recycled aggregates in concrete. 2.8 The magnesium sulphate soundness test The 7th edition of the Specification for Highway Works (Department of Transport et al 1991) has introduced the option of testing aggregates to BS812: Part 121:1989 (similar to ASTM C88 except that percentage of material retained rather than percentage material lost is quoted) in an attempt to put limiting values on “clean, hard and durable”. A limiting value of 75% for aggregates in roadbase was suggested in work by Bullas and West (1991), however this option was also introduced for unbound aggregates. The limit has subsequently been relaxed to 65% for unbound aggregates. Although poor results have been obtained in Japan for sulphate soundness tests on crushed concrete (see Hansen 1992), good results have been obtained in the US (see Hansen 1992) and in the UK (Mulheron 1986 and Woodside 1993). 2.9 Surface layer restrictions The 7th edition of the Specification for Highway Works (Department of Transport et al 1991), as well as permitting the use of crushed concrete as an aggregate in concrete, also introduces new requirements for aggregates in concrete surface slabs which could provide recycled aggregate with compliance difficulties. The water absorption of flint coarse aggregate with white flints for use in concrete surface slabs is restricted to a maximum of 3.5% for any separate nominal size fraction and to 2.0% for the total combination of coarse aggregates in the proportions to be used in concrete. Presumably for recycled aggregate containing white flint, enough flint would have to be extracted by acid dissolution of the cement matrix for absorption tests to be carried out on the flint.

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2.10 Cement bound material The 7th edition of the Specification for Highway Works (Department of Transport et al 1991) specifies four types of cement bound material (CBM1, CBM2, CBM3, CBM4), CBM1 and CBM2 being used as stabilized subbase, and CBM3 and CBM4 as lean concrete roadbase. CBM3 and CBM4 have the same aggregate specification as pavement concrete ie crushed concrete may be used if it satisfies the grading and quality requirements of BS882. CBM1 and CBM2 have fairly low strength requirements and very wide aggregate grading limits. The coarser material which is required for CBM2 must have a wet 10% fines value of 50kN or more. Other than this no restriction is made on the type of aggregate, and thus crushed masonry as well as crushed concrete is permitted as long as the plaster content (or other impurities) do not prevent adequate strength development and do not give rise to disruptive expansion. 3 European Standards Although European Standards for aggregates now being prepared under CEN Technical Committee 154 (Aggregates) have been required to include waste and recycled materials, a lack of progress in this area has led to calls for the requirement to be abandonned. At the meeting for the specification of aggregates for concrete (CEN TC154 SC2) which was held in November 1992, the meeting felt constrained to introduce a type of “health warning”: “NOTE. Recycled or waste materials may additionally require a much fuller examination of their properties. The purchaser should pay particular attention to this recommendation since the material which has been recycled eg concrete may have been put to widely different uses before recycling took place. Until the full range of requirements for recycled material is published in a harmonised standard, procedures described in national standards and regulations valid in the place of use may be applied.” This is less than satisfactory, and urgent action is required to develop specifications suitable for recycled material before the European specifications for aggregate are ready for public comment in 1994. The TC154 Task Groups which are developing specification limits are expert mainly in natural aggregates and there is a need either to reinforce the expertise on these groups or to set up a new Task Group specifically for recycled aggregate. To delay an input via Task Groups could be to “miss the boat”. A new British Standard Committee B502/8 (recycled aggregate) has been set up to co-ordinate UK input on these materials to TC154. As a general principle recycled material might be specified to conform to the limiting requirements being drafted for TC154, and with some extra requirements set to meet their special needs. The proposals for an EN specification for aggregates (mainly from natural sources) for use in concrete have been outlined in the recent survey of specifications (BRE 1993). There is no assurance that these are workable proposals with regard to recycled aggregate. Extra impurities found in recycled aggregate may affect performance but may also be visually obtrusive and any limits may reflect the maximum that a purchaser will be prepared to accept rather than the maximum that can be successfully

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used in a particular application. 4 References Arup Economics and Planning (1991) Occurrence and utilisation of mineral and construction wastes. HMSO, London. British Standards Institution (1983) BS1047 Air-cooled blastfurnace slag for use in construction. BSI, London. British Standards Institution (1985) BS6543 Guide to the use of industrial by-products and waste materials in civil engineering. BSI, London. British Standards Institution (1988a) BS812 Testing aggregates Part 117 Method for determination of water-soluble chloride salts BSI, London. British Standards Institution (1988b) BS1881 Testing concrete Part 124 Methods for analysis of hardened concrete. BSI, London. British Standards Institution (1989a) BS812 Testing aggregates Part 120 Method for testing and classifying drying shrinkage of aggregates in concrete. BSI, London. British Standards Institution (1989b) BS812 Testing aggregates Part 121 Method for determination of soundness. BSI, London. British Standards Institution (1990a) BS812 Testing aggregates Part 111 Methods for determination of ten percent fines value (TFV). BSI, London. British Standards Institution (1990b) BS3797 Specification for lightweight aggregates for masonry units and structural concrete. BSI, London. British Standards Institution (1991) BS5328 Concrete. BSI, London. British Standards Institution (1992) BS882 Specification for aggregates from natural sources for concrete. BSI, London. Building Research Establishment (1983) Digest 276 Hardcore. Reprinted with minor alterations 1991. BRE, Watford Building Research Establishment (1988) Digest 330 Alkali aggregate reactions in concrete. Revised 1991. BRE, Watford. Building Research Establishment (1991) Digest 357 Shrinkage of natural aggregates in concrete. BRE, Watford. Building Research Establishment (1993) Efficient use of aggregates and bulk construction materials (Volumes 1 & 2). BRE, Watford. Bullas J.C. and West G. (1991) Specifying clean hard and durable aggregate for bitumen macadam roadbase. Transport and Road Research Laboratory Research Report 284. TRRL, Crowthorne. Collins R.J. and Bareham P.D. (1986) Alkali-silica reaction: suppression of expansion using porous aggregate. Cem. Concr. Res., 17, 89–96. Concrete Society (1987) Alkali silica reaction: minimising the risk of damage to concrete. Technical Report no. 30. The Concrete Society, London. Crammond N.J. (1984) Examination of mortar bars containing varying percentages of coarsely crystalline gypsum as aggregate. Cem. Concr. Res., 14, 225–230. Department of Transport, Scottish Office Industry Department, Welsh Office and Department of the Environment for Northern Ireland (1991) Specification for Highway Works. HMSO, London. Gutt W. and Collins R.J. (1987) Sea-dredged aggregates in concrete. Information Paper 7/87. Building Research Establishment, Watford Hansen T.C. (1992) Recycling of Demolished Concrete and Masonry. RILEM Report

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No. 6, E & FN Spon, London. Mulheron M. (1986) A preliminary study of recycled aggregates. Institute of Demolition Engineers, Virginia Water, Surrey. Mulheron M. and O’Mahony M. (1987) Recycled aggregates: properties and performance. Inst. Demolition Engineers, Virginia Water. O’Mahony M.M. (1990) Recycling of Materials in Civil Engineering. DPhil Thesis, University of Oxford. Woodside A. (1993) University of Ulster. Personal communication.

6 RECYCLING OF CONSTRUCTION AND DEMOLITION WASTE IN BELGIUM: ACTUAL SITUATION AND FUTURE EVOLUTION J.VYNCKE and E.ROUSSEAU Belgian Building Research Institute, Brussels, Belgium Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract An analysis is made of the situation in Belgium related to the production, disposal and recycling of construction and demolition waste. Regional differences are highlighted and explained. Regarding the use of recycled materials in the construction industry the current state of practice is discussed. Attention is focused on recently worked out technical specifications for recycled aggregates. Issues related to the legal status of the application of recycled waste materials and to quality certification of recycled aggregates are addressed. An opinion is given on the relevance of the use of recycled construction and demolition waste as aggregates in concrete. Keywords: Construction and Demolition Waste, Recycled Aggregates, Concrete, Technical Specifications, Environmental legislation, Quality certification.

1 Introduction The concern about the environment in general has, over the last decades, drastically increased. On a social and political level the trend set by the “green” has gradually been followed and has widen its influence. In particular related to both the consumption and excavation of primary raw materials and the production and disposal of waste a strong social reluctance has originated. The “not-in-my-backyard-principle” generally applies. Its pressure is of coarse more heavily felt in densely populated areas. The “use-and-throw-away” mentality of the not so far past is steadily making place for a “recycling-notion”. Also the building industry is of course closely involved in this

Recycling of construction and demolition waste in Belgium: actual situation and future evolution evolution. Large quantities of locally available raw materials are traditionally consumed in this sector and a considerable waste stream results in the process of construction and demolition. At the same time opportunities for recycling in the sector are legion. However, economic constraints, lacking technical specifications for the recycled materials as well as the well-known conservatism in the construction industry constitute obvious barriers in the development of the use of recycled materials. Supporting actions are thus needed to give the evident opportunities a chance: • Information and sensibilisation of all the partners involved is a necessity. Responsibilities have to be redefined. • Specifications which relied thus far for a great extend on past experience with virgin materials of well known geological origin have to be reviewed and adapted. • Economic bottle necks have to be relaxed. Indeed, how strong the social concern about the environment may ever be, the final motivation for using recycled materials will always stay an economic one. As long as there is no real economic interest in using recycled materials instead of virgin raw materials the use of the former will last marginal. The economic feasibility for processing the waste is in this respect governed by: - the availability and thus the cost of virgin materials - the tipping charges and taxes for dumping the waste - and last but not least the cost of transportation. Regional variations in these factors have of course a major impact on the actual local level of recycling in the construction industry. The latter will readily be illustrated in describing the situation with respect to recycling of construction and demolition waste in Belgium.

2 The Belgian situation. 2.1 General Quite some differences are observed in relation to the use of recycled materials in Belgium’s three regions: Flanders, Brussels and Wallonia. In order to be able to appreciate these differences it is necessary to realise that there is a distinct geographical difference between the regions (fig. 1). Further more it has to be realised that since the mid eighties the regions are autonomous to develop their own environmental and building policy and legislation.

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Fig. 1. Map of Belgium.

2.2 Flanders Flanders (13,512 km2) which is situated in the North of Belgium has a very high population density of 422 inhabitants per square kilometre. Except for some winning of sea and river gravel no natural resources are available. The production of construction and demolition waste has been calculated to amount to circa 4.6 million tons per year, i.e. 807 kg per year and per habitant [1]. Tipping costs for construction and demolition waste are typically in the range of 150 to 400 Belgian francs per ton. An environmental tax of 350 Belgian francs per ton ads up to this. As key elements of the Flemisch Strategic Waste Action Plan 1991–1995 figure: prevention, recycling and reuse. In relation to this plan a new environmental legislation VLAREM II has been introduced late last year. By this legislation dumping of recyclable waste coming from construction and demolition is being prohibited. Taking this situation in account it is quite logic that in Flanders already a wellestablished recycling industry is operating. Approximately 40 recycling installations are currently in use. It is estimated that actually about 2 million tons demolition waste are being recycled each year. As future targets an overall 60% recycling by the end of the year 1994 has been put forward. In relation to the recycling of construction and demolition waste many initiatives are currently going on in Flanders. • Already in 1990 a working group dealing with the reuse of wastes was established on the initiative of the Ministry of the environment and infrastructure (LIN). The working group studied the necessary amendments to tender specifications in order to allow recycled aggregates to be used in public works.

Recycling of construction and demolition waste in Belgium: actual situation and future evolution • Also in 1990 the Association of Demolition Waste Recycling Corporations (VVS) has been founded. Its primary aim was to establish a certification procedure for its members. • Related to the reuse of waste the Public Flemish Waste Agency (OVAM) is involved with setting up regulations which aim at specifying environmental quality standards. • The Confederation of Flemisch Contractors (VCB) works towards sensibilisation of its members and established several working groups dealing with recycling. • The Belgian Road Research Centre (BRRC), the Belgian Building Research Institute (BBRI) and especially its affiliated company RECYMAT are conducting on behalf of OVAM several supporting studies. Most of the above initiatives have been bundled in a global action plan and some of them are in later sections and in [2] described in detail. 2.3 Brussels Brussels (161 km2) is the smallest of the three regions and counts 6025 habitants per square kilometre. Its territory is limited to the urban region of the city of Brussels. No quarries and dump sites whatsoever are available. The production of construction and demolition waste has been calculated to be 850.000 tons per year, i.e. 876 kg per year and per habitant [3]. For the evacuation of its waste Brussels has for the moment to rely totally on the recycling and dumping possibilities offered in Flanders and in Wallonia. No need to stress that this is a rather difficult situation for the Brussels region. The interest in recycling is then also manifest as well as the interest in prevention of waste. Actually about 30% of the waste find its way to recycling plants in Flanders that are situated close to Brussels. The remaining 70% is evacuated to the nearest dump site, i.e. a dump site in Wallonia. The aim of the Brussels Waste Plan that was approved in 1992 is to realise 70% recycling by 1996. In order to achieve this goal major attention is currently being directed by the Confederation of the Brussels Contractors (CCBC) and the Brussels Institute for the Environment (BIM) towards the evaluation of the possibilities offered by selective demolition. In collaboration with RECYMAT, the BBRI and the BRRC a study has been set-up in this respect last year [2]. 2.4 Wallonia allonia (16,844km2)

Wallonia is situated in the South of Belgium and has a population density of 190 habitants per square kilometre. A large number of quarries are dispersed over the territory. No official studies have yet been undertaken regarding the production of construction and demolition waste. Estimates indicate a production of about 2 million tons per year, i.e. 625 kg per year and per habitant [4]. Tipping costs are typically in the range of 80 to 300 Belgian francs per ton. An environmental tax of 150 Belgian francs per ton ads up to this. Although the number of authorised dump sites is very limited (in total only 14 of them

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exist) at the moment only one recycling plant is operating. Obvious this gives a problem as to the evacuation of the waste. In view of this situation the co-operation TRADECOWALL has been founded in 1991 by the Confederation of the Walloon Contractors (CCW) in collaboration with, amongst others, the regional authorities. The main aim of this co-operation is the establishment of an adequate network of dump sites for inert waste and the exploitation of stock sites for non-contaminated excavated soil (soil banks). Further, in line with the regional Walloon Waste Plan 1991, TRADECOWALL aims at relandscaping of existing unauthorised dump sites and closed quarries. Also the promotion of recycling is one of the goals. In this respect a project is being considered to set up a waste separation centre in the neighbourhood of the city of Namur. Yet a problem is the rising of the necessary funds. Indeed, in view of the geographical spread of the waste production (only 120 ton/year/km2 compared to 340 ton/year/km2 in Flanders for example) it is felt that the provision of waste to the centre may be to small to be efficient. Another possibility that is being considered is the establishment of a network of local stock sites for construction and demolition waste. At regular intervals a mobile chrusher could be installed on this sites to recycle the waste stocks. In this context however it is felt that the marketing of the recycled products will be a problem as primarily raw materials are cheaply and in large quantities available. Eventually, another evolution may be an interest of the raw material producers to take initiatives and to set-up recycling plants at their quarries. Anyhow, lately initiatives have been taken by the Ministry of Infrastructure and Transport (MET) to make amendments to their tender documents so as to allow the use of recycled materials in road construction. A working group was established early 1993 in which participate amongst others the BRRC and the BBRI. Further the different collective industrial research centres created RECYWALL, a Grouping of Economical Interest with as objective the study of new possibilities for recycling in all industrial sectors. 3 The recycling industry in Flanders 3.1 Capacity of the plants According to the Flemisch environmental legislation recycling plants are considered as polluting and so they have to get an exploitation permit (On a small scale, here too, the “not-in-my-backyard-principle” applies). According to an inventory, made in 1989 on the basis of the granted permits, some 40 plants are in operation [1]. They can be classified into: • actual fixed plants • mobile installations with a fixed location • actual mobile installations. About 75% of all installations belong to the first two categories. Essentially most plants were set-up by demolition contractors who in this way resolved the problems they faced in dumping their demolition waste. The most important plants

Recycling of construction and demolition waste in Belgium: actual situation and future evolution are grouped in the Association of Demolition Waste Recycling Corporations (VVS). The overall officially approved recycling capacity of all the installations together amounts to about 2,500 tons per hour, i.e. on average 62.5 tons per hour and per plant. On a yearly basis the total recycling capacity can thus be estimated at 4.4 million tons, which means that (theoretical) more or less the total quantity of construction and demolition waste could be covered by the plants. The real production does however not approach the approved capacity, because there is still a lack of sale potential mainly with regard to masonry rubble. So the latter, which accounts for approximately 40% of all the rubble, is at the moment only recycled to a small extent. Changes in this situation are expected to result from recent taken measures in relation to technical specifications (cfr. 4) and further expected measures which will be introduced in relation to selective demolition. As far as the regional distribution of the recycling plants is concerned it is noticed that the capacity is concentrated: • at the border between East and West Flanders • on the axis Antwerp-Brussels • in the Rupel region • in the region around Aalst • and last but not least in Middle Limburg. In view of the new VLAREM II legislation (cfr. 2.2), local initiatives are currently being taken by the Association of the Road Contractors in West Flanders to set up a new recycling plant [5]. Also some further interest to set-up still new plants is present in the circles of dump-site exploiters. 3.2 Plant lay-out A requirement for affiliation to the VVS is the engagement from the plant exploiter to work towards a quality label for the recycling plant and the finished products. This, in collaboration with and under supervision of an independent control organisation. A strict selection of the rubble at the entrance is therefor required, also minimum requirements regarding the installation must be fulfilled [6].

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Fig. 2. Plant lay-out.

The installations of the 18 affiliated members of VVS of course satisfy these minimum requirements and generally speaking they are composed of the following elements (fig. 2): • a weighting bridge to weight the rubble delivered and the aggregates sold • enough storage space to stock, the different kinds of rubble and the different grades of produced recycled aggregates, on separate stock piles • equipment for preprocessing the waste, this preprocessing makes it possible to eliminate coarse impurities (wood, metals, plastics,…) and to reduce big elements in size (using for example hydraulic nippers)

Recycling of construction and demolition waste in Belgium: actual situation and future evolution • the necessary equipment to feed the installation itself (excavators with open-worked tub, wheel loaders,…) • a preliminary sieve to eliminate earth, sand and gypsum before the material is fed into the chrusher • a primary chrusher, in general this is a jaw crusher • electrical magnet systems to remove steel • a sieve installation to separate the materials in various fractions • an air-sieve or a washing installation to separate wood, paper, textiles,… from the broken aggregates • a secondary chrusher and sieve installation to further reduce the aggregates in size and split up the different fractions produced Some plants are further equipped with blending bunkers in order to be able to produce aggregate fractions with a well-controlled continuous particle size distribution. Also a few plants are running next to their recycling activities a concrete production plant which is in an exceptional case linked to an industrial pre-cast concrete element manufacturing plant. In the latter case it is economically possible in view of the rather important concrete production to work on the basis of a partial replacement of the coarse aggregate fraction of the concrete (20% replacement). This is however rather the exception than the rule and if only a moderate concrete production is attained the interest lies of course in a full 100% substitution of the coarse aggregate fraction by recycled aggregates. 3.3 Use of recycled aggregates Generally speaking the types of recycled aggregates produced at present at the recycling plants are the following: • Concrete aggregates 80/200: This kind of aggregates finds their application exclusively in hydraulic works as filling material for river embankment protections. The market demand is anyhow rather limited. • Concrete aggregates 0/80, 0/56 or 0/40 (4/32): The market price of this kind of aggregates is about 220 to 240 Belgian francs per ton and as such about 100 Belgian francs per ton below the price of natural aggregates. These aggregates with a continuous particle size distribution are the bulk of the production and are mainly used in road construction applications, i.e. as roadsub base material, further they are also used in the private sector for soil filling and the creation of unhardened parking areas. At few occasions the material is split in a 0/20 and 20/40 fraction for example and recycled as aggregate in lean concrete. The limited number of recycling plants which have their own concrete mixing installation uses typically a 4/32 fraction for their concrete production. A full 100% substitution of the coarse aggregates by recycled aggregates is in this cases most generally used. • Sieve and chrusher sand: This material has a very low market price of about 80 Belgian francs per ton. Mainly the product is sold as sand for pavement subbases or for the construction of

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embankments. • Chrushed masonry 0/56: Masonry aggregates have a market price in the range of 150 to 170 Belgian francs per ton. If recycled the product is up to now only used in the private sector for soil filling and the creation of unhardened parking areas. • Asphalt: Recycled asphalt aggregates have a market price in the range of 200 to 220 Belgian francs per ton. These products are recycled as base materials for roads and parking areas and reused in new asphalt. Asphalt aggregates are mainly produced in the winter period considering that problems otherwise arise in relation to their processing. Undoubtedly at present the recycled aggregates are thus by far most used in road construction. However the way things are going now the consumption of recycled aggregates in the road sector may be expected to stagnate in the future, as: • already now road construction has to consume twice the amount of rubble it is producing • road renovation will increase over the construction of new roads. The latter is certainly the case in Flanders taking into account that already now there is an extreme high density of roads (Actually 5 kilometre of road per square kilometre of surface). So new markets for the recycled aggregates have to be further established and obvious the concrete market is a self evident one. Already 15 years ago the BBRI started research in this field and since many years it has been involved in promoting the use of recycled concrete in Belgium and abroad [7,8]. A large pilot project was for example set-up during the construction of the Berendrecht lock [9]. At the moment the applications of recycled concrete concern mainly local small scale private initiatives, as for example in the agricultural sector and some minor projects in the concrete block industry. Only rarely these applications are followed up. With the evolutions mentioned in following section however it is believed that a more general application will start to grow in the coming years. Also it is believed that a well organised follow up should be worked out in order to be able to set up sensibilisation actions. 4 Technical specifications and certification 4.1 General Sensibilisation is clearly one of the important issues in relation to the market acceptance of recycled products. In this respect the involvement of the authorities is essential. As the most important commissioner they can cooperate actively by setting the example and accepting the use of recycled materials in their projects. Of coarse this implies that proper technical specifications for recycled materials are worked out. The latter is a must as actually most technical specifications are imposing a barrier on the use of recycled

Recycling of construction and demolition waste in Belgium: actual situation and future evolution materials: • either because they strictly impose the use of “new” materials • or because they indirectly impose the use of virgin materials by specifying that the material should be of such or such geological origin • or because they impose materials characteristics such as for example densities which can not be met by recycled products • or just they are supposed to implicitly impose a barrier simply because they do not explicitly make allowance for recycled materials (in this case officials appear in most cases not at all keen on taking responsibility). So such specifications should be identified and amended with adequate essential requirements which would allow if they are met the use of recycled materials. 4.2 Road and hydraulic construction works In Flanders a working group was established in 1990 by the Ministry of the environment and infrastructure (LIN) with the aforementioned task as a goal. In relation to road construction works and hydraulic works a number of circulars specifying the provisions for recycled materials were approved in the course of 1991 and 1992. In the order of appearance following circulars were issued: • a circular which covers the use of recycled concrete and masonry for the construction of road subbases • a circular about the use of secondary materials for embankment protections • a circular dealing with the use of recycled asphalt in lower road layers • a circular about the use of “hot recycled” asphalt in upper road layers In the circulars a clear definition is given of the kind of recycled products that may be used in specific stated applications. As a strict requirement in all circulars it has been imposed that the recycled products should be supplied by recycling plants under control of a certification bureau. At present the independent organisation COPRO is performing this certification in Flanders. The circulars have the status of official tender specifications and are taken up in the governmental technical specifications as soon as the latter are revised. For road construction works currently the same kind of work is being done in Wallonia on initiative of the Ministry of Infrastructure and Transport (MET). 4.3 Specifications for recycled aggregates for concrete In relation to the use of recycled aggregates in concrete the existing standards and technical specifications were screened in order to identify possible barriers. It was found that in the existing national standards in fact no explicit barriers were present. Surprisingly however informal contacts brought about that the intention existed to take up explicitly in the new draft of NBN B15–101 (the Belgian implementation of EC2) that this standard was not applicable to recycled concrete! As far as concerns official tender specifications it was found that the most recent of

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them explicitly quoted that the materials to be used must be “new”. Yet in some older documents clauses were found in relation to the use of chrushed bricks [10]. Much of what was quoted however was to vague to be still useful. As an example following provisions were found in the 1979 version of the “General specifications for privateworks”: Clause 5.23.14. Masonry rubble. Masonry rubble is obtained by chrushing hard bricks or other well-fired clay products. Bricks from demolished chimneys, ovens or stables may not be used. The rubble may not contain any gypsum or saltpetre. Before use the rubble has to be saturated with water. Relevant literature was consulted by the LIN working group in the process of drafting specifications for recycled concrete. Of particular interest was the RILEM report “Recycling of Demolished Concrete and Masonry” as well as the link through the BBRI with the RILEM TC 121-DRG. The principle was adopted to draft the specifications along the lines of the recommendations which were in the process of elaboration in the aforementioned technical committee. The essential elements of the worked out specification are given in the next tables, they consist in requirements for the aggregates (table 1), clear definitions of acceptable applications (table 2) and design values for the recycled concrete (table 3). Two types of material are distinguished and allowed to be used in recycled concrete, i.e. coarse aggregates GBSB-I and GBSB-II. Acceptable grading curves for the material (fig. 3) are those given in NBN B11–101, making exception of the gradings 2/4 and 2/7.

Table 1. Mandatory requirements in relation to the composition of recycled aggregates for concrete.

GBSB-I Dry density (NBN B11–255) Water absorption at 24h. (NBN B11–255)

GBSB-II

>1600kg/m3 >2100kg/m3 <18%

<9%

Content of material with a density<2100 kg/m3

-

<10%

Content of material with a density<1600 kg/m3

<10%

<1%

Content of material with a density<1000 kg/m3

<1%

<0.5%

Content of broken natural stone, concrete, masonry or ceramic material (asphalt excluded)

>95%

Content of foreign materials (metals, glass, bitumen, soft material, …)

<1%

Fraction<80µm (NBN B11–209)

<5%

<3%

Recycling of construction and demolition waste in Belgium: actual situation and future evolution Organic material (NBN 589–207)

<0.5%

Chloride content (NBN B11–202)

<0.06%

Sulphate content (NBN B11–254)

<1%

Table 2. Field of application for recycled concrete. (A 100% substitution of the coarse aggregates by recycled aggregates is accounted for. The sand to be used is of natural origin).

MAXIMUM ALLOWED STRENGHT CLASS GBSBI

GBSBII

C16/20

C30/37

ALLOWED EXPOSURE CLASS • interior of buildings with dry environment (exposure class 1) • components in non-aggressive soil and/or water not exposed to frost (exposure class 2a) • interior of buildings with dry environment (exposure class 1) • components in non-aggressive soil and/or water (exposure class 2)

Table 3. Design values. (Worst case values to be adopted in the absence of more accurate experimental results).

Coefficients to be applied on the values stated in prENV 1992–1–1 GBSB-I GBSB-II Tensile strenght (fctm)

1

1

0.65

0.8

Creep (ф(∞,t0))

1

1

Shrinkage (εcso)

2

1.5

Modulus of elasticity (Ecm)

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Fig. 3. Grading curves for the recycled aggregates.

In a strict sense the specification worked out only apply for public works. It is however believed that they will also be used in the private sector and give a strong impulse to the use of recycled aggregates in concrete in general. 5 Environmental legislation In the process of recycling there must of course carefully be watched that no contaminated material enters the circuit. The recycling industry is quite well aware of this fact and realises that if such would arrive this could be very harmful for the further development of the sector. In this respect the acceptance policy at the plants is of major importance. The origin of the waste must be known, suspected material is to be refused and control procedures have to be established. Selective demolition has to be promoted! This is a necessity as well from a technical point of view as from an environmental point of view. The recycling plants try to promote selective demolition by using different dumping tariffs for mixed and clean material. By the authorities a system of demolition permits should be made obligatory. It should be the responsibility of the owner to make a report on the use of the building and the materials involved. If during the demolition not reported suspected materials are found, an auto control by the contractor will in this way come into play. A follow-up of the waste stream is further also needed. Anyway it is well realised that an integrated approach of demolition and further processing is needed [2]. The responsibilities of the waste transporter, demolition contractor and certainly also the commissioner of the demolition work, i.e. the building owner may not be underestimated and the responsibilities of each have to be clearly fixed. A lot of work still remains to be done in this respect. Of cause it should also be clarified what is understood under contaminated waste. Here too a lot of work remains to be done and even a lot of knowledge is lacking.

Recycling of construction and demolition waste in Belgium: actual situation and future evolution What is to be considered as contaminated waste? Which materials should be refused? What are acceptable limits of heavy metals, poly aromatic hydrocarbons and such? What are acceptable applications depending on certain pollutant concentrations? Globally in this respect a similar approach as in the Netherlands is followed by OVAM in Flanders, i.e. a classification depending on leaching characteristics and the chemical composition of the materials (fig. 4). On some points however quite another orientation is followed, i.e. for example related to hydraulic bound materials where the chemical composition is considered in quite another perspective.

Fig. 4. Environmental qualification of recycled materials.

Actually heavy discussions are going on regarding this matter and research proposals have been forwarded. In anyway care should be taken not to be drowned in “ppm’s” and “ppb’s” but rather realistic and workable solutions should be sought. It remains indeed a fact that most of the building and construction waste is in nature not harmful at all. Another legal problem that has to be resolved is this of the legal status of recycled construction and demolition waste. Is recycled construction and demolition waste still waste? Obvious not! But how far must the processing go before this is the case? Currently also this legal problem is being studied by OVAM and proposals are put forward to work towards a system of environmental attestation. 6 Conclusions In relation to the problem of construction and demolition waste quite a lot of things are moving in Belgium. Yet a distinct difference exists between the North and the South of the country. Specific geographical differences between the regions account for this situation and will probably always result in a different economic interest in recycling

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between the regions. Regarding environmental legislation a lot of work remains to be done and in this respect care should be taken not to be drowned in “ppm’s” and “ppb’s”. Realistic and workable solutions should be sought. A coordinated approach in the different regions should be aimed at in order to prevent confusion. In this matter the National Confederation of the Building Industry (NCB) can and will play an important role. The latter even on an European level through its involvement in the FIEC and in EEC initiatives. 7 References 1. Problematiek van bouw-en sloopafvalstoffen. Voorbereidend rapport i.o. van de OVAM. WTCB-Recymat. Januari 1990. (In Dutch). 2. B.Simons & F.Henderieckx. Selective demolition. Guidelines and experiences in Belgium. RILEM 3th International conference, Odense 1993. 3. Problematiek van bouw-en sloopafval in het Brussels Gewest. Rapport i.o. van het BIM. WTCB-Recymat. Maart 1991. (In Dutch). 4. H.Motteu & E.Rousseau. Recycleren van afvalstoffen in de bouw. WTCB-tijdschrift zomer 1992. (In Dutch and French). 5. Provinciaal recyclage-initiatief van de Westvlaamse wegenbouwers. Bouwbedrijf nr. 17, 23 April 1993. p. 30. (In Dutch). 6. C.De Pauw, W.Goossens & J.Vyncke. Recycling of construction and demolition waste. Plant concept. Organization and staffing. Essen, 1991. 7. C.De Pauw. Béton recyclé. CSTC-revue no. 2, juin 1980. (In French and Dutch). 8. C.De Pauw. Recyclage des décombres d’une ville sinistrée. CSTC revue, no. 4, décembre 1982. (In French and Dutch). 9. Hoe 80.000m3 gewapend beton veilig laten springen en recycleren. KVIV-WTCB studiedag. Antwerpen, 1987. (In Dutch). 10. B.Simons & J.Vyncke. Les Déchets de construction et de démolition. CSTC-revue printemps 1993. (In French and Dutch).

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7 PRACTICAL GUIDELINES FOR THE USE OF RECYCLED AGGREGATES IN CONCRETE IN FRANCE AND SPAIN A.MOREL and J.L.GALLIAS CEBTP, Saint-Rémy-Lès-Chevreuse, France M.BAUCHARD SDVM, Saint-Maur, France F.MANA ITEC, Barcelona, Spain E.ROUSSEAU Belgian Building Research Institute, Brussels, Belgium Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract This practical guideline has been produced within the framework of a european REWARD project (REcycling Waste Research and Development) and involving four European partners: the CEBTP (France), SDVM (France), ITEC (Spain) and CSTC (Belgium). A technical study involving the following stages has been conducted in France and Spain with a view to increasing the volume of recycled demolition material and developing its use in concrete: detailed characterization of recycled aggregates produced in France and Spain at present, examination of possibility of using these aggregates in concrete, study of influence of contaminants, plaster in particular. The results of this study have made possible the publication of a practical guideline for recyclers and users of demolition material, covering : criteria governing the selection of demolition waste for the purpose of producing aggregate for concrete, the tests required to control the quality of these aggregates, criteria governing the acceptability of the physical, chemical and

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mechanical properties of aggregates, practical advice on concrete manufacturing and using. Keywords: Recycling, Demolition Waste, Construction Materials, Aggregates, Concrete, Guideline.

1 Introduction Use of recycled materials in the EC countries is primarily directed toward embankments and filling, as well as road works. They are specifically employed for bound or unbound base or sub base, and in certain countries with some restrictions for pavement surface lay (Germany, Denmark, United Kingdom, the Netherlands). The use in concrete is even less common, and is primarily impeded by rules and regulations. However, some special specifications have been elaborated to allow their employment in the Netherlands and Denmark, and there also exist some recommendations for the U.S., Japan, and even the former USSR. These specifications address primarily the use of recycled concrete, but some are being elaborated to cover masonry rubble. The development of demolition materials recycling in France and Spain requires practical guidelines for new uses and specially in concrete. It was the aim of the EEC REWARD project which is presented hereafter. 2 Project overview 2.1 Objective Development of the use of recycled materials currently produced, in particular, in concrete. Recycling of materials still not or not often recycled today, because they contain impurities, in particular plasters. 2.2 Partnership The project is conducted in close collaboration among the following four organizations: The Centre Expérimental de Recherches et d’Etudes du Bâtiment et des Travaux Publics (C.E.B.T.P., France), Project Manager and Coordinator. The Sablières du Val de Marne (S.D.V.M., France). The Institut de Tecnologia de la Construccio de Cataluny (I.T.E.C., Spain). The Centre Scientifique et Technique de la Construction (C.S.T.C., Belgium). Also associated with the project in providing financial support are the “Syndicat National des Producteurs de Granulats de Recyclage” (SNPGR, France) which is a member of the

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“Union Nationale des Producteurs de Granulats” (UNPG), and the “Federation Nationale du Bâtiment” (FNB, France). 2.3 Timetable The work was carried out in two years starting from September 1991. 2.4 Work program The program consists of three phases: Comparative study of demolition materials recycling in the principal EEC Countries Technical Study Guideline

3 Situation of demolition materials recycling 3.1 Situation in France The demolition sector in France is currently producing about 25 millions tons of waste materials. It is estimated that 10–15 millions tons of these materials are recyclable, although only 20–30% of this potentiel is being transformed today. The producers of recycled aggregates have adopted a very stringent selection policy for demolition materials. More than 90% of materials processed are actually clean materials, with 60% of clean concretes, 33% of other clean materials and the remaining 7% diverse substances. In 1991, roughly 20 companies producing recycled aggregates from demolition materials were surveyed. The first plant was installed in the Paris area in 1976. Recycled aggregates production has recorded a very strong growth trend since 1987, moving from 1.5 million tons to 3 million tons in 1990. The recycled aggregates production areas are located in the large urban centers, with a very strong concentration in the Paris area, followed by the North of France, and to a lesser extent in Alsace and the Rhone Alps region. Production consists mainly of graded mix or sand-gravel mix (nearly 70%), and of smaller quantities of sands, gravels and cobbles. However, it should be noted that recycled aggregates account for only a very small part in France’s national production of aggregates (less than 1%), although today recycled aggregates do represent 25% of non quarry aggregates to 15% in 1987. The use of recycled materials in France is limited to roadworks and land filling (90% as aggregates, 10% with binders). 3.2 Situation in Spain The production of demolition wastes in the large urban centers of Spain is estimated at

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800 tons/day in the Madrid area, 500 tons/day for Barcelona, and 100 tons/day for medium-sized cities like Valencia and Bilbao. However, it seems that the recycling of demolition materials has only attained a significant level for the construction of olympic site facilities at Barcelona, where it has been extensively exploited. The waste materials are primarily obtained from the demolition of buildings located on the site of future olympic facilities. Demolition materials amounted to roughly 1.5 million tons. But materials from other demolition sites were also processed after a prior examination of their composition and inspection of demolition work sites. The recycling operation was set up by the firm DESTESA. It has an average recycling capability of 2 000 tons/day, but has attained 10 000 tons/day. A total of 1 million tons of recycled aggregates has been produced. Only inert materials (concrete, ceramic, stone, brick) obtained from the demolition of structures, enclosures, and foundations are accepted. Mixed materials or those containing impurities (wood, plastic, plaster, textile, iron, etc.) are rejected. To enable the greatest proportion of materials to be recycled, special attention has been directed toward the organization of demolition work sites (selective demolition, on site pre cleaning). Recycled materials have been used to build the olympic city’s streets and highway system, the base and sub base, as well as the protective rock fill structures of the encircling coastline. 4 Preliminary technical study A technical study of the means of production of recycled aggregates in France and Spain, and of the properties of aggregates produced was carried out as part of the REWARD project. The main results of this study, presented below, provided technical support in drawing up the practical guideline for use of recycled aggregates in concrete. 4.1 Recycling plants The production of recycled aggregates by two recycling plants in France (SDVM Paris) and in Spain (Destesa Barcelona) was monitored during the entire project (Figure 1). The aggregates produced by the SDVM plant are used in road construction. The materials accepted for recycling at the plant are obtained from various sources : earthworks, demolition of roads including natural unbound aggregates, gravel-cement, gravel-slag mixtures, bitumen-coated aggregates, etc. demolition of concrete or reinforced concrete construction works. After initial screening to 40 mm, the materials are crushed and screened into three aggregate sizes sand 0/6 mm

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gravel 6/25 mm stones 25/150 mm Because of their sources, recycled aggregates are a mixture of natural aggregates, mineral treated binder, or bitumen-coated aggregates and crushed concrete. Certain demolition materials are sometimes accidentally included in

Fig. 1: SDVM recycling plant

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Fig. 2: Demolition materials including walls with plaster coating

Fig. 3 et 4: Representative building selected for experimental study on contaminated demolition materials Before and during demolition

the recycled aggregate, e.g. concrete blocks, bricks, light partitions, various coatings, insulation, ducts, etc. Aggregates produced by the Destesa plant, derived from demolition work during

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construction of the Barcelona Olympic facilities, were mostly used for earthworks, embankment, and filling. 4.2 Characterization of aggregates Characterization tests in accordance with French Standards have been performed periodically on the three classes of aggregate produced at the SDVM plant. The results obtained (which were recently published [1]) show first of all the consistency of production. The physical, chemical and mechanical properties vary very little with time. Only three properties have values above the thresholds defined in the French Standard concerning aggregates for concrete (French Standard NF P 18 301): The coefficient of absorption, which varies between 5.5 and 7.0%, because of the high porosity of the recycled materials (the threshold specified by the Standard is 5.0%). The sulphate content, which varies between 0.70 and 0.35% (expressed in SO3), mainly due to the sulphates contained in the concrete and bound gravelsand mixtures (the threshold specified by the Standard is 0.40%) . The organic matter content is around 1%, mainly due to the presence of bitumen. The values of properties outside standard thresholds (the coefficient of absorption, sulphur content and organic matter content) are generally higher for sand than for gravel and stones. Tests have shown that the coefficient of absorption can be lower than the standard if the sand and gravel are produced by a second crushing of 25/150 mm stones. In the other hand, the content of light elements (elements of density lower than 1800 kg/m3) and the content of chloride ions remain negligible. The mechanical properties of recycled aggregates are also satisfactory. Similar results were obtained for aggregates produced by Destesa in Spain. 4.3 Use of aggregates in concrete Several concrete compositions were prepared with recycled sand and/or gravel from the SDVM plant, mixed with natural aggregates. Several properties were monitored: workability of fresh concrete, mechanical properties of hardened concrete, dimensional variations in relation to moisture, and durability parameters. The results obtained show that the use of currently produced recycled aggregates in concrete is entirely possible if certain precautions are taken to counteract their specific characters. The need to moisten aggregates before mixing, the use of plasticizing admixtures and water reducing agents, and concrete curing at an early stage to avoid major shrinkage are the main features, considering the high porosity of recycled aggregates. In addition, it has been shown that the sulphates and organic matter found in currently produced recycled aggregates do not impair the durability of concrete.

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4.4 Effect of impurities A large quantity of demolition material from masonry buildings or construction and rehabilitation sites is currently refused in French recycling plants because of the possible presence of gypsum impurities. The presence of gypsum in aggregates has been blamed for certain defects in road bases or foundation courses where recycled aggregates were treated with cement. This is because gypsum reacts with the cement to form hydrated calcium sulphoaluminates (ettringite) which, in certain cases, can cause damage due to expansion and cracking of the concrete. In order to resolve this problem, a building demolition site containing plasters was chosen for the preparation of recycled aggregates with high sulphate contents (Figures 2, 3 and 4). Concrete tests are currently in progress to determine the risk of swelling of the material in relation to the sulphate content. A study of solubilization of the sulphate ions in recycled aggregates was perfprmed in parallel, to determine a simple quantitative analysis batching method for verifying the production of aggregates. 5 Contents of the practical guide The first purpose of the practical guide for the use of recycled aggregates in concrete is to provide a reference document that meets the specific requirements of the producers and users of recycled aggregates. The main information is obtained from the preliminary technical study and from past experience in Northern Europe, which is more advanced in this field. The guide, which is currently being prepared by those involved in the project, is composed of two parts, summarized below. 5.1 Selection of materials for recycling and inspection of produced aggregates In the first part, the guide attempts to answer three essential questions: What criteria should be applied to the selection of demolition materials? What tests are necessary to verify the quality of produced aggregates, and how often should they be performed ? What are the thresholds of acceptability for the properties of aggregates ? Since the recyclers of demolition materials are generally separate from demolitioners, the selection of materials on reception by recycling plants is the key to the quality of stocks and thus of recycled aggregates. In this respect, French selection criteria are rather severe, and they exclude materials obtained from building demolition and construction site waste. The development of selective demolition methods and the increase in dumping costs should normally lead to

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less selective choice of materials, although still excluding materials from light partitions, plastering, organic coatings, etc., such as plaster, wood, insulation materials, plastic conduits, etc. As regards the characterization of produced aggregates, current French and Spanish statutory regulations specify the main properties to be controlled, test methods to be used and the acceptability criteria for use in concrete. However, the specific character of recycled aggregates requires greater tolerance regarding thresholds set by standards concerning the porosity of materials, sulphur content and organic matter content. The problems of porosity and water absorption of recycled aggregates can be resolved if the aggregates are properly moistened before being used in concrete. In addition, stoues can be crushed a second time to reduce the porosity of sand or gravel obtained from the first crushing operation. The critical sulphate content must take into account the quantity of sulphates that already exists in the form of hydrates in the cement which are completely harmless. Similarly, the presence of bituminous binders (bitumen and asphalt) must be taken into account in the critical organic matter content. Lastly, the test frequency must take into account the selection criteria, the size and uniformity of stocks of materials for recycling and the different recycling processes. Some preliminary periodic tests can determine an appropriate control frequency for each type of production. 5.2 Use of recycled aggregates in concrete The use of recycled aggregates in concrete requires certain measures in addition to the usual processes for preparation of concrete with natural aggregates. These measures are necessary because of the specific properties of recycled aggregates. They concern the composition, application, curing and use of concrete. The main relevant points discussed in the guide are given below. Use of concrete with recycled aggregates At present, the use of concrete with recycled aggregates can only be considered for less important works because of certain nonstandard properties of recycled aggregates and the lack of specific standards. Their use is also limited by builders’ psychological barriers and by the lack of experience feedback. However, concrete used for less important works (oversite concrete, mass concrete, slabs, secondary works, etc.) is usually exposed to attack by environmental factors (weather, water, etc.). Therefore concrete made with recycled aggregates must have properties that enable it to resist attack (low water/cement ratio, low permeability and high compactness). Concrete composition Cements with high C3A content must be avoided as they can react with any gypsum impurities. Therefore portland cements with added slag and slag cement are recommended. When mixtures of recycled and natural aggregates are to be used in a concrete composition, recycled aggregates must not be concentrated in the fines fractions (sand).

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The use of plasticizing admixtures and water reducing agents is strongly recommended if all aggregates (sand and gravel) are recycled, in order to avoid surplus water in the batch. In the case of mixted aggregate composition (i.e. recycled and natural), small quantities of admixtures can allow better control of the water in the batch. Corrective sands and very fine sands must be added to the batch if the recycled sand contains no fines. Mixing Premoistening of recycled aggregates is necessary for application of concrete. Aggregates must be moistened well in advance and the moisture level must be maintained until mixing, in order to avoid absorption of the water added for mixing, which can cause rapid premature stiffening of the concrete. The quantity of water absorbed in the aggregates during premoistening must be taken into account separately from the quantity of water outside the aggregate, which takes part in mixing and must be deduced from the quantity of water added. Early curing Because concrete mixed with recycled aggregates is very sensitive to evaporation, early protection (or even additional moistening) is required, especially when the concrete contains free surfaces (as in oversite concrete or slabs). Mechanical strength The mechanical strength of concrete can occur when all aggregates are recycled. However, this reduction is not crucial when concrete is used for less important works. In addition, the reduction of concrete’s modulus of elasticity can be an advantage in certain cases when the concrete is subjected to major strains. Durability The durability of concrete mixed with recycled aggregates is the key to the development of recycled aggregates for use in concrete. Experience feedback will overcome the users’ psychological barriers and encourage the development of technical specifications appropriate for the properties of recycled aggregates. In this respect, concrete mixed with recycled aggregates has certain advantages : very good frost resistance, often better than conventional concrete, permeability to air and water comparable to those of conventional concrete, On the other hand, there are two specific risks of defects with concrete containing recycled aggregates: ettringitic swelling due to the presence of any gypsum impurities, general cracking due to major shrinkage. As regards ettringitic swelling, the risk can be controlled if plaster is eliminated by the selection of materials at the recycling input and if the sulphate content of aggregates is monitored. As regards swelling, the quantity of water in concrete must be controlled during mixing (with possible use of admixtures), application (premoistening) and curing (protection against evaporation).

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6 Conclusions The need to develop recycling of demolition materials in France and in Spain has led recycling researchers and industrialists to join forces for the REWARD project. Thanks to this REWARD project, it has been possible to establish the state of the art concerning materials recycling in the two countries and to carry out an in-depth technical study of recycling processes and the properties of the aggregates produced. This work resulted in the compilation of a first practical guide for producers and users of recycled aggregates in France and Spain. This practical guide for the use of recycled aggregates in concrete shall contribute to the development of European technical specifications for recycled aggregates, which, by themselves, will make it possible to achieve the goal of 50% recycling of demolition materials by the year 2000. 7 References [1] A.MOREL and J.L.GALLIAS (1993) “Development of demolition material recycing in France and Spain” Proceedings of International Recycling Congress REC 93, Geneva.

8 CONCRETE/MASONRY RECYCLING PROGRESS IN THE USA C.J.KIBERT Center for Construction and Environment, University of Florida Gainesville, Florida, USA Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract Recycling of concrete and masonry in the U.S. is not governed by standards designed to address this issue. Existing standards are relied upon for testing the recycled aggregate and masonry material. An important issue in the recycling of concrete/masonry are their environmental impacts and the determination if it is feasible in an environmental sense to proceed with recycling operations. Keywords: Environmental Impact, Concrete Recycling, Masonry Recycling

1 Introduction The state of the art of recycling concrete/masonry demolition debris in the U.S. is advancing, although slowly. At the present time there are no U.S. national standards (ASTM/ANSI) and few specifications that deal specifically with the subject of recycling these materials. Generally concrete/masonry that is to be recycled is judged by existing standards for its suitability for reuse. 2 Environmental Impacts of Concrete Production The production of concrete has a number of significant impacts that ultimately affect decisions regarding its recycling. Energy consumption is perhaps the foremost concern because the embodied energy of concrete is very high. Table 1 indicates the breakdown of embodied energy for each component of a typical cubic yard of concrete, 1.7 million BTU/cubic yard (Wilson 1993). It should be noted that the embodied energy of cement is the dominant component although the cement itself is a minor constituent in terms of weight. Cement production is

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a very energy intensive industrial process and it also entails significant air and water pollution. In the U.S. the production of 80 million tons of cerment required about 0.5 quads of energy (1 quad=1015 BTU) orabout 0.6% of total U.S. energy production.

Table 1 Eabodied energy for cement and concrete production

BTU’s per ton % by weight Materials Hauling BTU’s/yard concrete Energy % Cement

12

5,793,000

504,000

1,574,000

94

Sand

34

5,000

37,000

29,000

1.7

Crushed Rock

48

46,670

53,000

100,000

5.9

6

0

0

0

0

1,700, 000

100%

Water TOTAL

100%

6,400,000

In terms of monetary value, by way of contrast, cement is only 0.06% of gross national product. Worldwatch Institute has stated that in developing countries, cement production can account for up to 66% of energy use. There is one positive note regarding the operation of cement kilns: the high temperatures can be used to destroy hazardous materials that can be used to fuel the kilns. This includes motor oils, inks, solvents, and scrap tires. Waste fuels now constitute up to 5% of the energy requirements for cement production. The production of cement also entails significant air pollution. For each ton of cement produced there are also 1.25 tons of CO2 released into the atmosphere (Table 2). Worldwide, cement production accounts for more than 8% of CO2 emissions, some 1.6 billion tons each year (Wilson 1993).

Table 2 CO2 emissions resulting from cement production

lbs CO2 per ton cement C02 emissions from energy use

lbs CO2 per cu yd concrete

Percent of total CO2

1,410

381

60

CO2 emissions from calcining limestone

997

250

40

Total CO2 emissions

2,410

631

100%

Water pollution resulting from washout water from concrete trucks is another environmental problem that concrete industry is attempting to solve. The alkalinity of the washwater can be as high as pH 12. High alkalinity water is toxic to fish and other

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aquatic life and environmental regulations are rapidly forcing the industry to consider alternate means for handling its washout water. 3 Classification/Applications for Recycled Concrete In general, recycled concrete is simply old concrete that has been processed to recover its aggregate content (Kosmatka and Panarese 1988). Reinforcing steel is also recovered but not for further use in concrete production. High quality. aggregate can be an expensive material depending on the geography. For example Florida generally does not have suitable aggregates for concrete manufacture and they must be largely imported from other states. This is true for both coarse aggregates and fine aggregates. In fact most construction projects in Florida utilize a fine aggregate that does not meet ASTM standards, but which has been tested by the Florida Department of Transportation (FDOT) as a technically suitable substitute. The fine aggregate material that is used is a commonly available sand. The concrete portion of demolition debris contains both coarse and fine aggregates that are contaminated with gypsum, cement paste, and other substances depending on the composition of the concrete, its age, and other conditions. The fine aggregate portion is unsuitable for making fresh concrete because it is composed largely of hydrated cement paste and gypsum. The coarse aggregate, in spite of similar contamination, is generally suitable for use in concrete manufacture. In general recycled concrete/masonry is classified into one of the following categories: (1) Crushed demolition debris: mixed crushed concrete and brick that has been screened and sorted to remove excessive contamination. (2) Clean graded demolition debris: crushed and graded concrete and brick with little or no contamination. (3) Clean graded brick: crushed and graded brick containing less than 5% concrete or stony material and little or no contamination. (4) Clean graded concrete: crushed and graded concrete containing less than 5% brick or stony material and little or no contamination. There are four main uses for these various classifications of recycled concrete/masonry: (1) General bulk fill (2) Fill for drainage projects: (3) Sub-base material in road construction (4) Aggregate for new concrete Table 3 shows the relationship between these applications and the classifications of recycled concrete/masonry (Kibert 1991). Recycled concrete/masonry material that has a high timber or sulfate content should not be used in critical bulk fill applications but can be used in less demanding applications such as landscaping, levelling, and acoustic barriers.

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4 Properties of Recycled Aggregates Currently in the U.S. there are no national specifications for recycled materials intended for use in road construction. In

Table 3 Suitability of Recycled Aggregates

Recycled Aggregate Category

General Bulk Fill

Fill in Drainage Projects

Material for Road Construction

Crushed Demolition Debris

Suitable

Usually Suitable Not Usually Suitable

Not Suitable

Graded Mixed Debris

Suitable

Usually Suitable Suitable in Some Cases

Suitable in Some Cases

Clean Graded Brick

Highly Suitable

Suitable

Suitable in Some Cases

Clean Graded Concrete

Highly Suitable

Highly Suitable Suitable

Usually Suitable

New Concrete Manufacture

Usually Suitable

the U.K. the Specification for Highway Works, Department of Transport, calls out crushed concrete as acceptable material for granular fill in such applications as drainage works, earth work, road base, and road sub-base. Although not specifically mentioned in U.S. Department of Transportation (DOT) specifications, recycled aggregates pass many of the requirements for application in road construction. Several local jurisdictions, such as the State of Minnesota DOT have specifications that define the conditions and tests for use of recycled concrete pavement materials in road construction (MDOT 1992, PCA 1980, Halverson 1981). Recycled aggregates intended for use in the production of new concrete must satisfy many requirements. They must be strong enough for the grade of concrete required and possess good dimensional stability. They cannot react with any of the other ingredients in the mix. The aggregate must also have a suitable particle shape and grading to produce a concrete with acceptable workability. Of the recycled aggregates, clean brick and concrete aggregates best meet these requirements. The main differences between recycled aggregates and virgin materials is as follows: (1) Particle size and surface texture: recycled aggregates tend to have a particle shape that is more irregular than natural aggregates and have a coarser surface. (2) Density: the density of recycled aggregates is generally lower than that of natural aggregates due to the presence of old mortar, bricks, and other low density material, making them unsuitable for many construction applications. (3) Water absorption: Recycled aggregates tend to hold significantly more water, 5–8% compared to 1.5–3% for virgin materials.

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(4) Durability: under freeze-thaw conditions, testing indicates that recycled aggregates are superior in durability to their natural counterparts. A comparison of the properties of natural aggregate concrete versus concrete produced from recycled aggregate is shown in Table 4 (Mehta 1986 and Frondistou-Yannas 1980). “Control” in this table refers to the characteristics of the natural aggregate concrete. In general recycled aggregate concrete has good workability, durability, and resistance to freeze-thaw action. The recycled aggregate concrete will have a lower density than conventional aggregate concrete (Kosmatka and Panarese 1988 and Ray 1980).

Table 4 Comparison of natural and recycled aggregate concrete properties

Natural Aggregate Concrete

Recycled Aggregate Concrete

Aggregate-mortar bond strength Aggregate primarily gravel from old concrete Aggregate primarily mortar from old concrete

Comparable to control 55% that of control

Compressive Strength

64–100% of control

Static Modulus of Elasticity

60–100% of control

Flexural Strength

80–100% of control

Freeze-thaw resistance

Comparable to control

Linear Coefficient of Expansion

Comparable to control

Length Changes for Specimens

Comparable to control

Slump

Comparable to control

The use of recycled aggregates is generally desirable from both economic and environmental standpoints (Buck 1976, Buck 1977, Halverson 1981). If concrete from building rubble is utilized care must be exercised as the material will undoubtedly contain large amounts of brick, glass, and gypsum as well as significantly high chloride content (ACI 1990). 5 Recycling of Pavement Materials The recycling of portland cement concrete pavement materials is an area that has been fairly well explored, with efforts dating back 30 years. There are several methods commonly used for recycling pavement materials (Table 5). As is the case with every attempt at recycling, the reuse of existing pavement materials has some advantages and disadvantages. Conservation of aggregates, lower construction costs, energy conservation, and environmental preservation are positive aspects of pavement recycling. On the negative side, the lack of equipment and contractors, the possible unsuitability of the original pavement material for recycling, and the distance to

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the recycling plant can make recycling unfeasible.

Table 5 Recycling methods for Portland Cement Pavements

Recycling Method

Comments

Crack and Seat

(1) Concrete left in place and cracked into small pieces. (2) Reduces reflective cracking for Asphalt Concrete overlay.

Rubblizing

(1) Concrete crushed in place, then rolled. (2) Concrete acts as aggregate base. (3) Reduces reflective cracking in Asphalt Concrete overlay.

Remove and Crush

(1) Used as aggregate base, backfill, or bituminous and concrete aggregate. (2) Allowed shoulder surface or base aggregate, and under pavement in some cases.

Additionally the procedures for mix design using recycled aggregates and the establishment of layer coefficients are not well known. The following are brief descriptions of each of these pavement recycling methods (MDOT 1992): (1) Crack and Seat: The terminology, ‘Crack and Seat’, refers to cracking unreinforced pavement into small pieces, rolling it to seat it with the underlying base, and overlaying it with asphalt mix. If the pavement is reinforced, the term, ‘Break and Seat’ is used. Cracking is accomplished, usually by means of a guillotine hammer dropped from a height of 18 to 24 inches. During the cracking, care is taken to insure the concrete is not rubblized. The cracking should result in fine cracks extending full-depth through the pavement. Care must be taken near joints to avoid longitudinal cracking and spalling. Once the pavement has been cracked, it is rolled to seat it firmly into the base. Experience has shown that this is best done with a pneumatic roller. Two passes with a 50-ton pneumatic roller has been shown to be very effective in this process. Rolling with steel drum or vibratory rollers results in improper seating of the cracked pieces. The overlay of asphalt concrete is usually laid at a ratio of 1.5 inches of asphalt to each inch of seated concrete. (2) Rubblizing: In the process of rubblizing, the concrete pavement is crushed to pieces 1 to 6 inches in size. The net effect is to turn the pavement into a crushed aggregate base. If there was an existing asphalt overlay, it must be removed prior to in situ crushing of the pavement by a high frequency, low amplitude pavement breaker. Any exposed reinforcing steel is removed and a vibratory roller is used to compact the material. Pieces range in size from 9" at the bottom of the slab to 1" at the top. (3) Remove and Crush: This method requires the removal of the pavement and crushing it for subsequent use as an aggregate base, backfill, or aggregate for both bituminous and concrete mixtures. The process involves the removal of all sealants and patches, breaking the concrete and removing reinforcing steel, crushing the concrete and removing additional rebar, and stockpiling the material.

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The State of Minnesota Department of Transportation (Mn/DOT) has two specifications that control the use of crushed concrete as (1) a surface or base course, or (2) a granular material. The following is a brief description of each application and its specifications (Halverson 1981). (1) Surface/base course (Mn/DOT Specification 3138): (a) The recycled material shall be blended with virgin aggregate material, shall not exceed 15% of the total aggregate weight, and shall be greater than 1/4" in diameter. (b) The base aggregate shall be placed on a granular subgrade provided the base thickness does not exceed 3". (c) If used as a surface or base aggregate in shoulder areas drains must be in place. (2) Granular material (Mn/DOT Specification 3149): (a) The recycled material shall be greater than 1/4" diameter and the material between 1/4" and 2" in diameter shall not exceed 15% of the total aggregate weight. (b) Concrete material greater than 2" is not restricted provided it is blended with other materials to meet all construction and gradation requirements. (b) For perforated drains used with walls/structures there are restrictions on placement within the zone above the invert of the drainage pipe.

6 Concrete Recycling Equipment The recycling of concrete involves the selection of equipment that differs greatly from that used to process the original aggregate (USAF 1988). The type of equipment utilized to break up pavement, for example, is heavy construction machinery, usually consisting of: (1) Diesel pile-driving hammer mounted on a motor grader that punctures the surface on a 0.2–0.3 m. grid. (2) Concrete pavement breakers of various types. (3) Rhino-horn-tooth-ripper equipped hydraulic rippers used to dislodge and expose the reinforcing steel. (4) Jack hammers and demolition balls for breaking the concrete into manageable pieces. (5) Cranes and front-end loaders for loading the rubble into dump trucks. (6) Jaw crushers (primary) and cone crushers and screens for processing the material. In the concrete crushing operation it may be necessary to wash the aggregate if the materials have become contaminated. In this case there are a wide variety of state and Federal environmental laws that must be observed in the disposal of the wash water. 7 Conclusions The recycling of concrete in the U.S. has been ongoing for a number of years and is

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directed principally at the recycling of pavement materials. There are no specific national standards addressed to the subject of concrete recycling procedures and material testing. Instead, existing national standards for concrete aggregates are applied and the recycled materials are in essence treated as would be new aggregate material. Local jurisdictions tend to be responsible for more detailed standards and specifications regarding the use of recycled concrete materials. 8 References ACI, 1990. ACI Manual of Concrete Practice (Part 1–1990), American Concrete Institute. Buck, Alan D., 1977. “Recycled Concrete as a Source of Aggregate,” ACI Journal, American Concrete Institute, Detroit, Michigan, May 1977, pp 212–219. Buck, Alan D., 1976. “Recycled Concrete as a Source of Concrete Aggregate,” Miscellaneous Paper No. C–76–2, U.S. Army Engineer Waterways Experiment Station, Vicksburg, Mississippi, April 1976, 17 pp. Frondistou-Yannas, Y.A., 1980. “Recycled Concrete as New Aggregates,” Progress in Concrete Technology, CANMET, Energy, Mines and Resources Canada, Ottawa, pp 639–684. Halverson, A.D., 1981. “Recycling Portland Cement Pavement,” Report No. 200, PHWA/MN–81–11, Minnesota Department of Transportation, St. Paul, Minnesota, May 1981, 49 pp. Kibert, Charles J. and D.L.Waller, 1991. “An Environmental Handbook for Florida Contractors,” Technical Publication No. 77, Center for Construction and Environment, University of Florida, pp 4.3–4.8. Kosmatka, Steven H. and W.C.Panarese, 1988. Design and Control of Concrete Mixtures, Portlartd Cement Association, p 44. Mehta, P.K., 1986. Concrete, Structures, Properties, and Materials, Prentice-Hall, Inc.,Englewood Cliffs, New Jersey, pp 231–232. PCA, 1980. “Recycling D-Cracked Pavement in Minnesota,” PL146P, Portland Cement Association, 1980. MDOT, 1992. “Recycling of Pavement Materials in the 1990’s,” Publication 92–05, Minnesota Department of Transportation, 1992, pp 10–15. Ray, Gordon K., 1980. “Quarrying Old Pavements to Build New Ones,” Concrete Construction, Concrete Construction Publications Inc., Addison, Illinois, October 1980, pp 725–729. USAF, 1988. “Standard Practice for Pavement Recycling,” Air Force Manual AFM 88–6, Chapter 6, August 1988, pp 5–1 to 5–3. Wilson, Alex., 1993. “Cement and Concrete: Environmental Considerations,” Environmental Building News, 2(2), March/April 1993, pp 1–12.

9 GUIDELINES AND THE PRESENT STATE OF THE REUSE OF DEMOLISHED CONCRETE IN JAPAN Y.KASAI College of Industrial Technology, Nihon University, Narashino, Japan Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract The demolished concrete is taken as a resource and its reuse has been considered in six guidelines. Summaries of the main text and commentary of three promising guidelines are described, though they have not been so far operated; (1) Proposed quality guideline for the recycled coarse aggregates and the commentary, the Ministry of Construction, 1986, (2) Proposed standard for the use of recycled coarse aggregate concrete for buildings, the Ministry of Construction, 1986, (3) Proposed standard for the use of recycled aggregate concrete for public works, the Ministry of Construction, 1986. Keywords: Concrete, Recycled aggregate, Recycled Concrete, Guideline, Waste Materials.

1 Introduction The amount pf concrete rubbles associated with the demolishing works was 25.4 miilion tons in the 1990 fiscal year, in which the degree of reuse was approximately 48%. The reuse was mostly for the road bases and a small amount of coarse aggregate and most of fine aggregate were also applied to back-fills and crusher-run under 40 mm in diameter, while dumping of the rest of the waste for reclamation has given rise to social problems. The law of recycling wastes was put into operation in October 1991 and the demolished concrete was nominated as a primary waste material for the promotion of recycling, and a definite policy which took the demolished concrete as a resource and reuse it for 100% was hammered out. Research into the reuse of demolished concretes as a concrete aggregate was initiated in 1973 by Y.Kasai [KASAI, Y.]. The Building Contractors Society in Japan established a Committee on Disposal and Reuse of Construction Waste (Chairman: Y.Kasai)

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followed by three years’ research. A fruit of the committee was proposed Draft standard for the use of Recycled Aggregate and Recycled Aggregate Concrete and Commentary issued in May, 1977 [BCSJ. 1977]. The Ministry of Construction conducted a wide range of research in terms of a five years’ research project, Development of Technology Applying Waste Materials to Construction Industry, in which guidelines (3), (4), (5) and (6) as mentioned below were formulated in November 1986. The present paper takes up a position that the demolished concrete rubble is a resource, and will summarize existing guidelines set forth to reuse it as a recycled aggregate for concrete structures, though actual operations have not yet made. The followings are six guidelines dealing with the reuse of demolished concrete; (1) Technical guideline for plant-recycling the demolished pavement materials. The Japan Road Association, 1992, (2) Draft standard line for the use of recycled aggregate and recycled aggregate concrete and commentary. The Building Contractors Society of Japan, May, 1977, (3) Draft guideline for the quality of recycled coarse aggregate for buildings and commentary. The Ministry of Construction, November 1986, (4) Draft guideline for the utilization of recycled coarse aggregate concrete for buildings and commentary. The Ministry of Construction, November 1986, (5) Draft guideline for the design and practice of recycled aggregate concrete for public works and commentary. The Ministry of Construction, November 1986, (6) Draft guideline for the quality of recycled aggregates for hollow blocks and commentary. The Ministry of Construction, November 1986. Among guidelines mentioned above, the first one is widely operated and the second one is forming a basis of the subsequent guidelines, the third to sixth, established in March 1986. The substance of the main part and commentary of (3), (4), (5) guidelines which are expected to be in actual operation in the future will be presented in this paper. 2 Background of the guidelines for recycling the demolished concretes [JRA (1992)] Utilization of demolished concretes for the road basis was beginning in 1978. Subsequently, The technical guideline for plant-recycling the demolished pavements materials was issued by The Japan Road Association in December 1992. This guideline is covering demolished asphalt concretes and demolished concrete. The demolished concretes coming either from buildings or public works can be recycled in this way. The recycled road base material The recycled road base material is a composite so as to perform specified quality by blending recycled aggregates from demolished asphalt concretes or

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demolished cement concretes with demolished road basis, to which supplemental materials such as crushed rock, blast furnace slag crusher-run and sand may be added if necessary. The rode base The quality of recycled crusher-run used for underlay road base is recommended in Table 1.

Table 1. Quality of recycled crusher-run used for underlay road base

Materials

Corrected CBR (%) Plasticity Index

Simple Pavement

Recycled crusher-run

10 over

9 under

Asphalt pavement

Recycled crusher-run

20 over

6 under

Cement concrete pavement

Recycled crusher-run

20 over

6 under

Note: The maximum grain diameter for underlay road base materials must be smaller than 50 mm

Note: The PI value of 0.4 mm passed recycled crusher-runs for concrete pavements can be lowered as low as 10 provided that either the support capability of the model road base can be measured or sufficient amount of success stories in the past are known. In this case, materials with PI value less than 15 can be used. Structural Design The percentage of weight loss of recycled cement concrete aggregate tested by Los Angeles abrasion test should be less than 50%. 3 Composition and comparison of guidelines for buildings and for public works The guidelines to be commented here are based on the preceding guideline established by Building Contractors’ Society which has been reported by the author at EDA/RILEM Conference in 1985. A distinction between building and public works was made in the guideline for the utilization of recycled aggregate mentioned in the previous section. This distinction may be peculiar to Japan, and can be attributed to the condition of structural design. Building structures have been required complicated rebar arrangement for seismic resistance and as a result, what is called wet consistency concrete with a slump from 20 to 23 cm has been used. The structure of public works, on the other hand, has larger cross section and simpler arrangement of rebars, and has required a medium consistency concrete with a slump from 8 to 14 cm. For this reason, specifications and technical guidelines have been different each other in building construction and in public works.

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4 Draft guideline of the quality of recycled coarse aggregate for buildings and commentary 4.1 General (1) Scope of this guideline This guideline is applicable when all or a part of coarse aggregate for concrete may be substituted by recycled coarse aggregate. (Com.) Commentary: This guideline proposes a quality standard of coarse aggregate for concrete made of demolished concrete. (2) Terminology Terms used in this guideline are defined as follows, Recycled coarse aggregate: coarse aggregate for concrete obtained by breaking the original concrete. Original concrete: concrete which can be a raw material for recycled coarse aggregate. Com.: The original concrete means a sound concrete such as plain concrete, reinforced concrete structure or precast concrete products which have been demolished or planning to be demolished. Alkali-aggregate reactivity or other harmful components should not be a cause of the demolition, and a possible chloride concentration should be measured beforehand. 4.2 Production of recycled coarse aggregate The recycled coarse aggregate should be produced by a plant capable of assuring the specified quality. Com.: The primary breaking may be made by jaw or impact crusher and the secondary breaking by jaw, impact or corn crusher. Magnetic sorter and floating sorter may be used for removing impurities such as steel bars and timbers respectively. If the original concrete contains no wood chips and less soil or mud, washing process may be omitted. 4.3 Quality of recycled coarse aggregate The quality of recycled coarse aggregate should be as specified in tables 4.1 and 4.2.

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Table 4.1. Quality of recycled coarse aggregate

Items

Test method

Recycled coarse aggregate

Specific gravity (absolute dry)

JIS A 1110

Equal or greater than 2.2

Water absorption (%)

JIS A 1110

Equal or smaller than 7

Removal by washing (%)

JIS A 1103

Equal or smaller than 1

Solid volume percentage (%)

JIS A 1104

Equal or greater than 53

attached document

Equal or smaller than 2%

Impurity concentration (%)

Table 4.2 Sieve analysis of recycled coarse aggregate

Com.: The recycled coarse aggregate comprises original coarse aggregates with attached mortar and mortar rubbles. The quality of the recycled coarse aggregate is affected by the mix proportion of the original concrete, crushing process, grading control and the amount of impurities. Supplemental table 4.1 Results of physical test for recycled aggregate [KASAI Y. et al. 1992] Specific gravity (ab.dry) Coarse range aggregate mean

2.09–2.50 1.75–10.07

0.75–1.42 1.33– 1.55

6.64–7.21 57.6–66.5

2.30

5.79

1.38

1.44

6.85

62.4

3≥

1.0≥

–

–

≥55

Standard ≥2.5 Value Fine range aggregate mean

Water Washing Specific Finess Solid vol. absorption test (%) mas modulus percentage (%) (kg/l) (%)

1.98–2.20 4.79–13.20

5.00–15.2 1.27– 1.46

2.86–3.99 63.2–70.2

2.07

9.73

7.93

1.39

3.29

67.3

3≥

7≥

–

–

≥53

Standard ≥2.5

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Value

Com.: Supple mental table 4.1 shows physical test results of recycled aggregate. Recycled aggregates have smaller bulk density and lager water absorption than normal aggregates, and a considerable loss can be found during the washing test. Test results normally show substantial scatter. These may be attributed to mortar component of the original concrete. An agreeable quality may be obtained with a degree of substitution by recycled aggregate less than 30%. A supplemental table 4.2 shows the limit of impurity concentration. Supplemental table 4.2 Limit of impurity attainable to 85% strength of normal concrete [BCSJ 1977] Impurity Conc. in vol %

Plaster

Mud

Cinder Concrete

Asphalt

Synthetic paint

6≥

5≥

20≥

1≥

0.2≥

4.4 Test Testing methods for impurities should be based on JASS 5.16 Test Method, and on the supplemental document attached to section if necessary. The supplemental document: Testing methods for impurities These testing methods are for detecting an approximate amount of impurities in recycled coarse aggregates. (1) Apparatus A balance with a resolution as high as 0.1 g. A vessel and a rod specified in JIS A 1104 Test method for specific weight and percentage of solid volume. A polyethylene beaker of 5 liters and a sieve with 0.15 mm opening. (2) Solution A glycerol solution with specific gravity 1.2 composed of 100 weigh metric % of glycerol and 25.5 % of tap-water. (3) Procedure Specimens are sampled in a vessel of 10 liters specified JIS A 1104, then sieved, weighed out 500 g, put into the 2 liters of solution, stirred and placed. The floating matters are decanted and sieved with 0.15 mm opening. The separated floating matters are washed by water and dried to a constant weight at 80 °C and then weighed.

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5 Draft guideline for the utilization of recycled coarse aggregate concrete in buildings and commentary 5.1 General (1) Scope of this guideline This guideline is applicable for concrete using recycled coarse aggregate, and subjects which may not be specified here should be based on Standard Specifications for Reinforced Concrete Work (JASS 5) issued by Architectural Institute of Japan and on another guidelines related to concrete. Com.: This guideline deals with cases when recycled coarse aggregate may be applied to reinforced concrete construction, plain concrete construction and precast concrete production, and with the case when sand is used for 100 % as fine aggregate and the recycled aggregate is used only as coarse aggregate. A guideline dealing with recycled fine aggregate has been issued by the Building Contractors Society. The mix design, production and construction of the recycled coarse aggregate can be performed along with the crushed aggregate concrete. (2) Terminology Terms used in this guideline are defined as follows, Recycled coarse aggregate concrete: A concrete whose coarse aggregates are substituted totally or partially by recycled coarse aggregate. 5.2 Grade and quality of recycled coarse aggregate concrete (1) Grade of concrete The grade of recycled coarse aggregate concrete depends upon the degree of substitution by the aggregate as shown in Table 5.1.

Table 5.1. Grade and quality of recycled coarse aggregate concrete

Grade

Fine aggregate (sand) in %

Degree of substitution in %

A

100

≥50

B

100

50> > 30

C

100

30≥

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Table 5.2. Quality of recycled coarse aggregate concrete

Standard design strength (Kgf/cm2)

Application field

150

—

180

Simple concrete

210

Structural concrete

(2) Design strength Recycled coarse aggregate concrete should fulfill specified performance requirements such as workability, strength and durability with small dispersion in quality. The standard design strength is also shown in Table 5.2. Com.: The application field of recycled coarse aggregate concrete may be a base concrete of timber construction for Type A, and for Type B when the degree of substitution is close to 50%. The simple concrete construction is defined in JASS 5. Type C concrete has no actual results and the standard design strength of 210 Kgf/cm2 is provisional. The structural concrete construction is defined in JASS 5. The quality requirements for recycled coarse aggregate concrete is basically equal to what is specified in JASS 5, however its characteristics with reference to normal concrete are as follows, (1) The amount of water per unit volume of concrete should be increased to have an equal slump as that of normal concrete only when the degree of substitution of recycled coarse aggregate exceed 30%. (2) Strength at an equal water to cement ratio is rather small. (3) Drying shrinkage is fairly large. 5.3 Mix proportion Mix proportion of recycled coarse aggregate concrete should be determined by taking the material quality, standard design strength and production method into consideration so as to attain the quality specified in the previous section of this guideline. It is also recommended to reduce the amount of water per unit volume of concrete with ensuring the specified performance, and a test mixing is necessary. Com.: The amount of water per unit volume of concrete should be as small as possible at a specified workability, and it is likely to increase due to mortar component attached to the recycled coarse aggregate, and as a result, its quality scatters. The test mixing taking all these factors into consideration is necessary. 5.4 Production Production of recycled coarse aggregate concrete should be made according to the

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production of normal concrete specified in JIS A 5308 Ready Mixed Concrete, section 6. Com.: Recycled coarse aggregate should be weighed accurately according to the degree of substitution. Pre-wetting may be necessary to determine the surface moisture content when water absorption of the recycled coarse aggregate is large, and the slump loss at pumping may become substantial rather than normal concrete if the moisture treatment of recycled coarse aggregate is insufficient. This should be assured by an experiment. For floor slabs, timely tamping may be effective to prevent cracking. 5.5 Conveying, placing and compacting Recycled coarse aggregate concrete should be conveyed so as to assure the specified performance, placed and compacted so as to be filled uniformly and densely. The compaction should be made appropriately according to slump and the subsequent curing. 5.6 Test The test of recycled coarse aggregate concrete as well as materials other than recycled coarse aggregate should be based on JASS 5.12 Quality Control. 6 Draft guideline for the design and practice of recycled aggregate concrete for public works and commentary 6.1 General (1) Scope of this guideline This guideline presents a standard for the design and construction of plain and reinforced concrete using recycled aggregate, and subjects which may not be specified here should be based on Standard Specifications for Plain and Reinforced Concrete Construction issued by Japan Civil Engineering Society. Com.: This guideline has been specified to use recycled aggregate for concrete in public works, and deals with cases in which both recycled fine aggregate and recycled coarse aggregate are used, or one of the pair is used. (2) Terminology Terms used in this guideline are defined as follows, Original concrete: concrete which can be a raw material for recycled coarse aggregate. Recycled aggregate: aggregate for concrete obtained by breaking the original concrete. Recycled aggregate concrete: concrete made of recycled aggregate or of recycled aggregate blended with other aggregate. Com.: The original concrete is the same as in the guideline for building though the demolished concrete pavement with asphalt should not be included as well

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as bricks. The recycled aggregate, both coarse and fine, should be put into a mill to remove mortar component and fine powder after the crushing process. The recycled aggregate concrete is termed even though some recycled aggregate is blended with normal aggregate at any degree of substitution. 6.2 Recycled aggregate (1) General The recycled aggregate should be assured the specified quality, and should not contain impurities with any harmful effects upon the quality of the concrete. The variance of quality should be small enough. Com.: The supplemental table shows an example of quality of two recycled aggregates reproduced, by the same crushing method, from high and low strength original concretes with a common original normal aggregate. A high strength original concrete may not always produce a high quality recycled aggregate and, especially for fine aggregate, a low strength original concrete may occasionally produce a better quality recycled fine aggregate. This may be attributed to an easier removal of mortar or paste component associated with the decrease in strength of the original concrete. Supplemental table 6.1 An example of the quality of recycled aggregate Degree of crushing

Strength of the original concrete

Specific gravity

Water absorption (%)

Degree of mortar adherence (%)

High strength

2.48

4.02

41.7

Low strength

2.38

5.18

29.4

High strength

2.57

2.48

26.5

Low strength

2.55

2.56

20.6

High strength

2.62

1.55

10.8

Low strength

2.66

1.06

2.5

High strength

2.37

7.84

29.0

Low strength

2.41

6.58

15.3

High strength

2.45

5.86

23.3

Low strength

2.52

3.76

9.3

Coarse & fine Primary Intermediate High

Fine Intermediate High

Note: High strength; approx. 400 Kg/cm2, Low strength; approx. 200 Kgf/cm2

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(2) Quality of recycled aggregate The recycled aggregate should have the quality shown in the Table 6.2.

Table 6.2. Quality of recycled aggregate

Sort Item

Recycled coarse aggregate Type 1

Type 2

Recycled fine aggregate

Type 3

Type 1

Type 2

Water absorption

3≥

3≥

5≥

7≥

5≥

10≥

% Stability

12≥

30≥*

12≥*

---

10≥

---

Note for a mark *: 40≥ when freeze/thaw resistance is not important Recycled aggregate which is physically or chemically unstable cannot be used except for a case that the safety is recognized on the basis of the application condition and test results.

Com.: The mortar adherence and water absorption related to it are taken as index of the quality of recycled aggregate. The limit values of the index in the table 4. are determined mainly by taking their effect on strength and durability of concrete into consideration. When the saturated surface-dry condition of recycled aggregate at water absorption test may be affected by the attached fine powder component, washing process should be considered based on JIS A 1103 (Washing test of the aggregate). When normal aggregate partially substituted by recycled aggregate is used, the quality of recycled aggregate should solely represent the quality of overall aggregate for a safety reason. Recycled aggregates may be physically or chemically stable at high possibility if the original concrete is sound. However an alkali-aggregate reaction may be present even in the recycled aggregate concrete depending on the mix proportion, so that a countermeasure as specified in JIS A 5308 (Ready Mixed Concrete) may be considered. (3) Grading A standard range for the grading of recycled aggregate is shown in Table 6.3. The sieving test should be based on JIS A 1102. The variance of finess modulus of recycled fine aggregate should not exceed more than 0.2 with respect to the finess modulus employed to set the mix proportion of the concrete.

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Table 6.3 Standard range for grading of recycled aggregates

Percentage of weight passed through the sieve (%) Sort of aggregate

Max sieve size

Recycled coarse aggregate

40 25 20

Recycled fine aggregate

50

40

30

25

100 95– 100

20

15

35– 70 100 95– 100 100 90– 100

10

5

2.5

1.2

0.6

0.3 0.15

10– 0–5 30 30– 70 20– 55

0– 10

0–5

0– 10

0–5

100 90– 80– 50– 25– 10– 100 100 90 65 35

2– 15

(4) Critical concentration of harmful components Critical concentration of harmful component is shown in Table 6.4. An advice of a responsible engineer is needed for the rest of the components.

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Table 6.4. Concentration of harmful components (% by weight)

Washing test

Recycled coarse aggregate type 1, 2, 3

Recycled fine aggregate type 1, 2

Wearing down of concrete surface

1.5

5

The other case

1.5

7

Com.: Main harmful components in the recycled aggregate may be residual soils attached to the original concrete and fine powder originated from the crushing process. A considerable amount of chloride may be occasionally found in the concrete, whose harmful effect, however, may be avoided by omitting the application of recycled fine aggregate to reinforced concrete structures. 6.3 Production of recycled aggregate Production of recycled aggregate should be made by a plant capable of assuring the specified quality. Com.: The quality of recycled aggregate is totally depending on the crusher. The layout of crushers may be made according to a crushed stone plant. Water absorption and quality stability of recycled aggregate may be improved by reducing the mortar component attached to the surface of the recycled aggregate. To this end, setting an additional final process jostling aggregate each other to eliminate the mortar is effective. The processing duration should be sufficiently long in the production line of recycled fine aggregates. The production cost of recycled aggregate of relatively low quality is not so much different from that of normal aggregate, while recycled aggregate of higher quality may require longer processing at the final stage and result higher cost. Production of recycled aggregates by types is shown in the supplemental table 6.2 as ratios with the weight of the original concrete for 100. Supplemental table 6.2 Quality of recycled aggregate and their composition of production Quality Type Coarse aggregate type Coarse aggregate type Coarse aggregate type 1 and fine aggregate 1 and fine aggregate 2 and fine aggregate Sort of type 1 type 2 type 2 aggregate Recycled coarse aggregate

27%

44%

44%

Recycled fine

31%

28%

40%

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aggregate Fine powder, fine sand

42%

28%

16%

6.4 Quality of recycled aggregate concrete (1) General Recycled aggregates concrete should have specified strength, durability, water tightness, workability and well-controlled quality. The Recycled aggregates concrete should also be an AE concrete with an appropriate air content. Com.: Amount of water per unit volume of concrete should be as small as possible. The recycled aggregate concrete should be an AE concrete. (2) Grade of recycled concrete The grade of recycled concrete according to the sort of aggregate is shown in Table 6.4.

Table 6.4. Grade and application of recycled aggregate for concretes

Grade Standard design strength (Kgf/cm2)

Coarse aggregate Fine aggregate

I

≥210

Type 1

Normal fine aggregate

II

>160

Type 2

Normal or Type 1

III

160>

Type 3

Type 2

Com.: Recycled aggregate concrete can not improve its strength so greatly when water-cement ratio is reduced, and generally a high strength orientation is not advantageous from the point of economy and quality. The above table shows an expected utilization range without increasing the amount of water per unit volume of concrete. The possible application field of the recycled aggregate concrete is shown in the supplemental table 6.3. Supplemental table 6.3 Application of recycled aggregate concrete Concrete

Structures

Reinforced concrete

bridge deck, retaining wall, tunnel lining

Plain concrete

block, base of road fittings, channels, drainage pot base, gravity retaining wall, joint concrete, precast armour unit, sand dam structure

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sub-slab concrete, non load bearing back filling concrete

Com.: Only Type 1 recycled aggregate can be used for reinforced concrete structure reflecting possible concentration of considerable chloride in the original concrete and recycled fine aggregate may not be used. 6.5 Management of recycled aggregate (1) Conveying and stock Recycled aggregates should be treated without breaking, separating particles of different size and being contaminated by dust or other sort of aggregates. (2) Control of moisture content Recycled aggregate concrete should be stocked with a constant and uniform moisture content. Com.: The control of moisture content is rather difficult for a recycled aggregate with higher water absorption and pre-wetting may be necessary in some cases. In an experiment, no increase in moisture content was observed after the water spraying for 24 hours. 6.6 Mix proportion (1) General Mix proportion of recycled aggregate concrete should have an amount of water per unit volume of the concrete as small as possible to attain the specified strength, durability, water tightness and workability, and should be designed on the basis of experiments in principle. Com.: Since recycled aggregate concrete is likely to have considerable amount of water per unit volume of the concrete, test mixing is necessary to determine the mix proportion. (2) Air content in the AE concrete Air content of AE concrete using recycled aggregate should be 4 to 6% of the volume of the concrete depending upon the maximum size of coarse aggregate and other conditions, and should be tested on the basis of JIS A 1118 (volumetric method) or JIS A 1128 (pressure method). Com.: The attached mortar component on the recycled aggregates may result an increase in entrapped air. For this reason, entrained air content necessary for assuring sufficient durability is set fairy larger than normal concrete. The aggregate correction coefficient is necessary to be determined when the air content is measured by the pressure method.

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6.7 Mixing, conveying, placing and curing Mixing, conveying, placing and curing of recycled aggregate concrete should be made so as to obtain a concrete with uniformity and specified quality. 6.8 Quality control and testing Quality control and testing of recycled aggregate concrete should be based on the section 24 of Standard Specifications for Plain and Reinforced Concrete Construction issued by Japan Civil Engineers Society. 6.9 Structural design Structural analysis of recycled aggregate concrete should be made according to those of normal concrete. 7 Present state of the reuse of the demolished concrete Only 50% of demolished concrete rubbles have been so far reused as a road base and back fill in Japan, while a higher degree of reuse could be attained by utilizing the demolished concrete as a concrete aggregate. The present guidelines as reviewed above have been specified separately in each side of building construction and of public works, which still have no actual application to structures. The Ministry of Construction in Japan started a 5 years’ technical development project entitled Development of Technology for Restriction and Accelerate Reuse of Construction By-products from 1992, where a reconsideration of existing guidelines for recycled aggregate concrete and measures promoting the reuse will be developed. A simulation study of reusing concrete rubbles associated with a total reconstruction of a collective housing area followed by a test construction can be a feature of the project. The Tokyo Metropolis is executing an experiment to reuse demolished concrete for the peripheral constructions of the conference hall in the down town. Application of the recycled aggregate for the precast concrete products has been studied in Eastern Japan Cement Products Association from 1991 to 1992, and now comes into a stage of marketing development and commercializing in this year. The state of the reuse of recycled aggregate for concrete in Japan is thus turning from the laboratory study to the practical application. The demolished concrete should not be considered as an industrial waste for which a place for dumping is hard to find but as an important resource just in the city, and a positive utilization will be made on this basis.

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8 References Kasai, Y., et al. (1973), Some experiments on recycled coarse aggregate concrete, Summarize of technical papers of annual meeting, Architectural Institute of Japan BCSJ (1977) Draft standard for the use of recycled aggregate and recycled aggregate concrete and commentary (in Japanese) JRA (1984) Technical guide for recycling the demolished concrete pavements, The Japan Road Association (in Japanese) Kasai, Y. (1985), Studies into the reuses of demolished concrete in Japan, EDA/RILEM Conference Reuse of Concrete and Brick Materials (1985) Kasai, Y., et al. (1992), Investigation of recycled concrete aggregate for precast concrete products. Proc. Japan Concrete Institute, Vol. 14 (No.1) 235–240 (1992) (in Japanese)

10 THE PROCESSING OF BUILDING RUBBLE AS CONCRETE AGGREGATE IN GERMANY R.-R.SCHULZ Fachhochschule Frankfurt am Main, Germany Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract This paper reports about the development of natural aggregate resources and substitute potentials in Germany. It shows which formal prior conditions are necessary to recycle building rubble as concrete aggregate. Steps against the varying properties of the processed rubble as particle density and water absorption are discussed from a practical point of view. It is reported about the first attempts on performing large scale tests concerning the reuse of concrete and masonry as concrete aggregate in Germany. Keywords: Concrete Aggregates, Priorities for Reuse, Guidelines, Standards, Properties of Aggregates, Bulk Density, Water Absorption, Pilot Projects,

1 Introduction Recycling of structural material in Germany is still far from getting a real closed-looprecycling-system. Though building rubble is increasingly recycled more than discarded as sanitary landfill, valuable demolition rubble is still reused for secondary purposes as subbase for roads and noise protection walls. If a closed-loop system is to be achieved, this material has to serve its original purpose. The commonly used procedure can be compared with a declining spiral. That is why the recycled material is decreasing in usefulness and value. Probably a real closed-loop cannot be achieved. Just in a few exceptional cases the quality of the recycling products will be similar or even higher than the quality of the original material. Nevertheless reuse on the highest level should be aimed at to delay the descending motion of that spiral. How can construction rubble be reused according to its former function?

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2 Natural aggregates and potential substitutes 2.1 Natural gravel and sand One part of the reduced consumption of river gravel and sand in the time between

Fig. 1. Development of aggregate consumption (Data provided by industrial associations)

1970 and 1990 (Fig. 1) may refer to the trade cycle. The other part can only be explained by diminishing resources, which force reduced consumption. Despite the slight increase in the last few years the tendency of reduction is inevitable. Shortage and price rise (Fig. 2) will accelerate as a result of increasing restrictions. Protection of drinking water reservoirs and environmental reasons make it much more difficult to obtain prospect licences. Some owners of gravel-pits are reducing their production in order to keep the deposits on a long-term basis. 2.2 Crushed rock The most important substitute for gravel and sand is crushed rock (Fig. 1 and 2). That is why its usage has increased nearly by the factor of ten in the last decade. Until then crushed natural stone was preferred for special purposes, which means it was used where a good cohesion of fresh formed concrete products (paving blocks) or an improved abrasion resistance or a high flexure or splitting or impact strength is needed (pavements). Concretes which are continuously exposed to high temperatures need

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crushed rock with a reduced quartz content. Because of the scarcity of gravel and sand and meanwhile balanced prices (Fig. 2), crushed stone is used for nearly all purposes in concrete production. 2.3 Lightweight aggregate Today artificial lightweight aggregate is preferred for the production of porous insulation concrete bricks and walls and is less used for structural concrete. A potential might exist for the substitution of natural aggregate but this is restricted by the inevitable high consumption of primary energy.

Fig. 2. Returns for natural aggregate without carriage and tax, Mergelsberg (1989)

Fig. 3. Demand for concrete aggregates in 1990 compared to the amount of demolition rubble in 1989

2.4 Industrial byproducts and recycled aggregates The sources of alternative structural material are also restricted. This is true for industrial byproducts (slag, ashes from power and incinerator plants) as well as for recycled building material. In principal, valuable primary supplies can be saved by the usage of those alternatives but we have to consider that the whole demand for concrete aggregate is much larger than the amount of substitutes. Additionally, it must be considered that

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industrial byproducts are already being reused at a very high rate (slag: 100%). Fig. 3 shows the difference between the total aggregate demand and the supply of recycled material in the westem parts of Germany (1989/1990). Only a part of the 23 million tons of building rubble per year is capable of being reused as concrete aggregate. It is known that the sand fraction of recycled material will cause problems and cannot be reused for concrete. 2.5 Priorities for utilization Valuable rubble, which could be used as concrete aggregate is also attractive for road building purposes. For this reason priorities must be set to distribute the raw materials among the various fields of application. The main task is to save the natural resources and to reuse the alternative materials in the most appropriate way. At first it has to be found out how the most appropriate method of usage and the optimum level of reuse for all purposes can be achieved. Valuable natural aggregates should not be dissipated for minor purposes (foundation, equalizing beds) in order to keep them for tasks where they are urgently needed; for example, bridges and other high loaded structural elements. In all other cases materials should be used which just comply with the reduced requirements. That is why, for example, in dry environments aggregates with reduced frost resistance can be used. This could also be a typical application for alternative structural material. Normally all this will be governed by the price, but with recycled aggregates, additional difficulties have to be conquered. 2.6 Aspects of performance Beside questions of distribution and transportation the casting of concrete with different aggregate types requires additional storage capacity. Average ready mixed concrete plants have got limited facilities. They are not able to offer concrete with crushed rock or lightweight aggregate in addition to concrete with gravel and sand. There is a certain risk to frequent changing in the type of bin content because mix-up or colour change may occur. To avoid complicated arrangements and to avoid problems as mentioned above the number of bins has to be increased. Besides the necessary investments there are some particular features which have to be considered when casting concrete by using recycled aggregates (see chapter 4 and 5). For this reason recycled aggregate has to be significantly cheaper than natural aggregate to maintain a profit by using it 3 Specifications 3.1 Standards and permissions Numerous scientific results prove that the properties of concrete with crushed concrete aggregate can be quite similar to those of normal concrete. Despite this it is very difficult to reuse demolition rubble as aggregate for structural concrete in Germany. Concrete for structural elements and stiffeners of reinforced or plain, normal or heavy

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concrete with dense structure, has to be cast according to DIN 1045. Aggregates have to conform to DIN 4226. Standardized concrete requires standardized aggregate since DIN 1045 has been installed by law as a convention of technic. Except for crushed brick, recycled aggregates do not correspond with the standards. Building material, structural elements and construction types, which are not commonly used and approved (new material), may be used if their practicability has been proved. General permissions or test marks are needed. Alternatively a case permission has to be obtained from the major or assigned authorities. As origin, components and properties of recycled aggregates are changing continuously, there is no basis for a general permission or a test mark. That is why only the case permission procedure remains, which might be justified if the constituents of a larger quantity with nearly uniform origin and/or quality could be evaluated. Nevertheless, even this procedure is time consuming and expensive and has to be repeated in each case if the conditions are changing. Standardization may be considered in case of general permission, but the material must be produced by several companies and used during a longer period. When will a case license procedure be worth while? Until now processed rubble is not much cheaper than normal aggregate. On the other hand the properties are not better than those of natural aggregate. More likely they are worse. In addition, manufacturing of concrete with recycled aggregates is more difficult. Taking this into account, it is easy to understand why this kind of recycling is not popular. Despite this, political institutions should not only regard economical aspects. They are responsible for environmental interests and for supplies, as well. That is why initiatives should be expected at least from this side. Unfortunately, the present financial problems, which are a consequence of the unification, prevent the government or local authorities from performing experimental projects. As it is obvious that the increasing scarcity and the decreasing land fill areas will strongly influence the price, investments will be encouraged very soon. After all, it has to be regarded that the amount of processed rubble can never substitute the whole demand of aggregate. Additionally, the use of alternative resources as aggregate competes with other uses, for instance, in road construction. 3.2 Specifications for concrete pavements As opposed to structural and stiffening elements, ‘used material’ has been recently allowed for use in pavement concrete. To support technical progress, the latest edition of ZTV Beton-StB (1991) remarks that recycled material can be used if tender conditions permit that. However, the requirements for concrete aggregate were tightened up. The aggregates for the surface layer must conform to DIN 4226 or TL Min StB and must also meet the extended requirements for frost and thawing agents (eFT). The aggregates must have a reduced content of expanding organic particles (eQ). Road classes SV and I to III require better particle shape and an adequate resistance against abrasion. It will be difficult to meet all these requirements with recycled aggregates. That is why recycled material may be considered as suitable just for the second layer (see chapter 6.3).

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4 Properties of recycled aggregate 4.1 Composition The limitation of main and secondary constituents is an important prior condition for sufficient equal and calculable properties. The classification, testing and evaluation of processed masonry and concrete rubble can be performed according to Stichting voor onderzoek (1984). As the composition of the products varies even during one day to a wide extent the manufactured concrete will vary as well. It is recommended to homogenize at least daily production by preselection, stockpiling, shifting and mixing enough that it could be regarded as a unity. Procedures like this are known for example from the cement production. To evaluate the homogeneity and to obtain data for mixture design, quick tests are recommended. Necessary tests, simple alternatives and depending parameters are discussed by Schulz (1986 and 1988). 4.2 Contamination Not only from a technical but also from an economical point of view the question has to be answered how far contaminants have to be removed and which maximum content of contaminants could be tolerated. Recycled aggregates should not contain more harmful constituents than are allowed to normal aggregate (s. DIN 4226). Special kinds of contaminants as asphalt, paper, plastics, glass etc., which frequently occur with recycled rubble, are unusual for normal or lightweight aggregate. That is why DIN 4226 gives no information. As the legislator demands separate demolition, there are good chances to obtain more clean and uniform material. Another way to influence the amount of contaminants will be the price for the reception of demolition rubble, which has to depend on the quantity of contaminants. As contaminants are concentrated in the fine particles of rubble and water absorption is increased, it is recommended not to reuse fine rubble.

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Fig. 4. Correlation between bulk density and particle density

4.3 Particle density and bulk density The particle density is a very important value for mix design and for the accuracy of batching. Properties like strength and modulus of elasticity can be calculated by the particle density, too. Variations in the composition of recycled material also produce variations in the particle density. Additionally the accuracy of batching is influenced by the moisture content of the particles. This is scattering at wide range and also depending on the composition of the demolition rubble, on its origin and on the kind of storage. That is why mix design has to be adjusted frequently. Consideration of these influences presumes that the particle density and the moisture content are tested in short intervals. Testing of particle density is a difficult and time-consuming procedure. The disadvantages become apparent when the production is scattering at wide range and the test has to be performed frequently. Compared with this, testing of bulk density is much simpler and faster. That is why it is of great interest whether the accuracy will meet the requirements and whether the particle density can be calculated. According to experiences with lightweight aggregate there is a strong correlation between particle density and bulk density. This is true for aggregate from concrete and masonry rubble, too (see fig 4). Bulk density is used as compliance criteria for the production of lightweight aggregate. Whereas lightweight aggregates have a low and uniform moisture content, this cannot be expected for recycled aggregates. That is why the recycled aggregate has to either be dried before testing or otherwise be soaked with water. Drying is on the one hand time consuming and on the other hand accuracy suffers from soaking, because it is difficult to assure a complete saturation and a surface-dry-state simultaneously. Moisture on the surface will influence the degree of dispersal and the

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bulk density.

Fig. 5. Correlation between bulk density and water absorption

4.4 Water absorption The absorption capacity of the aggregate poses severe problems for the production of concrete. The properties of fresh and hardened concrete cannot be predicted with the needed accuracy. Since the pores are not saturated, they can extract water from the paste, which will impair workability and reduce the water cement ratio. That means, beside the influences of particle strength, particle shape, particle composition, and mix composition by scattering particle densities the properties of the cement paste will also be affected significantly. Water absorption after 30 minutes is normally used for lightweight concrete mixtures to estimate how much mixing water will be absorbed by the particles and to determine the supplementary water addition. This part of water is not available for the cement paste. Water absorption after 24 hours of storage in water provides the necessary information about the saturation behaviour for lightweight aggregate concrete which has to be pumped. Information about the water absorption of recycled material is less useful because the soaking velocity will be retarded with increasing particle size. Additionally it is depends on the consistence and from the existing water content of the aggregates, which scatters at a wide range, as well. Only if the aggregate is dry, test results may be useful estimates for the maximum quantity of expected water absorption. In these cases water can be batched up to this limit to improve consistence. This will reduce the danger to exceed maximum water/cement ratio. The values of the initial tests are likely to be exceeded if

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aggregates have an unknown moisture content. 5 Effects on concrete technology 5.1 General As recycled aggregates are porous, experiences from the lightweight aggregate concrete technology can be adopted to a wide extent. Water absorption of the aggregate, influence of the particle strength on the concrete strength, increased deformability, that means reduced modulus of elasticity and the retarded but in total higher shrinkage have to be mentioned. 5.2 Workability of fresh concrete Experiences show that the efficient design of consistence and the observance of the effective water/cement ratio suffers from changing water absorption. The water absorption capacity and absorption rate of processed rubble depends from the kind, quantity and particle size of each constituent and from the quantity of free water. 5.3 Consideration of water absorption in practice The following methods are considered by using experiences from lightweight concrete. 1. Increasing the supplementary water addition according to the results of water absorption test after 30 minutes. 2. Saturation of the aggregate by pre-soaking. 3. Water addition on the construction site according to the required workability. Further modifications or combinations are possible but all of them have both advantages and disadvantages, Moser (1991). Method 1: Experiences with lightweight aggregates show that the water absorption after 30 minutes is a characteristic value of sufficient accuracy, which has proved itself in practice. The supplementary water addition is increased by this quantity. As mentioned above, the existing water content of recycled aggregate cannot be predicted with the same accuracy during production. For this reason free water may exceed the calculated maximum content. More than lightweight aggregate the absorbed quantity of water depends on consistence. For this reason tested water absorption coefficients do not directly correspond to the absorption behaviour in concrete. The more liquid the fresh concrete becomes, the more water will be absorbed. If the total amount of supplementary water is added at once into the mixer, the concrete becomes too liquid at first. Then there is a certain risk that concrete spills out of the mixing unit each time truck mixers accelerate Method 2: This method is theoretically the best and most certain one. But it is not the most liked in practice because several necessary arrangements have to be made. Though pre-soaking of lightweight aggregate has not proved itself because the water is kept in the

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pores over a long period and affects the insulation behaviour of the concrete, it may be suitable for recycled aggregate concrete because this material will not be used for insulation purposes. Besides this, the pore structure of crushed rubble will help to support the drying process. The aggregate must be completely saturated but surface dry. This will avoid any water exchange with the fresh paste. Under these circumstances water absorption tests can be abandoned. Nevertheless additional equipment and storage capacity will be necessary to prepare the aggregate during a longer period and to keep it in a homogeneous saturated condition. Spraying of the aggregate requires a sufficient shape and size of the stockpiles and a drained underground. Alternatively the aggregates could be stored in water basins. Though water absorption may be more thorough, there are some severe disadvantages. First the efforts for filling and discharging the basins have to be considered and the efficiency depends on the size and capacity of the basins. The aggregate may be too wet, which could influence the effective water/cement ratio. The latter method is recommended in connection with wet cleaning techniques. In any case the moisture content has to be adjusted up to the batching process. That means the aggregate must be sprayed with water on the way from the stockpile to the batch bin. Problems may occur in winter when the water on the particle surface and the spraying equipment is going to freeze, Moser (1991). Compared with other methods the weight of the fresh concrete will be higher and transportation costs will increase. Besides this, particle density in wet condition must be tested. Method 3: This method will be preferred by the site personnel because workability has the first priority. As the soaking behaviour and the surface condition vary in a wide range, the correlation to the initial tests may be worse than for normal and lightweight concrete. The effective water/cement ratio will scatter, too. The maximum supplementary water addition has to be determined by initial tests and has to be restricted by vessel charge or water meter. Another problem may be excessive stiffening during transportation. 6 Performed projects Because of the rigid specifications in Germany, it is difficult to make any progress in reusing recycled aggregates as concrete aggregate. Nevertheless there are some first steps and even positive results worth mentioning. 6.1 Pilot project in Berlin At the end of 1987 the building senator of Berlin took the initiative for a pilot project in West Berlin. For the construction of a new recycling plant a foundation wall was to be built using 5000 tons of recycled aggregate. Based on extensive initial tests, Schulz (1988) and permission tests BAM (1989) a case license was obtained for this project. The results of the initial tests showed that the properties of the coarse recycled aggregates of four recycling plants in Berlin and of the concrete with these aggregates were sufficient for this purpose. It was pointed out that the results could only be relevant and reproducible if the composition of the used aggregate did not change significantly. Since

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the specimens were taken from the current production they could not meet these requirements. First it was planned to stockpile and homogenize the whole needed amount on the site. Finally the original plan to reuse mixed rubble was stopped, since in the course of demolition and repair of the ‘Avus’-highway in

Fig. 6. Chloride content in the top layers of the pavement compared to the recycled concrete

Berlin a sufficient quantity of homogeneous and valuable concrete rubble was found and could be used for the purpose mentioned above. The permission tests were performed with this material. It has to be mentioned that the pure concrete rubble was mixed with some masonry rubble when being processed. The initial tests showed a relatively high chloride content in the surface layers of the original concrete pavement. As expected the chloride content decreased in deeper layers. The chloride content of the mixture after crushing is shown in Fig. 6 compared with the maximum values in the surface layers. The author did not exclude in his report, Schulz (March 1988) that singular particles with high chloride content could cause a certain corrosion risk for the imbedded steel if these particles come into contact with the reinforcement. The secondary constituents and contaminants were neither disapproved by the investigating institution, BAM (1989), nor by the permission authority. The case license just demanded that concrete with recycled aggregate must comply with DIN 1045. The material should not be used for higher strength classes than C 20/25. Additionally it was planned not only to perform conformity control but also to research the development of several properties during a longer period. The results should be compared with similar constructions of the same age with normal concrete. This information would be helpful for future general permission procedures.

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After the fall of the Berlin wall the raw material supplies in Berlin and the landfill areas have changed so completely and so rapidly for the better that politicians stopped the project just before it had begun. The license is fixed to this project. Though the suitability of the recycled aggregate has been proved, it is impossible to use it for a different project without performing a new permission procedure. Whether the project will be continued or not just depends on political decisions. At the end of 1992 leading politicians announced to start this project again, but until now nothing has happened. 6.2 Pavement blocks After two years of development the concrete block manufacturing of Kronimus AG in Iffezheim started in 1991 a production of blockstones which contain about 30% recycled aggregates. The aggregate is recycled from the companies’ own production rubble and from exchanged old blocks. The company guarantees to produce blocks according to the standards with uniform high quality. Meanwhile this idea has been adopted by other companies for different products as well (for example drain blocks). 6.3 Concrete pavement At the moment a 17 km section of the A 27 highway in northern Germany is beeing renewed by using recycled aggregates. The pavement is cast in two layers. Only the first layer contains crushed old concrete. The upper (thickness: 7 cm) is cast fresh in fresh with normal concrete. The recycled rubble was recovered from the old pavement. Only particle sizes above 10 mm will be reused. 45% of the whole aggregate is recycled concrete. 7 Conclusions The visible scarcity of natural raw material is forcing the concrete manufacturers to handle these resources with care. Considering this, the kind and quality of the aggregates should be chosen based on the actual requirements of each purpose. By doing this there will be better chances to preserve valuable gravel and rock for more exacting purposes. On the other hand natural aggregates with lower qualifications and recycled material shall be used wherever they meet the requirements. Scientific research and experiences abroad showed that recycled aggregate can be reused as concrete aggregate in principle. More pilot projects are necessary in our country to extend experiences and to override the formal restrictions. As a first step it should be allowed to use a quantity of 10 to 20% of coarse recycled material for concretes with reduced requirements, since the influence on concrete quality is slight, Rahlwes (1991). From a technical and economical point of view the use of crushed concrete and masonry as concrete aggregate will be the maximum level of reuse. This is the best way to approach the ideal of closed-loop-system and that is why it is most desirable. At last a note of warning. All of the substitutes for sand and gravel must not be only suitable for concrete but also have to fulfill environmental requirements and may not

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cause any risk for health. Concrete may not be abused as a waste disposer. Otherwise, we will certainly have some more problems. 8. Literature Schulz, R.-R., Wesche, K.: Recycling von Baurestmassen—Ein Beitrag zur Kostendämpfung im Bauwesen. Forschungsbericht gefördert durch das Bundesministerium für Raumordnung, Bauwesen und Städtebau. RWTH Aachen, Aug. 1986, IRB-Verlag. Schulz, R.-R.: Eignungsprüfungen an Zuschlägen aus aufbereitetem Bauschutt für das Pilotprojekt Nonnendammallee 8, Berlin. Prüfungsbericht des Instituts für Baustoffprüfung, Waldkirch, March 1988, im Auftrage des Senators für Bau- und Wohnungswesen, Berlin. Schulz, R.-R.: Concrete with recycled rubble—developments in West Germany. Proceedings of the Second International RILEM Symposium on Demolition and Reuse of Concrete and Masonry. Nihon Daigaku Kaikan, Tokyo, Japan, Nov. 7–11, 1988, Volume 2, pp. 500–509 Rahlwes, K.: Recycling von Stahlbeton- und Stahlverbundkonstruktionen. Ansätze zu einer umweltökonomischen Bewertung. Deutscher Betontag, Berlin, 1991. CUR-rapport 125: betonpuingranulaat en metselwerkpuingranulaat als toeslagmateriaal voor beton. Civieltechnisch centrum uitvoering research en regelgeving (CUR), NL, Gouda, 1986 Stichting voor onderzoek, voorschriften en kwaliteitseisen op het gebied van beton (CUR-VB): Aanbeveling 4: Betonpuingranulaat als toeslagmaterial voor beton. Aanbeveling 5: Metselwerkpuingranulaat als toeslagmaterial voor beton. Zoetermeer, november 1984 (CUR-rapport 125). Mergelsberg, W.: Wirtschaftliche Situation und Zukunftsaspekte der deutschen Kiesund Sandindustrie. In: Steinbruch und Sandgrube (1989), No. 12, pp. 758–761 ZTV Beton-StB 91 (Zusätzliche Technische Vertragsbedingungen und Richtlinien für den Bau von Fahrbahndecken aus Beton): Forschungsgesellschaft für Straßen- und Verkehrswesen Köln; Edition 1991 BAM (Bundesanstalt für Materialprüfung): Prüfungszeugnis No. 2.1/22673/1, Prüfung von Recycling-Material als Betonzuschlag, im Auftrage des Senators für Bau- und Wohnungswesen—H IX -, Berlin, 30 June 1989 Moser, F.: Zum Einfluß des Saugverhaltens von Recycling-Zuschlägen aus Abbruchbeton auf die Eigenschaften eines damit hergestellten Konstruktionsbetons. Diplomarbeit, Technische Fachhochschule Berlin, 1991

PART THREE PRESENTATION OF THE WORK DONE BY RILEM TC 121-DRG

11 REPORT ON UNIFIED SPECIFICATIONS FOR RECYCLED COARSE AGGREGATES FOR CONCRETE A.HENRICHSEN Dansk Beton Teknik A/S, Copenhagen, Denmark Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract At the first meeting of TC-121-DRG, September 1989, it was decided to form a task force with the following terms of reference: Prepare Technical Recommendations leading to * Guidelines for production of concrete with aggregates of recycled concrete and masonry * Guidelines for demolition and processing of demolition waste with respect to the reuse of concrete and masonry. The task force decided that the first objective should be given highest priority and it is the result of this work which is presented in the present draft of guidelines for the use of recycled demolition rubble as aggregates in concrete. The work in the task group has taken its basis in the following European drafts and national documents: - Eurocode 2 - Danish Concrete Association; Recommendations for the Use of Recycled Aggregates for Concrete in Passive Environmental Class. - CUR Recommendations 4 and 5 for the use of crushed concrete rubble and crushed masonry rubble respectively as aggregates in concrete. - CUR Report 125; Crushed concrete rubble and masonry rubble as aggregates for concrete. - Belgium draft for a guideline for reuse of building and demolition waste as aggregates in concrete for buildings and civil engineering structures. The task force document gives the framework for a RILEM guideline dealing with recycled coarse aggregates for concrete. It is presumed that the sand fraction of the

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concrete is composed of materials meeting traditional, national specifications for this constituent. Consequently, recycled fines may be used as substitute for all or part of the traditional sand as long as the above mentioned material specifications are complied with for the total sand fraction. The guidelines are prepared as an attachment to Eurocode 2 and specifies the requirements to three types of aggregates; - Type I aggregates which are implicitly understood to originate primarily from masonry rubble. - Type II aggregates which are implicitly understood to originate primarily from concrete rubble. - Type III aggregates which are implicitly understood to be a combination of primary raw materials and recycled aggregates of type I and II. In addition to the specifications for the aggregates the guideline indicates the fields of application of the different types of concrete with recycled aggregates in terms of environmental exposure class and strength class. As a conclusion of the guidelines the design values to be adopted for the different types of concretes are defined in relation to the type of aggregate which is used.

12 DEMOLITION AND REUSE FOLLOWING DISASTERS C.DE PAUW Belgian Building Research Institute, Brussels, Belgium Demolition and Reuse of concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon. 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7 Abstract In 1989 the RILEM technical committee TC-121-DRG was established. One of the Task Forces of this TC had as terms of reference the elaboration of a state of the art report dealing with the demolition of structures and reuse of demolition waste following disasters. This paper presents the essential issues, which were brought together by the members of this committee, concerning damage assessment and classification, demolition of damaged structures and recycling of debris as part of an integrated disaster relief. Keywords: Damage assessment and classification, site-clearing, demolition, recycling, integrated disaster relief.

1 Preface In the early eighties, the RILEM technical committee “TC-37-DRC Demolition and Recycling of Concrete” was established. During the work of this committee, which was concluded by the end of 1988, it became evident that the field of demolition and reuse of building materials contains some very interesting aspects with consideration to many problems in connection with rescue operations, site clearance and rehabilitation of urban areas overtaken by disasters. Disaster relief got more attention when on 11 December 1987, the UN General Assembly declared the 10-year period 1990–1999 the “International Decade of Natural Disaster Reduction (IDNDR)”. At the end of 1988 UNESCO and the Secretariat of RILEM discussed the possibilities of co-operation concerning earthquake disaster relief in relation to the earthquake in Armenia. On the basis of the work in TC-37-DRC a new RILEM technical committee was established in 1989 i.e. “TC-121-DRG Demolition and Reuse Guidance”. At the first meeting of the committee in Copenhagen, September 1989, it was decided to establish two task forces to cope with the objectives of the Technical committee. The starting point

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to set up the Task Force 2 was the idea to set up, an intervention team that could, with its expertise in the field of demolition and reuse, assist rescue teams for example in cases of post-earthquake interventions. The objective of Task Force 2 was to prepare a Stateofthe-art-report on site clearing and demolition of damaged concrete structures with respect to the reuse of concrete and protection of the remaining structures. Special emphasis was to be put on earthquakes and war damaged structures. 2 Integrated disaster relief In accordance with The World Bank’s terminology [4], disasters basically include all occurrences, natural or technical, resulting in damages to local communities to such an extent that outside help is required. The disaster concept is normally associated with typical natural disasters, e.g. earthquake, flooding, volcanic eruption, etc. In addition there are medical disasters (epidemics) and man-made technological disasters, such as armed conflicts, air crashes and industrial disasters. The demand for disaster assistance and relief is global, and the demand is much more comprehensive and long-term than the one for emergency human rescue teams. There is a great demand for assistance, especially preventive and mitigating measures, but also for demolition, rehabilitation and reconstruction. The need is very differentiated, depending on the actual character of the disaster and the geographical position. In order to give effective disaster assistance it is necessary to look at the assistance as an integrated entirety based on co-operation across professional and political believes. The concept of disaster assistance can be divided into 5 phases as shown here below (fig. 1). The phases mentioned are completely differently structured, regarding both financing and management.

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Fig. 1: Five phases of disaster assistance [5]

In the post disaster period the task of the building and construction engineer is very differentiated and its importance is often underestimated. It is accepted that immediately after the event the priority is to get the survivors and dead bodies out as soon as possible. Heavy machinery, normally used for demolition and site clearing, and experienced engineers are very useful for the act of rescue work. The machinery is needed for lifting and aiding pedestrian rescue workers. As soon as the rescue phase has come to an end, the site clearing process has to start. Priority has to go to the rehabilitation of lifelines and the restoration of the infrastructure (opening of blocked roads, installation of emergency bridges, etc.). Another important task for the building engineers in this stage is the damage assessment work. As soon as possible buildings should be inspected and classified as to whether they should be demolished, rehabilitated or sustained no damage. This avoids further victims due to uncontrolled reuse of damaged dwellings, and improves the speed with which the demolition and site clearing process can start and thereby the recovery of the region. It is vital that the demolition and site clearing phase will not start before the rescue phase has completely ended, because no risk of injuring trapped people or covering of dead bodies will be accepted. The final step will concern the reconstruction. Here it is very important to consider the feasibility of recycling the debris. In the post-disaster period large quantities of debris are

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to evacuate. At the same time, however, there is an enormous need for building materials for the reconstruction. In all these post-disaster activities a good co-operation between local, national and international authorities and organisations is necessary. And because the relief activities interfere on different levels there should also be a good information interchange and continuity between the different activities. In accordance with the terms of reference of the Task Force 2 of TC-121-DRG the three dependent and successive activities: damage assessment, demolition and recycling, will be discussed further in this paper in detail. 3 Damage assessment and classification 3.1 Significance After a large scale disaster like an earthquake many relief activities are developed. To make the transportation of personnel, relief goods and material into the area possible, the rehabilitation of the infrastructure is very important, and should occur as fast as possible; blocked roads should be opened, emergency bridges installed, bridges repaired, etc. Another main concern after a disaster with many casualties is that essential facilities as hospitals and medical organisations, police and fire departments, are put into service again. A thorough damage assessment will be necessary and these facilities will get first priority for inspection. Last but not least is the problem of housing. Many houses are damaged or have collapsed and homeless people are searching for shelters. Uncontrolled reuse of dwellings can augment the amount of victims, due to building collapse caused by aftershocks or inhabitancy, and can obstruct certain relief activities. To avoid the uncontrolled reuse of buildings it is very important that the buildings are examined as soon as possible and that the entry to hazardous dwellings is prohibited. An estimation and quantification of the actual damage is not only for the aforecited reasons required but further also necessary to: (a) prepare quick repair guidelines to enable the structure to be placed back in service, providing the population with shelters. (b) take decisions about repair, demolition and reconstruction. (c) take decisions about financial relief and financial responsibility. (d) give an idea of the amount and kind of waste which is of interest for a well grounded policy of site clearing, recycling and new construction. (e) develop new design guidelines and methods by statistical processing of the collected data. Since the technical expertise of the persons entrusted with the investigation of the damage affected by a disaster will inevitably cover a very broad range, inspection should be carried out by a unified method or, at least, a standard approach concerning the question of assessing the extent of damage to structures. This method will be summarised in a manual that will guide the surveying engineer in the field and will contain

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assessment, classification and posting guidelines as well as an appropriate survey form. 3.2 Assessment strategy The major problem for a quick damage assessment of dwellings after a disaster is, that trained, experienced manpower will be in short supply. Even with the assistance from outside the area and the help of many volunteers, there is normally much more work than can be handled by the available staff. A good assessment strategy that takes account for this is the three level evaluation system developed by the Applied Technology Council [8], which contains the following evaluation stages: (a) Rapid Evaluation: This is the first level of evaluation and its aim is to make a quick safety and usability evaluation, based on primarily externally visual conditions. The inspection procedure takes about 10 to 20 minutes per building. (b) Detailed Evaluation: This second level is used to evaluate the damage of buildings whose conditions are still doubtful after the Rapid Evaluation. It consists of a thorough visual examination of the entire building, inside and out, particularly its structural system. This assessment level collects more information about the building, which can be used to make a decision whether to repair or whether to demolish and replace the construction. The inspection takes 1 to 4 hours per building. (c) Engineering Evaluation: Whenever a building has been damaged to such an extent that it is not possible to use visual inspection techniques alone an Engineering Evaluation is required. This assessment level uses more sophisticated, partly destructive, examination techniques, must be ordered by the owner of the building and takes several days. These are the reasons why this level is not considered as being part of the real emergency relief activity. Concerning this assessment level valuable information is given in the CEB report “Diagnosis and Assessment of Concrete structures” [1]. 3.3 Survey forms and manuals Regarding the damage assessment there are two major requirements: quickness and reliability. Although the Rapid and the Detailed Evaluation level have a different aim and use a different skilled assessment team, this can be met for both by the use of suitable survey forms and efficient manuals. In developing the form it is important to decide how much and which information is required. The more detailed is the analysis (and the more information is taken in account) the more reliable may be the results. However, a great number of parameters to be considered during the survey involves a lot of time and expenditures. This choice depends of course on the objectives of the assessment, so will the Rapid Evaluation need an easier and a more compact form than the Detailed Evaluation. To obtain objective and reliable information, and to make the survey repeatable and checkable, an instruction manual has to exist. Developing a universal manual might be impossible because it will be influenced by different local ethnic, cultural, politic and economic conditions. However, the manual should contain guidelines about three main subjects:

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(a) guidelines how to make the damage assessment: where to look, and how to fill in the forms. (b) guidelines how to classify the damage in different levels in accordance to some qualitative and/or quantitative parameters. (c) guidelines about the posting system being used and how to post the building. 3.4 Damage classification Once the degree of damage of the construction elements has been locally assessed during the Detailed Evaluation, attention must be paid to the effect on the construction as a whole. At this stage the surveyed construction should be classified according to a proposed damage classification system. This classification will not only give a usability and safety information; but it will also be a major index for later decisions concerning repair, demolition and reconstruction. Damage classification information together with detailed data about the event and the structural system, size and function of the

Table 1. Classification of the damage rate for reinforced concrete structures [3]

Damage Characteristics of rate damages

Judgement by the settlement S (m) of the building

Judgement by the tilt angle θ (radian) of the building

Judgement by the damage rate of the building

Slight

Some parts of nonbearing walls have cracks. Some parts of girders, columns and walls have visible cracks.

Crack widths are so small that it is difficult to recognise them with the naked eye (crack width is under 0.2 mm).

Small

Non-bearing walls have cracks. Girders, columns and walls have visible cracks, and some members partially have substantial cracks.

S≤0.2

θ≤0.01

Clearly visible cracks can be seen with the naked eye (crack width is between 0.2 and 1 mm).

Medium

Many columns and walls show remarkable shearing or bending cracks, and many members have partial shearing damage and buckling in axial reinforcing bars.

0.2<S≤1.0

0.01<θ≤0.03

Comparatively large cracks form, but fallen off concrete is not substantial (crack width is between 1 and 2 mm).

Demolition and reuse following disasters Severe

Main bearing walls are broken, and the axial reinforcement of columns is exposed by buckling, while the structure is not collapsed.

Collapse Many columns and walls are fallen off and have failed due to buckling of axial reinforcing bars. The building is totally or partially collapsed.

S>1.0

137

0.03<θ≤0.06

The number of large cracks (more than 2 mm) and fallen off pieces of concrete is severe, reinforcement is exposed.

θ>0.06

Reinforcement bars are buckled and internal concrete of reinforcement is crushed, Deformation along the vertical direction of the columns (or bearing walls) can be seen at a glance. The settlements and tilts of building can be a feature of collapse. In some cases, reinforcement is broken.

buildings can also be used for statistical analyses that can lead to new seismic design guidelines and methods. In the literature many different damage classification systems are found, varying in the kind of classification guidelines and the amount of classification levels. Most of the time they are also written in terms of the aim (e.g. repair) they were developed for. There are two kinds of classification criteria respectively based on qualitative and quantitative judgement. Quantitative judgement is based on a precise range of values that some objective and measurable quantities take on (width of cracks, settlement, tilt angel). Qualitative judgement is based on a visual assessment only, which makes a quicker evaluation possible, but will be more influenced by the judgement of the damage inspector. Most classification systems, however, use a combination of both criteria. The quick usability assessment [8] uses three classes: safe, unsafe and doubtful. The Detailed Evaluation will give more information about the damage condition of the structure, and will generally use five or six classification levels. An example of a classification system for reinforced concrete buildings is proposed by the Japanese Ministry of Construction [3]. It classifies the damaged buildings in five damage degrees (table 1). 3.5 Posting of the building A major task for the survey team is to inform the civilians about the condition of their dwellings, the surrounding buildings, the lifeline facilities (gas, water, electricity) and the safety of the area. It can reassure the people about the safety of their houses and can avoid further victims by uncontrolled reuse of damaged buildings. An important tool for doing this, is posting the building after the assessment and barricade dangerous areas.

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A three levels posting system is found the best choice and the most straightforward to use. A system that only uses the two posting possibilities, safe and unsafe, is found difficult or even impossible to use. The posting system proposed by ATC [8] uses the following three posting levels (Table 2).

Table 2. ATC posting system [8] Inspected/Safe Green

No apparent hazards found, although repairs may be required. Original lateral load capacity not significantly decreased. No restriction on use or occupancy.

Limited Entry Yellow Dangerous condition believed to be present. Entry by owner permitted only for emergency purposes and only at own risk. No usage on continuous basis. Entry by public not permitted. Possible major aftershocks hazard. Unsafe

Red

Extreme hazard, may collapse. Imminent danger of collapse from an aftershock. Unsafe for occupancy or entry, except by authorities .

Posting the building can be done by using placards or painted marks. In addition to the posting required for the building as a whole, there could also be need to designate certain unsafe areas, either inside or outside the building, as unsafe (e.g. if a falling hazard is observed like a badly damaged parapet). 4 Demolition of damaged structures 4.1 General New demolition and recycling techniques that have been developed in Japan and Europe in order to produce an efficient alternative to the traditional and often cumbersome methods of demolition should be considered more closely in relief work. The traditional methods normally involve little environmental regard when dealing with demolition and often the resulting debris is disposed in uncontrolled sites. The extent of recycling is minimal and the waste of potential materials is immense. As a basis for the choice of working methods for the demolition of damaged buildings and structures a special regard should be paid to the instability of the structure due to the damages. In general a variety of methods can be applied to the demolition of concrete: crushing, chopping, splitting, blasting with explosives or chemical agents, cutting and drilling The demolition techniques that can be used in the disaster scenario will depend on: the environmental risk (is the building close to collapse or is the building a link for spread fire), structural stability (is the collapsed building unstable) and the sensitivity (does the building contain expensive/important material or are the surroundings sensitive).

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4.2 Reuse of construction elements In connection with emergency housing shelters, it would be possible to use large portions of the element construction from damaged buildings to construct temporary housing with simple and rapid techniques. In this way the undamaged concrete elements can be reused. However, this depends on the accessibility to lifting equipment immediately after the earthquake. Heavy lifting machinery has highest priority for the rescue phase in connection with removing fallen members trapping survivors. 4.3 Coarse demolition The most common forms of large scale coarse demolition involve the mounted hammer, wrecking ball and the use of explosives. Dependent on the availability of the heavy machinery needed and the accessibility to the building in question, it is often relatively easy to decide upon the method to be used. For all types of coarse demolition, it is important that the building to be demolished is separated from the surrounding constructions. Crushing with a ball and chopping with a hydraulic harmmer or a manual hammer may have a serious impact on the structure and might cause danger to the working personnel and others due to risk of falling materials from unstable structures. Both techniques require experienced operators. However, these two methods are rapid and efficient techniques for the total demolition of buildings. If the building is severely damaged and there is difficult access for machinery and no sensitive surrounding buildings exist, then blasting may be considerably favourable. This obviously requires a qualified and experienced explosive engineer on site. Blasting of a building quickly eliminates the possibility of the building collapsing due to after-shocks, internal strength deficiencies or inhabitancy. With short preparation times, few days for planning, preparing and blasting, the total demolition is relatively rapid and does not risk labourers on or near the building with handhold equipment. Additionally this method is favourable since it requires minimal machinery, which is seldom available for demolition in the emergency relief phase. Supply of explosives, detonators and equipment may come direct from military supplies, although co-operation between contractors and the military engineers is favourable in order to share expertise. However, there will always be problems with the use of explosives in some countries since private use by contractors is not permitted, thus causing barriers for explosive engineers. Other possible barriers to the use of explosives involve the local populations fear of trapping survivors or dead bodies of loved ones by the collapsing of the building. The choice of demolition for total construction clearance after a disaster is heavily dependent on the available resources in the locality. 4.4 Partial demolition Partial demolition is carried out in connection with the rehabilitation of concrete structures that may be damaged. This may, for example, involve the removal of

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supporting beams for replacement. The number of techniques for localised removal or cutting of concrete are numerous and dependent on the accessibility, availability and work force skills. The elements to be replaced are cut from their surroundings and removed, making way for the replacement. In this way, if lifting equipment is available, it is possible to remove layer by layer of the either collapsed or severely damaged building. There are various methods of localised cutting the concrete and reinforcement bars, including mini-blasting, diamond saw, water jet and handhold hammers. The principal choice of methods is depending on the situation of the relief. In case of rescue operation or emergency relief, the time consumption and the impact on the structure will be the decisive factor. 5 Recycling of debris 5.1 Introduction On the basis of the European and American experiences it may be concluded that the present technical level of know-how in the field of recycling and reuse of building and construction materials is sufficient to implement these techniques into the continuous rehabilitation process that takes place in the urban areas of developed countries. Therefore, it is recommended to consider these techniques as integrated parts of Systems of Disaster Relief in the occurrence of disasters and urban development projects. From a purely economical point of view, recycling of building waste is only attractive when the recycled product is competitive with natural resources in relation to cost and quality. Recycled materials will normally be competitive when there is a shortage of both raw materials and suitable deposit sites. With the use of recycled materials, economical savings in transportation of building waste and raw materials can be obtained. This is especially apparent when there is a local combination of demolition and new construction, making it possible to recycle large amounts of building waste at the work site or in the vicinity (e.g. in an area heavily damaged by an earthquake). Assessment of the damage to the dwellings and the materials involved should be done as soon as possible to get an idea of the quantities of building waste and the needed extend of the recycling plant. In the literature only very few examples of recycling in connection with larger site clearing and reconstruction projects following a damaging disaster can be found. Two interesting projects are reported on in what follows. 5.2 El Asnam (Algeria) 1980, [2] The first example is a pilot project involving the recycling of building waste, undertaken by the Belgian Building Research Institute with support of the Belgian government, after the earthquake in El Asnam in October 1980. After the earthquake the Algerian authorities made a thorough investigation of no less than 6.538 constructions. The investigation was performed by 100 engineers over a two

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month period. On the basis of the damage reports, the evaluation of the traditionally used quantities and kinds of materials and air photographs, it was possible to get a picture of the quantities of debris and of the places where they were located. The most suitable demolition techniques for El Asnam, appeared the use of explosives. However, considering the fact that many buildings were again occupied and that in the devastated districts slums were erected, the use of explosives was prohibited. Thus considering that the demolition would be performed using limited technical possibilities it was expected that about 700.000 tons of debris could be recycled, i.e. the output over 1 year of 3 recycling plants. Due to the poor quality of the rubble structural recycled concrete was not advisable. So it was decided to recycle the debris into building blocks, as such it was possible to cope with the lack of selective demolition. Debris unsuitable for recycling into building materials could still be used for the restoration and strengthening of riverbanks. One of the conditions for the acceptance of recycling was anyhow that it could be demonstrated that with the average debris (i.e. without having to take too many precautions as to the separation of the different components) in local working conditions with “normal” means (breaking facilities and block making machines) it would be possible to produce blocks of an acceptable quality, i.e. of about the same quality of the traditional building blocks made from natural aggregates. A pilot recycling plant was set up. The debris used in the demonstration project were what could be called the worst possible. Recycled building blocks were made under local conditions (i.e. heavy sunshine), with local production means and local workers. Drying occurred during sunshine and dry wind and regular water spraying as is usual in these areas. This procedure was chosen in order to reach the absolute minimum strength of the blocks. The results were compared with reference blocks based on natural aggregates and produced in the same conditions. The obtained results were very convincing and proved that it was indeed feasible to recycle the debris as aggregates in concrete. However, although realistic the project was halted because of political and mainly for sociological reasons, i.e. opposition of the local people to use debris under which some of their beloved have died as a construction material. 5.3 Leninakan (Armenia) 1988, [9] The second example concerns the installation, by the German Red Cross, of crushing plants in connection with the clearing and reconstruction work after the Armenian earthquake from December 1988. After this heavy earthquake, which caused 25.000 casualties and more than half a million roofless people, the German Red Cross ordered the installation of a recycling plant for debris, for the suffering region of Leninakan. The local conditions for installation were very difficult: 1600 meter altitude, strong winters, hot summers and heavy rainfall in spring and autumn, bad roads and transport conditions, insufficient water and electricity supply, etc. Another fact was that most of the debris—at the time of arrival of the recycling plant—was already transported and temporarily disposed. This means that the building debris was mixed with all kinds of waste going from household equipment to dead pets.

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A particular problem was the transport of the installation to Leninakan. The installation was transported by plane, with a Soviet Antonov An-124, to Eriwan. In January 1990, after an immobilisation in Eriwan, everything was transported by trucks to Leninakan, 150 km away. Without sufficient lifting machinery and with a lack of skilled local workers the German team managed the installation in seven weeks, and handed the installation to the Armenian authorities on 15 May 1990. One German stayed stand-by for the maintenance of the equipment. The installation designed for 120 t/h reached a capacity of more than 200 t/h and worked with no major problems. The produced construction material was primarily used for roadwork. 6 Conclusions The importance of construction engineers in the post disaster relief activities is obvious. Damage assessment and classification, demolition and recycling of debris are accepted as being an important part of the post disaster rehabilitation processes. Although the necessary know-how is available, the work in the field often meets to many political, social and economical barriers to be very successful. Therefore, it is time to discuss these problems on an international level to achieve an international agreement on an integrated disaster relief. In accordance with well-known medical relief organisations as the International Red Cross or the Médecins Sans Frontières, it should be considered to set up an international intervention team of construction engineers that can interfere immediately after a destroying disaster. 7 Acknowledgements This contribution has been drawn up on the basis of the state of the art report on demolition of structures and reuse of demolition and construction materials following disasters, elaborated by the members of the Task Force 2 of the RILEM TC-121-DRG: S.Buchner, Ph.D. Gifford & Partners Ltd., England H.Joynes, Ph.D. Joynes, Pike & Associates Ltd., England Y.Kasai, Professor Nihon University, Japan E.K.Lauritzen, DEMEX Consulting Engineers, Denmark J.Vyncke, BBRI, Belgium. C.De Pauw, BBRI, Belgium, Chairman TF2. The contribution of the individual members of the Task Force in compiling the report is greatly acknowledged. 8 References [1] CEB, “Diagnosis and assessment of concrete structures”, State-of-the-art report of the ‘Comité Euro-International du Beton’, Information bulletin N°192, Lausanne, January

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1989. [2] De Pauw C., “Recyclage des décombres d’une ville sinistrée.”, BBRI Bulletin N°4, December 1982, Belgium. [3] Kasai Y., “General statements of the present condition of the seismic disaster reduction and its countermeasures in Japan.”, Nihon University, September 1991, RILEM-121-DRG Task Force 2 report. [4] Kreimer A. and Munasinghe M., “Managing natural disasters and the environment”, Environment Department, World Bank, Washington, 1990. [5] Krimgold F., “Pre-disaster planning”, Vol. 7, Department of Architecture, KTH Stockholm, Sweden, 1974. [6] Lauritzen E.K. and Petersen M.B., “Demolition of damaged structures”, January 1993, RILEM-121-DRG Task Force 2 report. [7] RILEM TC-121-DRG, “State-of-the art report on demolition of structures and reuse of demolition & construction materials following disasters.”, 1993. [8] Rojahn C., ATC-20 report; “Procedures for post-earthquake safety evaluation of buildings”, 1989, Applied Technology Council, Redwood City, California. [9] Steinforth H., “Baustoff—Recyclinganlage in Leninakan”, Baustoff Recycling+Deponietechnik 2/91, April 1991.

PART FOUR RECENT DEVELOPMENTS IN DEMOLITION TECHNIQUES

13 EXPERIENCE GAINED IN DISMANTLING OF THE JAPAN POWER DEMONSTRATION REACTOR (JPDR) M.YOKOTA, Y.SEIKI and H.ISHIKAWA Japan Atomic Energy Research Institute, Tokai-mura, Japan Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract Actual dismantlement of the Japan Power Demonstration Reactor (JPDR) has been carried out since 1986 using the dismantling techniques developed in the Japan Atomic Energy Research Institute (JAERI). Highly activated components such as the reactor internals, the reactor pressure vessel (RPV), and activated inward surface of the biological shield concrete have been removed using remotely operated tools to prevent radiation exposure of workers. The actual dismantling of the JPDR is proceeding satisfactorily. These dismantling activities, especially dismantling of the biological shield concrete is described in this paper. Keywords: JPDR, Decommissioning, Arc saw, Water jet, Controlled blasting.

1 Introduction There are 42 nuclear power plants with approximately 33,400 MW electricity generation as of December 1992 in Japan. However, some of these nuclear power plants are expected to terminate their duty life in the near future. Based on the national policy of the decommissioning for the nuclear facility, the decommissioning program of the JPDR has been performed by the JAERI under a contract with the Science and Technology Agency. The objectives of the program are to develop the dismantling technology applicable to the decommissioning of nuclear power plants and to get the knowledge and experience for reactor decommissioning through the actual dismantlement of the JPDR. By the end of December 1992, almost activated and contaminated components were dismantled, and more than 99% pf total radioactivity was removed from the JPDR site. During the dismantling activities, the highlight was dismantling highly activated components such as the reactor internals, the RPV and the biological shield concrete

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using newly developed dismantling techniques with remote operation. So far, the dismantling activities are in progress successfully, and various data on the dismantling activities have been collected and accumulated in the decommissioning data base. This paper describes the dismantling activities, the results of the data analysis and the obtained experience. 2 JPDR Decommissioning program The JPDR (BWR, 12.5 MWe) decommissioning program consists of two major phases. Phase 1, technology development, was started in 1981 to develop a set of various techniques needed for reactor decommissioning. In particular, considerable efforts were made to develop remotely operated cutting tools to minimize radiation exposure to workers in dismantling highly activated components. Table 1 shows the developed cutting tools. These were designed not only to dismantle the JPDR but also to take into consideration of the applicability to commercial nuclear power plants. Phase 2, actual dismantling of the JPDR, has been carried put since 1986 using developed dismantling techniques to demonstrate these techniques for the future commercial power reactor decommissioning. The primary considerations for the dismantling work are safety of workers and prevention of release of radioactive materials. So, a local ventilation system and dismantling machines with remote operation are used to minimize radiation exposure to workers. The activated components and structures were almost dismantled by September 1992. All buildings will be demolished and the site will be landscaped by 1994.

Table 1 Cutting techniques, ability and components to be dismantled by developed cutting tools

Technique

Components to be dismantled Cutting ability

Underwater arc saw

Reactor pressure vessel (RPV)

Underwater plasma arc Reactor internals

250 mm thick carbon steel in water 130 mm thick stainless steel in water

Rotary disc knife

Piping connected to RPV

12 inch, Sch 160 (stainless steel)

Shaped explosive

Piping connected to RPV

26 inch, Sch 80 (carbon steel)

Mechanical cutting

Biological shield

cutting efficiency: 1.3 m2 per hour

Abrasive water jet

Biological shield

450–600 mm thick reinforced concrete

Controlled blasting

Biological shield

Blasting efficiency: 0.1 m3 per hour

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3 Dismantling of reactor steel structures 3.1 Removal of reactor internals The reactor internals were removed by the two types of underwater plasma arc cutting systems, a master-slave robotic manipulator and a mast type manipulator. The masterslave robotic manipulator was used for handling the plasma torch to demonstrate and verify its newly developed robot technology. The plasma torch was operated in the most cases by the mast type manipulator having five degrees of freedom in movement. The system was controlled by a microcomputer to keep constant angle, elevation and distance between the torch and the reactor internals being cut. The cutting work and torch positioning were monitored with four TV cameras installed in the RPV. The cutting process was basically divided into two steps to perform the cutting work efficiently. First, the reactor internals were cut into large pieces then cut into smaller pieces suitable for packing into shielded storage containers. Table 2 shows the cutting conditions and results of the plasma torch. A miniaturized TV camera was effective to monitor the underwater cutting work because it could be installed in a narrow space in the RPV. Although the camera has to be placed away from the highly activated cutting object in some cases, the cutting work was performed successfully using its zoom functions.

Table 2 Cutting conditions and results of the plasma torch Cutting current

500A

Voltage

170 V

Gas f low

Ar+H2 50 (30+20) 1/min

Cutting length (MAX)

2500 mm

Thickness of cut (MAX)

110 mm

Cutting time (MAX)

1410 sec

To prevent the spread of airborne contamination, a green house was installed over the working area. To further contain radioactivity, aerosols and gases were collected by an air curtain positioned above the water. Almost no increase was detected in the concentration of radioactivity at the upper part of the air curtain. Figure 1 shows the typical concentration of radioactivity in air during cutting. Although the hydrogen concentration at the collecting line increased when cutting began, the measured hydrogen concentration was less than 0.02%. Fig. 2 shows the hydrogen concentration during cutting of core shroud. The water was filtered by a 0.5 µm mesh when the cutting work was completed, but the concentration of radioactivity in the water in the RPV could not be reduced.

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Consequently, the water was passed through an ion exchanger. This reduced the concentration of radioactivity under the limit of detection.

Fig. 1 Typical concentration of radioactivity in air during cutting (Core shroud)

Fig. 2 Typical hydrogen concentration during cutting of core shroud

3.2 Dismantling of RPV After removing the reactor internals, the RPV was dismantled using the underwater arc saw cutting system. Prior to dismantlement, a water tank was installed in the narrow gap

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between the RPV and the biological shield to allow the RPV to be submerged in water while being cut. The rotating saw blade of the arc saw cuts steel structures vertically and horizontally along a predetermined cutting pattern. The system was remotely operated from a control room located outside the reactor enclosure. The RPV was cut vertically and horizontally into 65 pieces. The pieces were about 60 to 90 cm by 75 to 85 cm. The cutting speed was 0.2–0.5 mm/s at the top flange portion of the RPV, having a maximum thickness of 250 mm. Cutting speed for the remaining part of the RPV was 1 to 4 mm/s. Cutting work on the first row progressed slowly due to trial-and-error in control of the current supplied and the speed of advancement pf the saw blade. This difficulty was caused mostly by the width of the piece being cut. The first row was the flange portion of the vessel and had a maximum thickness. As the thickness of the material being cut increases, the arc current at the side wall of the saw blade increases. This causes a decrease pf proper arc current at the circumference of the saw blade. Therefore, cutting a very thick section takes a long time. After cutting the first row, the operator had the necessary skill to select the correct operating parameters for each cut. The remaining rows proceeded very smoothly. Figure 3 shows cutting characteristics of the arc saw cutting technique. As cutting progresses, the radius of the saw blade decreases. The total number of spent blades for cutting the RPV was twenty-four. A specially developed device was used to hold and lift the cut-off pieces. The pieces with high activity were stored in shield containers. Pieces with lower activation were put in 1 m3 containers. Dross generated during cutting was accumulated in a dross collecting saucer. Fine particles remaining in the water were collected by the cartridge filter. Figure 4 shows the flow diagram of dross collecting system.

Fig. 3 Cutting Characteristics of Are Saw Cutting Technique

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Fig. 4 Flow diagram of dross collecting system

4 Dismantling of biological shield concrete The JPDR biological shield is reinforced concrete that contains a number of cooling pipes and neutron detector guide tubes. The inner part of it, has been activated by neutron irradiation during reactor operation. Thus, a remotely controlled and powerful dismantling machine is required to remove the JPDR biological shield concrete. Some techniques were therefore developed in the early stage of JPDR decommissioning program. Figure 5 shows the structure of JPDR biological shield, applied techniques and measured dose equivalent rates. The upper part of the highly activated inward protrusion of the biological shield concrete was removed using the diamond sawing and coring system. The lower part of the highly activated inward protrusion of the biological shield concrete was dismantled using the abrasive water jet cutting system. The remaining lower activated concrete has been demolished using controlled blasting.

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Fig. 5 Stucture of JPDR biological shield concrete with measured dose equivalent rates

4.1 Dismantling by diamond sawing and coring system The system consists of the sawing and coring machine, the power unit, the controller, the concrete block handling device, the ventilation unit, the slurry treatment unit, etc. Two types of blades were used, cubic boron nitride (CBN) and diamond blades. The CBN blades are durable at high temperature and were introduced to enhance the cutting of the steel liner. Diamond blade were mainly used to cut the concrete and the reinforcing bars embedded in it. The cutting operation was controlled from the control room outside the reactor enclosure. Cutting speed was automatically controlled by keeping supply current constant. Figure 8 shows the dismantlement of the biological shield concrete using the diamond sawing and coring system. Figure 7 shows the average working time to cut and remove one block. Blocks and cores dismantled were lifted up to the service floor and put into the steel containers. The water mist and dust generated during the cutting operations were exhausted through the temporary dust collector system. The water used during cutting and the slurry generated were treated by the slurry processing system. Table 3 shows the radioactive waste produced by the diamond sawing and coring technique. The results obtained from the actual dismantlement using the diamond sawing and coring system are summarized as follows. (1) The sawing and coring system was installed easily and accurately. Dismantlement of the biological shield concrete proceeded as previously planned. (2) Modification of cutting plan after the mock-up tests extensively reduced the cutting

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time. (3) The perfonnance of the sawing and coring system is able to demolish biological shield concrete remotely without the spread of consequential contamination. After the removal of the upper portion, the remaining lower portion of the highly activated biological shield concrete was dismantled by the water jet cutting system.

Table 3 Radioactive waste produced by diamond sawing and coring technique

Material & Container

Produced Mass

Number of Blocks

9 Blocks (5.7 t)

Number of Cores

101 Cores (3.6 t)

Waste Water

104 t

Sludge

1.7 t

Number of Containers

3×3 m3 Containers

Fig. 6 Dismantlement of biological shield concrete using diamond sawing and coring system

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Fig. 7 Working time to cut and remove one block (Removed block size L1200×W400×H1200)

4.2 Dismantling by water jet cutting system The water jet cutting system cuts reinforced concrete and steel plate by directing a pressurized water jet containing steel grit onto the material being cut. The system consists of the cutting robot, the water jet generating unit, the abrasive supply unit, the lift assembly, the block bucket, the slurry treatment unit, the dust collector and the control system. The maximum water pressure is about 2000kg/cm2 and the water flow rate is about 50 l/min. Steel grit is used as the abrasive material. This was selected during the conceptual and mock-up tests conducted earlier. The size of the abrasive ranges from 0.7 to 1.0 mm in diameter. The nozzle traversing speed is 30 cm/min. The dismantling was done from the bottom to top of the lower protrusion of the biological shield concrete. The protrusion was divided into 7 rows and each row was divided into 15 or 16 blocks. A total of 102 blocks were removed during this dismantling work. The cutting depth was increased by repeating the cutting passes of the nozzle. Figure 8 shows the number of horizontal cutting passes for the fourth row. This figure indicates that these area of the conerete that contained reinforcing bars, cooling pipes, and neutron guide tubes requires a large number of cutting passes.

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Fig. 8 The number of horizontal cutting passes for the fourth row

In cutting work, an operator confirmed the cutting operation was satisfactory by observing the inside of the kerf with a TV camera. When detached, the blocks dropped into the block bucket. The block were transferred to the conditioning area where they were put into 3 m3 containers. The mist and dust generated during the cutting operation were treated by the dust treatment unit. The slurry produced was collected by the slurry treatment unit. The slurry was separated into abrasives, sludge, and waste water in the separatin tanks of this unit. After separation, the abrasive and sludge were mixed with cement. Most of this mixture was put into 200 liter drums where it solidified. The remaining mixture was used to fill the voids in the 3 m3 containers that contained the removed blocks. Table 4 shows radioactive waste produced by the abrasive water jet cutting system.

Table 4 Radioactive waste produced by abrasive water jet cutting system

Materials & Containers

Produced Mass

Removed Blocks

30 tons

Abrasive

35 tons

Sludge

7 tons

Waste Water

600 tons

3 m3

container

13

1 m3

container

3

200 liter drum

84

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The results obtained from this dismantling phase are as follows. (1) The biological shield concrete was dismantled successfully. However it was necessary to replace eight failed high pressure hoses and thirteen nozzles. (2) When reinforcing bar or cooling pipe was cut, partial scans of the nozzle were repeated until bar or pipe was cut completely. The TV cameras were effectively used to confirm the cutting results. (3) When compared with the mass of the removed blocks, a large and significant amount of secondary wastes were produced from this dismantling activity. In the future it may be necessary to develop methods to reduce the quantity of secondary wastes. 4.3 Dismantling by controlled blasting The highly activated portion of the biological shield concrete was dismantled by remote operation using the diamond sawing and coring system and the water jet cutting system. As a result of these operation, the dose rate in the cavity of the biological shield concrete decreased to 0.03 mSv/h or less, and it is possible to dismantle the remaining concrete manually. The controlled blasting has been therefore applied to dismantling the remaining portion of the biological shield concrete. This method utilizes a platform for dismantling work such as drilling and mechanical crushing, a contamination control envelope, a ventilation unit and a waste transporter. The potion dismantled using the controlled blasting was the inner portion of the biological shield concrete. The explosive was Urbanite, which is an improved form of Dynamite and has a relatively slow detonation velocity. The amount of explosives used for each blasting was determined using the empirical formula of Hawser and the data obtained from the mock up test. Figure 9 shows the conceptual diagram of vertical blasting. The planned blasting block size was about 2m in width, 0.4 m in depth and 1.8 m in height. To make the demolition easier and to control the demolition area within the planned volume, slits were cut to a depth of about 0.25 m at the boundary of each block scheduled to be demolished. Next, vertical blasting holes were drilled and explosives were charged in the holes, which were then sealed with tamped sand. The portion of the concrete shield undergoing demolition was covered with mats and sheets to prevent the scattering of debris and to limit the generation of airborne dust. After all workers evacuated from the reactor enclosure, controlled blasting was initiated using delayed detonators having ignition time intervals of 0.025 seconds. The remaining undetached concrete was fractured and f reed using a jackhammer. The exposed reinforcing bars were cut by an oxyacetylene torch.

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Fig. 9 Conceptual diagram of vertical charge blasting

Fig. 10 Relationship between the measured acceleration and the distance from the blasting portion

The radioactive waste generated by dismantling was packed in 200 liter drums and 1 m3 containers. These blasts were conducted two times a day on the.average. A total of 48 kg of explosives were used for blasting a volume of 76 m3 of concrete, which is much more than needed for the demolition of normal reinforced concrete. Table 5 shows the data on waste generation and blasting.

Table 5 Data on the dismantling work - data on waste generation weight of waste

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158

:

178.7 tons (concrete)

:

27.9 tons (metal)

:

708 (200 litter drams)

blasting volume

:

76.0 m3

blasting times

:

108

weight of explosives

:

48 kg (560 g/m3)

containers - data on blasting

The blasting noise level was measured at two points, the third floor in the reactor enclosure and at a distance pf 10 m from the blasting location outside the reactor enclosure. The maximum noise level was about 120 dB(A) in the band of 25–200 Hz in the reactor enclosure. Vibration due to the blasting was also measured at three points, 10, 15, and 30 m from the blasting point outside the reactor enclosure. The acceleration varied from 20 to 200 gal ( m/s2). Figure 10 shows the relationship between the measured acceleration and the distance from the blasting portion. The results obtained from the actual dismantlement using the controlled blasting technique are as follows. (1) The controlled blasting technique was successfully applied to demolishing the lowlevel radioactive portion of the JPDR biological shield concrete. The slits cut in the boundary were very effective in improving demolishment performance of the massive steel-lined reinforced concrete structure. (2) Because protection mats and sheets were used to cover the surface being demolished, the amount of airborne dust generated by the explosions was less than expected. (3) Shocks and vibrations generated by the explosions had no influence on the integrity of the components in the reactor enclosure and in the other facilities. The remaining portion of shield concrete will be efficiently dismantled using horizontal charge blasting. 4.4 Comparison between three methods Table 6 shows data related to the dismantling work for the biological shield concrete. The diamond sawing and coring technique and the water jet cutting technique both were able to remotely cut blocks from the planned location. In cutting by the water jet technique, the cutting slits were wider than those of the diamond sawing and coring system. Furthermore, since the nozzle had to be repeatedly moved over the same path to cut the embedded reinforcing bars, the cutting slits in the concrete were deeper than planned. This increased the production of sludge. The cutting speed of the diamond sawing and coring system was strongly influenced by the material being cut. For example, the blade traveling speed was slower for the steel liner and the embedded reinforcing bars than for concrete. Also, the coring procedure needed much time to bore adjacent holes at the back of the concrete blocks being

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removed. Generally, the cutting time per unit of weight of dismantled concrete needed by the diamond sawing and coring system was longer than the time needed by the abrasive water jet system. In addition, diamond sawing could not be used for the thick lead tubes covering the neutron detector guide tubes. However, the abrasive water jet cutting system cut the concrete, embedded reinforcing bars, and the lead tubes. This resulted in a higher cutting efficiency in total. Although the controlled blasting can demolish the reinforced concrete most effectively, it is not suitable for demolishing the highly activated shield concrete.

Table 6 Data related to the dismantling work

Cutting operation

:

Diamond sawing and coring

: Abrasive water : jet

Controlled blasting

Manpower expenditure

:

2,300 man-days

:

5,400 man-days

:

3,700 man-days

Radiation exposure

:

7.40 man-mSv

:

8.80 man-mSv

:

2.07 man-mSv

Duration

:

107 days

:

190 days

:

153 days

Cut blocks

:

9.3 tons

:

29 tons

:

200 tons

Cutting time

:

260 hours

:

120 hour

:

—

5 Management data Various management data on the dismantling work have been accumulated since the start of the JPDR dismantling. These data are stored in the decommissioning data base and used for future commercial power reactor decommissioning as well as for the management of JPDR dismantling activities. Typical management data collected during the JPDR dismantling activities are illustrated in Fig. 11.

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Fig. 11 APPENDIX:—Dismantling schedule, manpower expenditure, radiation exposure to workers, and decommissioning waste produced during JPDR dismantling activties (through September 1992)

(1) Manpower expenditure The cumulative manpower expenditure from the start of the dismantling through December 1992 was 77,000 man-days. During this period, approximately 45 workers per day and 140 workers at the peak time have been engaged in this dismantling. In the JPDR dismantling, the approximate job analysis consists of 21% for the supervising, 65% for the site work and 14% for the radiation control. The percentage of workers for dismantling of the biological shield concrete is found to be larger than that of other dismantling item. This high value resulted f from applying three kinds of dismantling techniques, diamond sawing and coring, water jet cutting and controlled blasting to accumulate reactor decommissioning experience. (2) Radiation exposure The cumulative radiation exposure to workers and maximum cumulative personal radiation exposure from the start of the JPDR dismantling through December, 1992 were 300 man-mSv and 9 mSv, respectively. Dismantling of the activated and/or contaminated components were almost completed, therefore the exposure to workers will not increase any more. The dismantling work accompanied with high-level radiation exposure was as follows: the decontamination of the spent fuel storage pool, the installation of the water tank for cutting the RPV, and the other preparatory work such as the installation of the remotely controlled devices. Since the highly activated components such as the reactor internals, the RPV and the biological shield concrete were dismantled remotely, the cumulative radiation exposure to workers during the cutting work for these components was found to be less than those for preparatory work. (3) Radioactive waste

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The cumulative amount of the solid radioactive waste as of Dec. 1992 was 1800 tons. Various types of containers have been used for storage of the radioactive waste during the decommissioning of the JPDR. Selection of the type of container is based on the material, size and radioactivity of the waste. High level radioactivity waste was placed in shield containers which have different wall thickness. As of December 1992, 34 shield containers, 43×3 m3 containers, 438×1 m3 containers and 4083×200 liter drums were used for the storage of the solid radioactive waste. These containers have been transferred to the new radioactive waste storage building in the JAERI site. 6 Concluding remarks The JPDR decommissioning program is proceeding satisfactorily without any problems about safety, radiological and environmental matters. Various cutting tools with remote operation developed in the early stage of the program have been applied successfully in dismantling the highly activated components such as the reactor internals, the RPV and the biological shield concrete. These techniques were proved to be useful to minimize the radiation exposure to workers and to prevent contamination. The wide variety of the results obtained through the JPDR dismantling are expected to make a valuable contribution to decommissioning of commercial power reactors.

14 BLASTING DEMOLITION OF SIX-STOREY REINFORCED CONCRETE APARTMENT BUILDING (Part 1: Experimental blasting of reinforced concrete components)* K.KUROKAWA NOF Corporation, Aichi, Japan T.YOSHIDA Housei University, Tokyo, Japan T.SAITO All Japan Association for Security of Explosives, Tokyo, Japan M.YAMAMOTO Asahi Chemical Co. Ltd, Tokyo, Japan S.NAKAMURA Nihon Carlit Co. Ltd, Yokohama, Japan Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract In anticipation of increased demand for effective blasting demolition of urban structures, the Ministry of International Trade and Industry determined that there was a need to establish technological safety standards for the use of explosives, and entrusted this task to the All-Japan Association for Security of Explosives in fiscal year 1987. The Committee for Blasting Measures for Demolition of Urban Structures was established by the association, and in 1988, the blasting demolition of a six-story reinforced concrete apartment building was carried out. As preliminary experiments prior to actual demolition work, certain columns, walls, and beams comprising the structural body of the apartment building were blasted. The fragmentation effect, vibration, noise, fly rock, etc., resulting from the blasts were measured using instruments. This report constitutes the first of three reports with the same title, and it

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163

describes the siting of the building, gives a summary of the building, and presents the results of these preliminary experiments. Keywords: Demolition, Blasting, Explosives, Reinforced concrete, Fragmentation, Vibration, Noise, Fly Rock.

1 Building location The building selected for this test of blasting demolition was Apartment Building No. 40 at the defunct Takashima Coal Mine of Mitsubishi Coal Mines Co., Ltd. located at Takashima-machi, Nishihitsuki-gun, Nagasaki Prefecture. Figure 1 is a location map of Takashima island. Takashima is located off the Nagasaki Peninsula in Nagasaki Prefecture, and is shaped roughly like an inverted triangle about 2.1 km from south to north and about 1 km from east to west. The highest elevation is Gongen-zan mountain in the center of the island, which rises to about 115 m; there is an observatory near the summit which served as an observation point for visitors at the time of the experiment. Takashima-machi consists of Takashima and Hajima, an island in the waters southwest of Takashima, and was known as the cradle of the Japanese coal industry. The pits, however, became defunct in October 1986. The population of the island at the time of the experiment was about 900, mostly dwelling along the eastern coast of Takashima, and there were about 40 apartment buildings for mine workers in close proximity to each other. Of these buildings, Apartment Building No. 40 was selected as the demolition specimen. It is situated at an elevation of about 70 m, the highest of these buildings, and there are sparse woods and grass-covered slopes to the south and west. The slopes continue upwards to the observatory at Gongen-zan, 200 m to the west. To the north, an old people’s home, the only building needing to be secured, is situated a horizontal distance of 50 m away. It is 10 m below the long side of the building, at the bottom of a cliff. To the east, Apartment Buildings No. 38 and No. 39, which are of the same construction as the specimen, are situated about 20 m away. These buildings are uninhabited. Figure 2 shows the surroundings of the building. 2 General appearance of the building This apartment building is a six-story rigid box-frame type of reinforced construction with 36 rooms, and was constructed in 1961. It is 36 m on the long side, 8 m on the short side, and 18 m in height. Figure 3 shows the west elevation, Fig. 4 the north elevation, and Fig. 5 is a photograph showing its outside appearance. There are six apartments on each floor and three sets of stairs each sandwiched between two rooms, as shown in Fig. 6.

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Fig. 1 Map of Takashima Island

The structural characteristics of the building are summarized below. (1) As the building is of six-story rigid box-frame reinforced concrete construction, there are more walls than in an ordinary rigid frame reinforced concrete structure, with about 17 cm/m2 in the span direction (12 cm wall thickness) and about 12 cm/m2 in the girder direction (15 cm wall thickness). In particular, the three stair halls—including the C4 wall columns—are important from the point of view of the overall strength of the building (refer to Fig. 6). (2) The floors are of concrete construction except at the 1F. The 1F has a wooden framework of ground sills, sleepers, floor joists, etc., with a finish level of GL +850. The ceiling height is also higher, 3550 mm, than on the other floors (2670 mm). (3) The strength of the construction materials was estimated to be about the same as that measured in the entrance wall of the 1F of the No. 38 building with a Schmidt concrete test hammer, since the two buildings were constructed in the same year, i.e. Fc296-358 kgf/cm2. The reinforcing bars used were round steel (SR24). The design was found to be one that stressed economy; main reinforcing bars of two different thicknesses were used in the same member, etc.

Blasting demolition of six-storey reinforced concrete building

Fig. 2 Layout of surroundings of No. 40 building

Fig. 3 West elevation

Fig. 4 North elevation

165

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166

Fig. 5 External photograph

Fig. 6 Plan of typical floor

3 Experimental blasting 3.1 Summary of experiment Prior to the actual blasting demolition experiment, test blasts were carried out on columns, stair hall walls, frames, and other walls forming the structural body of the specimen apartment. The collapse method was adopted, and the range of fragments, fly rock, and vibration and noise generated by the blasts was measured with instruments. The analyzed data was used to determine the methods employed in the following actual blast experiment. In the blasting of columns and wall columns, the fragmentation was compared for different types of explosives. Also, the isolation effectiveness of walls was investigated using shaped charges and comparisons of different methods of stair column drilling, etc., were carried out.

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3.2 Method of blasting Ten specimen locations forming part of the structural body of the apartment building were selected for blasting. The formula for calculating the amount of each charge was as follows. L=C·A (1) where L: Amount of explosives (kg) C: Coefficient of blasting (kg/m2) A: Cross-sectional area of column (m2) Since the ratio of reinforcement in the reinforced concrete columns selected for these preliminary experiments was about 0.95%, while that of ordinary columns in the specimen building was 0.91–1.10%, calculating a coefficient of blasting for these columns was expected to lead to slight over charging in the actual demolition. A blasting coefficient of C=0.6 kg/m2 was selected, since it was necessary to plan for complete collapse. Table 1 summarizes the specimens and explosives used in these experiments. Figures 7 to 11 show the drilling and charging patterns for each respective experiment. The explosives used were No. 3 Kiri dynamite, emulsion explosives, type 2 detonating fuses, and COBLAC. The composition and features of these explosives are as follows. No. 3 Kiri Dynamite Chemical composition

Nitroglycerin

18–24%

Ammonium nitrate

65–75%

Nitro compounds

0–7%

Combustibles, etc

3–11%

Initial density

1.30–1.35 g/cc

Detonation velocity

5,500–6,300 m/s

Emulsion explosives Chemical composition

Ammonium nitrate, etc.

70–90%

Water

5–15%

Oil, etc.

5–15%

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Fig. 7(a) Experiment No.1

Fig. 7(b) Experiment No.2 Initial density Detonation velocity

1.10–1.20 g/cc 4,800–5,800 m/s

Type 2 detonating fuse Core chemical Detonation velocity

PETN 6,000–6,500 m/s

10 g/m

PETN 6,000 m/s

100 g/m

COBLAC Composition Detonation velocity

Blasting demolition of six-storey reinforced concrete building To initiate the explosives, No. 6 DS delay electric detonators were used.

Fig.8 (a) Experiment No.3

8(b) Experiment No.4

169

Demolition and reuse of concrete and masonry

8(c) Experiment No.5

Fig. 9(a) Experiment No.6

170

Blasting demolition of six-storey reinforced concrete building

Fig. 9(b) Experiment No.7

Fig. 10 Experiment Nos. 8 and 9

171

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Fig. 11 Experiment No. 10

Table 1. Specimens and explosives used

Amount of explosives Experiment Type of No. specimen

No. of drill holes

Charge Total (g) charge (g)

Type of explosives

Blasting pattern drawing No.

1

Column

4

150

600

Dynamite

Fig. 7(a)

2

Column

4

300

1200

Dynamite (2 holes) Fig. 7(b) Emulsion (2 holes)

3

Wall

4

150

600

Dynamite

Fig. 8(a)

4

Wall

6

50

300

COBLAC

Fig. 8(b)

5

Wall

4

150

600

Dynamite

Fig. 8(c)

6

Column for stairs

2

50×2

200

Dynamite

Fig. 9(a)

7

Column for stairs

4

50

200

Dynamite

Fig. 9(b)

8

Beam

1

50×2

100

Dynamite

Fig. 10

9

Beam

4

50

200

Dynatmite

Fig. 10

Blasting demolition of six-storey reinforced concrete building 10

Wall

40 mm(W)×800 mm(l)

1716

Shaped charge

173 Fig. 11

Experiment No. 1 is on a typical column of the structural body. Experiment No. 2 is an example of an irregular column in which a six-inch straight pipe penetrates from the 1F to RF as a flue. No. KD and emulsion explosives were used on both the upper and lower parts of the same column to examine the fragmentation effectiveness of the different explosives at the same time. Experiments Nos. 3 to 5 are on wall columns 250 mm in thickness and 2,880 mm long. They form a rigid box stair hall which contributes to the overall strength of the building. Accordingly, the aim was to achieve complete blasting of these columns. The experiments made use of various blast designs and types of explosives. Experiments Nos. 6 and 7 are on stair columns, which are an important factor in the structural strength of the stair hall. Experiments on comparative fragmentation effectiveness were carried out using various blast designs, aiming at attaining complete fragmentation. Experiments Nos. 8 and 9 are on beams, and these were conducted by placing some charges in downward-facing boreholes from above the slab and some in boreholes on the beam sides. The aim here was to compare fragmentation effectiveness for the isolation of beams and columns, etc. Experiment No. 10 was conducted to test the effectiveness of slitting blasting using shaped charges on the walls. The shaped charge was placed 510 mm above floor level and was held in place using old Tatami mats (refer to Fig. 11). 3.3 Method of vibration and noise measurement Measurements included the three components (two horizontal components and one vertical component) of vibration velocity and the measurement of ordinary noise (A response) and low-frequency noise (LSL response). There were five measurement points in total, two near the blasted building and three points at locations close to 50 m, 100 m, and 200 m distant, respectively. The distance of the first two measurement points from blasting source was 3 to 20.5 m. 4 Results and consideration 4.1 Fragmentation results and consideration The fragmentation achieved in each experiment is shown in Photos 1 to 8. The following is a description of the fragmentation achieved in each case. (1) Experiment No. 1 As shown in Photo 1, not only were the pilasters destroyed by the blast, but also part of the walls; A hole 1,000×1,400 mm was formed in the external wall surface and the fragmentation was considered sufficient.

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Since the boreholes were drilled at the center of the column width, there were some cases in which vertical reinforcing bars interfered with the blast, and they had to be cut with a jet lance. For this reason, it might be considered advantageous to stagger the boreholes in the vertical direction. (2) Experiment No. 2 The presence of the six-inch flue had a great effect and the fragmentation effectiveness was reduced. As shown in Photo 2, about 25% of the column cross-section remained unfragmented after the blast. This failure to fully fragment is ascribed to the fact that the embedded flue and the orthogonal walls in the ridge direction at the rear affect the results; to overcome this problem, the borehole positions should be varied for each level. (3) Experiment Nos. 3, 4, and 5 Although the pilasters were completely fragmented as intended in experiment nos. 3 and 5, as shown in Photos 3 and 5, the fragmentation effectiveness was generally better in the case of experiment No. 5 and this experiment also produced less fly rock. In the case of experiment No. 3, a few old Tatami mats that had been fixed to the handrails of verandadhs about 4 m away from the blast to give protection were blown down, along with the handrail; together with fly rock, they were scattered up to about 13 m away by the blast. The fragmentation did not differ much between experiment Nos. 3 and 5. In the case of experiment No. 4, although it is considered that increasing the number of boreholes at the top and bottom would ensure complete fragmentation of the pilasters, it is preferable to increase the depth of the boreholes from the point of view of workability (refer to Photo 4). (4) Experiment Nos. 6 and 7 These blasts led to incomplete fragmentation. Although some unfragmented portions were left at both the top and bottom of the free surface side (totaling 250 mm in column width), breakage was almost complete. The collapse of the external wall of the toilet was insufficient, a result of the high resistance of the external wall. The fragmentation effectiveness was somewhat better in experiment No. 6 if both experiments are compared. Looking individually at these results, there were portions that remained intact at the top and bottom near bootleg in the case of experiment No. 6, while in the case of experiment No. 7, the manner of failure was not satisfactory between the boreholes. Thus in this case it was considered that the charge was insufficient for the spacing of holes. The following improvements may be considered: 1 Although implementation of the work by means of boreholes on the longish side is satisfactory, the method should be improved so as to prevent interference with the reinforcing bar arrangement. The walls below the stairs should be removed in advance. 2 The external walls of the toilet should be slotted as one of the pre-work measures. 3 With the drilling and charge to serve both as fragmentation of the

Blasting demolition of six-storey reinforced concrete building

Photo. 1 Experiment No. 1

Photo. 2 Experiment No. 2

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Photo. 3 Experiment No. 3

Photo. 4 Experiment No. 4

176

Blasting demolition of six-storey reinforced concrete building

Photo. 5 Experiment No. 5

Photo. 6 Experiment No. 7

Photo. 7 Experiment No. 8

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178

Photo. 8 Experiment No. 10

intermediate beam, the crossing portion with beams is to be blasted. Comparing the quantity of concrete destroyed in experiment Nos. 6 and 7, experiment No. 6 was has a slight edge with 0.13 m3 compared with 0.09 m3 in experiment No. 7. (5) Experiment Nos. 8 and 9 As shown in Photo 7, experiment No. 8 led to such fragmentation that the slab had a hole about 150 mm in radius with cracks in a radial pattern. Although the stirrup web bars bulged toward the exterior by about 50–100 mm, they were not severed. Looking at the fragmentation in experiment No. 9, the slab was completely fragmented below the beam and overall fragmentation was relatively effective due to destructive forces in the up and down direction. Since two of the stirrups had already been severed on one side at the time of drilling, the stirrups on the opposite side were extended and cut off by the blast. The volume of concrete fragmentation was about the same in both experiments. The results of these experiments, led to a number of improvements being implemented in the actual blasting operations, as follows. 1 From the point of view of fragmentation effectiveness and ease of cleaning, severing should by blasting using downward boreholes. 2 To prevent loss of fragmentation effectiveness due to the restraining force of the slab on the surface, the charge on the upper face of the deck should be made 100 g. (6) Experiment No. 10 The results of this experiment to test the effectiveness of slitting demolition of walls using shaped charges show that the fragmentation effectiveness was extremely good. The form of the fragmentation was plane rather than linear and the floor surface below the blast location in the wall was also considerably shattered. The fragmentation is shown in Photo 8; this photo indicates that the 90 wall bars generally failed to rupture, with most of them slipping or bending. Therefore, it was decided not to adopt shaped charges in the actual demolition experiment.

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4.2 Fly rock Since blasting took place with no protective measures against fly rock on the interior side, there was naturally considerable fly rock inside the building. In the case of experiment No. 1, the scattering of rock was completely controlled by using old tatami mats and protective sheets suspended externally near the blasting location. No protective work was carried out in the case of experiment No. 3, and several mortar fragments were discharged to a distance of about 30 m by the blast; they were found on the road. These are thought to have escaped through openings, such as stair well windows, etc. No rock was found outside the building in any of the other experiments. As regards protective work, to investigate the effectiveness of protection against fly rock, etc., resulting from blasting near the external walls of the building, old tatami mats were covered in protective sheets and suspended outside the building near the blasting locations. These were found to give adequate protection and this method making use of old tatami mats will continue to be employed in the future. 4.3 Results of vibration and noise measurements The Z component of vibration 50 m from the blasting location was 0.029–0.140 cm/s and the vibration propagating through the building as a result of blasting demolition was less than that in the case of ordinary rock blasting for excavation. Based on the data obtained in these experiments, a formula for estimating the vibration generated by demolition has been derived, as follows. V=133R−2.0 L0.75 (2) where, V: Vibration velocity (cm/s) R: Distance (m) L: Charge per delay (kg) For example, in a case where the maximum charge per delay is 20 kg, the estimated vibration at a point 50 m from the blast location is 0.5 cm/s. At a point 100 m from the blast, it is 0.13 cm/s. At this level, some complaints can be expected. As the normal noise level is 97–107 dB at a point 50 m from the blasting location, an increase of about 10 dB can be expected given the estimates of the charge to be used for demolition. However, since blasting noise is instantaneous, this is not considered a level which will cause structural damage or physiological damage to nearby residents. 5 Conclusions The preliminary experiments conducted at this time checked the fragmentation effectiveness that can be expected in the blasting demolition of columns, pilasters, beams,

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walls, etc. Data which can be used to predict the method of collapse were obtained. Also, by measuring the vibration, noise, and scattering of rock, estimates for the actual collapse experiment could be made, and the data needed to plan protection methods, procedures for taking shelter, etc., were obtained. Although it gives a slight over charge, a decision was made not to change the formula used to calculate charge since complete collapse of the building was required. Accordingly, protective measure to cope with fly rock and dust given a certain overcharging are considered an important issue. The vibration and noise expected to result from the actual demolition charging plan were predicted. For example, at a point 50 m from the blasting location, a vibration of 0.5 cm/s and noise of about 120 dB are predicted. No particular problems are expected from this level of vibration and since the noise is instantaneous, it is not likely to cause damage. It is, however, necessary to take measures to protect against fly rock discharged through open stair well windows, etc.

15 BLASTING DEMOLITION OF SIX-STOREY REINFORCED CONCRETE APARTMENT BUILDING (Part 2: Demolition plan, pre-work measures, collapse conditions)* Y.KASAI College of Industrial Technology, Nihon University, Japan T.SAITO All Japan Association for Security of Explosives, Tokyo, Japan Y.SEKI Shimizu Corporation, Japan K.TOMITA Architectural Division, Hazama-Gumi Ltd, Japan J.ISHIBASHI Architectural Engineering Department, Kajima Corp., Japan Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract The experimental demolition of a six-story reinforced concrete apartment building of 36 apartments was carried out by blasting at the defunct Takashima Coal Mine of Mitsubishi Coal Mines Co., Ltd. This is the first example of the blasting demolition of a full-size RC structure in Japan’s history. A committee was established within the All-Japan Association for Security of Explosives, Inc., and a demolition plan was prepared after carrying out a preparatory investigation. After preliminary experiments, blasting took place on October 12, 1988 and the demolition work was safely accomplished as planned. In this report, we describe how demolition of the RC apartment building was planned in consideration of its typically seismic design, give details of the preparatory work prior to demolition and the protective work, and present the condition of the apartment building after collapse. Key words: Demolition, Preparatory work, Collapse.

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1 Examination of collapse To implement this blasting demolition experiment on an RC building, it was necessary to select a collapse configuration for the building in question. Depending on the configuration chosen, isolation or removal of walls and related action was to be taken as preparatory work to make the building more susceptible to collapse. A structural analysis was carried out to estimate the effects of these preparatory measures. The retained horizontal bearing strength of walls before and after the preparatory work was calculated, and this formed part of the data needed for the blasting demolition experiment. The calculation of retained horizontal bearing strength is summarized below. (1) A computer program was used. The loading increment method was adopted and an approximate distribution of Ai was adopted as the assumed external force distribution. (2) The loading increment was automatically established in such a way that a single plastic hinge occurs at each step. The calculation was repeated until one of the following conditions was fulfilled: a. The specified floor deformation angle was reached (d/h≥1/50) b. The specified displacement in the horizontal direction was reached (d≥100 cm) c. The building became unstable (3) As the initial value of external force distribution, the base shear coefficient was made 0.1. (4) The rigidity of any walls that could not be regarded as bearing walls after the preparatory work was disregarded.

Table 1. Before Preparatory work

Story

Story Weight (ton)

Total Weight (ton)

Ai

X direction (ton)

Ci

Y direction (ton)

Ci

6

271.0

271.0

1.813

125.3

0.462

153.5

0.567

5

287.2

558.2

1.496

212.6

0.381

260.4

0.467

4

284.6

842.8

1.329

285.1

0.338

349.5

0.415

3

288.8

1131.6

1.206

347.4

0.307

426.4

0.377

2

293.8

1425.4

1.104

400.4

0.281

492.1

0.345

1

341.2

1766.6

l.000

449.6

0.255

553.4

0.313

(5) The vertical load was considered to be the dead load only. (6) The direction of the external force at the time of analysis was considered to be from both right to left and left to right along- the beam direction (X direction) and along the span direction (Y direction).

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The results of this analysis are shown in Tables 1 and 2, respectively. The retained horizontal bearing strength is given in the analysis in the direction of the building’s collapse.

Table 2. After Preparatory work

Story

Story Weight (ton)

Total Weight (ton)

Ai

X direction (ton)

Ci

Y direction (ton)

Ci

6

271.0

271.0

1.813

122.5

0.452

62.7

0.232

5

287.2

558.2

1.496

207.5

0.372

106.7

0.191

4

284.6

842.8

1.329

278.0

0.330

143.1

0.170

3

288.8

1131.6

1.206

338.7

0.299

174.4

0.154

2

293.8

1425.4

1.104

390.1

0.274

200.9

0.141

1

341.2

1766.6

1.000

437.7

0.248

225.4

0.128

2 Preparatory work Prior to blasting demolition, it was necessary to take preparatory measures to ensure that the building collapsed as planned. The measures taken in this case were mainly of two types, as follows. (1) The removal of interior equipment and fittings from each apartment. (Ceilings, closets, sinks, etc.) (2) The removal or isolation of RC walls. (Isolation below beams, above floors, and next to columns, etc.) The scope and details of this work are indicated below. 1) The interior equipment and fittings were removed from all floors. 2) The RC walls were isolated or removed to achieve the following: a. The building was cut so as to divide it plan-wise into three sections (refer to Photo 1). b. Walls and floors were broken up using hammer breakers. c. Between the IF and 3F, the entire perimeter of the RC walls was slit (refer to Photos 2 and 3). d. Between the 4F and 6F, the RC walls was partly slit (refer to Photos 2 and 3). 3) Walls on east side (Line 7) were isolated by slitting for a width of about 10 cm at locations above the 1F, 3F, and 5F. Additionally, plans were made to cause a fall in a southwesterly direction by tensioning between Line 6 and Line 7 with wires. Flying debris from the blasting also had to be prevented from scattering toward the old people’s home. To ensure this, columns on

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184

Line 7 were blasted by means of V-cuts. 4) The penthouse was isolated by slitting it to a width of about 20 cm at a position above the rooftop (Photo 4). The preparatory work is shown in Photos 1, 2, 3, and 4, respectively. 3 Protection It was assumed that at blast time a large number of people would gather to watch, including those participating in the experiment, reporters, etc. Selecting a safe enough observation point for this purpose was awkward because of the topographical conditions at the site, so measures to prevent flying debris had to be improved. Protective measures were also taken at the observation site itself. Protection work included both perimeter protection and interior protection. Details of this protection work are given below. (1) Perimeter protection was undertaken as follows. 1) On the south side, six tatami mats were arranged vertically side by side on the verandah of each apartment and fixed in place. 2) The exterior walls at charge positions on both the south and north sides were protected by tatami mats. The exterior walls at positions where beams held charges were also protected by tatami mats (refer to Photo 5). 3) Beam recesses adjacent to the stair columns on the north side were covered with protective sheeting. 4) All four sides (1F–6F) of the building other than places covered with protective sheeting were enshrouded in wire netting to offer secondary protection. 5) The charge locations on the east and west sides were protected on the outside using tatami mats. (2) Within the building, the following protective measures were taken: 1) Tatami mats were placed over charges in beams. 2) Tatami mats were placed over charges located in the stair slab. These protective measure are shown in Photo 5.

Blasting demolition of six-storey reinforced concrete apartment buildings

Photo 1.

Photo 2.

185

Demolition and reuse of concrete and masonry

Photo 3.

Photo 4.

186

Blasting demolition of six-storey reinforced concrete apartment buildings

187

Photo 5.

4 Collapse and demolition results The building was examined after blasting to check the achievement of each main point in the initial plan. The results of this investigation are given below. (1) Fall direction The building was found to have fallen in the southwest direction as planned. Although there was no concrete proposal for the horizontal displacement of the collapse, the actual displacement was found to be small. (2) Blasting of columns between 1F and 3F All columns between the 1F and 3F were completely severed as planned, verifying that the collapse of the building was caused by the blast. (3) Blasting of columns between 4F and 6F The complete destruction of stair columns and wall columns on the 4F and severance of the 5F columns were achieved as planned. The acceleration of the collapse due to the impact of columns falling on Line C was found to be effective. (4) Blasting of columns on Line 7 Practically no flying debris was seen on the east side (towards the old people’s home), accomplishing the aim of preventing the escape of debris. (5) Wiring The structure on Line 7 did not move nor slip toward the west, and the collapse direction was as planned. This can be considered due to the effectiveness of the wiring. (6) Blasting of beams on the long side The beam slab between the 2F and 3F was found to have undergone no horizontal movement whatsoever, and it was assumed to have fallen on the spot. It is assumed that beam slabs between the 4F and RF collapsed while maintaining their box shape. The scenario in which the whole beam slab

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188

Photo 6. (One second after the blast)

deforms into a parallelogram shape and is displaced substantially in the horizontal direction due to blasting at both ends was not observed. (7) Blasting of beams on the short side The blasting of one beam end on both sides of the stairs proved to be an effective way to demolish a stair hall of high rigidity. (8) Plan-wise division of the building into three The division of the building into three reduced its rigidity and accelerated the horizontal displacement of the building to the west. Moreover, the building was seen to crease at the divisions, and this helped to accelerate secondary disintegration. (9) Delay time The biggest role in the successful collapse of the building in the planned direction was the delay time. We consider that the delay sequence chosen for the experiment was basically correct. (10) Preparatory work on the penthouse The penthouse tumbled down and broke away from the structure proper as a result of the impact force when the 4F–6F portion hit the ground. Little secondary disintegration occurred after this and the penthouse retained its original form. More thorough preparatory work will be needed in the future. Figure 1 shows the anticipated behavior. Photos 6 to 9 are serial photographs of the blasting process. Photo 10 shows the results of demolition and collapse (on the west side). After blasting, the demolished building was crushed using a hydraulic crusher and the material spread over the site (refer to Photos 11 and 12).

Blasting demolition of six-storey reinforced concrete apartment buildings Photo 7. (Two seconds after the blast)

Photo 8. (Three seconds after the blast)

189

Demolition and reuse of concrete and masonry Photo 9. (After blasting)

Photo 10.

190

Blasting demolition of six-storey reinforced concrete apartment buildings Photo 11.

Photo 12.

191

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192

Fig-1 Estimation Drawing of Blasting Demolition Behavior

5 Conclusion A six-story RC building of seismic design was successfully demolished by blasting as initially planned. The collapse direction and methods of providing protection were as initially planned. For the future, there is a need to improve blasting demolition methods and further develop them on the basis of the experience acquired through this experiment.

16 BLASTING DEMOLITION OF SIX-STOREY REINFORCED CONCRETE APARTMENT BUILDING (Part 3: Blast design, noise and vibration)* I.SAWADA Taisei Corporation, Tokyo, Japan U.YAMAGUCHI .3 of Tokyo, Tokyo, Japan N.KOBAYASHI Chuo University, Tokyo, Japan M.NAKAJIKU All Japan Association for Security of Explosives, Tokyo, Japan H.SHIBATA Sato Kogyo Co. Ltd, Tokyo, Japan T.SHINDO Kacoh Co. Ltd, Tokyo, Japan Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract This report describes the blasting demolition of a six-story reinforced concrete apartment building carried out in Takashima-machi, Nishisonogi-gun, Nagasaki Prefecture, Japan on 12th October, 1988, and forms Part 3 of the full report of this title. The work was implemented using 153.8 kg of explosives and a total of 1,194 electric detonators. 8 stages of DS delay blasting was used. Described in this part of the paper are the explosives and blasting machine used, the blasting and demolition plan, the design of charges for each location, the layout of charges and the charging operation at each location, the timing of delay blasting, and the wiring circuits, etc. In addition, the amounts of vibration, noise, and fly rock generated are described based on measurements made at the site. Keywords: Demolition, Blasting, Explosives, Reinforced concrete, Delay

Blasting demolition of six-storey reinforced concrete apartment building

195

blasting, Vibration, Noise, Fly rock.

1 Preface Following Part 2 of this report under the same title, Part 3 describes the explosives used, the blasting plan, the blasting design, the layout of charges, the timing of delay blasting, and the resulting vibration, noise, and fly rock, in the blasting demolition of a six-story reinforced concrete (referred to as RC) apartment building. For a full understanding of the report, refer to Part 2 of the report which gives a summary of the demolished building, the pre-blasting measures, the collapse conditions, and secondary breakage, etc. 2 Explosives and blasting machine used Two types of explosives were used for the demolition work, No. 3 Kiri Dynamite (reffered to as No. 3KD) and Coblac. The approximate composition and special features of these explosives are as follows. No. 3KD

Coblac

(Product of Nippon Oil & Fats, 123.8 kg used) Nitroglycerine

18~24%

Ammonium nitrate

65~75%

Detonation velocity

5,500~6,300 m/sec

(Product of Asahi Chemical, 300 m used) Core chemical

PETN 100 g/m

Detonation velocity

6,000 m/sec

For initiation of the explosives, No.6 DS delay electric detonators and Type 2 detonating fuses were used. The approximate capacity and special features of these detonators are as shown below. No. 6 DS delay detonator (Product of Nippon Kayaku, 1,194 used) Standard delay

0.25 sec/delay

Type 2 detonating fuse (Product of Japan Carlit, 254 m used) Core chemical

PETN 10 g/m

Detonation velocity

6,000~6,500 m/sec

To fire the charges, a newly developed high-capacity blasting machine with the following characteristics was used. Condenser voltage

1,020 V

Demolition and reuse of concrete and masonry Condenser capacity

196

627 µ F

3 Blasting Demolition Plan The building in question is of the rigid box-frame type RC construction. Since the building is symmetrical left and right, ground plan of half part of the building is shown in Fig. 1. Further, as it is an apartment building there are many partitioning walls and stair walls in addition to the wall columns. All walls are of RC

Fig. 1. Plan of the demolished building

construction, also. Taking into consideration its relatively low six-stories, the rigidity of the building as a whole is quite large, making it difficult to demolish. The building naturally incorporates the aseismic design required to comply with Japanese building laws. For this reason, a key question in the blasting plan was how to reliably destroy by blasting a building that is specifically built to be hard to demolish. The result was a plan that required the use of explosives in large amounts. The following is a summary of the overall blasting plan. (1) The fall direction was selected to be towards the front of the building (southwest direction) considering the availability of vacant land there. (Refer to Fig. 1) (2) The plan was to remove all walls on the 1F to 3F in advance by completely removing them or cutting them in the circumference direction, leaving all columns and wall columns to be completely demolished by the subsequent blasting. (3) Since stair hall columns and wall columns on the 4F were expected to be rigid and strong, it was decided to destroy them completely by blasting. However, it was decided that the other columns on the 4F were not to be blasted. All columns on the 5F were to be severed by blasting in the middle, aiming to reduce the rigidity of the 4F, 5F, and 6F sections, respectively. It was decided that columns on the 6F were not to be blasted.

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(4) Not withstanding (2) and (3) above, the plan was to cut off the bases of the 1F, 3F, and 5F columns in Line 7 by blasting only to weaken them, in order to prevent fly rock over a nearby old people’s home (refer to Fig. 6 below). (5) It was decided to pull down the columns on Line 7 from the Line 6 side using wire rope to prevent them slipping down the slope to the east at the time of demolition. (6) To make collapsing the building toward the long side easier, both ends of all beams parallel to the long side on each floor were to be cut off by blasting. However. beams parallel to the short side were not to be blasted. (7) Since the stair halls were considered the most rigid sections, it was decided to blast the panel zones at the intersection of the C6 column and the G12 beam on the 2F, 3F, and 4F, respectively (refer to Fig. 3 below). (8) Since the building is especially extensive in the direction of the long side. it was decided to demolish, as part of the pre-blast work, the 2F~RF slabs’ concrete at the Line 3 and Line 5 positions so as to divide the whole building into three parts.

4 Charge design for each location The blasting of this six-story apartment building was done entirely by borehole blasting and No. 3KD was used in most locations. For wall columns C4, Coblac was used since they were thin, i.e. 250 mm. The columns were blasted in consideration of the fact that, basically, blasted concrete lumps were to be discharged outside the main bars and hoop bars so as to allow the upper structure to fall freely without hindrance. Based on the fragmentation effectiveness as obtained in the experimental blasting reported in Part 1 of this report, the amount of explosives required was calculated using Formula 1, below. L=CA×A

(1)

where, L: Amount of explosives (kg) C : Coefficient of blasting (kg/m2) A A: Cross-sectional area of member (m2) Because the major aim was to completely demolish the six-story building by blasting, the charge design was carried out on the basis of CA=0.6 kg/m2 in the above formula, accepting that this design would lead to a slight over charging. Table 1 gives as an example the charge design for the 1F columns while Table 2 is for the 2F beams. The tables also show the value of Cv in Formula 2 below for reference. L=CV×V where, L: Amount of explosives (kg) C : Coefficient of b lasting (kg/m3) v V: Cubic volume of member (m3)

(2)

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Table 1. Charge design for columns on 1F

Table 2. Charge design for 2F beams (Amount of charge per point to be cut by blasting)

5 Layout of charges and the charging operation at each location Fig. 2 shows as an example the layout of charges on line C and Fig. 3 the layout on line 2. The C6 column has no charge layout entered in Fig. 2 because the figures would be difficult to read. The layout of charges for this column is shown in Fig. 3. Figure 4 is the charging detail drawing for the 1F columns and 2F beams. The essential features of this charging layout are as follows. (1) Columns of ordinary portions on the 1F~3F were charged in horizontal boreholes laid out at regular intervals between the inside measure of the height.

Blasting demolition of six-storey reinforced concrete apartment building

Fig. 2. Charging layout on line C

Fig. 3. Charging layout on line 2

199

Demolition and reuse of concrete and masonry

200

Fig. 4. Charging detail drawing

(2) Columns of ordinary portions on the 5F were charged in horizontal boreholes made midway up the height (refer to Fig. 2). (3) C6 columns in the stair hall portion were charged by drilling in two horizontal directions over the whole height of the columns between the 1F and 4F, including the crossing points with the G12 beams (panel zones). (4) Since the C5 columns on Line 7 are to be weakened by blast severing, charges were placed in horizontal boreholes at the column bases on the 1F, 3F, and 5F (refer to Fig. 2). (5) The C4 wall columns on the inner side of the stair hall were charged by drilling horizontally parallel to the wall (refer to 1C4 of Fig. 3 and Fig. 4, respectively). (6) Beans in ordinary portions were charged in vertical boreholes laid out at both ends (refer to 2G1 of Fig. 4). (7) Beans on Line C were charged in horizontal boreholes laid out at both ends (refer to 2G7 of Fig. 2 and Fig. 4, respectively).

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Charging operations were implemented in the following sequence. (1) The required amount of explosives were moved into the explosives reserve station en masse. Three days were spent charging and wiring and one day wiring the series circuits and performing continuity tests. Wiring of the parallel circuits and connection of blasting cables were carried out on the day of blasting. (2) After the completion of safety work, the area within a 50 m radius of the building was placed off limits to all except authorized personnel, and the charging operation was then carried out. (3) Continuity tests were carried out on all electric detonators in the pyrotechnics shop using a photocell tester. (4) Before beginning the charging operation, it was confirmed that there were no leakage currents within the site. (5) The primer cartridges for No. 3KD were prepared in the pyrotechnics shop, while electric detonators were fitted to the Coblac and detonating fuses were attached in the charging location. (6) The tamping stick was wooden and the tamping material was sand paeked in vinyl sacks. To insulate each cable, Protight was used. (7) After each day’s charging operations were finished, the unused explosives were stored in an explosives reserve station, which was guarded throughout the night. (8) Continuity tests were carried out on the circuits using a photocell tester, and the electrical resistance of the circuits was measured using a digital tester. (9) On the day of blasting, the area within a 200 m radius was placed off limits and the parallel circuits were connected to leading wire. The electrical resistance of the circuits was also measured.

6 Quantities of explosives, delay time, and circuits Table 3 shows the types and quantities of explosives on each floor. Figure 5 shows the timing layout of the electric detonators and Table 4 the number of electric detonators used. Table 4 also shows the delay times with respect to stage 1.

Table 3. Types and quantities of explosives by floor

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Table 4. Numbers of electric detonators used

Table 5. Quantities of explosives used by stage (unit: kg)

Table 6. Vibration measurement positions (unit: m)

Table 7. Instruments used for vibration measureraents

Instrument

Manufacturer

Type

Sensitivity

Vibration velosity meter

Geo-Space

Three component in one body

0.265 V/kine

Table 8. Results of vibration measurements

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Fig. 5. Timing layout of electric detonators

All detonators were DS delay blasting electric detonator, and it was decided to implement the delay from southwest to northeast on a common plane for all floors in order to aim for a collapse in a south westerly direction (to the side of the building). The basic time difference between each stage was fixed at 0.25 seconds. This ensures that one stage is blasting just as the previously blasted section has begun to fall. However, in order to ensure that the momentum toward the direction of collapse is sufficiently large between stages 2 and 3, the time delay was fixed at 0.50 seconds in this case. The time delay before the last stage was fixed at 0.30 seconds according to the product specifications supplied with the electric detonator. Table 5 shows the explosives used for each stage. The series and parallel wiring of the electric detonators was implenented. Twelve series circuits were formed with 97~99 detonators in a group, and these were wired in parallel to form a single circuit. From each of these series circuits, a cable was drawn out for connection to a confirmatory detonator (dummy cap) for verification of complete detonation. 7 Results of vibration measurements Measurments of vibration were conducted to quantify the amount of vibration caused by blasting and collapse of the building. Fig. 6 shows the measurement locations, Table 6 the distance to the measurement locations, Table 7 the instrumentation, and Table 8 the measured results. Because the site is situated on a hill and there are large differences in elevation, the elevation difference between the demolished building and measurement locations, as well as the actual straight-1ine distance between them. is also shown in Table 6. The vibration at measurement position No. 1, a distance of 48.0 m from the blast, was 0.138~0.332 kine; this was categorized by the description “blasting vibration is substantial and some complaints

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Fig. 6. Location of vibration measurements (same as noise measurement locations)

are likely to be voiced.” On the other hand, the vibration at measurement position No. 2 located 119.1 m from the blasting point was 0.066~0.077 kine, a level summed up by the description “blasting vibration is perceptible, but few complaints can be expected.” At measurement position No. 3 located 218. On from the blasting point the reading was 0.010~0.023 kine, the level at which “blasting vibration is nearly inperceptible.” From measurements taken during the experimental 1 blasting, Formula 3 as shown below has been derived for estimating the blast-induced vibration at this site (refer to Part 1). V=K×L0.75×R−2.0 (3) where, V: Vibration velosity (cm/sec) K: Constant L: Quantity of explosives per stage (kg) R: Distance (m) Using Formula 3 and taking the quantity of explosives per stage to be 28.45 kg, the maximum amount per stage taken from Table 5, constant K was obtained from the measured vibration results given in Table 8 by an inverse process. The calculated values of K are as shown in Table 9, from which the average value of 65.2 was obtained.

Table 9. K values obtained by inverse process

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8 Results of noise measurements Noise measurenents at the time of blasting were carried out at the same positions as the vibration measurements (refer to Fig. 6 and Table 6). Table 10 shows the instruments used and Table 11 the results of the noise measurements.

Table 10. Instruments used for noise measurements

Instrument

Manufacturer

Type

Characteristics

Impuls precision noise level meter

RION

NA-61 A-characteristics

Low frequency noise level meter

RION

NA-17 LSL-characteristics

Table 11. Results of noise measurements

The measured level of low-frequency noise was greater by about 5 dB than the measured value of general noise. The peak noise level of general noise exceeded 100 dB(A) even at the No .3 position which was 218.0 m distant from the blasting point. However, since blasing noise is instantaneous, this is not considered a level which will cause structural damage or physiological damage to nearby surrounding residents. 9 Fly Rock After the blast, the fly rock materials by the blasting process was investigated, yielding the following results: (1) Old tatami (rice straw) mats were scattered around the building to offer some protection from the blast. (2) On the 2F and 3F balconies of the nearby No. 38 and No. 39 Apartment Buildings, which are about 12~17 m from the blasting point (refer to Fig. 6). several mortar and concrete fragments the size of a fist were found. Many smaller fragments than this were also seen. No damage to window panes on these balconies was found. (3) Out to a radius of about 30 m around the perimeter of the demolished building many fragments were discharged by the collapse. (4) No damage was sustained to window panes at the old people’s home about 50 m from

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the demolished building. (5) Around 50~70 m from the demolished building, six or seven fragments of mortar about 3~5 cm in size were discovered. (6) Around 110 m from the demolished building, two small fragments were found.

10 Conclusions The blasting demolition work reported in this paper was implemented by the All Japan Association for Security of Explosives. Before commencing work, a committee was organized for the purpose of obtaining technical information concerning building blasting and preparatory treatment of the structure, as well as basic data concerning effects on the surroundings. Little work of this type has been carried out on a full scale in Japan and so literature on the subject is scarce. As a result, much of the demolition project proceeded on a trial-and-error basis, but nevertheless much knowledge was acquired through this experience. The demolished building was a six-story reinforced concrete constr uction with many internal walls, which made it awkward to demolish by blasting. For this reason, as predicted, the building was not completely reduced to tiny fragments, unlike some cases reported in other countries where the whole of a building is reduced to rubble. Of course, such complete blasting could have been obtained if more dynamite had been used in a greater number of locations. However, considering the structural rigidity of the building and the effects of blasting on the surroundings, this experience of blasting demolition can be taken as a yardstick for such work in Japan. The “Guidelines for Security of Blasting Demolition Technology for Concrete Structures” were established in March 1991 by the All Japan Association for Security of Explosives, and future blasting demolition of buildings will carefully follow these guidelines while also operating in accordance with related laws, regulations, and local ordinances. However, the fact remains that blasting demolition work is likely to proceed little by little in special locations, such as within large industry sites, for the time being in Japan. For the present, there is little demand for blasting because demolition using mechanical methods is flourishing, there are few high-rise buildings suitable for blasting demolition, and the administrative authorities require the consent of surrounding residents over a wide area if blasting is to be performed. References All Japan Association for Security of Explosives, (1989) Report on Blasting Demolition Experiment of RC Apartment Building, Tokyo

17 PROGRESS OF BLASTING DEMOLITION TECHNIQUES FOR REINFORCED CONCRETE CONSTRUCTIONS IN JAPAN* Y.KASAI College of Industrial Technology, Nihon University, Japan K.HASHIZUME Explosives and Catalysts Division, Nippon Kayaku, Japan T.SHINDO Engineering Department, Blasting Division, Kacoh, Japan Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract This paper gives matter to be considered in future blasting demolition in Japan FOR foreign companies and engineers who operate blasting demolition in order to promote demolition by blasting in Japan. The contents of the paper are: (a) The reason why urban blasting demolition has not been progressed in Japan. (b) The historical stages of today and a brief outline of progress of blasting demolition techniques. (c) Recent technical development of blasting demolition techniques by the government and blasting, explosives manufacturing and construction industries, (d) Some proposals for the development of blasting demolition techniques, etc. key word: Blasting, Concrete Construction, Demolition, Explosives, History,

1 Introduction It is commonly said that the first dynamites were imported from Nobel’s company, UK in 1879.1) It was four years after the invention of gelatine dynamite by Alfred Nobel. In the next year, 1890, dynamite was used for civil works and mining blasting. Since then, explosives has often been used for blasting works mentioned above and scarcely for demolition. On the contrary, in Europe and North and South America, many buildings with midhigh storied building have been fell down by blasting instantaneously. And these

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spectacles have been introdused by Japanese televisions. This paper gives matter to be considered in future blasting demolition in Japan to foreign companies and engineers who operate blasting demolition in order to promote it in Japan. 2 Reasons why blasting demolition has not developed in Japan The followings are the analysis and consideration of impeding factor for the development of blasting demolition techniques in Japan. (1) The buildings are very close together in Japanese cities. On the ocasion of blasting demolition, it is considerably difficult to judge the proper distance (space) between the building and the adjacent buildings. This problem is deeply concerned with the kind of structures, ie, assembled, RC, SRC, S, and the height or plane. There are some cases that the distance between the buildings is only some 10 cm or so in the urban area composed of 5 to 6 story RC buildings. It is necessary to develop following techniques: (a) to prevent flying objects by blasting, (b) to control the direction of falling down the construction, (c) to protect the adjacent buildings. (2) Many citizens have an image to the consumption of explosives as dangerous. As the result of the government policy which strictly controls the firearms and explosives, the citizens feel danger of the blasting demolition in the urban area with a lot of explosives. (3) Consumer of explosives obliged to obtain prior permission of prefectural authorities. It is necessary to obtain prior permission of a prefectural authorities to transfer and consume explosives. On the cite close to private houses, the consumers are sometimes directed by the authorities to obtain the written consents from the neighboring inhabitants which are very difficult to obtain due to the circumstances mentioned above. Even if the consents were obtained and the application for permission was submitted to the prefectural authorities, it takes long time to obtain permission because of the examination by them and the consultation with the central government. Therefore, demolition companies will not adopt blasting demolition except special cases. (4) RC constructions in Japan are very strong and solid. Japan is an earthquake country. the Great Kanto Earthquke in 1923 was magnitude 7.9 and 2 to 5 degree on the seismic scale. Five big earthquakes that RC structures were destroyed or heavily damaged have occured since 1945 as shown in the chronological table.2) By Fukui Earthquake (1948) in particular, a seven stories department store was destroyed. some buildings were destroyed or heavily damaged by Tokachioki Eartbquakes (1968) and Miyagi-oki Earthquakes (1978). Most of RC structures have large columns and beams in section (ie. the section of a column of 5–6 story building is more than 600×600 mm) in order to withstand such a violent earthquakes. The wall thickness is 120 mm in minimum and 150–180 mm in general. These walls connected to the surrounding columns beams, so the construction is built up an extremely strong and solid. In case of masonry construction in general, once the lower story of a building is

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blasted, the upper stories of the building will be broken during falling and will finally be crushed to pieces. The ratio of the reinforcing bar (section of reinforcing bar/section of the element) in RC construction in Japan is 2–3% in columns, 1–2% in beams and 0.5– 1% in walls. In some cases, the distance of the reinforcing bar is less than 100 mm in the top and bottom of pillars. Thus, RC constructions in Japan is essentially different from masonry constructions in the Western countries where no earthquake occurs. it is necessary, in advance, to remove the combination of walls from columns, walls and beams by cutting each joint in order to make blasting demolition. (5) Laws, standards and guide lines for blasting demolition have not established yet, because there were few actual cases of blasting demolition in the urban area. In recent years, a certain concrete plan for blasting demolition was formed through investigation and studies for making a guide-line by All Japan Association for Security of Explosives. In the future, the detailed manuals or the like are hoped to prepare. 3 Annual report and outline of tradition of blasting demolition In Japan, there is few instances of blasting demolition and few studies. So, we made a chronological table of blasting demolition and collect some papers and reports to be able to utilize the development of blasting demolition in Japan. 3.1 History of blasting demolition History of blasting demolition after the Second World War may have been devided into the following steps.3) Period 1st. Between the end of the second World War and the end of the Korean War. (1945– 1953) Period 2nd.

Before Tokyo Olympic. (1954–1964)

Period 3rd. Before Oil Shock. (1965–1973) Period 4th. Up to now through RILEM 2nd DRC Symposium of Tokyo. (1974–1993)

3.2 The progress of blasting demolition (1) Period 1st (1945–1953) After the Second World War, the buildings and houses which were destroyed by the war were started to demolish for RCconstruction. There are a few official reports, one of them, a small scale blasting is shown below. a) The removal of Yaesu Bridge4) This bridge had two span-arch type SRC structure with two abutments and one piar, and were demolished in two steps. In the first step (1953), the lower part of abutments were removed to have 2 or 3 free face. In the second step (1958), because of the surrounding condition, one free face blasting were undertaken in almost all cases, so

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more amount of explosives were used than that in the first step. In the first step, 606 Kg of Carlit explosives and 8,475 pieces of electric detonators were used in order to blast 1,994 m3 of concrete. In the second step, 733 Kg of Kozumite, a kind of powdered TNT explosives, and Shin-kiri dynamite, anmonium gelatine dynamite, and 5,114 pieces of electric detonators were used in order to blast 840 m3 of concrete. (2) Period 2nd (1954–1964) In these period, there are also few instances of blasting demolition. a) The removal of “Sukiyabashi Bridge (1957)”5) This overpass was located in the urban buisiness quarters in which many people were gathered, and near the building of newspaper office. RC foundations were demolished. And the foundations were contacted with ubes of electric wire, gas, water etc. Prevention against flying objects were as follows. (a) Railroad ties were suspended in front of bore holes (lateral holes). The outside was covered with wire nets and Japanese Tatami mats reinforced with canvas sheets. (b) The surroundings of cite were protected with wire nets and canvas sheets. (c) Open wiring and pipings for electricity, gas, water and the like were protected with oine boards and canvas sheets. The blasting demolition was safely completed without any damage by scatterings due to the above protection. In this works, 152 Kg of Black Carlit explosives and 2477 pieces of electric detonators were consumed for demolishing 730 m3 of RC structures. The powder facter was 0.208 Kg/m3. b) Demolition of beams at Export-Import Bank of Japan (1961–1962) PT6) RC beams were removed by means of cutting exposed steel bars using acetylene welder after blasting each end of beams. Explosives used were 81.9 Kg of ammonia gelatine dynamite in 20 mm diameter and 3726 pieces of detonators. The volume of concrete was about 335 m3 and the powder factors were 0.244 Kg/m3 and 11 pieces/m3. (3) Period 3rd (1965–1973) This period is the period of developing the Japanese economy after Tokyo Olympic Games and demolition works were increased. There are two remarkable blasting demolitions. On the other hand, investigation and research were started. a) Demolition of the Safe Room, the old building of the Bank of Japan.7)

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Fig. 1. Steelcrete (The Bank of Japan)

About 34000 m3 of concrete at the old buildings of the Bank of Japan were demolished, and the building was employed to the basement part of this building in which there was a safe room constructed by RC structure and steelcreet structure consisted of a special expandedmetal and pebble with concrete. The wall of steelcrete (70 cm thickness) was drilled 30 cm distance each other by jetrance and was blasted 100 g of explosives each hole by pocket shot to expand the charge holes. Expanded holes were charged and blasted to break. RC pressure resistant mat (1.5 m thickness) and column (0.9–1.5 m square) were drilled by drilling machine and blasted. Explosives used were 8050 Kg of ammonia gelatin dynamite and 3525 pieces of electric detonators. The powder factors were 10.46 Kg/m3 for steel-crete part and 0.69 Kg/m3 for the RC part. These are 3–5 times compared with the conventional powder factor to blast RC

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Fig. 2. Demolition of underground beam (Osaka World Fair)

structures. Because the site was in the underground, there were not any flying objects to the outer side and the blasting works were finished in the scheduled term of works. b) Demolition of the underground beams, the House of USA. Osaka World Fair (1967) 8)

Vinyl pipes had been buried into the underground beams before placing concrete. Explosives were charged in the vinyl pipes. Beams of the House of USSR were also demolished by the same method. c) Development of Concrete Breaker (1968)9) There are Concrete Breakers (named SLB and CCR) which are developed in 1968, and have very low burnibg rate (40–60 m/sec). These can apply pressure to the wall of bore hole and break concrete with little flying objects. d) TN Blasting Method (1970)10) The principle of this method is one of the application of decoupling effect. Explosive used in this method has a small diameter and low detonation velocity, so it applies the pressure to the wall of the borehole gradually, and can break the concrete with lower vibration and noise. e) Type of Collapse of Concrete Structure (1970)11)

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Some types of collapse of concrete structure are classified and the order to break the each element are shown by blasting. (a) falling down to one side (b) falling down inside (c) falling down to the center (d) falling down outside f) Investigation Committee of Demolition Techniques in USA (1971) 12) The committee investigated the large machinery to demolish a very high building and the method of blasting demolition by meeting engineers in USA. g) Experiment of RC Short Column (1971)13) 75 cm (height)×50 cm×50 cm RC short column was blasted by 24 g RDX (detonation velocity 8700 m/sec). In this result, concrete outside of the steel bar was scattered, but inside concrete had a lot of cracks and was collapsed easily by stick striking. h) Experiment of demolition by Concrete Breaker (1972)14) Japan Building Constructors Society had experiments on demolition of RC column beam and foundation by using Concrete Breakers. In this result, it was made clear to be able to break RC elements with little flying objects. But Concrete Breaker has not been extended demolition work.

Fig. 3. Result after Test Blasting of Under ground Beam by Concrete Breaker.

(4) Period 4th (1974-now) In this period, there are just 3 works to demolish the upper part of building by blasting. The Committee of Blasting Demolition of Concrete Structures in Urban Area started in All Japan Association for Security of Explosives and a old apartment house was blasted. After some experiments and investigations on blasting demolition, a guide line was made. a) SBM Method (1977)15) SBM Method is to break structures by striking a heavy steel ball after blasting the head

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of column, bridge foot and beam by Concrete Breakers. But at this time, mechanical nibbler is developed, then SBM Method is not extended. b) The Removal of Dolphin at Toyo Wharf (1970)16) and Old Yokohama Doc of Mitsubishi Heavy Industry (1985)17) Both structures were massive reinforced concrete in the urban area. 40.4 Kg of dynamite in the former work, and 6600 Kg of water gel explosives, the latter, were used. c) Blasting Demolition of the UN Dome of Peace, the International Science Exposition in Tsukuba (1985)18) UN Dome of Peace was a semi spherical shll structure which had 41 m in diameter, 23.7 m in height and 154 pieces of RC precast panel were assembled by PC steel wire to stress the dome, horizontally and vertically. It was difficult to demolish by conventional mechanical method, because of (a) danger when PCsteel wire release the stresses, (b) a term of works and economical efficiency. CDI in USA designed the blasting pattern and gave Japanese blasting engineers guidance. It was a elemental demolition method to release the stress at the all fixed part, then to break the lower part of column by delayed blasting, and to fall down

Fig. 4. Demolition of the UN Dome of Peace (International Science Exposition in Tsukuba)

the entire dome to some direction. The foundations were blasted at the same time. 1261 bore-holes were drilled and 311.7 Kg of emulsion explosives, “Kayamite”, and 1265 pieces of electric detonator were used. After firing, although Dome began to fall down, whole dome did not break because of some misfires of charge. But we believe that this first blasting demolition in Japan had achieved the original purpose which is the

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introduction of blasting demolition. d) Blasting Demolition of Takashima 6 story RC Apartment House (1989)19) This demolition work was done as a part of the investigation and research activities of All Japan Association for Security of Explosives. Please refer to other part of this proceedings in detail. e) Blasting Demolition of Biwa Lake Side 11 Story SRC Hotel (1992)20) This building began to build for a hotel in 1968, but had been left as it was for more than 20 years. In 1989, the owner proposed to blast the building to local authorities. After 3 years, the proposal had been received but it needed furthermore 9 months judgement to permit the blasting demolition. This building consisted of 3 parts, Northern, Middle and Southern part. Each part has independent rigid frame structure and was connected by expansion-joint. It had one story basement and 11 story, and 130 m length, 45 m maximum width, 36.4 m maximum height and 16500 m2 total floor area. There were a national road (about 16 m) and private houses (about 65 m) in front of the building. Wreckers’ in UK designed the blasting pattern and gave engineering guidance. The building was planed to fall down to the Biwa Lake Side. Before blasting, some parts of wall were removed, and coverings were Japanese tatami, blasting sheet, wire net and blasting fence. Explosives used were reported 269.1 Kg of ammonia gelatine dynamite, 1250 m of detonating cord and 748 pieces of electric detonator. This very strong and earthquake-resistance designed building fell down completely without any flying objects to the direction of road. The upper parts over 7th story had box shaped structure and these parts were not broken. f) Blasting Work of Base Mat of a SRC Building of Daiichi Life Insurance (1992)21) This building existed in the center of Tokyo city area had been the office of GHQ after the second World War. The building was very rigid by SRC structure. Pressure resistant foundation and caisson in the underground were prtially blasted by explosives. Pressure resistant foundation in 4th floor of basement was blasted experimentally and ground vibration and air blast were measured at the boundary of the building site on the ground. Weight of charge was 400–900 g of emulsion explosives, Kayamite, and the vibration level was less than 70 dB, but sound level was more than 90 dB and maximum 108 dB. For this kind of construction works, the controll values are recommended less than 75 dB of vibration level and less than 85 dB of sound level by Tokyo Prefecture. So, especially it was necessary to reduce sound level caused by blasting. The method to reduce the sound level were as follows. (a) the charge weight blasted at one delay was less than 50 g. (b) the blasting area was covered by sand. Nonel system was introduced for the initiation system, because electric equipments and construction machinery were worked near the blasting area. Explosives used at one delay were 0.5–1.6 Kg and the value of sound level was acieved below the controll value. The concrete had only cracks by blasting but the plate was demolished by machinery after blasting. This demolition work was succeeded and suggested the blasting demolitions will be adopted even in the urban area.

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4 Summary of Investigation, Experiment and Technical Direction of Security by All Japan Association for Security of Explosives All Japan Association for Security of Explosives was entrust by the Ministry of internatinal Trade and Industry in 1987, and the Committee of Blasting Demolition of Concrete Construction started. After referring the instances and reteratures, RC short columns were blasted for the experiment on fragmentation. Takashima 6 story RC Apartment was demolished successfully by blasting. And then, RC short columns were blasted for the experiment on the prevention of flying objects, and the methods that flying objects were controlled completely, were studied.22) Based on these results, Technical Recommendation of Security on Concrete Blasting Demolition was established in the 1991 fisical year. In this recommendation, it is described that technical management of security is necessary to keep disaster prevention and public safety in case of demolition by blasting the whole or part of structures. On October 1992, Explosives Controll Law was made a partial amendment and criteria on consumption techniques of explosives for blasting demolition in which the followings have been shown. Technical Recommendation of Security consists of (a) General (b) Investigation and sheme (c) Execution of works (d) Control of preservation of environment. In the chapter of Investigation and sheme, it is described that demolition site and environment of the building should be investigated and the demolition method should be decided not to induce disasters by blasting. Blasting works are in the urban area, it is necessary to have a plan that the safety of adjacent inhabitants and houses should be considered sufficiently. In the chapter of Execution of works, it is described that experimental blasting tests have to be done to have the fragmentation effect from the planned design of blasting, the degree of protection method, and the level of ground vibration and blast noise. And management system of safety should be made and responsible persons who have well experiences in handling the explosives should be selected. In the chapter of Control of preservation of environment, the maximum allowable values of ground vibration and blast noise are shown, and the values less than this maximum values should be determined for the target controll value. And the counterplan to protect flying objects and dusts are also described. 5 Conclusion On the change of the blasting demolition method in Japan, we described as follows: (a) Reasons why blasting demolition has not developed in Japan (b) A chronological table of blasting demolition method (c) Typical instances of blasting demolition (d) Typical experiments on the elements of RC construction. Although there are some instances of demolition of underground construction, there are only a few instances on the upper part of construction. Then it is necessary to have more instances to progress the blasting in the urban area.

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Now in conclusion, we propose some ideas to develop the blasting demolition work. (1) It is easier to apply the blasting demolition to the underground constructions than the upper part of constructions. It is very effective and safe to apply the blasting method to underground beams, resisting pressure plate, foundations and so on. (2) To increase the instances and experiments of blasting demolition when the factories and schools have spaces around. the blasting demolition should be performed with a careful plan and investigation. At this time, it is necessary never to cause any accident. (3) To develop the method to prevent flying objects and to develop the method to protect the adjacent buildings from flying objects and blast wave. (4) To develop the method not to occur misfires or remaining charge, the method to certify the occurrence of misfire, the method to process the remaining charge safely and very insensitive explosives not to detonate during crushing the debris. (5) To make concrete content manuals for safe blasting demolitions in the urban area. (6) To cultivate a better understanding of citizens on the safety of blasting demolition and to obtain easily the written consent for using explosives. (7) To accumulate accomplishments to be permitted smoothly by the local authorities. 6 Reference (These references are all written in Japanese.) 1) Committee of Edition of Japanese History of Industrial Explosives, “History of Industrial Explosives in Japan”, pp 32–33, 1967, Society of Japanese Industrial Explosives 2) National Astronomical Observatory, “Rika-nenpyo (Chronological Scientific Tables)”, pp 822–852, November 1992, Maruzen Co., Ltd. 3) Y.Kasai, Concrete Journal, Vol. 30, No. 8, August 1992 4) The Industrial Explosives Society Ed., “New Blasting Handbook”, pp 301–308, May 1989, Sankaido 5) The Industrial Explosives Society Ed., “New Blasting Handbook”, pp 308–309, May 1989, Sankaido 6) S.Ishida. Building Engineering Magazine, No. 151, pp 45–55, May 1964 7) H.Kamiyarna, Construction Management, Vol. 12, pp 25–42, August 1970 8) Okushima, et. al., Concrete Journal, Vol. 9, No. 9, 1971 9) Committee of Edition of Japanese History of Industrial Explosives, “History of Industrial Explosives in Japan, No. 2”, p 3, May 1984, Society of Japanese Industrial Explosives 10) M.Wada et al., Construction Management, Vol. 13, pp 67–70, December 1971 11) Y.Kasai, 41th Research & Lecture Meeting of Kanto Chapter, Architectural Institute of Japan pp 289–291, 1975 12) Y.Kasai, Concrete Journal Vol. 9, No. 9, pp 54–57, September 1971 13) M.Sakaguti et. al., Proceeding of the Conference of Industrial Explosives Society, pp 13–14, May 1971 14) The Committee of Method of Demolition of RC Structure, “Report in 1973”, 1973, Japan Building Constructors Society 15) T.Tanaka, et.al., Construction No. 159, pp 35–48, July 1979 16) T.Takeraoto et.al., Doboku Seko, Vol. 11, No. 10, pp 31–37, 1970 17) Y.Kasai et.al., Cement and Concrete No. 470, pp 18–28, April 1986

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18) M.Maeda, Blasting No. 15, pp 23–36, August 1986 19) The Committee of Blasting Demolition of Concrete Structures in Urban Area “Report of Experimental Result”, All Japan Association for Security of Explosives, March, 1989 20) K.Sueyoshi, Explosion, Vol. 2, No. 3, pp 254–257, December 1992 21) All Japan Association for Security of Explosives, Explosives and Security. Vol. 24, No. 4, pp 31–39, October 1992 22) The Committee of Blasting Demolition of Concrete Structures in Urban Area “Report on Protection against Flying Objects”, All Japan Association for Security of Explosives, March, 1990

Table 1. Progress of Blasting Demolition Techniques for RC Structures in Japan

18 FRACTURE CONTROL TECHNIQUES FOR PARTIAL DEMOLITION OF CONCRETE BY BLASTING* Y.NAKAMURA and S.KUBOTA Yatsushiro National College of Technology, Yatsushiro, Japan J.MUKUGI and T.OHHARA Nishimatsu Construction Co. Ltd, Tokyo, Japan H.MATSUNAGA and M.YAMAMOTO Asahi Chemical Industry Co. Ltd, Tokyo, Japan Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract The controlled blasting methods available for localized cutting and partial demolition of concrete are presented. The first is a blasting method utilizing the charge holder with two wedge-shaped air cavities. The charge holder produces shock converging effects in a borehole and the shock wave pressure acts effectively on the cavity walls. The tensile stress fields are produced on the borehole at the locations of the apexes of cavities and controlled cracks are initiated. The second is a combined method of a split-tube charge holder and a notched borehole. The dynamic deformations of the split tube under the action of shock waves and gases driven by the ex¯ plosion produce highly concentrated tensile stresses on the borehole at the notch locations. The stress fields initiate cracks which form the controlled fracture plane. The effectiveness of these methods is demonstrated by a series of model experiments with electric detonators, mortar specimens and lead ones. Keywords: Controlled blasting, Partial demolition, Charge holder, Notched borehole.

1 Introduction Controlled or careful blasting of concrete is a technique which is based on the same principle as modern rock blasting. Fracture control is very important in partial demolition

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of concrete structures with blasting. As pointed out by Lauritzen (1989), blasting works must be done without damaging the remaining part of the structure. Then, it is necessary to develop the controlled blasting method available for localized cutting and partial demolition of concrete. A number of methods for achieving fracture control have been suggested by several researchers. Fourney, Dally and Holloway (1978) presented the blasting method with the ligamented splittube charge holder. By Nakagawa, Nishida, Ono and Kawakami (1986), blasting experiments were carried out to examine the effectiveness of the notched blast hole technique. Katsuyama, Kiyokawa and Sassa (1983) suggested the blasting method using sleeves with slits in a borehole. The conversion and the transmission of explosive energy to the surroundings, which are caused by blasting, constitute a very com plicated process with shock waves and gases. In this paper, the following new methods for achieving high degree of fracture control, based on the dynamic effects caused by the shock wave interactions in a borehole, are presented. The first is a blasting method utilizing the charge holder with two wedge-shaped air cavities, suggested by Nakamura (1991). The charge holder produces shock converging effects in the borehole. The second is a combined method of a splittube charge holder and a notched borehole. The dynamic deformations of the split tube under the action of shock waves and gases driven by the explosion produce highly concentrated tensile stresses on the borehole at the notch locations. The stress fields initiate cracks which form the controlled fracture plane. The new drill system with grooving tools, so-called the “Wing Bit”, developed by Mukugi and Ohhara (1992) enables us to get easily the borehole with notches. The effectiveness of these blasting methods is demonstrated by a series of model experiments with electric detonators, mortar specimens and lead ones. 2 A method utilizing the charge holder with two wedge-shaped air cavities 2.1 Experimental methods The mechanism of crack initiation controlled by the charge holder producing shock converging effects is shown in Fig. 1. In this method, the dynamic mechanism of shock waves in the borehole is effectively utilized for achieving fracture control. Basically the charge holder consists of two hemi-cylindrical parts made of mild steel, and forms two wedge-shaped air cavities. The shock converging effects are produced by the air cavities. Radially outgoing shock waves converge toward the apex of cavity. The shock wave pressure acts effectively on the cavity walls. The tensile stress fields are produced on the borehole at the locations of the apexes and controlled cracks are initiated. Model experiments with electric detonators, mortar specimens, 450×300×100 mm, and lead specimens, Ø100×110 mm, were made to evaluate the effectiveness of the charge holder in controlling the fracture process. Lead is usualy used as a model material for the Trauzl test of explosives. From the fracture patterns formed in the mortar specimens and the plastic deformations produced in the lead specimens, we can see the effects on fracture control by the charge holder. The geometrical shapes of the charge holder used in the experiments are shown in Fig. 2. In the charge holder with slits (Type I), it is

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considered to produce localized stress concentrations. The holders with two wedgeshaped air cavities (Type II-1, II-2), furthermore, produce shock converging effects as the dynamic mechanism in the borehole. These charge holders are 70 mm long. An electric detonator was used as the explosive charge. A cushioned charge was made in the loading conditon with the decoupling index D.I=2.73, defined by the ratio of the inner diameter of the charge holder to the diameter of the detonator. A circular disk spacer was used to fix the electric detonator in the charge holder, so that a symmetrical annular air gap exists

Fig. 1. Mechanism of controlled crack initiation by the charge holder producing shock converging effects.

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Fig. 2. Details of the charge holders.

around the charge. Clay and epoxy resin were tamped near the top of the charge holder. The experiments were perforraed nine times with mortar specimens and four times with lead specimens to show to be reproducible. 2.2 Results and discussion The top views of lead specimens fired with the charge holder are shown in Fig. 3. From the distortions of rectangular elements, which were drawn on the surface of the specimen before blasting, we can see the blasting effects produced by the charge holders. It might be supposed that the deformations of the specimen about the borehole is axisymmetric in blasting without the charge holders. However, it is evident from Fig. 3 that the striking deformations in the direction perpendicular to the N-N' lines along the slits (Type I), or the apexes of the wedge-shaped air cavities (Type II-1, II-2) are caused by using the charge holders. These blasting effects caused by the dynamic actions of shock waves and gases in the charge holders initiate the cracks forming a control fracture plane. The deformation effects produced by the charge holders, Type II-1 or II-2, are larger than those of Type I. Sectional views of the lead specimens along the A-A' lines in Fig. 3 are shown in Fig. 4. These figures show that cracks are initiated on the borehole wall at the locations of the apexes of the cavities in blasting with the charge holders, Type II-1 and II-2. These cracks are produced by the dynamic actions of shock waves, i.e. “shock converging effects”. The fracture patterns and fracture surface produced in a mortar specimen with the charge holder (Type II-1) are shown in Fig. 5. It can be seen from Fig. 5(a) that cracks propagate along the control fracture plane. It is also evident from Fig. 5(b) that strength and stability of the borehole wall are maintained and smoothness of the fracture surface is achieved. In Fig. 6, cracks are initiated at specified locations and propagated along the specified diagonal fracture plane. These experimental results show that the charge holders with two wedge-shaped air cavities enable us to control the number of fracture planes, the initiation sites and the direction of fracture propagation. The charge holder (Type II-1) reconstructed after blasting is shown in Fig. 7. It shows that the apex of cavity

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corresponding to the location of the main charge of the detonator is opened. This results means that the gas dynamic actions of shock waves and gases generated by the explosion of the charge in the charge holder, which drive the fracture front, are caused. The length and the angle of cracks along the contol fracture plane were measured and the evaluation of controlled blasting was made by the examination of the fracture patterns and damages about the borehole in the mortar specimens. It was shown from comparison of the experimental results that the charge holder with two wedge-shaped air cavities (Type II1, II-2) is superior to the charge holder with slits (Type I) in driving the controlled cracks to greater distances and in the feasibility of controlled fracture in blasting, and that the charge holder, Type II-2, have advantage over Type II-1 in smoothness of the fracture surface.

Fig. 3. Top views of the lead specimens after blasting. The charge holders were used.

Fig. 4. Sectional views of the lead specimens along the A-A' lines shown in Fig. 3.

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Fig. 5. Fracture patterns and fractur fracture surface near the borehole in a mortar Specimen. (a) Fracture patterns (b) Fracture surface.

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Fig. 6. Cracks along the specified diagonal fracture plane.

Fig. 7. The charge holder reconstructed after blasting (Type II-1).

3 A combined method of a split-tube charge holder and a notched borehole 3.1 Experimental methods A way of guiding the cracks is to make a primary indication in the borehole. Langefors

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and Kihlström (1979) suggested the crack control method utilizing the notched borehole. Recently, Mukugi, Ohhara, Akiyoshi and Kunitake developed the new drill system with grooving tools, so-called the “Wing Bit”. The schematic representations of the system are shown in Fig. 8. The “Wing Bit” may be easily attached to the rod connected the usual type drifter. The system enables us to drill the borehole with wedge-shaped notches and to control the notch locations. It is known that notching of the borehole can initiate blast cracks from the notch tips. It may be expected that the combined method of the splittube charge holder and the notched borehole is effective in driving the controlled cracks which are initiated at the notch locations to greater distances. The split tube with two longitudinal slits serves to protect the wall of the borehole and the slits produce localized concentrations of deformations of the split tube caused by the dynamic action of shok waves and gases. The geometry of the notches used in the model experiments is shown in Fig. 9. The notches, Type II, are intended as that obtained by the “Wing Bit”. The geometry of the split-tube charge holder is shown in Fig. 10. The split tube was fabricated from a mild steel bar and used in an attempt to generate a single fracture plane by driving two diametrically opposite cracks. The split tube was inserted in the notched borehole, Type II or Type III, as shown in Fig. 11. The loading conditions are the same as the conditions described

Fig. 8. Schematic representations of the new drill system with grooving tools, the “Wing bit”.

Fig. 9. Geometry of the notched boreholes used in the model experiments.

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Fig. 10. Details of the split-tube charge holder with two longitudinal slits.

Fig. 11. Schematic views of the split-tube charge holder inserted in the notched borehole.

in the previous section. The experiments were performed four times with mortar specimens and lead ones.

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3.2 Results and discussion Principal stress trajectories about the notched boreholes under a static internal pressure p in an infinite elastic medium calculated by Kubota are shown in Fig. 12. The figures show that the distortions of the stress fields are caused by the notches, and that there are considerable stress concentrations in the vicinity of the notch tips, the magnitudes of which depend on the notch depth. The instantaneous photographs of the explosion phenomena in the

Fig. 12. Principal stress trajectories about the notched boreholes under a static internal pressure p in an infinite elastic medium with Poisson’s ratio, 0.167. The values of the stress are normalized by the internal pressure. Solid lines show the principal tensile stress, and dotted lines show the principal compressive stress.

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Fig. 13. Shadowgraphs of the explosion phenomena in the air produced by the split-tube charge holder.

Fig. 14. Deformations of the lead specimen in the vicinity of the notched borehole after blasting.

air produced by the split-tube charge holder are shown in Fig. 13. These photographs were taken by the laser-shadowgraphy. It may be seen that the dynamic actions of shock waves and gases in the specified directions are produced by the split tube. The deformations of the lead specimens in the vicinity of the notched borehole are shown in Fig. 14. These results indicate the effects of the notches which produce the localized deformations and make possible initiations of the cracks at the notch locations. The deformations of the lead specimens in the vicinity of the notched boreholes caused by using the split-tube charge holder are shown in Fig. 15. These results show that the combination of the split-tube charge holder and the notched borehole is effective and the deformation effects near the notches driving controlled cracks are larger than those without the split-tube charge holder. The results in mortar specimens obtained by the combined method are shown in Fig. 16, where sketches of the crack patterns are shown. In Fig. 16(c), the split-tube charge holder was inserted in the borehole without notches and the small cracks were initiated about the borehole regardless of the slit locations. It can be

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Fig. 15. Deformations of the lead specimen in the vicinity of the notched borehole after blasting with the split-tube charge holder.

Fig. 16. Crack patterns produced in mortar specimens by the combined method.

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Fig. 17. Deformed split tubes after blasting.

seen from Fig. 16(a) and (b) that controlled cracks were initiated and propagated in radial directions along the specified diagonal fracture plane. Comparison of the results of Fig. 16(a) with (b) shows that the combination of the split-tube charge holder and the notches, Type II, is superior to Type III in driving the fracture front to greater distances. In Fig. 17, the split tubes after blasting are shown. The photographs show that the deformations in the vicinity of the slits of the split tube inserted in the notched borehole (Type II) are larger than Type III. It is evident from these results that the large deformations of the split tube caused by the combination with the wedge-shaped notches play an important role in driving the cracks initiated from the notch tips to greater distances. 4 Concluding remarks In concrete blasting, determinations of the borehole parameters, i.e, diameter and depth, etc, are restricted by the geometry and dimensions of concrete structures. It is required to produce a maximum of controlled blasting effects with the use of a minimum of explosives. In this paper, fracture control methods utilizing the charge holder with the wedge-shaped air cavities, the split-tube charge holder with slits and the notched borehole were presented. Results obtained from model experiments showed that these methods are feasible means for achieving fracture control in partial demolition and localized cutting of concrete. The charge holders are effective in eliminating the damage to the borehole walls and in driving the controlled cracks to greater distances.

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Acknowledgements The authors wish to express their thanks to Prof. M.Fujita and Associate Prof. K.Kaneko of Kumamoto University, Prof. K.Matsuo of Kyushu University, and Prof. M.Inoue of Kumamoto Institute of Technology for valuable discussions and encouragements. These works were partly supported by the financial aids for the research promotion from the Japan Ministry of Education and Science. References Fourney, W.L., Dally, J.W. and Holloway, D.C. (1978) Controlled blasting with ligamented charge holders. Int. J.Rock Mech. Min. Sci. and Geomech. Abstr. 15, 121– 129. Katsuyama, K., Kiyokawa, H. and Sassa, K. (1983) Control the growth of cracks from a borehole by a new method of the smooth blasting. Mining and Safety. 29, 16–23. [in Japanese] Lauritzen, E.K. (1989) Development of explosives and blasting technology for the demolition of concrete. Demolition Methods and Practice (edited by Y.Kasai, Chapman and Hall). 49–58. Langefors, U. and Kihlström, B. (1978) The Modern Technique of Rock Blasting. 296– 300, Wiley (New York). Mukugi, J., Ohhara, T., Akiyoshi, N. and Kunitake, S. (1992) Developments of a new blasting method; “Wing Bit and Wing Hole Blasting Method”. Tunnel and Underground. 23, 41–45. [in Japanese] Nakagawa, K., Nishida, T., Ono, Y. and Kawakami, J. (1986) Blast crack control and smooth blasting using notched blast hole technique. Proc. JSCE, 373(VI–5), 131–138. [in Japanese] Nakamura, Y. (1991) Effects of decoupling on motion of stress waves and fracture control by utilizing charge holders. Proc. Int. Conference. Engi. Blasting Technique. 346–353. Nakamura, Y., Matsunaga, H., Yamamoto, M. and Sumiyoshi, K. (1992) Blasting methods for crack control by utilizing charge holders. J. Industrial Explosives Soc. Jpn. 53, 31–37. [in Japanese]

19 PROTECTION METHODS FROM FRAGMENTATION IN BLASTING DEMOLITION (Part 1: Evaluation of cover materials and protection methods)* K.SUEYOSHI Building Construction Division, Hazama Corporation, Japan Y.KASAI College of Industrial Technology, Nihon University, Japan T.SAITOU All Japan Association for Security of Explosives, Tokyo, Japan K.TOMITA Building Construction Division, Hazama Corporation, Japan S.KOBAYASI Technical Development Bureau, Nippon Steel Corp., Japan Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract The Ministry of International Trade and Industry of Japan has foreseen the increasing demand of blasting method capable of demolishing urban concrete structures efficiently, and necessary tasks to set the security criteria in the use of explosives were then entrusted to All Japan Association for Security of Explosives in 1987. A technical committee was organised in the Association and the results of the effect cover materials upon fragmentation were obtained followed by the blasting experiment in FY 1988. As a result, it was proved that hexagonal wire-netting combination with crimped wire-netting, 3.2 mm dia. covering was quite useful to prevent fragmentation from flying out thanks to the gas-releasing capability. Key words: Blasting, Reinforced concrete construction, Demolition, Dynamite, Fragmentation, Protection

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1 Introduction The Ministry of Internationa1 Trade and Industry of Japan has foreseen the increasing demand of blasting method capable of demolishing urban concrete structures efficiently, and necessary tasks to set the security criteria in the use of explosives were then entrusted to All Japan Association for Security of Explosives in 1987. A technical committee was organised in the Association and the results of the effect cover materials upon fragmentation inbiased or centered charge were obtained followed by the blasting experiment of reinforced concrete structure in FY 1988. The draft of the security criteria was examined subseqently in 1989 FY on the basis of above results, and a supplmental experiment to check the effect of cover materials upon flying objects was considered to be necessary. 2 Scope of the experiment To get knowledge capable of specifying the security criteria for blasting practice by means of comparative estimation of the effect of cover materials upon flying objects. 3 Method of the experiment 3.1 General This paper (part 1) describes the outline of “estimation of the effect of cover materials upon flying objects in biased or centered charge” and measurement of velocity, distance and weight of flying objects with respect to the amount of exprosives in biased or centered charge” by Y.Ogata is mentioned in Part 2. The condition of the experiment is shown in Table 1, in which the coefficient of blasting is defined as follows; L=C×A Where L is amount of exprosives in kilogram,C is the co efficient of blasting and A is the cross section of a spec imen. If the charge point is not centered (biased) which is shown in figure 1, A is to be calculated as an area of a square with a side twice as much as the minimum resisting length. 3.2 Exprosives The exprosives employed was 4.6 kilogram of No. 3 Kiri dyna mite (35×200 g) which has also been used in the previous blasting test in 1987, and the blasting was initiated by 20 pieces of No. 6 electric detonators.

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3.3 Model columns A reinforced concrete model column, a typical Housing Corporation apartment house in Japan which is shown in figure 2 was used. The size was 800×800×2,400 mm buried 400 mm in the ground. The specified desgin strength of the concrete (Fc) was 210 kgf/cm2 (average strength 351 kgf/cm2), the reinforcing bars were of SR-24 with diameters being 25 mm ø and 9 mm ø for main and hoop rods, respective1y.

Table 1 Description of experiments

Exp. No.

Cover Materials

No. of Measured Value of Drilling Amount of Coefficient Hole Point (mm) explosives of Blasting Fig. (ø= (9) Symmetry Min. Depth No. 37mm) resisting of Length Hole

5

W+SB

1

biased

320

504

250

0.6

2

6

W+R

1

biased

320

500

250

0.6

3

7

W+T

1

biased

320

504

250

0.6

4

8

SB

1

biased

325

506

250

0.6

5

9

R+B

1

biased

320

507

250

0.6

6

10

T+SB+R+W

2

centered

395

508

250×2

0.4

7

11

W+SB

2

centered

405

508

200×2

0.3

8

12

W+T

2

centered

395

505

200×2

0.3

9

13

SB

2

centered

390

503

200×2

0.3

10

14

W+W"+B

2

centered

400

500

200×2

0.3

11

Attention: Exp. No. 1~4 are described in the next paper (Part 2). W: Crimped wire net (ø=3.2 mm, cell size 30 mm) W": Hexagonal wire net (ø=0.7 mm, cell size 10 mm) B: Blasting mat (1.09 mm thick, 4.0×6.0 m) SB: “Super Blasting Sheet” R: Rubber mat (10 m thick, 1.0×2.0 m or 0.5×2.0 m) T: Tatami mat

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Fig. 1 Model Columns and Blasting condition

238

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239

Fig. 2 Model column, Size and Reinforcements.

4 Results and discussion The experimental results of blasting the specimens are listed in Table 2 and 3, and the protection works of blasting materials are shown in figure 3 through 12.

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4.1 Evaluation of single cover materials a. Crimped wire net Crimped wire net was applied to 7 specimens. Since crimped wire net was not broken, it was quite useful. But on the blasting condition of 250 g×2 exprosives, there occured large opening at the tie steel wires of combining ends of net. The wire net should be jointed by the same sort of wire to form a cylinder to be resistant to explosion. b. SB sheet (A special blasting mat, named DYNEEMA R) SB sheet was applied to 5 specimens. Blasting made slight tear in the SB sheet. Then if SB sheet has large tensile strength, it may be torn by scattering. Since fastening belt tore and put out, SB sheet should be covered loosely to the gasreleasing capability. c. Rubber sheet Rubber sheet was applied to 3 specimens. The sheet was not broken but turned up by blasting and there were considerable fragmentation. d. Tatami mat Tatami mat was applied to 3 specimens. Tatami mat was applied in combination with crimped wire net. There were no breakage of Tatami mat. But there will be considerable fragmentation when a fastening belt puts out and Tatami mat is pulled up. e. Blast sheet Traditional blast sheet was not useful to prevent concrete fragments flying. It will be useful only to prevent small concrete fragments combination with crimped wire net and hexagonal wire net. f. Hexagonal wire net Hexagonal wire net was useful only to prevent small concrete fragments in combination with crimped wire net formed in a cylinder. 4.2 Evaluation of multipule cover materials a. Crimped wire net+SB sheet (No. 5, 11) Crimped wire net and SB sheet was applied to 2 specimens. They were not broken, so that.it was useful. But on the blasting condition of No. 5 specimen there occured 3 small tears at back surface, so that there were medium amount from opening of SB. The fastening belt of the SB sheet should be form continuity to be resistant to explosion. b. Crimped wire net+Rubber sheet (No. 6) Crimped wire net tied with steel wire and Rubber sheet were tested. Rubber sheet was turned over and there were considerable extrusion from opening of rubber sheet. The joint of the wire net must be hundeled to form a cylinder to be resistant to explosion. Rubber sheet was applied at 3 specimens in the experiment. Sheet was turned up but

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241

no broken by blasting. c. Crimped wire net+Tatami mat (No. 7, 12) Crimped wire net was applied to 2 specimens. There were no broken of Tatami mat combination with crimped wire net. But there will be considerable extrusion when fastening belt put out and Tatami mat was turned up. It was considered that joint method of skirt should be improved. d. Rubber sheet+Blast sheet (No. 9) Sheet was turned up but no broken by blasting and there were considerable extrusion. Blast sheet was not useful to prevent concrete fragments. It was considered that joint method of skirt should be improved. e. Crimped wire net+Tatami mat+Rubber sheet+SB sheet (No. 10) There was no flying fragments in order to 4 plies cover materials. It was considered that joint method of skirt should be improved. f. Crimped wire net+Hexagonal wire net+Blast sheet (No. 11) There was no flying fragments in order to 4 plies cover materials. Crimped wire net was not broken, so thatit was quite useful. Hexagonal wire net and blasting sheet will be useful only to prevent small concrete fragments combination with crimped wire net.

Table 2 Experimental Results

EXP. No.

Blasting condition

5

Results in the biased charge

6

Cover Material

W+SB

250 g ×1 charged at a biased position

W+R

Distance of protection

Damage of Cover Materials

Effects of Cover Materials

10 cm

W: sound, SB: 3 small tears at back surface. (Fig. 3)

No extrusion but medium amount from opening of SB.

10 cm

W: sound, R: Turned up but no damage. (Fig. 4)

Considerable extrusion and medium amount from gap of R.

W: sound, T: sound. (Fig. 5)

No extrusion but Considerable amount from skirt of W.

7

W+T

10 cm

8

SB

10 cm

SB: slighitly No extrusion but teared. a little from holes Fastening belt and an opening

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put out. (Fig. 6)

9

10

R+B

200 g ×2 centered position

11

Results in the centered charge

14

R: Turned up no damage. B: Medium amount entirely of extrusion. teared. (Fig. 7)

T+SB+R+W

10~30 cm

W: 6 large tears. T, SB, R: sound. (Fig. 8)

W+SB

10 cm

W, SB: sound. (Fig. 9)

No extrusion.

10 cm

W: slightly teared. T: sound. (Fig. 10)

Nearly no extrusion.

10~30 cm

SB: 11 small holes. Fastening belt put out. (Fig. 11)

Considerable extrusion from an opening of SB.

10~30 cm

W: slightly teared. W", B: Nearly no damaged. extrusion. (Fig. 12)

12

13

10 cm

of SB.

W+T 250 g ×2 charged at a centered position

SB

W+W"+B

Medium amount of extrusion from an opening of SB.

Table 3 Effects of Cover Materials

Blasting condition

250 g×1 charged at a biased position

W+SB

No extrusion but a little from opening of SB. W and SB not broken out. Opened at the joint of SB. Exp. No. 5 (Fig. 3)

W+R

Considerable extrusion and a little from the gap of R. W and R not broken.

200 g×2 charged at a centered position

250 g×2 charged at a centered position No extrusion. W and SB not broken. Exp. No. 11 (Fig. 9)

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Exp. No. 6 (Fig. 4)

W+T

No extrusion except for the edge of W. W and T not broken. Exp. No. 7 (Fig. 5)

No extrusion. W and T not broken. Exp. No. 12 (Fig. 10)

SB

No extrusion but a little from the opening of SB. A large tear in SB and opened at the joint. Exp. No. 8 (Fig. 6)

Considerable extrusion from an opening of SB. 11 small tears and a large opening at the joint of SB. Exp. No. 13 (Fig. 11)

R+B

Medium amount of extrusion. R not broken butpulled up. An entire tear in B. Exp. No. 9 (Fig. 7)

T+SB+R+W

A medium extrusion at the opening of SB and a large opening at the joint. T, SB and R not broken. Six tears in W. Exp. No. 10 (Fig. 8) No extrusion. One tear in W and damages in W" Two tears in B. Exp. No. 14 (Fig. 12)

W+W"+B

5 Conclusion In the experiments from No. 5 to No. 14, evaluation of cover materials and methods of protection were investigated by the centered charge by 200 g×2 explosives with 50 cm distance. As a result, it was proved that the crimped wire net acompanied with hexagonal wire net covering is quite useful to prevent concrete fragments from flying out thanks to the gas-releasing capability. The perfect protection would probably be possible if SB sheets (of polyethylene high strength fabric) or TATAMI-mats are applied in combination with the crimped wirenetting. In such application, the joint of the wire net must be bundled by the same sort of wire to form continuity to be resistant to explosion, and by the same reason, SB sheet must be attached loosely by a fastening belt with sufficient strength.

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Fig. 3 W+SB (No. 5) Crimped wire net+SB sheet Biased charge Coefficient of Blasting 0.6 crimped wire net was combined with tie steel wire and they were broken.

Fig. 4 W+R (No. 6) Crimped wire net+Rubber sheet Biased charge Coefficient of Blasting 0.6

Protection methods from fragmentation in blasting demolition

Fig. 5 W+T (No. 7) Crimped wire net+Tatami mat Biased charge Coefficient of Blasting 0.6

Fig. 6 SB (No. 8) SB sheet

245

Demolition and reuse of concrete and masonry Biased charge Coefficient of Blasting 0.6

Fig. 7 R+B (No. 9) Rubber sheet+Blast sheet Biased charge Coefficient of Blasting 0.6

246

Protection methods from fragmentation in blasting demolition

247

Fig. 8 T+SB+R+W (No. 10) Tatami mat+SB sheet Rubber sheet+Crimped wire net Centered charge Coefficient of Blasting 0.4 Crimped wire net was jointed and formed cylindrically with a same sort of wire. There were no leakage of fragments.

Fig. 9 W+SB (No. 11) Crimped wire net+SB sheet Centered charge Coefficient of Blasting 0.3

Demolition and reuse of concrete and masonry

Fig. 10 W+T (No. 12) Crimped wire net+Tatami mat Centered charge Coefficient of Blasting 0.3

Fig. 11 SB (No. 13)

248

Protection methods from fragmentation in blasting demolition SB sheet Centered charge Coefficient of Blasting 0.3

Fig. 12 W+W"+B (No. 14) Crimped wire net+Hexagonal wire net+Blast sheet Centered charge Coefficient of Blasting 0.3

249

20 PROTECTION METHODS FROM FRAGMENTATION IN BLASTING DEMOLITION (Part 2: Dynamic movement of fragments)* Y.OGATA, K.KATSUYAMA and Y.WADA National Institute for Resources and Environment, Tsukuba, Japan U.YAMAGUCHI Tokyo University, Japan K.HASHIZUME Nippon Kayaku Co. Ltd, Tokyo, Japan T.SATO Nippon Kouki Co. Ltd, Tokyo, Japan S.OHTSUBO Chugoku Kayaku Co. Ltd, Tokyo, Japan Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract Experimental blastings of model concrete columns were carried out in order to obtain technical informations on fragmentations caused by the blasting demolition of concrete columns. The reinforced concrete model columns for typical apartment house in Japan were applied to the experiments. The dimension of concrete test column buried 400 mm in the ground was 800×800×2400mm . The specified design strength of the concrete was 210 kgf/cm2, there inforcing bars were of SR-24 and they were distributed 12–25 ø mm for axial reinforcements, 9 ø–200 mm in pitch for hoop reinforcement (refer to Part 1). These columns were exploded by the blasting with internal loading of dynamite. Fragmentations were observed by a high speed camera with 500 and 2000 fps and high speed video with 400 fps. The fragmentations normally spread within a range of 100 m, and the most frequently within 25 to 50 m. As one of results, the velocity of fragmentations, blasted 330 g of explosive with

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252

the minimum resisting length of 0.32 m, was measured as much as 40 m/s. Keywords: Reinforced concrete, Blasting demolition, Fragmentations, Highspeed camera and video, Orbit of fragmentation, Characteristics of spread fragmentations.

1 Introduction Blasting to break the rock using the energy of explosives is one of the important operation in mining and civil engineering. In recent years blasting demolition for old buildings has become of major interest in Japan. But there are some problems to introduce the blasting demolition to Japan in the viewpoint of aseismatic structure and environmental conditions in the urban area, so the Ministry of International Trade and Industry of Japan set to work the security criteria in the use of explosives were entrusted to All Japan Association for Security of Explosives in 1987. Many technical data were obtained by blasting demolition experi ments of reinforced concrete structure in 1988. As the results of these experiments, it is the most important thing to control the dynamic movement of fragmentations which damage directly neighbouring buildings and inhabitants around the blasting demolition. The flying and spread characteristics of dynamic movement of fragmentations were investigated in the blasting of reinforced concrete model columns. 2 Experimental Methods The flying and scattering characteristics of dynamic movement of fragmentations were considered by blasting experiments using the reinforced concrete columns without cover materials. The velocity, distance and weight of fragmentations in the experimental blasting were measured in both cases of the centered charge and the biased charge. 2.1 Model columns The reinforced concrete model columns for typical apartment house in Japan were applied to the experiments. The dimension of concrete test column was 800×800×2400 mm. The reinforcing bars were of SR-24 whose diameter were 25 mm and they were distributed 12–25 ø mm for axial reinforcements, 9 ø–200 mm in pitch for hoop reinforcement. The test columns were buried 400 mm in the ground. The specified design strength of concrete was 210 Kgf/cm2 and the strength for 28 days later indicated 351 Kgf/cm2 in the test piece. 2.2 Blasting Methods The four kinds of blasting experiments which had no cover materials were carried out. The blasting conditions of experiments were shown in Table 1. The charge of explosives was defined as follows;

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L=C·A where L is amount of explosives in kilogram, C is the coefficient of blasting and A is the cross section of a specimen. If the charge point is biased, A is to be calculated as an area of a square with a side twice as much as the minimum resisting length. The explosives used in the experiments were No. 3 Kiri dynamite (35 mm in diameter, 200 g) and initiated by No. 6 electric detonators. The diameter of drilling hole was 37 mm. The four kinds of experiments are shown in Fig. 1~4.

Table 1 Blasting conditions of experiment

No.

Numbers of drilling

Centred or biased

Charge (g)

The minimum resisting length

Coefficient of blasting

1

1

biased

167

0.32 m

0.4

2

1

biased

250

0.32 m

0.6

3

1

biased

333

0.32 m

0.8

4

2

centred

250×2

0.40 m

0.4

Fig. 1 Test column in the No. 1

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Fig. 2 Test column in the No. 2

254

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Fig. 3 Test column in the No. 3

255

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Fig. 4 Test column in the No. 4

2.3 Measurement of dynamic movement of fragmentations Two kinds of high-speed Camera (2,000 and 500 fps) and one kind of

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Table 2 Specifications of the high-speed camera and video

high-speed video (400 fps) were used to observe the dynamic movement of fragmentations and to measure the velocity and the flying phenomena. Specifications of the high-speed cameras and the video are shown in table 2. The high-speed camera and video were set up perpendicularly to the flying direction of fragmentations. The arrangement of the high-speed cameras and the video is shown in Fig. 5.

Fig. 5 Arrangement of high-speed camera and video in the experiment

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258

Fig. 6 Color paintings of surface on the column

2.4 Measurement of spread fragmentations The distances of spread fragmentations were measured in the area of 56 m on right and left and 300 m in front of blasting point. The weight of fragmentations were also measured. The test columns were painted four kinds of colors which were red, yellow, blue and brown on the blasting face. The generated points for test columns and spread characteristics were considered. The colors of blasting face is shown in Fig. 6. 3 Results and Conclusions of Experiments 3.1 Measurement of Velocity of Fragmentations The initial velocity of fragmentations were presumed by observations with the high-speed cameras and high-speed video. It is clear that the velocity of detonation gas near the blasting face has attained hundreds of meter per second and the fragmentation has been discharged with extremely high velocity. The velocity of discharging gas has attained over 180 m/s in No. 1, failure in No. 2, over 140 m/s in No. 3 and over 220 m/s in No. 4 column. But a few second later the fragmentations lose velocity rapidly and showed constant movement. The velocity of fragmentations have attained 30 m/s in No. 1 column, 40 m/s in No. 2, 40 m/s in No. 3, 50 m/s in No. 4. It is assumed that the fragmentations generated near the blasting face were accelerated by expansion gas and

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then the velocity of fragmentations which were far from the blasting face became constant because of low acceleration of expansion gas and air resistance. The results of observations with high-speed video were shown in Fig. 7. The results of analysis of velocity was shown in Fig. 8. 3.2 The orbit of fragmentations The orbit of fragmentations scattered in the blasting face were

Fig. 7 The observations of high-speed video

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260

Fig. 8 Velocity of fragmentations in the No. 1

observed by the high-speed cameras and the high-speed video. It is impossible to observe the fragmentations near the blasting surface of test columns under the detonation gas and blast dust, so the orbit of fragmentations were observe at a few meters near the test columns. Four pieces of fragmentations generated in No. 4 column were analysed and each one indicate fragmentation ~ in the fig. 9. As the results of analysis the velocity of fragmentations have become constant in front of blasting face, the velocity of fragmentations is as follows; Vs=21 m/s, Vs=23 m/s, Vs=6 m/s, Vs=10 m/s. The fragmentations

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Fig. 9 Velocity and displacement of fragmentations in the No. 4

flied in low velocity as compared with discharging gas velocity. It is assumed that the small change of velocity and displacement is due to the reading error and revolution of fragmentations. The orbit of fragmentation was calculated using the least squares, it was clear that every fragmentation was flying on the parabolic motion. The maximum flying distance of each fragmentation have become l=28.5 m, l=20.2 m, l=4.0 m and l=10.8 m which was calculated by the parabolic motion expression. The fragmentation flied in low velocity compared with fragmentation , but the maximum flying distance was anymore. The

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Fig. 10 Velocity and displacement of fragmentations in the No. 1

Fig. 11 Velocity and displacement of fragmentations in No. 3

results by the high-speed camera was shown in fig. 9. As the results of these analysis, it was clear that the fragmentations were flying in constant velocity and the angle of elevation of fragmentations was the most significant factor to decide the flying distance.

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The results of column No. 1 and No. 3 were shown in fig. 10 and 11 respectively.

Fig. 12 The spread fragmentations in the No. 1

Fig. 13 The spread fragmentations in the No. 2

3.3 Characteristics of the spread fragmentations The fragmentations generated in the biased charge blasting (test columns No. 1~3) had a tendency to spread in left side of test columns which was the same direction of bore hole. The Maximum distance and numbers of fragmentations increased as the charge increased.

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The fragmentations

Fig. 14 The spread fragmentations in the No. 3

Fig. 15 The spread fragmentations in the No. 4

generated in the central charge blasting (test columns No. 4) were spread symmetric on right and left side of test column. The Maximum flying distance of fragmentation was 34 m in the No. 1 test column, 55 m in the No. 2, 91 m in the No. 3 and 65 m in the No. 4. All of the fragmentations which flied in the long distance were the blocks painted by four kinds of color on the blasting face. The spread fragmentations in the test blasting were

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shown in Fig. 12~15. 4 Conclusion The experimental blastings in order to get informations of fragmentations have been carried out. Main results obtained are as follows; 1) The velocity of burst gas spread in the surface of test columns were some hundreds of meters per second, but some milli-seconds later the burst gas lost its velocity and the velocity became tens of meter per second. 2) It is clear that the fragmentations were flying in the constant velocity and on the parabolic orbit in the area of a few meter far from blasting surface of test columns. The angle of elevation of fragmentations was one of the most important factor to decide the flying distance of fragmentations. 3) The fragmentations in the biased charge blasting spread mainly in the direction of the bore hole. The quantity of charge have the important effect for the flying distance of fragmentations. As the results of the observations the fragmentations in the nearest of the blasting point showed the maximum distance.

21 NON-EXPLOSIVE DEMOLITION AGENT IN JAPAN H.HAYASHI and K.SOEDA Construction Materials Research Laboratory, Onoda Cement Co. Ltd, Sakura, Japan T.HIDA and M.KANBAYASHI Research and Development Laboratory, Onoda Cement Co. Ltd, Sakura, Japan Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract The main component of non-explosive agent is CaO, and the demolition mechanism is expansion by CaO hydration, which produces static pressure causing tensile fracturing. Demolition work with this agent is therefore free from noise, vibration, dust and flying debris. Non-explosive demolition agent was developed for the first time in Japan in 1979. This agent has become increasingly popular because it has no environmental or safety problems. Recently, we have been developing fast-acting non-explosive demolishing agent and slow-acting non-explosive demolishing agent. Fast-acting demplition agent cracks rock and concrete in 1 to 3 hours (Normal type demolition agent cracks them in 12 to 24 hours). Slow-acting demolition agent is used to remove heads of Benoto piles, and it cracks pile heads in 4 to 5 days. The demolition system has improved every year, and non-explosive demolition agent has been used for many demolition projects. This paper presents the latest developments in non-demolition agents in Japan, considering both the demolition agent and demolition system. Special application of non-explosive demolition agent for a demolding system for false teeth is also discussed, as well as an anchoring system for FRP tendons etc. Keywords: Non-explosive demolition agent, Expansive pressure, Fast-acting non-explosive demolition agent, Slow-acting non-explosive demolition agent, Demolition system

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1 Introduction In recent years, the use of heavy demolition equipments and explosives in the work of demolishing rock and concrete structure has been restricted or prohibited with consideration for the environment and safety. In these circumstances, the world’s first non-explosive demolition agent was developed in Japan in 1979. Demolition system with non-explosive demolition agent possesses many advantages that is able to use for the demolition work of restricted condition (narrow space, limited demolition) etc. So, nonexplosive demolition agent has been popular, in the other side, this agent has possessed of disadvantages that demolishing time (12 to 24 hours) is rather long, and it is difficult to demolish RC structure and thin concrete structure. Recently, however, fast-acting nonexplosive demolition agent was developed and the demolition system has also improved. So disadvantages of non-explosive demolition agent has been decreasing. This paper presents the latest circumstance of non-demolition agent in Japan. 2 History of non-explosive demolition agent The main component of non-explosive agent is CaO. Historically, there were many attempts to utilize CaO for the demolition work, but, since the hydration velocity of CaO is extremely rapid, it is very difficult to pour the CaO into holes before hydration occurs. Even using retarding agents such as glycerine or ethanol and pouring into holes, the gun phenomenon occurred, so it was very difficult to use CaO for demolition work. In 1979, the world’s first non-explosive demolition agent to overcome these difficulties was developed and commercialized in Japan. Since then, non-explosive demolition agent has been used in many demolition projects, and 5 companies have commercialized it In 1982 a slow-acting non-explosive demolition agent appeared which cracks concretes in 4~5 days. This agent has been mainly used to demolish the top of Benoto piles. Non-explosive demolition agent has many advantages, but the demolition time is rather long, so demands grew for a for fast-acting agent. To meet this demand, fast-acting nonexplosive demolition agent which can demolish concrete within 3 hours was developed in 1985. 5 companies now produce fast-acting non-explosive demolition agent. On the other hand, demolition methods using non-explosive demolition agent have also been improved, for example, controlling crack direction using a bit with slit, demolition in water and demoltion of the surface of concrete structures. Recently, non-explosive demolition agent has been applied not only for demolishing rock or concrete but also an anchoring system for FRP tendons, for removing the highstrength gypsum molds used to make false teeth without damage to the product, etc. 3 Types of non-explosive demolition agent Non-explosive demolition agents are classified as either normal type or fast-acting type according to cracking time. There are also slow-acting types that are utilized to remove

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the heads from Benoto piles. These agents are available in three forms: bulk, briquette, and capsule. Quantities of non-explosive demolition agent (normal type and fast-acting type) sold are shown in Fig-1.

Fig 1 Quantities of non-explosive demolition agent sold

3.1 Normal non-explosive demolition agent This type of non-explosive demolition agent, cracks plain concrete (600×600×600) in no less than 3 hours. Usually, this agent cracks plain concrete in 12 to 24 hours. Commercialized normal non-explosive demolition agents in Japan are show in Table 1.

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Table 1 Commercialized normal non-explosive demolition agents in Japan

3.2 Fast-acting non-explosive demolition agent This type of non-explosive demolition agent, cracks plain concrete (600×600×600) within 3 hours. Previously, we sougnt to reduce the cracking time. If the hydration velocity of demolition agent is accelerated, the required demolition effect is achieved faster. Unfortunately, if hydration is too rapid, the temperature in the hole reaches 100°C, causing hot demolition agent to burst from the hole (the “gun” phenomenon). There are three ways to prevent this phenomenon from occurring: 1) Release of high-pressure steam. 2) Packing the hole with a stopper and increasing the binding strength. 3) Increasing the compacting ratio, increasing the binding strength and reducing the amount of free water to prevent high pressure. Commercialized fast-acting non-explosive demolition agents in Japan are shown in Table 2. Prevention of the “gun” phenomenon is most important when using fast-acting nonexplosive demoltion agent. For example, to prevent the “gun” phenomenon, “Super Bristar 1000” (produced by Onoda Cement Co., Ltd.), is in granular form rather than the

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powder form of normal-acting demolition agents. Steam is released through the spaces between the grains, preventing the “gun” phenomenon. In the case of “High-Calmmite 30” (produced by Nihon Cement Co., Ltd.), the agent is wrapped with a permeable capsule, and the top of the hole is capped with hardening material after charging, preventing the gun pnenomenon.

Table 2 Commercialized fast-acting non-explosive demolition agents in Japan

Fig 2 shows the expansive pressure of normal non-explosive demolition agent and fastacting non-explosive demolition agent. Photo 1 shows the demolition of a rock plate in a tunnel using fast-acting non-explosive demolition agent. Cracks occurred 10 minutes after charging with the agent, and cracks connected the holes within 15 minutes.

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Fig 2 The expansive pressure of normal non-explosive demolition agent and fast-acting non-explosive demolition agent

Photo 1 Demolition of a rock plate in a tunnel using fast-acting non-explosive demolition agent

3.3 Slow-acting non-explosive demolition agent Recently, in constructing basements, the Benoto method has been adopted when setting piles because it causes less noise and vibration. In this method the pile head, which is very weak due to slime rising up from the bottom, is removed. In the past, this was done by hand, causing noise and vibration. Slow-acting non-explosive demolition agent was developed to complete this operation more effectively. Slow-acting non-explosive demolition agent is set before the concrete is

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cast. Concrete can not be cracked using normal agent because hydration of the agent occurs before the concrete hardens. By adding retarding agent such as citric acid and by making the particle size of the agent extremely large, the hydration speed of the slowacting non-explosive demolition agent matches the hydration speed of the concrete. Fig 3 shows the relationship between concrete strength and expansive pressure of the agent. Photo 2 shows the process of removing pile heads with slow-acting non-explosive demolition agent.

Fig 3 Relationship between concrete strength and expansive pressure of the agent

Photo 2 Removing Benoto pile heads with slow-acting non-explosive demolition agent

4 Applications of non-explosive demolition agent Non-explosive demolition agent has been continuously improved along with demolition method. For example when demolishing reinforced concrete structures with many reinforcements, this agent was rarely used in the past. However, by combining this agent with hand breakers, diamond cutter, etc., this agent has been used more and more to demolish reinforced concrete structures. Examples of actual demolition work and demolition tests using non-explosive

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demolition agent are shown below.

Fig 4 Special bit

4.1 Control of crack direction It is necessary to control crack direction to demolish materials as planned. Crack direction is controlled and cracking time is reduced by cutting slits through the holes. When drilling the hole, the special bit shown in Fig 4 is used. Fig 5 shows the results of demolishing plain concrete both with and without a slit. By preparing the slit, crack direction was intentionally controlled and cracking time was reduced 30%. Using this method, reliability of the planned demolition increases, and the demolition period is reduced. Furthermore, it is more economical.

Fig 5 Results of demolishing plain concrete in both with and without slit

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4.2 Demolishing the surface of concrete structure utilizing narrow trenches In the past, when the surface of a concrete slab or concrete road was damaged, the surface was removed by hand, a very troublesome and time-consuming process. A much better method is to prepare narrow trenches with a concrete cutter and then pour non-explosive demolition agent into the trenches, causing the surface of the concrete to crack. The damaged surface is then easily removed Fig 6 shows method for demolishing concrete surfaces using trenches.

Fig 6 Method for demolishing concrete surface using trenches

4.3 Demolition of rock plate in sea water A flow chart showing the process for demolishing rock plate in sea water is shown in Fig 7. Fig 8 shows charging system of non-explosive demolition agent. Photo 3 shows the ship (SEP) loading, drilling and charging machines. The agent was pumped through the hollow of the drilling rod while pulling out the rod. After 3 days we carried out secondary demolition using a breaking rod. The result was that the average depth penetrated with one hit was 3.5 cm using non-explosive demolition agent, while the average depth penetrated with one hit was 1.1 cm without the agent. So the agent proved to be effective. There had been some concern about the possibility of pollution caused by use of the demolition agent, but both the pH and the muddiness of the sea water around the job site were normal. This method is free from pollution and increases the efficiency of demolition work, so it should be widely adopted for demolition work in water.

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Fig 8 Charging system for non-explosive demolition agent

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Photo 3 SEP loading drilling and charging machines

5 Special applications for non-explosive demolition agent In this chapter, we will introduce special applications unrelated to demolition of rock and concrete. 5.1 Demolding system for false teeth False teeth are made using high strength gypsum molds. When false teeth are removed from the mold they are easily damaged because strong mechanical force is needed to demolish high-strength gypsum. This can result in serious defects, for this reason, the authors developed a demolding system for false teeth using non-explosive demolition agent. Holes are made with a rubber tube before the gypsum is cast. After charging the holes with the agent, the gypsum mold is immersed in hot water (40°C), and the gypsum is demolished into pieces after 15 minutes. The false teeth are left undamaged. (See Photo 4)

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Photo 4 Situation of demolishing gypsum mold

5.2 Demolition of urethra calculus Urethra calculuses are found in oriental people, sometimes as large as 30–50 mm in diameter. Large calculuses are surgically removed, but this is a major operation involving significant risk. The authors have developed a demolition system to solve this problem. A 10 mm pipe is inserted to human body, and holes are drilled in calculuses, and nonexplosive demolition agent is charged into the holes. Damage to human body is controlled minimum to adopt this method. We carried out demolition tests using model calculuses, and it was found that they are demolished perfectly in condition that hole diameter is over 6 mm and hole length is over 15 mm. We are now studying for practical use. 5.3 Anchoring system for FRP tendons Recently, fiber reinforced plastic (FRP) rods or strands have been used in the construction field. FRP rods or strands have some excellent properties such as high strength, non-corrosion, light weight, very small relaxation and non-magnetization. Utilizing these advantages, FRP rods arc used as prestressing tendons. The most important consideration when FRP are used as tendons is the anchoring system. Ordinal anchoring systems are not suitable because the surface of FRP is more delicate than P.C bar for shear force or local stress concentration in the anchorage. FRP are strong only in the axial direction. The authors have developed a new anchorage system for FRP tendons. The principle of this method is as follows. First, non-explosive demolition agent is mixed with water and poured into steel or FRP pipe, into the center of which FRP tendon is inserted. The agent

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hardens and generates high expansive pressure which reaches 50 MPa in 48 hours. It is transmitted in a manner similar to that of fluid. FRP tendon is perfectly gripped by high expansive pressure without stress concentration. Fig 9 shows the general concept or this system.

Fig 9 General concept of anchoring system of FRP tendons

6 Conclusion As mentioned above, non-explosive demolition agent has been adopted widely in demolition work because this agent is safe and non-polluting. Both the non-explosive demolition agent and methods for its use have been continuously improved. However, the demolition efficiency of this agent is still less than that of explosives, it will therefor be necessary to increase expansive pressure of this agent or to combine non-explosive demolition agent with other methods (Explosives, Oil-pressure Breaker, etc.). In order to develop this safe and pollution-free demolition method further, we hope to encourage mutual cooperation among all parties involved in its development. 7 Reference T.Kawano (1982) Non-explosive demolition agent. Gypsum & Lime, No. 176, pp. 41–48. M.Kanbayashi, T.Hida, S.Matsui (1991) The basic study on planed demolition using nonexplosive demolition agent. Proc. of 46th Japan society of civil engineers symposium pp. 208–209. K.Soeda, H.Hayashi, et al. (1993) Fast-acting non-explosive demolition agent. Proc. of 3rd International RILEM Symposium T.Katayama, et al. (1985) A new method of cracking gypsum after false teeth polymerization using expansive pressure. The Journal of Dental Technics, Vol. 13, No. 11, pp. 1341–1358. T.Harada, et al. (1990) A New anchoring method of FRP tendons using non-explosive demolition agent Symposium on development of prestressed concrete, pp. 251–256.

22 FAST-ACTING NON-EXPLOSIVE DEMOLITION AGENT* K.SOEDA and H.HAYASHI Construction Materials Research Laboratory, Onoda Cement Co. Ltd, Japan T.HIDA Research and Development Laboratory, Onoda Cement Co. Ltd, Japan K.TSUCHIYA Construction Materials Research Laboratory, Onoda Cement Co. Ltd, Japan Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract A non-explosive demolition agent which utilizes the hydration expansion properties of calcium oxide was first development in Japan in 1979, and eliminates the problems of flying debris, noise, ground vibration, dust, and so on. This agent has become increasingly popular. However, since it takes about 20 hours to achieve the demolition effect, there have been growing calls for a faster-acting agent. To meet this requirement,we have developed two types of fast-acting non-explosive demolition agent. Type 1 agent is in granular form rather than the powder form of the conventional agent. Steam is released through the spaces between the grains, preventing the gun phenomenon. Type 2 agent has significantly lower water-to-agent ratio which is obtained by adjusting the distribution of particles of different size within the mixture. The reduction in the amount of free water prevents the occurrence of the gun phenomenon. This paper describes the optimum distribution of particles and the properties of fast-acting non-explosive demolition agent. Keywords: Fast-acting non-explosive demolition agent, Expansive pressure, Granular, Hydration, Gun phenomenon

1 Introduction Recently, demolition work in close quarters has been increasing, involving the removal of rock in civil engineering projects or the demolition of reinforced concrete structures.

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Therefore, the use of explosive is becoming more and more restricted for reasons of both safety and environmental pollution control. As a result, non-explosive demolition agent which utilizes the hydration expansion properties of calcium oxide was first developed in Japan in 1979. Since demolition work with this type of agent is safe and free from environmental problems, this agent has become increasingly popular. But since about 20 hours are required to achieve the demolition effect, there have been growing calls for a fast -acting agent. To meet these calls, we have developed two types of fast-acting nonexplosive demolition agent. Type 1 agent is in granular form rather than the powder form of the conventional agent. Steam is released through the spaces between the grains, preventing the gun phenomenon. Type 2 agent has significantly lower water-to-agent ratio which is obtained by adjusting the distribution of particles of different size within the mixture. The reduction in the amount of free water prevents the occurrence of the gun phenomenon. This paper examines the optimum distribution or particles for producing two types of fast-acting non-explosive demolition agent. The influences of temperature and hole diameter etc. are also examined. 2 The mechanism of fast-acting demolition The hydration velocity of the agent can be accelerated to shorten demolition time, but this alone is inadequate. For example, if low-temperature agent is used in high temperature, the gun phenomenon would occur. Therefore, to achieve rapid demolition, the hydration velocity of the agent should be accelerated while the gun phenomenon is prevented. Calcium oxide, the main component of non-explosive agent generates heat when hydrating. If the heat velocity is balanced with the diffusion velocity of generating heat to demolished materials, the gun phenomenon does not occur, If the heat velocity exceeds diffusion velocity, generating heat is accumulated in the agent slurry and the temperature of the slurry will exceeds 100°C. Therefore, free water becomes steam and the slurry of agent bursts out of the hole due to steam pressure. We call this the gun phenomenon. The followings methods can be used to prevent the gun phenomenon. (1) Prevent an increase in steam pressure, releasing steam through the spaces between the grains by making the agent granular. (2) Reduce the amount of free water. Obtain a significantly lower water to agent ratio by adjusting the particle size distribution of the agent. (3) To increase the friction between the agent and the side wall of the hole, by adding hardening materials. Fast-acting non-explosive demolition agent Type 1 is in granular form rather than the powder form of the conventional agent, utilizing method (1). Steam is released through the spaces between the grains, preventing the gun phenomenon. Type 2 agent has significantly lower water-to-agent ratio which is obtained by adding hardening materials and adjusting the distribution of particles of different size within the mixture utilizing methods (2) and (3). The reduction in the amount of free water and the addition hardening materials prevents occurrence of the gun phenomenon.

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3 Materials and mix proportions of agents 3.1 Clinker for Type 1 and Type 2 agent The chemical composition pf clinker for Type 1 and Type 2 agent are shown in Table 1. The same clinker is used for both Type 1 and Type 2 agent.

Table 1. Chemical composition

ig.loss

SiO2

Al2O3

Fe2O3

CaO

SO3

Total

2.2

2.3

0.7

0.2

94.5

0.1

100

3.2 Hardening materials The hardening materials which were developed by the authors consists of aluminum cement, ordinary portland cement, and retarding agent to increase working time. 3.3 Mix proportion of Type 1 and Type 2 agent Mix proportions of Type 1 and Type 2 agent are shown in Table 2 and Table 3.

Table 2 Mix proportion of Type

No.

Grain size (mm)

1

Under 7

2

7~0.3

3

7~0.7

4

7~0.8

5

7~1.2

Table 3 Mix proportion of Type 2

No.

Grain size (mm)

Amount of powder (%)

Amount of hardning material (%)

1

7~2.5

0

30

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2

7~2.5

10

30

3

7~2.5

20

30

4

7~2.5

30

30

5

7~ 2.0

10

30

6

7~ 1.2

10

30

7

Under 7

10

30

4 Experimental method 4.1 Method for measuring the compacting ratio The compacting ratio was devised by the authors to evaluate the pore volume of the agent. As shown in Fig 1, a 500 ml cylinder was filled with agent, 1/3 at a time, and tamped 25 times after each 1/3 of the cylinder was filled. Measuring the weight of the agent, the compacting ratio was obtained by equation (1). The specific gravity of the agent was assumed to be 3.23. Compacting ratio (%)=(sample weight) g/(3.23×500) (1)

Fig 1 Method for measuring the compacting ratio

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Fig 2 Method for measuring expannsive pressure

4.2 Method for measuring expansive pressure As shown in Fig 2, the strain gauges were attached to the steel pipe, and the agent was then mixed with water and poured into the pipe. The expansive pressure was calculated using the strain on the steel pipe. 4.3 Method for testing the gun phenomenon Using the apparatus shown as Fig 3, a slurry of agent was poured into the steel pipe and the presence of gun phenomenon was observed. The tests were repeated 10 times at both 20°C and 30°C.

Fig 3 Method for testing the gun phenomenon

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5 Results and discussion 5.1 Results and discussion about Type 1 Fig 4 shows the relationship between the expansive pressure of the agent, the limits of grain size and the compacting ratio. The expansive pressure tends to fall, as the minimum grain size becomes larger. We assume that the compacting ratio goes down and the structure of the hydrated agent becomes rough, when the minimum grain size becomes larger. Fig 5 shows the relationship between the probability of the gun phenomenon, the limits of grain size and the compacting ratio, The probability of gun phenomenon occurring is reduced as the minimum grain size becomes larger. The minimum grain size becomes larger, the pore volume of the agent increases, so that steam is released, preventing an increase in steam pressure. There was a higher probability that the gun phenomenon would occur at 30°C than at 20°C because the hydration velocity of the agent is accelerated at higher temperature. When the minimum grain size of the agent was 0.7 mm, the probability of gun phenomenon occurring was zero at both 20°C and 30°C. From the above results, we can assume that the optimum grain size of Type 1 agent is 7~0.7 mm.

Fig 4 Relationship between expansive pressure, grain size and the compacting ratio (Type 1)

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Fig 5 Relationship between the probability of the gun phenomenon, grain size and the compacting ratio (Type 1)

5.2 Results and discussion about Type 2 (1) Relationship of expansive pressure, water-to-agent ratio and the compacting ratio Fig 6 shows the relationship between the compacting ratio and the water to agent ratio. Fig 7 shows the relationship between the compacting ratio and expansive pressure. As the compacting ratio becomes larger, the water to agent ratio decrease and expansive pressure increases. This is because the amount of agent increases in volume, when the water-to-agent ratio is reduced.

Fig 6 Relationship between the compacting ratio and water-to-agent ratio

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Fig 7 Relationship between the compacting ratio and expansive pressure

(2) Influence of the amount of powder Fig 8 shows the relationship between the amount of powder and expansive pressure, The maximum expansive pressure was obtained with a 10% powder content. This expansive pressure depends on compacting ratio rather than the amount of powder. That is to say, the agent with a 10% powder content has the maximum expansive pressure, because it has the maximum compacting ratio and the minimum water-to-agent ratio. Thus the agent reaches maximum unit volume. Fig 9 shows the relationship between the amount of powder and the gun phenomenon. It was clear that the probability of the gun phenomenon occurring becomes greater with a powder content over 10%. When the powder content was under 10%, no gun phenomenon was observed. Since the water-to-agent ratio increases when the powder content is over 10%, the amount of free water which could cause the gun phenomenon increases. From the above results, we judge the optimum powder content to be 10%.

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Fig 8 Relationship between the amount of powder and expansive pressure (Type 2)

Fig 9 Relationship between the amount of powder and the probability of gun phenomenon (Type 2)

(3) Influence of grain size The expansive pressure increases as the minimum grain size becomes larger, as shown in Fig 10. We assume that as the compacting ratio becomes larger and the water-to-agent ratio is reduced, the amount of agent increases. The minimum grain size becomes larger when adding the appropriate powder and hardening materials. The probability that the gun phenomenon will occur increases as the minimum grain size becomes smaller as shown in Fig 11. When minimum grain size was 2.5 mm, no gun phenomenon was observed. When the compacting ratio becomes larger and water-to-

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agent ratio reduces, free water which could cause the gun phenomenon is reduced. From the above results, we determined that the optimum range of grain size is 7~2.5 mm.

Fig 10 Relationship between grain size and expansive pressure (Type 2)

Fig 11 Relationship between grain size and the probability of gun phenomenon (Type 2)

6 Properties of the expansive pressure of commercialized fast-acting nonexplosive demolition agent Fast-acting non-explosive demolition has been commercialized based on the above mentioned study. In this chapter, this agent is compared with conventional agent in terms of the influence of curing temperature and diameter on the properties of expansive

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pressure. 6.1 Comparison of fast-acting Type 1 and Type 2 to conventional nonexplosive demolition agent Fig 12 shows the expansive pressure of fast-acting Type 1, Type 2 and conventional agent. Conventional agent generates 19.6 MPa of expansive pressure in 18 hrs., while Type 1 generates 29.4 MPa in 2 hrs. at 20°C and Type 2 generates 29.4 MPa in 3 hrs. at 20°C.

Fig 12 The expansive pressure of fast-acting Type 1, Type 2 and conventional agent

6.2 Influence of temperature on expansive pressure Fig 13 shows the influence of temperature on expansive pressure of Type 1. Fig 14 shows the influence of temperature on expansive pressure of Type 2. The steel pipes used in this experiment were buried in concrete specimens because the gun phenomenon was also observed. Expansive pressure was therefore higher than that in water. In both types of agent, expansive pressure increases as temperature rises, because hydration of the agent is accelerated at higher temperature. No gun phenomenon was observed with either agent at 5~30°C.

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Fig 13 The influence of temperature on expansive pressure of Type 1

Fig 14 The influence of temperature on expansive pressure of Type 2

6.3 Relationship between hole diameter and expansive pressure Fig 15 shows the influence of hole diameter on expansive pressure of Type 1. Fig 16 shows the influence of hole diameter on expansive pressure of Type 2. The steel pipes used in this experiment were buried in concrete specimens. In both types of agent, the larger the hole diameter, the larger expansive pressure becomes, because heat is accumulated in the slurry when hydrating. In addition, hydration is accelerated as the hole diameter becomes larger. No gun phenomenon was observed with either agent when hole diameter was Ø 38~52 mm.

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Fig 15 The influence of hole diameter on expansive pressure of Type 1

Fig 16 The influence of hole diameter on expansive pressure of Type 2

7 Applications of fast-acting non-explosive demolition agent Photo-1~2 shows examples of demolition work using the two types of fast-acting nonexplosive demolition agent.

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Photo 1 Reinforced concrete bridge pier Appearence of cracks 30 min. after loading of Type 1. Drill holes: Approx. ø 42 mm, 500 mmL Drill hole spacing: 500 mm

Photo 2 Prepacked concrete Appearence of cracks 4 hr. after loading of Type 2. Drill holes: Approx. ø 40 mm, 1000 mmL Drill hole spacing: 300 to 500 mm

8 Conclusion (1) To achieve rapid demolition, hydration of the agent should be accelerated. At the same time it is necessary to prevent the gun phenomenon. To prevent the gun phenomenon, the following three methods can be employed: (a) To prevent an increase in steam pressure, steam is released through the spaces between the grains by making the agent granular. (b) To reduce the amount of free water, a significantly lower water to agent ratio is

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obtained by adjusting the particle size distribution of the agent. (c) To increase friction between the agent and the side wall of the hole, hardening materials are added. (2) Type 1 is in granular form rather than the powder form of the conventional agent utilizing method (a). Steam is released through the spaces between the grains, preventing the gun phenomenon. The optimum grain size of Type 1 agent is 7~0.7 mm. Conventional agent generates 19.6 MPa of expansive pressure in 18 hrs., while Type 1 generates 29.4 MPa in 2 hrs. at 20°C. (3) Type 2 agent has significantly lower water-to-agent ratio which is obtained by adding hardening materials and adjusting the distribution of particles of different size within the mixture utilizing the method (2) and (3). The reduction in the amount of free water and hardening materials prevents the occurrence of the gun phenomenon. Optimum powder content is 10%, and the optimum grain size is 7~2.5 mm. Type 2 generates 29.4 MPa of expansive pressure in 3 hrs. at 20°C. (4) In both Type 1 and Type 2, it is recognized that the higher the temperature, the larger the expansive pressure. The larger the hole diameter, the larger the expansive pressure. We assume this is because hydration of the agent is accelerated at higher temperature and with a larger hole diameter. (5) Fast-acting non-explosive demolition agent generates greater expansive pressure faster than conventional agent. However, conventional agent has some advantages, such as long working time and the ability to use a mortar pump. Therefore it is necessary to select the appropriate non-explosive agent when considering the conditions of the demoltion work. 9 Reference K.Soeda, T.Harada The mechanism of expansive pressure generation using expansive demolition agent. Japan society of civil engineers(Now printing) K.Soeda (1989) Non-explosive demolition agent. Construction Machine, No. 295, pp. 4551.

23 EXPANSIVE ENERGIES OF NONEXPLOSIVE DEMOLITION AGENT* H.HANEDA and Y.TSUJI Department of Civil Engineering, Gunma University, Japan M.HANADA Yoshizawa Lime Industry Co. Ltd, Japan Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract Non-Explosive demolition agent (NEDA) breaks rocks and concrete quietly using expansive pressure during hydration reaction of calcium oxide without environmental problems. The mechanism of expansive pressure generation in NEDA has not been clearly proven, although there are a number of theories to explain this phenomenon. It is important to clarify the phenomenon not only to make an effective demolition plan, but also to improve NEDA. This paper examines the relationship among expansive energy, degree of restraint and direction of restraint in NEDAs under the restraint of inside and outside steel pipes. Expansive strains of axial and circumferential directions were measured by wire strain gages. The conclusions of the experiments and analyses are as follows; Calculating equations of expansive pressure transferred to the each direction of NEDAs are proposed based on the measured expansive strains at the surface of steel pipes. Radial transferred expansive pressures caused by inside steel pipe and outside steel pipes are about the same value. Axial transferred expansive pressures under the restraint of outside steel pipe are larger than those of inside steel pipe. Radial transferred expansive energy becomes larger as the restraint of steel pipe becomes larger. Key Words: Non-Explosive demolition agent (NEDA), Expansive energy, Restraint of inside and outside steel pipes, Degree of restraint, Radial transferred expansive pressure

1 Introduction Non-Explosive demolition agents (NEDAs) are well accepted with its wide range of

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application and performances, because demolition work with this NEDA for development of urban and industrial areas is safe and free from noise, vibration, and flying debris. The mechanism of expansive pressure generation in NEDA has not been clearly proven, although there are a number of theories to explain this phenomenon. The fast acting grades of NEDA have become available. It is important to clarify the phenomenon not only to make an effective demolition plan, but also to improve NEDA. Calculating equations of expansive pressure transferred to the each direction of NEDAs are proposed based on the measured expansive strains at the surface of steel pipes. This paper examines the relationship among expansive energy, degree of restraint and direction of restraint in NEDAs under the restraint of inside and outside steel pipes. 2 Experimental Program 2.1 NEDA NEDA is a powder that consists mainly of specific lime compounds. The NEDA using in this paper was prepared specially to prevent the blow-out phenomenon even in the large pipes; ø 100. Its chemical composition is showed in Table 1 and its Blaine fineness was 2680 cm2/g. A bulk of NEDA was mixed with water and became slurry, which was poured into the pipes.

Table 1. Chemical composition of NEDA (wt %)

ig. loss

SiO2

Fe2O3

Al2O3

CaO

MgO

SO3

Total

1.88

3.83

2.94

1.02

84.36

2.27

2.72

99.02

2.2 Specimens and Measuring Method Specimens were made with inside and outside steel pipes (JIS G 3454, Carbon Steel Pipe for High Pressure, SCH-80) as shown in Fig. 1. The outside pipes were unchanged, and the inside pipes were changed as shown in Table 2. The degree of restraint in NEDA under the restraint of inside and outside steel pipes was referred to the ratio of the areas of cross section with inside and outside steel pipes to the area of cross section with NEDA.

Table 2. Specification of Specimen

Specimen

roo (mm)

roi (mm)

rio (mm)

rii (mm)

Degree of Restraint p (%)

A

57.05

48.45

–

–

38.65

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B

57.05

48.45

16.93

12.73

50.06

C

57.05

48.45

24.25

20.43

69.66

D

57.05

48.45

38.10

31.55

152.2

Each one of wire strain gages was attached to the surface of pipes of Specimens as shown in Fig. 1. The gages are type of four axes and waterproofed. The specimen of steel pipes was vertically set up in a water bath kept a fixed temperature at 20°C as shown in Fig. 1 and Photo. 1. After the slurry of NEDA was poured into the pipes, the circumferential and axial strains at the surface of pipes were measured. The temperature of NEDA was measured by C.C. thermocouple meter located between inside and outside steel pipes. Each experiment has been carried out in the room kept the temperature and humidity at 20°C±2°C, and 80% RH respectively.

Fig. 1. Specimen

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Photo. 1 Specimen

3 Estimation Method of Expansive Energy After the slurry of NEDA is poured into the specimen of between inside and outside steel pipes, the circumferential and axial strains at the surface of pipes generated by NEDA are measured successively. And expansive pressures of NEDA in each direction are calculated with the corresponding circumferential expansive strains εcro, εcri and the axial strains εclo, εcli as follows; 3.1 Expansive Pressure and Energy by the Theory of a Thin-walled Cylinder Radial transferred expansive pressure σcr and radial transferred expansive energy Ucr of NEDA caused by inside and outside steel pipes are calculated by equation (1) and (2) by using the elastic theory for a thin-walled cylinder.

(1)

(2) where, Es: Young’s modulus of steel pipe v: Poisson’s ratio of steel pipe Ac: Area of cross section of NEDA to=roo-roi: thickness of outside steel pipe ti=rio-rii: thickness of inside steel pipe

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It is assumed that the axial strains of each position of cross section between the inside and outside pipe are constant, and NEDA is made no slides on surface of the steel pipes. In the equilibrium condition of steel and NEDA, the axial transferred expansive pressure σcl and axial transferred expansive energy Ucl caused by inside and outside steel pipes are calculated by equation (3) and (4).

(3)

(4) where, Aso=π (roo2-roi2): Area of cross section of outside steel pipe Asi=π (rio2-rii2): Area of cross section of inside steel pipe p=(Aso+Asi)/Ac: degree of restraint 3.2 Expansive Pressure by the Theory of a Thick-walled Cylinder Radial transferred expansive pressures σcro, σcri of NEDA caused by inside and outside steel pipes are calculated by equation (5) and (6) by using the elastic theory for a thickwalled cylinder.

(5)

(6) Also, based on the assumption adopted as 3. 1, axial transferred expansive pressures σclo, σcli caused by inside and outside steel pipes are calculated by equation (7) and (8).

(7)

(8)

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4 Result 4.1 Behavior of Expansive Strain Fig. 2 shows the change of circumferential strain and axial strain at the surface of pipes generated by NEDA with elapsed time. It was observed that the circumferential expansive strains at the surface of the outside steel pipe generated by NEDA were tensile strains, and the circumferential expansive strains at inside steel pipe were compressive strains. It was certainly observed that the axial expansive strains at the inside and outside steel pipe were both tensile strains. If tensile stress is generated at the steel pipe in the circumferential direction, compressive strain is generated in the axial direction by Poisson’s effect. Though the tensile strain at the surface of outside steel pipe was generated in circumferential direction, tensile strain was generated in axial direction also. It was meant that the tensile stress corresponding to the amount of such strain was generated in the axial direction. The amounts of strain generated at outside steel pipe were over 1300×10−6, the steel pipe was yielded, therefore in this paper it is examined in an elastic range. Fig. 3 shows the relationship between the strain of each direction and degree of restraint. The values of circumferential strains of outside pipes are equal regardless of the degree of restraint. The values of axial strains of inside pipes are also equal regardless of the degree of restraint. On the other hand it can be seen that as the steel restraint ratio is increased, axial strain of outside steel pipe is decreased.

Fig. 2 Change of expansive strain in each direction with elapsed time

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Fig. 3 Relation between expansive strain in each direction and degree of restraint

4.2 Expansive Pressure Fig. 4 shows the change of the radial transferred expansive pressures σcr and the axial transferred expansive pressures σcl that are calculated with above mentioned expansive strains by using the elastic theory for a thin-walled cylinder. It can be seen that as the elapsed time increases, and the expansive pressures in both directions are increased. As shown in Fig. 5, as the degree of restraint is increased, the axial transferred expansive pressure is increased. However a minor difference in the radial transferred expansive pressure is observed.

Fig. 4 Change of expansive pressure in each direction with elapsed time

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Fig. 5 Relation between expansive pressure in each direction and degree of restraint

Also, expansive pressures in each direction σcro, σcri and σclo, σcli are calculated with equation (5) (6) and equation (7) (8) based on the elastic theory for a thick-walled cylinder. Fig. 6 shows the expansive pressures in each direction are increased with elapsed time. The values of expansive pressures in each direction are increased in order of σcl≥σclo>σcro≥σcri>>σcli.

Fig. 6 Change of expansive pressure in each direction with elapsed time

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Fig. 7 Relation between expansive pressure in each direction and degree of restraint

Fig. 7 shows the relation between expansive pressures with inside and outside steel pipes in each direction and degree of restraint. It can be seen that even though the degree of restraint is increased, the radial transferred expansive pressure of both inside and outside steel pipes are almost equal. On the other hand the axial transferred expansive pressure of outside steel pipe is increased as the degree of restraint is increased, but the amounts of expansive pressure are extremely small. 4.3 Expansive energy Fig. 8 shows the relationship between the expansive energies per volume unit of NEDA calculated by the equation (2) (4) based on the theory of thin-walled cylinder and degree of restraint. It can be seen that as the degree of restraint was increased, the radial transferred expansive energy was increased linearly, but the axial transferred expansive energies were equal or decreased. The amount of the axial transferred expansive energy was very small value compared with the radial transferred expansive energy. As compared with the radial transferred expansive energy per volume unit of NEDA restrained by steel pipe, it can be seen that the radial transferred expansive energy was increased almost linearly as the degree of restraint was increased. The amount of expansive energy of Specimen D had been approximately 4 times as large as that of Specimen A. However, it can be seen that the radial transferred expansive pressure of NEDA was equal approximately regardless of the degree of restraint as shown in Fig. 5. Accordingly, radial expansive energies per volume unit of NEDA were calculated on the assumption that the restraint was considered as only the outside steel pipe and the results were showed in Fig. 9. It can be seen that these radial expansive energies are almost equal regardless of the degree of restraint. It can be concluded that the amount of increase of expansive energy per volume unit of NEDA equals the amount of expansive energy caused by the restraint of inside steel pipe and the replaced volume of the NEDA with inside steel pipe. That is to say that radial transferred expansive energy with outside steel

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pipe was caused equally regardless of the degree of restraint.

Fig. 8 Change of expansive energy in each direction with elapsed time

Fig. 9 Relation between expansive energy in each direction and degree of restraint

5 Conclusion In this paper the expansive behavior, expansive pressure, and expansive energy of NEDA under the restraint of inside and outside steel pipe were discussed. It may be said within the scope of the experiments. (1) The radial transferred expansive pressure caused by restraint of inside and outside steel pipes are almost equal regardless of the degree of restraint. (2) The axial pressure of outside steel pipe is extremely large value compared with that of inside pipe. (3) The radial transferred expansive energy is induced with the degree of restraint. (4) The expansive energies of outside steel pipes are equal regardless of the degree of

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restraint. References T.Kawano. (1982) Non-Explosive Demolishing Agent, Gypsum & Lime, No. 176, 41– 48. Estimating system about construction techniques of Notification No. 1236 by the Ministry of Construction Japan (1981) A.Watanabe, T.Goto, H.Matsuda. (1982) CAJ Proceedings of Cement & Concrete, No. 36, 183–186. T.Idemitsu, M.Okada, M.Shintoku. (1983) Proceeding of the Annual Conference of SEIBU-Branch of Japan Society of Civil Engineers, 482–483. T.Harada, T.Idemitsu, A.Watanabe. (1986) Demolition of Concrete with Expansive Demolition Agent, Proceeding of the 38th Annual Conference of Japan society of Civil Engineer, 5, 539–540. Y.Tsuji, M.Ochiai, T.Takeuchi. (1989) Expansive Behavior of Expansive Concrete under the Restraint of Inside and Outside Steel Pipes, CAJ Proceedings of Cement & Concrete, No. 43, 584–589. Y.Tsuji, M.Yoshida, T.Okuizumi, and T.Hashimoto. (1991) Expansive Energy of Expansive Concrete Restrained by Steel Tubes with Different Arrangement, Proceedings of the Japan Concrete Institute, Vol. 13, No. 1, 303–308.

24 RECENT DEMOLITION TECHNIQUES USING ELECTRIC POWER IN JAPAN W.NAKAGAWA Maeda Corporation, Tokyo, Japan Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract This paper describes five reinforced concrete demolition technologies, to have developed or being developed in Japan, among other methods, in which electric power is used. The first technique comprises a system where rebars are electrically heated for stripping demolition of concrete with the rebars. This technique is classified into direct-and indirect-current-application methods; in the former, a current is applied directly through rebars and, in the latter, an induction current is used for indirect heating. According to the third technique, concrete is molten by laser beam for cutting demolition. Finally, two unique technologies based on electric heating are explained. A technology in which sulfur mortar is heated and softened to facilitate drawingout of an anchor is being studied. The other technique refers to static breakers using shape memory alloys, where electric heating is employed to derive recovery force of the alloys. Keywords: Demolition Techniques, Electric Heating, Applying Current through Rebars, Induction Heating, Laser Beam, Sulfur-coated Anchor, Shape Memory Alloy

1 Stripping demolition by electric heating applying current through Rebars 1.1 Overview When a bulk current is applied through rebars in a concrete structure to be demolished, via electrode terminals attached at both ends of the rebars, the rebars are heated by Joule’s heat and begin swelling and create a great temperature gradient in the concrete

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body around the rebars. Consequently, bonding force between the rebars and the surrounding concrete is lost suddenly while creating cracks in the concrete. By applying a current sequentially through adjacent rebars, such cracks grows and expand between current-applied rebars (see Fig.1). After completion of applying current, such cracks are hammered by a breaker or the rebars are pulled out. Thereby the concrete peels in laminar shapes along cracks. Therefore, the concrete can easily be stripped off together with rebars, in planes containing current-applied rebars. 1.2 Experiments and applications 1) Mock-up test of stripping demolition for RC shield walls Mock-up tests were carried out for demolishing the surface of a reinforced concrete wall with built-in rebars. Deformed bars of 38 mm in diameter were embedded at depths of 200 mm and 340 mm apart from concrete surface. Applied current and voltage were 4,000 A and 14 V, respectively. At 8.5 minutes after the start of current application, the temperature of rebars increased to 500°C. Immediately after that, the concrete was broken using a hydraulic hammer, as a second demolition step (see Fig. 2). Demolished fragments were planar along crack surfaces. The methods above have been proposed as a stripping demolition system suitable for breaking a facial portion radioactivated as a biological shield wall of a nuclear reactor. 2) Application of the stripping demolition technology to opening a hole in a diaphragm wall shaft The technology has been applied to demolition works for forming starting and arriving holes in diaphragm wall shafts constructed under the ground, for operating” a shield machine. In this type of a demolition work, working environment is poor because a work site is located deep under the ground and the space is very limited. It is also requested to demolish high-strength concrete with many rebars, within a short time. Rebars to which a current is to be applied are constructed beforehand at a location where an opening in a shaft will be formed (see Fig. 3). Normal diameter and pitch of rebars are 22 mm and 200 mm, respectively. By applying a current of 1,000 A for 10 minutes, rebars are heated up to 400°C. Specifications of typical

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Fig. 1 Internal cracks spanning heated rebars [Ref. 1]

Fig. 2 Secondary break-up of a shield wall after heating [Ref. 1]

Table 1 Specifications of equipments for electric heating

Equipment

Inverter

Transformer

Capacity

200 kVA 100% continuous rating

67 kVA (×3 units) 100% continuous rating

Input/Output

Input

Output

Input

Output

Phase

3 phases 3 wires

3 phases 3 wires

phases 2 wires

phase 2 wires

Voltage (V)

200

40 to 400 variable

max. 400

max. 50

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50 or 60 switchable

400

310

max. 167

max. 1,330

400

400

equipments practically used are shown in Table 1. Using the equipments, three rebars are heated at the same time. 3) Application to demolition for locally forming an opening at partition wall between houses in apartment The technology was applied to a demolition work for forming an opening in a part of a house-partition wall of a reinforced concrete apartment. The thickness of the wall was 12 cm and the wall contained round bars of 9 mm in diameter, in pitches of 200 to 250 mm. All vertical and horizontal bars, located within a range to be opened, were heated by applying current thereby creating cracks on the wall. After that, the wall was secondarily broken by pressing the wall using a small hydraulic jack. Demolished fragments were in small blocks which were separate from the rebars (see Fig. 4). 4) Experiment for developing partial demolition technology for opening a part of thick wall It will normally be difficult to dismantle a thick reinforced concrete with a large lot of rebars under various restrictive conditions such as low noise, vibration

Fig. 3 Rebar cage arranged in a diaphragm wall shaft [Ref. 1]

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Fig. 4 Secondary break-up of a party wall after heating [Ref. 1]

and dusting. However, even such a reinforced concrete can be demolished under the same restrictive conditions, by using the following procedures. Step 1: Rebars and cover concrete of a structure to be demolished are heated up by applying a current through rebars. Step 2: Static demolition agent is filled into holes drilled in a suitable pattern on remaining concrete (freed from the constraint of rebars) and the concrete is broken and demolished. An experiment was performed using these steps for forming openings in a reinforced concrete wall. The results are as follows. (a) By filling a static demolition agent into the wall, widths of internal cracks in the concrete, created by applying current, increased. (b) The static demolition agent was effective to create cracks that connected the filling holes, because the facial layer of the wall was made less constrained. (c) Widths of cracks, caused by the static demolition agent, did not expand because of the constraint of concrete body around the openings. In order to enlarge crack widths, forming a slit-like free plane in the wall was effective. (d) To form such a preceding free plane, filling holes having an oblique angle to the wall surface were drilled parallel to each other (see Fig. 5). The angle a between holes should be at least 75°. The angle of 90° brought a much better result. Such a preceding free plane can easily manually be formed by filling up a static demolition agent into the holes. (e) A preferable pattern of holes for filling a static demolition agent is an arc shape open to the preceding free plane (see Fig. 6). The angle β of opening the arc should be at least 90° and more preferably 120°. 1.3 Development in the future When demolishing a reinforced concrete structure, rebars often obstruct demolition work. The electric-heating

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Fig. 5 Forming a preceding free plane

Fig. 6 Arrangement of filling holes

demolition technology is unique in that concrete is more easily broken by taking advantage of the rebars. The features of the technology include 1) the denser the rebars, the greater the effect, 2) little amount of dust in demolition work, and 3) no harmful effect to the base structure without applying current. Making the most of these features, new applications of the technology besides the improvement of equipments have been studied; which include the demolition of foundation concrete, partial demolishing of a reinforced concrete structure, and removing of steels by drawing. 2 Stripping demolition by induction heating of rebars 2.1 Overview In an induction heating system, an electric conductor located in an alternating magnetic field is heated up by an eddy current loss created in the conductor when the magnetic field alternates. This system has already been applied widely to heating, melting, processing and treating metal materials. Applying this principle to demolishing reinforced concrete has been carried out; a coil (as shown in fig. 7) is placed on the surface of a reinforced concrete structure to be

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demolished, to which a high-frequency current is applied to heat up rebars indirectly. Compared to a system where a current is applied directly through rebars, this system is more advantageous in that a preparatory work for attaching electrode terminals directly to rebars is no longer required. 2.2 Results of the experiments The following knowledge has been acquired from the experiments. (a) By inductive heating rebars, concrete around the rebars cracked, thereby a stripping load was halved so as

Fig. 7 Coil set on specimen [Ref. 2]

Fig. 8 Internal cracks [Ref. 2]

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Fig. 9 Cracks observed at the surface (5 min.) [Ref. 3]

to facilitate stripping of cover concrete (see Fig. 8). (b) The larger the electric output, the more quickly the temperature of the rebars increased. A difference caused by frequency was rather small. Where a grid of deformed rebars of 38 mm in diameter was embedded at a covering depth of 100 mm, the temperature of the rebars increased to 400°C as a result of induction heating of an electric power of 200 kW for 3 minutes. (c) The smaller the covering thickness of concrete, the more quickly the temperature of the rebars increased with a smaller area of created cracks (see Fig. 9). (d) Stripping load was smaller by heating a wider range by moving the coil. (e) Where the surface of concrete is covered with a steel plate, the plate could easily be stripped by inductive heating it for an extremely short time. 2.3 Development in the Future One of the features of this system is that rebars embedded in concrete can be effectively heated without being exposed. Taking this advantage, the system is applicable to stripping demolition of surface layers in the shield wall of a nuclear reactor. In addition, proposed applications of the system include dismantling of walls and slabs of general structures and reinforced concrete in irregular shapes. Matters to be developed in the future include controlling of a heating area and the development of practical coils.

3 Cutting demolition using CO2 laser beam 3.1 Overview Laser beam is often applied to the processing of various materials such as metals. An oscillator for generating laser beam consists of a laser medium, laser resonator, and a pumping device. Applicable laser media include CO2, CO, He-Ne and other gases and solids such as YAG (Yttrium-Aluminum-Garnet) and ruby. The pumping device excites atoms and molecules using electric energy. Using of laser beam for cutting demolition of concrete structures has been conducted. Laser beam, focused into a small diameter in a light-focusing system, is provided with

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power in a very high density and can melt a metal or concrete. Cutting work is conducted while removing dross using a gas. 3.2 Results of the experiment Major results acquired in the experiment were as follows in view of cutting demolition of reinforced concrete. (a) The CO2 laser is most suitable because of the highest output available at present. (b) The slower the cutting speed, the greater the cutting depth results. A cutting depth can be well represented by a linear equation of a logarithm of cutting; speed (see Fig.10). (c) A cutting depth increases with a radiation energy (an amount of laser output, divided by a cutting speed). This is also represented well by a linear equation of a logarithm of radiation energy (see Fig.11). (d) An assisting gas of air or N2 is used for rebar-free concrete. For steel materials, using an oxygen assisting gas can increase a cutting depth. Cutting depths obtained from the experiments were 30 cm for rebar-free concrete (Fig.12), 25 cm for concrete with embedded deformed bars of 10 mm in diameter (Fig.13), and 17 cm for concrete with deformed bars of 41 mm in diameter. 3.3 Development in the future Laser cutting of reinforced concrete is still in the stage of laboratory research testing, at present because of problems in cutting capacity and cost. However, regarding cutting capacity, a new resonator having an output of 40 kW to 50 kW will soon be developed. Relating to cost, the laser system can possibly compete other systems for a

Fig. 10 Maximum cutting depth vs. cutting velocity [Ref. 4]

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Fig. 11 Maximum cutting depth vs. radiation energy [Ref. 4]

Fig. 12 Cut surface of plain concrete specimen [Ref. 5]

Fig. 13 Cut surface of reinforced concrete specimen [Ref. 5]

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special structure such as concrete with rebars disposed in a high density, the same covered with a thick steel plate or such concrete as being embedded with a large lot of steel materials. From this viewpoint, the appropriateness of the laser system has been proposed for the demolition of surface layers in a shield wall of a nuclear reactor. 4 Removal of sulfur-coated earth anchors by electric heating 4.1 Overview Sulfur concrete or mortar uses a binding material of sulfur instead of ordinary cement paste, for manufacturing a curable substance. The sulfur concrete can effectively resist acids and salts and has a great feature of short curing time. Consequently, it is utilized for floors in chemical works, underground structures, concrete for emergency work, or the like. However, the greatest shortcoming conventionally acknowledged is lower resistance to heat. A study has been conducted by taking advantage of this shortcoming to develop a new anchor that is removable after the completion of a construction work. Although the strength of sulfur mortar is equivalent to or higher than conventional cement mortars, at a normal temperature. However, at about 120°C, sulfur content melts while suddenly losing the strength. That is, bonding of the sulfur cement onto an anchor can be controlled by virtue of thermo-plasticity of sulfur (see Fig. 14). According to a new system under development, a Nichrome wire is wrapped beforehand on a tension member of an anchor, through which a current is applied for heating and melting sulfur mortar to reduce bonding force and remove the anchor. 4.2 Results of the experiments 1) Bonding force of sulfur anchor using expansive cement The bonding force of an anchor coated with sulfur mortar was tested. It was obviously confirmed that the sulfur-mortar-coated anchor has a similar strength to a cement-mortarcoated anchor, in terms of resistance to removal by drawing. It was also revealed that a rupture surface of removal by drawing existed on a boundary plane between the coating and surrounding cement paste, not between rebars and coating. 2) Removal of sulfur anchor by electric heating Two types of test specimens were produced by wrapping Nichrome wires on the surface of rebars and sulfur mortar, respectively, and energized for heating (see Figs. 15 and 16). It was confirmed that, when temperatures of sulfur mortar approached the melting point of sulfur, coated

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Fig. 14 Viscosity of molten sulfur

Fig. 15 Specimens of sulfur-coated anchors [Ref. 7]

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Fig. 16 Temperature vs. current-application time [Ref. 7]

Fig. 17 Load of pushing off vs. current-application time [Ref. 7]

sulfur mortar softened so that the anchor rebars could easily be removed by drawing (Fig. 17). Rupture planes of both types existed on a boundary between the rebars and the coating. It was also acknowledged that the larger the number of turns for the Nichrome wire, the smaller the drawing load resulted even with the same power consumption. 4.3 Development in the future A result of the experiment is that a sulfur-mortar-coated anchor can replace conventionally used anchors provided the bearing strength of a ground base for construction is satisfactory and an expansive cement is used as a grout material. Another

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conclusion of the experiment is that an anchor is easily removable by applying current Into sulfur mortar and then drawing the anchor. It is expected that the behavior of this type of anchor is confirmed in a full-scale model test at a field and the technology is practically accepted. 5 Demolition using silent breakers with shape memory alloys 5.1 Overview A silent breaker is a machine using shape memory alloys (SMA) in place of a hydraulic jack, whose recovery force is utilized to break concrete. When a cylindrical SMA (15 mm in diameter and 29 mm in height), beforehand compressed by a compressor, is heated up, the SMA expands at 50°C to 100°C, resulting in a recovery force of about 10 tf. Electric heating is employed at that time. Examples of conventional SMA breakers are shown in Figs.18 and 19. The first step of demolition procedures is that several SMAs are disposed in a load platen while forming a breaker which is inserted into a bore hole. In the next step, a

Fig. 18 Load vs. displacement (Ti-50.5 Ni: 400 Co, 1hr) [Ref. 9]

Fig. 19 Section of SMA breaker (6-cascaded) [Ref. 10]

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Fig. 20 Breaking of boulder sandstone [Ref. 10]

Fig. 21 State of created cracks of pile head [Ref. 10]

current of 400 W at a single-phase voltage of 200 V is applied to a cartridge heater in order to heat up the SMAs through a heater block. Thus, concrete can be broken along a row of bore holes. 5.2 Examples of application 1) Demolition work for rock or rebar-free concrete Bore holes are drilled in suitable intervals Into a concrete to be demolished, into which SMA breakers are inserted and energized. Thereby, the object concrete is broken into small fragments. Fig. 20 shows a case of a sandstone, whose estimated uniaxial compression strength is 600 to 800 kgf/cm2. The interval of drilled holes was 25 cm and current-application time was 2.5 minutes. 2) Experiment for applying breakers to the treatment of the head of a site-cast

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concrete pile After a laboratory test, disposal of pile heads was tested for demonstration using the SMA breakers at an actual work site. At that time, PVC tubes were buried before casting concrete, so as to omit a work for drilling holes into which the breakers were inserted. In addition, heat-insulation material was wrapped around rebars in the pile head from which concrete was removed (Fig. 21). 5.3 Development in the future The SMA breaker is advantageous in compact size, light weight and repeated applicability. Research and development of the breaker has been conducted to improve work efficiency by mounting the breaker on a hydraulic drill, and the use of twodirectional SMA. Acknowledgment The study on the demolition technology by electric heating through rebars was conducted under the leadership of Prof. Y.Kasai and in cooperation with K.Nishita, T.Sugawara and Y.Tomita (Maeda Corporation). In particular, T.Hirayama (Onoda Corporation) cooperated for the study on the static demolition agent. For the other four techniques, the following people provided the author with variable information and references. M.Mashimo (Tokyo Electric Power Services Co.), concerning induction heating of rebars A.Kutsumizu (Obayashi Corporation), concerning CO2 laser cutting M.Miyajima (Iwata Construction Co.), concerning removal of sulfur-coated anchor T.Inaba and T.Kasamatsu (Nishimatsu Construction Co.), concerning breakers using shape-memory alloy The author expresses his sincere thanks to all of them. References [1] Nakagawa, W., (1991) A Study on Development of Stripping Demolition Method of Cover Concrete by Applying Electric Current through Reinforcing Bars, Annual Report of Technical Research Institute of Maeda Corporation, Vol. 31–1. [2] Mashimo, M., Nishizawa, Y., (1989) Induction Heating Method, Architectural Product-Engineering, No. 281, Shokoku-sha, pp. 82–85. [3] Mashimo, M., Seya, Y., Omatsuzawa, K., Nishizawa, Y., (1989) Fundamental Study on Dismantling Method of Reinforced Concrete by Inductive Heating—Part 7, Summ. of Tech. Papers of Annual Meeting of AIJ (Architectural Institute of Japan), No. 1173, pp. 345–346. [4] Kutsumizu, A., Moritaka, I., Wakizaka, T. and Moriya, M., (1987/1988) CO2 Laser Beam Cutting Tests of Concrete—Part 1 & 2, Fall Meeting of Atomic Energy Society of Japan, Vol. 2, pp. 267/pp. 269. [5] Obayashi Corp., (1991) Research and Development of Laser Cutting Technology and

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Robots Used for Dismantling Nuclear Power Facilities, ROBOTICS IN NUCLEAR FACILITIES Special Issue for Exhibition of SMiRT-11, in English. [6] Kutsumizu, A., (1991) Demolition Using Laser Beam, Concrete Journal, Vol. 29, No. 7, Japan Concrete Institute, pp. 48–52. [7] Inuzuka, M., Imai, M. & Sasaki, K. (1990) Reduction of Removing Force of Sulfur Concrete by Electric Heating, Proc. of the 45th Annual Conf. of JSCE (Japan Society of Civil Eng.), 5, pp. 150–151. [8] Sasaki, K., Miyajima, M. & Inuzuka, M., (1990) Bonding of Sulfur Anchor Using Expansive Cement Paste, Proc. of the 45th Annual Conf. of JSCE, 5, pp. 152–153. [9] Inaba, T. & Miyashita, T., (1993) Rock and Concrete Breaker Using Shape Memory Alloy, Journal of JSCE, January 1993, pp. 10–13. [10] Inaba, T., Kaneko, K., Nishida, M. & Yamauchi, K., (1992) Application of Silent Rock Breaker Using Shape Memory Alloys for Construction Site, Proc. of the 24th Symp. on Rock Mechanics, JSCE, pp .415–419. [11] Yamanouchi, J., Miyashita, T., Iizuka, S. & Shiokawa, M., (1993) Development on the Method of Removal of Cast-in-Place Concrete Pile Head Using Shape Memory Alloy, Summaries of Technical Papers of Annual Meeting of AIJ, to be published.

25 THE EXPLOSIVE DEMOLITION OF TALL BUILDINGS G.T.WILLIAMS Bullen and Partners, Croydon, UK Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract The paper outlines the reasons for wanting to demolish tall apartment buildings in the United Kingdom and explains the explosive based techniques that are being used. Some typical contracts are described, measured ground vibrations are tabulated and details are given of the organisation on site on the day of the blowdown. Keywords Demolition, Explosives, Ground Vibrations, Tall Buildings, Collapse Mechanisms.

1 Introduction In the 1960’s there was a boom in the construction of tall apartment buildings in the United Kingdom. The need for new housing was pressing after the damage caused in war-time and the long period that followed during which building materials and skilled labour were in short supply and construction activity low. The British people were not accustomed to the idea of living in tall flats and viewed the idea with suspicion. However in the new age that was dawning, they were told, the lightness and space of high-rise dwellings and the modern facilities that were offered would be such an improvement on the eighteenth and nineteenth century inner city terraces that many of them were used to in pre-war years that their lives would be transformed. To speed up the building process, and to minimise the use of steel and skilled labour, factories were set up to manufacture precast and prestressed concrete units to be assembled on site. Many hundreds of blocks were built in areas such as the East End of London, Glasgow, Birmingham and Liverpool. Standards of construction were not always high and designs were not always suitable. In particular thermal insulation was often poor, waterproofing of roofs and windows

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unsatisfactory and heating inadequate. Electric underfloor heating was often chosen for economy of installation. This was expensive for tenants to run and not effective enough to combat damp from condensation and water leakage. Some designers had a fondness for open deck access and open deck drying and recreation areas which were not well suited to the British climate. All in all the industrialised building boom of the 1960’s and 1970’s produced very many tower blocks that now require extensive improvement or total reconstruction. Many are being refurbished and operated under a better management structure but there is a hard core where the preferred option is demolition and redevelopment of the site. Demolition of such buildings, up to 25 storeys in height and usually surrounded by dense housing developments, poses many problems including safety and disruption to the lives of other people living in the neighbourhood. Structures of this height cannot be demolished from the ground with cranes and wrecking balls, neither can they be pulled or pushed over with mechanical plant. Demolition by dismantling, using tower cranes in the reverse order of construction, is feasible but slow, expensive and dangerous. Fully enclosed scaffolds are essential but there is a large element of handwork that poses dangers to workers and the possibility of material being dropped putting adjacent properties and occupants at risk. The work is noisy and produces dust over a long period. 2 Demolition by Explosives The explosive method of demolition has been used extensively in the United Kingdom over the last ten or more years and a description of it, as used on multi-storey housing developments, is the subject of this paper. Since 1979 some thirty to forty tall blocks between twelve and twenty-five storeys in height have been demolished by explosives in different parts of the Kingdom. In all cases a vertical mode of collapse was adopted and the results of the demolition were satisfactory. However in two instances a full collapse did not occur on the detonation of the charges. In one case collapse was arrested after failure of about ten floors, leaving a further twelve to go, and in the other the building remained supported on the cladding for a short while until it was released by a prod with a pusher arm at a vital point. No significant damage was caused to neighbouring structures and certainly no injury to people. Each time the demolition was completed without the need for further charges and without undue disturbance to the neighbourhood. In every case when alternative tenders were sought for conventional and explosive demolition the explosive option was cheaper and occupied a shorter time. The Clients for almost all of these operations have been Local Authorities, as responsible public officials they have been appreciative of both the risks and the financial benefits of a speedy and economical solution to their problem. They are also quick to realise the publicity afforded by a successful and spectacular display of their determination to get on with the job. The client will normally appoint an experienced engineer to advise on suitable methods, draw up a tender list of contractors, invite tenders and advise on the results but

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one or two contractors have acquired sufficient expertise to enable them to secure contracts directly by negotiation. 3 Collapse Techniques In the demolition of a high rise building it is necessary to achieve a collapse into as small an area as possible and within the immediate confines of the building site. This generally rules out felling the building by producing a hinge at the base and allowing it to fall flat on the ground, as would be done traditionally with a tall chimney. A technique has been developed in France for inducing a hinge at about one-third height and felling the upper part, leaving a stump for removal by machine. As far as is known neither this method nor felling has been used in the United Kingdom. The word ‘implosion’ has been adopted to describe the telescopic method of collapse where internal supports are systematically destroyed to force the building to fall into itself and form a compact heap on its original site. This is an ideal mode of collapse for several reasons, it is progressive over several seconds, makes the most use of the rubble pile for absorbing the shock of thousands of tons of rubble hitting the ground and it requires the least amount of space. The difficulty is not so much in achieving it as doing so without expending so much work that the process becomes uneconomic and competitive contracts cannot be secured. After all when the support to a section of building is removed its natural tendency is to drop straight down, it will only move in some other direction if forced to do so. Among the first buildings to be demolished in this way in the UK were Oak and Eldon Gardens in Birkenhead in about 1978, followed by a building at Rochester in 1979 and Newtown and Stratford Points in the London Borough of Newham in 1980. There was not a great deal more activity in this field until a report was commissioned in 1985, by the Greater London Council, on the feasibility of using explosives to demolish Northaird Point in the London Borough of Hackney. Northaird Point was one of seven twenty-two storey apartment blocks on the Trowbridge Estate, a mixture of low and high rise buildings. It was suspected of suffering from structural weaknesses and was unpopular with tenants. The Borough had plans to demolish all the tall blocks, starting with Northaird Point, and to progressively redevelop the whole site. The tall blocks were system-built using large panel precast wall and floor slabs. Joints were formed in-situ incorporating projecting reinforcement and longitudinal lacing bars, it was the integrity of these joints that gave rise to the original suspicions about the strength of the buildings, suspicions that were to be shown as unfounded in no uncertain manner later on. The walls were made of high density precast concrete and were arranged in a close pattern, an egg-box type of construction that had a great many structural redundancies and many different load paths which made them difficult to transform into a mechanism with the required properties for collapse. Cladding was in storey height concrete sandwich panels and these panels turned out to be, indirectly, the biggest problem of the whole demolition. Heavy cladding panels perform several useful functions during an explosive

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demolition contract, they confine the noise and dust of the preliminary stripping and drilling works, keep down complaints from neighbours and more importantly they contain flying particles and air blast during the explosion, making the collapse an inward looking ‘implosion’ rather than a devastating ‘explosion’. Also they are not easy to remove, blasting is undesirable because of ‘fly’ from the outside of the building and the height rules out any other sort of convenient system except for scaffolding or tower crane which defeats the main object. Yet if cladding panels are left intact there is not only the risk of their being blown free and falling in one piece but they can seriously hamper the main collapse mechanism. This happened at Northaird Point. The feasibility study was in favour of an explosive demolition and a contractor was appointed who, whilst experienced in the use of explosives, had not previously been involved in tower block demolition. He was careful but cautious and the result of his efforts was a half collapsed building resting on a mound of rubble. See Figure 1. The core walls and most of the internal walls up to the eighth floor had been blasted away but the cladding provided a high degree of support that was not ruptured until, at a late stage in the sequence, the first two floors were totally destroyed by the charges and the building as a whole dropped by two storey heights to the ground. The shock of this impact was sufficient to start a general telescoping but only up to about the tenth floor. It was instructive to see that the upper twelve storeys of Northaird Point could be allowed to fall bodily for thirty metres without suffering any apparent damage, not even broken windows, and this after years of worry about vulnerability of tall buildings to gas explosions! Fortunately the twelve storeys were just within the reach of a crane and ball and the work was completed by this means, still

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Fig. 1 DEMOLITION OF NORTHAIRD POINT, HACKNEY 1985

within the contract period. The next building on the same estate to be demolished by explosives was a similar block, Highworth point, and as it provides a good example of a successful collapse mechanism the various stages are described here in some detail. The mechanism chosen was the ‘slice’ method whereby a row of supports was removed by blasting at one end of the building allowing a bay of floors and walls to fall, although remaining hinged to the rest of the block. An instant later the next row was also

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blasted setting the hinge back a further bay and at the same time deforming walls and slabs to develop fragmentation. Thus the collapse proceeded in slices until completed in a total time of about three seconds. A decision had to be made on which floor levels were to be blasted, it was not necessary to blast at every floor but if too few levels were destroyed there was a danger of a ‘Northaird Point’, too much stiffness remaining and not enough momentum built up in the fall to complete the destruction. At Highworth Point the main blast floors were ground, 5th, 8th, 11th, 14th, 17th and 20th. That was the plan. To achieve it on site the work went through several stages, the first being a soft strip of fittings and non-structural walls at blast floors. The second stage was to prepare the supporting structural walls for blasting. There is a balance to be struck here between breaking out by hand all structurally redundant walls, leaving only those absolutely necessary to hold up the structure, and letting the explosives do all the work. However to achieve the latter it is necessary to cut openings in long walls for drilling shot holes since the only effective way of blasting concrete walls without excessive noise and fly is to drill in from the end, parallel to the face. It is not normally practicable to drill more than about one and a half to two metres in depth without risk of running off line and so walls longer than about four metres have to be broken into sections by manually cutting out door shaped openings. This work constitutes the pre-weakening stage, the building must be checked to ensure that sufficient strength remains to resist wind forces etc. Pre-weakening is followed by drilling, charging, setting up the initiation system and finally by the blast sequence. In the case of Highworth Point a successful collapse was achieved with good fragmentation and a compact debris pile. The overall time delay between the first and last explosions was three seconds. Explosives were GURIT ‘A’ and 80% GELIMEX initiated by NONEL detonators, low energy detonating cord and an instantaneous electric detonator. A year later a third similar block on the same estate was demolished with equally successful results. This demolition set the pattern for much future work, including buildings at Solihull and Glasgow. Work in Sheffield on buildings containing more in-situ concrete floors and columns and less structural redundancies has shown that satisfactory collapses can be achieved with blasting at fewer floor levels—in fact five in twenty-two floors rather than the seven at Highworth Point. 4 Ground Vibrations The fears in the minds of building owners when they contemplate demolition by explosives lie in the direction of damage to neighbouring people and property from air blast,missiles and ground vibration. Convincing answers to these worries can be given partly from theory but mainly on the basis of past experience. In earlier days reliance had to be placed on experience from industrial demolitions and quarry blasting. Industrial demolitions such as power stations and steelworks tended to have been carried out away from the public eye, as was most quarry and open cast work and were certainly

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Fig. 2 DEMOLITION OF HIGHWORTH POINT, HACKNEY 1986

not in the middle of densely populated residential areas. Nevertheless records were available of the spread of ground vibrations from both the explosion and impact phases of industrial demolitions. Quarry blasting had always been approached systematically in

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relation to building damage, using test blasts and measurements of resulting vibrations to extrapolate the effects on any given site. This avenue was not open to the demolition engineer. In parallel with the uncertainties of propagation were uncertainties of the effects on buildings. Current practice in recording ground vibrations is to express intensity of vibration in terms of the peak particle velocity, usually the square root of the sum of the squares of the peak velocities in three orthogonal directions (SRSS values). Records show a clear differentiation between vibrations arising from the explosive charges and those from the building impacting with the ground. The first lie generally in the 30–40 Hz frequency range and are lower in magnitude than the second which are in the range 5–15 Hz. It is the lower frequency vibrations which have the greater potential for causing building damage. Tables have been drawn up by a number of authorities indicating the threshold levels likely to cause damage to buildings of various types and a useful guide to these is contained in the CIRIA technical note referred to below. Experience to date has been that these tables are conservative, certainly as far as explosive demolitions are concerned which are ‘one off’ events as opposed to say pile driving or quarry blasting. Any building sited close to a proposed demolition needs to be carefully inspected to determine its vulnerability to damage. In general modern buildings are both highly resistant and only likely, if at all, to suffer superficial damage. On the other hand a medieval cathedral would need to have its weak spots clearly identified and measures taken to make them secure before blasting in the vicinity could be undertaken. The spread of ground borne vibrations is influenced by the nature of the ground, this has been shown to be so with quarry blasting but is not nearly so evident for building demolition, probably because the vibration caused by impact is predominant and cannot be reproduced with any degree of accuracy from site to site for the purpose of comparison. Table 1 on the following page shows the broad results of some forty-six peak particle velocity measurements made on the sites of four major demolitions. Building heights varied from twenty-two to twenty-four stories and it is evident that for any given distance from a demolished building, measured from the nearest point, an approximate upper bound limit for ground vibration may be estimated. In no case was any damage to adjacent structures recorded. Taking a figure of 15 mm/sec as a modest level of vibration unlikely to cause damage to a domestic building (the figure for a framed building would be higher) it is seen that a major explosive demolition could be carried out at a distance of sixty metres from an adjacent house without there being undue risk of damage from ground vibration. These figures are not offered as a firm guide to safe practice, which must take local factors into account, but are an indication of the scale of the problem based on values measured on working sites.

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Table 1 Measured Peak Particle Velocities at Four Sites

Site

Structure

Distance metres

SRSS Peak Particle Velocity mm/sec Explosion

Impact

Northaird

Sewer

7

10

45

Wishford

Sewer

8

30

41

Northaird

Ret.Wall

9

13

65

Highworth

Ret.Wall

9

16

116

Wishford

House

18

10

21

Wishford

House

18

26

27

Highworth

Club

20

8

22

Northaird

Bridge Pier

22

8

18

Northaird

Bridge Deck

22

6

11

Royston

Building

25

19

16

Royston

House

30

9

12

Highworth

Sewer

32

6

10

Wishford

Club

35

9

12

Highworth

Tower

40

4

7

Royston

Wall

43

16

9

Northaird

House

45

6

19

Royston

Bldg.

46

7

7

Northaird

Bldg.

60

2

6

Wishford

Bldg.

65

5

11

Highworth

School

65

6

9

Wishford

School

95

2

5

Northaird

Office

130

1

3

Highworth

Road

140

2

4

5 Organisation on Site. Any proposal to demolish a tall block of flats will excite interest in the local community,

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the more so when it is to be done by explosion. This is a spectacular event and will be covered by local and probably national press, radio and television. If the work is to be done safely and without arousing feelings of ‘never again’ a great deal of advance planning in the community is needed. Many people will be frightened of the effect that a large explosion may have on them and on their property and may not have a clear idea of the difference between a controlled demolition and the work of a bomb. The pre-tender planning will identify an area of ‘Exclusion Zone’ which will surround the building to a radius of about one and a half or more times the height and is an area that must be totally free of people at the time of the blow-down. The debris and the worst of the ground vibration will be confined to well within this zone. Inside the exclusion zone, and much smaller, will be the contractor’s working area in which work will continue throughout the contract as in any other contract. The exclusion zone will only be maintained on the day of the blow-down. All households in the neighbourhood, not only those within the exclusion zone, will be informed by letter, well in advance of the date of the blowdown, which areas are to be evacuated, where people who are evacuated will go, what (if anything) they should take with them, what should happen about their pets and valuables, what arrangements will be made for the sick and housebound and all other similar matters. The contractor will be present at a public meeting where full information on previous similar operations can be made available and questions asked and answered. Needless to say full cooperation with police and emergency services as well as with transport companies whose services may need to be diverted on the day is essential. It has been found to be most convenient if the demolition is arranged for mid-day on a Sunday, thus leaving time for a limited postponement if necessary or for any clearing up that may be needed before people return to their houses. Those within the exclusion zone will be asked to leave their houses by 10 am by which time the area will be roped off and patrolled by police and contractor’s look-out men equipped with radios. Housing Department staff and police will round up stragglers and ensure security of unoccupied premises until the area is handed over to the contractor at 11 am for a final security check and blow-down at 12.00 After blow-down the debris is checked by the contractor’s explosives engineer and when he is satisfied that, as far as he can ascertain, the debris pile is safe the occupants of property within the exclusion zone will be allowed to return—again under police supervision. Only when the householders are back in their property is the general area reopened to the public. These precautions are elaborate but essential if confidence is to be maintained. There is no doubt at all that less overall inconvenience is caused by an explosive demolition with its one day of disruption, dust and excitement than a conventional demolition with its unending noise, dirt and danger lasting for six or nine months. 6 Conclusion Experience has shown that concrete tower blocks up to at least twenty-five storeys in height can be safely demolished by the use of explosives without causing damage to

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adjacent properties or serious interference with the local community. There is less risk of accidents to personnel on and off the site and the cost is generally less than when more traditional methods are used. References Head, J.M. and Jardine, F.M. (1992) Ground-borne vibrations arising from piling. Construction Industry Research and Information Association, London.

26 THE APPLICATION OF MODIFIED WATER JETS AS TOOLS FOR DEMOLITION* A.W.MOMBER WOMA Apparatebau GmbH, Duisburg, Germany Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract The paper contains a description of general problems of using abrasive and discontinuous water jets, respectively, for the demolition of plain and reinforced concrete. Different principles of modified jet generation are discussed, including general aspects of action and loading. The discussion encloses abrasive injection jets, abrasive suspension jets, water cannons, water air jets, and pulsating water jets. Keywords: Water jet, Demolition, Concrete, Abrasive, Water Cannon, Pulsating Jet, Cavitation, Cutting.

1 Introduction Plain high-pressure water jets are used as tools for concrete processing worldwide. They are applicable for cleaning, roughening and removing the material. By modifying plain water jets the field of application as well as the efficiency of the tools can be forced up. In general two methods of jet modification exist (Fig. 1): discontinuous water jets and abrasive water jets. 2 Discontinuous water jets 2.1 Theoretical background The term “discontinuous” describes the intended generation of a discontinuous loading regime on the processed material surface. The principle of discontinuous jets is based on drop impact phenomena. Figure 2 show that the impact pressure pi—the so-called “water hammer pressure”—exceeds the conventional stagnation pressure ps. So the aim of discontinuous jet generation is the controlled interruption of the jet stream. These jets are

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characterized by amplitude (impact pressure) and frequency (impact number). Figure 3 shows shows some types of discontinuous jets one can discern. 2.2 Single impact jets The general type of a single impact device is the water cannon. The principle of a water cannon consists in acceleration of a stationary water volume. The

Fig. 1. Subdivision of water jets.

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Fig. 2. Impact pressure and stagnation pressure in relation to jet velocity.

acceleration energy is provided by pressurized air or exploding gas. Depending on nozzle geometry, transmission regime and other factors, the fluid particles can reach velocities of some thousand meters per second. More details are described by Momber (1993). For the material behaviour under this kind of loading see Labus (1991). Atanow (1991) reported on the usage of a water cannon for the demolition of concrete structures. A 60 cm thick reinforced concrete wall and the overflow channel of a power station were totally destroyed. Table 1 contains technical and efficiency values. The prototype was charged 100,000 times without expensive repair. The demolition was done free of dust and vibrations. Concrete and reinforcement bars were separated during the destruction performance. 2.3 Self-resonating and cavitating water jets Johnson et al. (1982) who have developed some types of self-resonating jets have found that the so-called SERVOJET is acceptable to create in air-pulsed jets. A tandem-orifice Helmholz resonating chamber is turned so as to exite a standing wave within the organpipe section. See Chahine et al. (1983) for further details 01 the performance of these systems. Figure 3 shows the structure of a SERVOJET and some experimental results obtained on rock samples. It can be seen that up to a certain jet velocity the selfresonating jet works more effectively than a conventional continuous jet. Field tests in concrete cutting using cavitating water jets have been carried out by Conn et al. (1984, 1987) and Conn (1986). A field trial of the so-called CAVIJET has demonstrated that substantial time and cost savings may potentially be gained with this new approach, relative to either conventional pavement cutting methods such as diamond

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saws or pneumatic pavement breakers, or a 240 MPa abrasive water jet. The heart of the system is a centre body nozzle design. An example for cutting pavement concrete using this unit is seen on Figure 4. Figure 5 shows a cost comparison between different methods for cutting holes in pavements. Nebeker (1984) has modulated the discharge of water through the jet nozzle by cycling the discharge flow above and below its average value. The so-called percussive jet was used to treat concrete members. In result the author found that the percussive jet was able to cut the aggregate at a pressure level of 140 bar. 2.4 External resonating jets Some experience exists in concrete cutting using mechanically interrupted jets. The most common techniques to generate this type of jets are perforated rotating discs (Vijay et al., 1992), rotating gear wheels (Louis, 1982) and turbine pulsator (Louis, 1982). It is possible to control pulse length and frequency by variation of rotating velocity and—for example—number of holes or cogs. The disadvantages of these methods are the quick wear of the moving parts and the losses of jet energy due to water deflection (Lichtarowicz and Nwachukwv 1978, Vijay et al. 1992). Figure 6 contains some results of concrete cutting using mechanically interrupted water jets. The disintegration of continuous water jets due to laser pulses is discussed by Mazurkiewicz (1983). In demolition practice no case of application of this principle is known. Momber (1992) has developed and tested a so-called water-air jet. He obtained an efficiency gain of 150 per cent compared to a plain water jet. Also he found that optimum air contents exist for the material removal (Fig. 7).

Fig. 3. Rock cutting results by SERVOJET using according to Chahine et al

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(1983).

Table 1. Application of a gas-driven water cannon for concrete demolition according to Atanow (1991).

Parameter System mass

20,000 kg

Cannon mass

2,600 kg

Gas pressure

4 MPa

Water pressure

450 MPa

Nozzle diameter

10.5 mm

Water flow rate

2–3 m3/h

Frequency

12 shots/min

Efficiency - concrete wall

1.5 m3/h

- overflow channel

0.5–0.6 m3/h

Fig. 4. Pavement cutting using cavitating water jet (Dynaflow, Inc.).

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Fig. 5. Cost comparison of different pavement cutting methods (Conn et al., 1987).

Fig. 6. Concrete cutting using mechanically interrupted jets (Louis, 1982).

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Fig. 7. Water-air jet unit as tool for concrete processing.

3 Abrasive water jets 3.1 Theoretical background Abrasive water jets are water jets which contain a certain amount of small solid particles (abrasives), for example garnet, quartzite and olivine (Fig. 8). The water jet accelerates these particles to velocities of some hundred meters per second. The high number of abrasives (about a million per second) leads to an accumulation of crack growing performances and to the material failure. Abrasive jets are well known as tools for cutting and trenching reinforced concrete and steel. The first case of field application was described by Dombrowski (1974). In general one can discern two groups of abrasive jets: abrasive injection jets and abrasive suspension jets. 3.2 Abrasive injection jets (AIJ) The principle of AIJ is based on a partial vacuum generation inside a mixing chamber. After mixing the water-abrasive-air mixture passes a focus for acceleration. A new development is the usage of plunger pumps instead of intensifiers for pressure generation. Figure 9 shows cutting rates for different materials using a three plunger pump and an air driven abrasive cutting head. WOMA (1993) reports on the cutting of breaches in concrete ceilings in a chemical factory. The cutting rates for 400 mm thick reinforced ceilings and 250 mm thick members were 1.0 m/s and 2.4 m/h respectively. The tool works without vibrations and during production. For optimising the concrete cutting performance using AIJ see Momber (1991).

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3.3 Abrasive suspension jets (ASS) The general idea of ASS is the common crossing of water and abrasives as a suspension through a single nozzle. The abrasives are placed in a pressure vessel. The main advantages of this solution are the absence of air and the high coherence of the resulting jets. In practice, ASS work at a low pressure level of about 400 bar. The usage of an ASS-based cutting tool for building reconstruction is described by Fossey et al. (1992). They report on the cutting of holes for ventilator installation in 240 mm thick reinforced concrete walls. The cutting rate was about 0.4 m/h. Surle (1991) reports on submerged ASS cutting. For a 100 mm thick concrete member (water depth 150 m) the feed rate lies between 6 and 30 m/h. A sandwich construction (concrete/steel) was cut with 3 m/h (water depth 300 m). Figure 10 shows the application of an ASS for cutting niches into a tunnel wall. 4 Conclusions Modified water jets have a great potential for augmenting the performance of concrete and reinforced concrete cutting. The application of discontinuous and abrasive water jets, respectively, allows the productivity and safety of conventional water jet tools to be enhanced.

Fig. 8. Garnet sand as abrasive material (ASIKOS Strahlmittel GmbH).

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Fig. 9. Cutting rates of different materials by AIJ (WOMA Apparatebau GmbH).

Fig. 10. Application of ASS for concrete cutting (Genflow Engineering GmbH).

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5 Acknowledgements The author is grateful to Prof. H.Louis (Hanover University), Dr M.M.Vijay (National Research Council, Canada), Mr K.Kalumuk (Dynaflow, Inc., Fulton) and Mr H.Alba (Genflow Engineering) for leaving information and photographs. The author thanks WOMA Apparatebau GmbH for its support in preparing and publishing the paper. 6 References Atanow, G. (1991) The impulsive water jet device: a new machine for breaking rock. Int. J. of Water Jet Technology, 1, 85–91. Chahine, G.L., Conn, A.F., Johnson, V.E. and Frederick, G.S. (1983) Cleaning and cutting with self-resonating pulsed water jets, in Proc. 2nd US Water Jet Conf. (eds. D.A.Summers and F.F.Haston), Univ. of Missouri-Rolla, pp. 167–176. Conn, A.F. (1986) Rapid cutting of pavement with cavitating water jets, in Proc. 8th Int. Symp. on Water Jet Techn. (ed. D.A.Saunders), Durham, pp. 231–240. Conn, A.F., Gracey, M.T., Rosenburg, W. and Gauthier, S.W. (1987) Development of cavitating jet equipment for pavement cutting, in Proc. 4th US Water Jet Conf. (eds. M.Hood and D.Dornfeld), Univ. of California, Berkeley, pp. 57–64. Conn, A.F., Johnson, V.E., Lindenmuth, W.T., Chaine, G.L. and Frederick, G.S. (1984) Some unusual applications for cavitating water jets, in Proc. 7th Int. Symp. on Jet Cutting Techn. (eds. I.A.Walls and J.E.Stanbury), Ottawa, pp. 1–12. Dombrowski, H. (1974) Betonschneiden mit dem WOMA-Hochdruck-Strahlwassersystem. Sonderdruck aus Beton-Information 2/1974. Fossey, R.D., Blaine, J.G. and Summers, D.A. (1992) The feasibility of commercial DIAJET use, in Jet Cutting Technology (ed. A.Lichtarowicz), Kluwer Academic Publishers, Dordrecht, pp. 255–266. Johnson, V.E., Chahine, G.L., Lindenmuth, W.T., Conn, A.F., Frederick, G.S. and Giaccino, G.J. (1982) Cavitating and structured jets for mechanical bits to increase drilling rate. ASME Publication 82-Pet-13. Labus, J. (1991) Pulsed fluid jet technology, in Proc. First Asian Conf. on Recent Adv. in Jetting Techn. (ed. J.S.Y.Tan), Singapore, pp. 136–143. Lichtarowicz, A., and Nwachukwa. (1978) Erosion by an interrupted jet, in Proc. 4th Int. Symp. on Jet Cutting Techn. (eds. J.Clarke and H.S.Stephens), BHRA Fluid Engineering, pp. 13–18. Louis, H. (1982) Bericht zum Forschungsvorhaben Nr. 4703/78; FK.: FE 100, 3. Teilbericht Universität Hannover/WOMA Apparatebau GmbH, Duisburg. Mazurkiewicz, M. (1983) An analysis of one possibility for pulsating a high pressure water jet, in Proc. 2nd US Water Jet Conf. (eds. D.A.Summers and F.F. Haston), Univ. of Missouri-Rolla, pp. 15–23. Momber, A. (1991) Betonbearbeitung mit Abrasiv-Druckwasserstrahlen. Bautechnik, 68, 242–249. Momber, A. (1993) Handbuch der Betonbearbeitung mit Druckwasserstrahlen. erscheint im Betonverlag, Düsseldorf. Momber, A. (1992) Untersuchungen zum Verhalten von Beton unter der Belastung durch Druckwasserstrahlen. VDI-Fortschrittsberichte Nr. 109, VDI-Verlag Düsseldorf.

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Nebeker, E.B. (1984) Potential and Problems of rapidly pulsing water jets, in Proc. 7th Int. Symp. on Jet Cutting Techn. (eds I.A.Walls and J.E.Stanburry), Ottawa, pp. 51–68. Surle, R.J. (1991) Hyperbaric abrasive water jet cutting trials for offshore industrial application, in Jet Cutting Technology (ed. D.Saunders), Elsevier Applied Science, London, pp. 525–545. Vijay, M.M, Remisz, J. and Shen, X. (1992) Fragmentation of hard rocks with continuous water jets. Unpublished manuscript. WOMA. (1993) Schneiden von Betondecken. Interner Bericht.

27 INVESTIGATION INTO THE CUTTING OF BONDED PRESTRESSING BARS DURING DEMOLITION* A.BELHADJ Department of Civil Engineering, University of Bristol, UK P.WALDRON Department of Civil and Structural Engineering, University of Sheffield, UK Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract Cutting of large bonded tendons during the demolition of post-tensioned concrete structures is particularly an interesting field where results from the study of steel-concrete bond under impact loading are needed. The debonding mechanism associated with the release of such tendons is yet to be fully understood. In this paper laboratory tests that simulate the basic characteristics of cutting large grouted tendons during demolition are described and results obtained from the experiments are presented. Results from this investigation indicated little risk of the tendon being ejected during demolition provided the grout in the duct is complete and in good condition. Severe cracking of the surrounding concrete resulting in a loss of lateral restraint might, however, present a potential danger. Keywords: Bond, Impact, Demolition, Prestressed Concrete, Post-tensioned Concrete, Grout.

1 Introduction One of the most important prerequisites of reinforced and most prestressed concrete construction is the bond between steel and the concrete. A considerable amount of work on the static bond strength between steel and concrete has been done, but very little attention has been given to the dynamic bond characteristics. Although nowadays there is a greater risk of structures being exposed to impact loading, with disastrous consequences, the knowledge about bond under such loading is still very limited. In fact

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very few researchers have investigated the behaviour of steel-concrete bond when subjected to high rates of loading. Hanson and Liepins (1962) and later Vos and Reinhardt (1982) found that there was a negligible effect of loading rate on bond of smooth bars and prestressing strands. There was, however, a strong influence in the case of the deformed bars. This was mainly due to the fact that both the compressive and the tensile strength of concrete and mortar increase with increasing loading rate. In other words this apparent bond strain-rate sensitivity can be attributed to the concrete itself as deformed bars produce more cracking in the surrounding concrete or mortar. Examples of structures that are, or could be, subject to impact loading and, where bond between steel and concrete could play an important role in the response to such loading, are: piles during driving, off-shore structures, power plants and storage silos. Another case where the bond between steel and concrete is subject to impact loading is as a result of the cutting or the sudden failure of bonded prestressing tendons in post-tensioned concrete structures. This latter case is particularly important for three main reasons: (i) Because of the increasing number of prestressed concrete structures that will eventually need to be safely demolished, there is an urgent need for a better understanding of the behaviour of bonded tendons cut during demolition. (ii) Because of the growing fears about the failure of grouted prestressing tendons in post-tensioned concrete structures, there is an urgent need for an assessment of the structural integrity and “residual” strength of the large number of such structures constructed to date, especially bridges. (iii) The nature of the problem presents a new challenge to the researcher as it deals with bond under compressive impact loading rather than the usual “pull-out” tensile loading, and the highly non-linear response due to the huge energy release involved.

2 Demolition of prestressed concrete A large number of special or unconventional structures such as nuclear and off-shore platforms, prestressed concrete bridges and slabs, progressively stressed buildings and chemical and industrial plants, are being constructed. The demolition of these special categories of structures is potentially dangerous and, therefore, need a high level of engineering expertise if they are to be demolished safely. Despite the fact that some attention has been given to the subject in recent years, research in the area is still very limited and is at a very early stage. The movement of unbonded tendons in flat slabs cut during demolition has been investigated experimentally and analytically by Williams and Waldron (1988). Research in the area of demolition of prestressed concrete structures containing bonded tendons has so far been limited to insitu monitoring of a small number of prestressed beams. Lindsell and Buchner (1988) gave a good summary of the results obtained from the controlled demolition of a variety of such structures. While there seems to be no major risk in dismantling pre-tensioned members, there exists a potential danger in cutting large grouted tendons in post-tensioned beams, In this latter case a high level of strain energy, initially stored in the loaded tendon within a

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relatively small cross-sectional area of surrounding concrete, is suddenly released on cutting the tendon. This could result in severe cracking, bursting of end anchorages and possibly collapse of the whole structure, depending on the quantity of shear reinforcement, local condition of grout and friction between wires or strands. The likely response, however, cannot be predicted yet. Laboratory tests on simplified models have been carried out and some of the early results are presented in this paper. The experiments were designed to simulate the cutting of large grouted prestressing tendons during demolition in particular but can be used to investigate the behaviour of steel-concrete bond under impact loading in general. The data obtained are being used to explain the complex mechanics involved in the dynamic debonding process and to calibrate a Finite Element model for use in general impact bond problems. 3 Laboratory investigation 3.1 Design and scope The experiments were designed to simulate the main characteristics of cutting large bonded tendons in demolition. The principal requirements were to design a cutting mechanism that ensured the fast release of tendon load, a concrete element that would at least crack under such a load, and a safe testing environment. Preliminary tests helped to achieve the above goals and to select a suitable data acquisition method to use. Details of these tests have been reported previously by the authors (1991). Because the ultimate aim of this project is to develop an analytical model that will solve general impact bond problems, two main simplifications were adopted in modelling the test specimens: (i) Plain bars with different surface finishes were adopted instead of strands or groups of strands. This would help in developing a generalised bond model. (ii) The concrete beam was modelled by a cylinder that had a diameter (2c+d) where c is the smallest concrete cover and d the tendon diameter. This would simplify the analysis from a 3-D to a 2-D one. 3.2 Specimens and materials Figure 1 shows a specimen ready for testing. It consists of a 70 mm diameter PVC pipe of 2 mm wall thickness positioned horizontally within five circular bearings to provide lateral support. Rubber rings and grease were used to isolate the pipe from these supports. A 20 mm diameter Macalloy stainless steel bar was centred within the pipe and stressed between two stiff steel reaction plates to a load of about 200 kN using a hydraulic jack. The load was maintained by a hydro-pneumatic accumulator mounted in parallel. The bar was left for 24 hours for any initial relaxation to occurr and then the pipe was filled along the required length by cement or mortar grout. The specimen was then left to cure for 3 to 4 days. Three different finishes were adopted for the Macalloy bars: smooth, knurled and

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threaded. The smooth and threaded bars were obtained directly from the factory while the knurled ones were modified by finely roughening its original smooth surface in the laboratory workshop. A longitudinal groove 2.4 mm wide by 10 mm deep was machined along a distance just over the grouted length of each bar. Five strain gauges were placed in the groove at different positions as shown in Table 1. A sixth gauge mainly used for determining the stress wave front initiation was placed near the cut point and outside the grouted area of the bar.

Fig. 1. Specimen in position just before testing

Gauge wiring was housed inside the groove and brought out at one end of the groove for connection with the data acquisition system (Figure 2). The gauges and their wires were protected by filling the groove with epoxy resin. The PVC pipe in which grout was cast

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was also instrumented by strain gauging around its circumference at the same positions as shown in Table 1.

Table 1. Position of strain gauges along specimen

Gauge position number Distance from end (m)

1

2

3

4

5

Tests 1, 2, 4, 5

0.075

0.345

0.825

1.365

1.905

Tests 3 & 6

0.075

0.255

0.480

0.825

1.365

Fig. 2. Instrumented bars details

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Table 2. List of experiments

Experiment number

Bar surface

Grout mix

Grout compressive strength (N/mm2)

Grout tensile strength (N/mm2)

1

Smooth

A

25

1.75

2

Knurled

A

28

1.87

3

Threaded

A

30

1.94

4

Smooth

B

37

2.42

5

Knurled

B

36

2.51

6

Threaded

B

38

2.65

Fig. 3. Cutting test set up

The types of grout used were: (i) a cement grout mix (Mix A) composed of rapid hardening Portland cement (RHPC), water and a mortar air entraining admixture with the proportion w/c=0.45 and 0.1561 of admixture per 100 kg of cement; and (ii) a mortar grout mix (Mix B) composed of RHPC, sand, water and a superplasticising, water reducing admixture with the proportions w/c=0.45, S/C=1/3 and 0.311 of admixture per 100 kg of cement. The two types of grout and the three bar surface finishes were combined to make up a set of six tests (Table 2). 3.3 Set up and measurements The general arrangements of the cutting tests are shown in Figure 3. For safety reasons, the entire cutting mechanism and the loaded specimen were positioned within the side walls of a rigid steel frame. The disk cutter was adjusted to 1 or 2 mm from the surface of the bar and protective sheets of steel-faced plywood were clamped top and bottom of the frame to enclose the whole system. From a remote distance the cutter and the motor that controlled its movement were switched on. The collection of the data was started by triggering a computer containing a high speed Analogue to Digital Converter (ADC) board and advanced data acquisition software. Outputs from different channels were sampled at a rate of 6 kHz/channel for a

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period of 15 seconds, the time within which the snapping of the loaded bar occurred. Six channels were used to record the axial strains along the bars, five channels for the hoop strains on the PVC pipe containing the grout and two channels for the end loads. 4 EXPERIMENTAL RESULTS AND DISCUSSION 4.1 General observations Total debonding of the smooth bar in the cement grout (Test 1) was apparent although the displacement of the bar was limited. The load at the remote end in this case reduced to zero. The movement of the other smooth bar cast in mortar grout (Test 4), however, was restrained to some degree by the apparent high friction. Load at the remote end reduced but not fully, some residual compression still being recorded. In both tests radial cracks near the cut end of the grout specimen were apparent. These cracks were formed in at least three planes. The propagation of these cracks in the longitudinal direction was limited in both cases but was longer in the case of the mortar grout (about 20 mm long for Test 1 and 30 mm for Test 4). There was a single plane, however, in which the crack extended about 200 mm and 300 mm along the Test 1 and Test 4 specimens respectively. These represented the weakest planes. The reaction against the bearing plate at the remote end caused the formation of a single radial crack about 300 mm long in the case of the cement grout (Test 1) and 350 mm long in the case of the mortar grout (Test 4). In the remaining tests where knurled and threaded bars were used, response was characterised by compressive crushing of the grout specimen at the remote end in contact with the bearing plate. Cement grout used with the knurled and deformed bars (Tests 2 and 3) experienced more severe crushing compared to mortar grout when used with the same bars respectively (Tests 5 and 6). The main longitudinal cracks reached a distance of about 1.25 m in the case of the knurled bar and 1.50 m in the case of the threaded bar when used with the cement grout (Tests 2 and 3). Shorter crack lengths were observed in the case of the mortar specimens (Tests 5 and 6), 0.75 and 0.80 m respectively. In each of these cases (Tests 2, 3, 5 and 6) there was only one other radial crack in addition to the main one referred to above. This had a maximum length of 40 mm. It was also noticed that deformed bars caused more pronounced crushing at the remote end than did the knurled bars when used with the same type of grout. 4.2 Typical strain outputs Figure 4 shows a typical strain output from the five gauges placed along the bar. It clearly shows the unloading stress wave generated on cutting the bar. This is shown in the time delay between the “vertical” parts of the strain history curves of the five gauges representing the sudden drop in tensile strains in the bars. The residual tensile strain in this case provides evidence of bar re-anchorage in the grout after debonding. The afterimpact behaviour represents the free-vibration of the bar-grout specimen system. This

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Fig.4. Axial strain in the bar—Case: Smooth Bar/Mortar Grout

mechanism is also a sign of the existence of high friction between the bar and the grout on one hand and the limited amount of cracking generated by the impact on the other hand. Figure 5 shows the hoop strains on the PVC pipe at the same positions corresponding to those of the gauges in the bar considered above. These plots confirm the conclusions made previously. It should be noted that strains measured on the PVC pipe might appear to be much higher than the grout ultimate tensile strain while in reality it should not have exceeded it. This happens especially when the grout is under very high compressive load. When this happens cracking must be considered to have happened. But when the output peak tensile strain in the grout does not reach that limit it does not necessarily mean that cracking has not occurred. In fact there were cases where the measured hoop strains were below the ultimate tensile strain and yet cracking was seen at the measurement locations. A possible explanation of this could be that under impact the crack in the grout specimen did not form instantaneously across the whole section but it rather initiated locally at the inner face in contact with the bar and then propagated radially out towards the surface.

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Fig 5. Hoop strain in the grout—Case: Smooth Bar/Mortar Grout

4.3 Strain distribution along specimen The change in axial strain in the bar (smooth and knurled cases) as a result of prestress force release is shown in Figure 6. The tensile strain distribution along the bar is plotted at five selected times: (i) just before snapping of the bar; (ii) when the unloading stress wave front in the bar reaches approximately the middle of the specimen; (iii) just before the stress wave reaches the end bearing plate; (iv) after the wave reaches the end plate; and (v) when the system stops vibrating (residual strains). Comparing Figures 6(a) and 6 (b) it can be seen that the friction was much higher in the case of the stronger mortar grout. In both cases the curves show how debonding of the smooth bars progresses as the stress waves travel along their lengths. There was complete slip of the bar in the weaker cement grout while slip of the bar in the mortar grout was limited and the bar re-anchored after debonding.

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Fig. 7: Grout Hoop Strain at Different Times

The examination of Figures 6(c) and 6(d) indicates that knurled bars had a very limited debonding length compared to the smooth bars. In addition to friction the interlocking of the rough surface of the knurled bar with grout helped build up the transfer of the compressive load to the grout specimen as the wave travelled along the bar. By the time the stress wave reached the remote end the whole specimen was loaded in compression with a high concentration of stress at its remote end in contact with the bearing plate. These high stresses caused crushing of the grout specimen at that end which resulted in a sudden re-distribution of strain along the specimen. Grout hoop strains obtained in the smooth and knurled bars cases are shown in Figure 7. Figures 7(a) and 7(b) show again

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the total slip of the smooth bar in the weak grout and the re-anchorage of the same bar in the stronger grout. Figures 7(c) and 7(d) indicate that knurled bars have caused much higher hoop strains in the surrounding grout. The very high residual hoop strains at the end remote to the cut point are due to the grout crushing in that region. The computed impact fracture strain for both grouts used is about 270 µε. Although cracking occurred in all the specimens tested this strain limit was not reached except where knurled and deformed bars were used. A reason for this could be that the wedging effect in these cases helped the transfer of a relatively large compressive load from the bar to the surrounding grout over a short length. Thus, the grout cracks because of the Poisson’s effect induced. The cracking mode caused by the smooth bars is different. The apparent low hoop strains measured in these tests might be due to the fact that the cracks open and propagate to the surface after being initiated at the bar-grout interface as mentioned before. The results of the threaded bar cases, not presented here, were similar to those of the knurled bars but with less debonding length and with a higher degree of grout cracking and crushing. 5 Conclusions Experiments on smooth bars showed that friction between grout and steel was the main cause for limited movement of the bar after initial debonding, especially in the case of a strong grout. The roughness of the knurled bar and the threads of the deformed bar limited the debonding length of these bars. Severe cracking, however, resulted from the cutting of these bars. Based on the test results excessive movement of grouted tendons cut during demolition of post-tensioned concrete structures is unlikely provided the grout in the duct is complete and in good condition. Further analysis using finite elements techniques will explain some of the features observed in the tests such as the cause and mode of cracking of the grout. The continuing development of such tools will enable the consequences of cutting full-scale tendons to be assessed. 6 References Belhadj, A., Waldron, P. and Blakeborough, A. (1991) Dynamic debonding of grouted prestressing tendons cut during demolition, Intl Conf on Earthquake, Blast and Impact, UMIST, Manchester, pp. 411–420. Hanson, R.J. and Liepins A.A. (1962) Behaviour of bond under dynamic loading, Journal of the American Concrete Institute (ACI), 59, No 4, 563–583. Lindsell, P. and Buchner, S.H. (1988) Dismantling of continuous post-tensioned structures, Proc of Intl Conf on Decommissioning, UMIST, Inst of Civil Eng, pp. 131–135. Vos, E. and Reinhardt, W. (1982) Influence of loading rate on bond behaviour of reinforcing steel and prestressing strands, Materials and Structures, 15, No 85, 3–10.

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Williams, M.S. and Waldron, P. (1988) Demolition of structural concrete containing unbonded tendons, Proc of Intl Conf on Decommissioning, UMIST, Inst of Civil Engrs, pp. 121–130.

PART FIVE PROPERTIES OF CONCRETE WITH RECYCLED AGGREGATES

28 RECYCLING OF CONCRETE IN AGGRESSIVE ENVIRONMENT F.R.GOTTFREDSEN Danish Building Research Institute, H rsholm, Denmark F.THØGERSEN Building Materials Laboratory, Lyngby, Denmark Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract When concrete is recycled in an aggressive environment it is important to make sure that proceeding alkali aggregate reactions do not cause damages in the new structure. Accelerated tests have shown that there is a risk of deleterious expansions and cracking. Expansions can be delayed and reduced if fly ash is added to the recycled concrete. The effectiveness of the fly ash depends on the maximum grain size of the recycled aggregate. With a low content of recycled coarse aggregate (20%) no critical expansions were recorded. Keywords: Recycling, Durability, Alkali Aggregate Reactions, Aggressive Environment, Accelerated Tests, Fly Ash.

1 Introduction The extensive research on recycling of concrete in Denmark during the last 25 years has lead to the conclusion that recycling of concrete is possible in a dry environment. Specifications for this is given in the Danish recommendation for recycling of concrete in passive environmental class [1]. When recycling concrete in structures placed outside or in an otherwise humid and aggressive environment two major problems need concern. These problems are: Frost-resistance Alkali-aggregate reactions. The subject of this presentation is the latter problem, which previously has been given very little attention. Only a few projects have been found in the literature [2], [3].

2 Alkali-aggregate reactions In the following paragraphs the causes, the effects and the prevention of alkali aggregate reactions (AAR) will be discussed. 2.1 The progress of AAR Three components have to be present in a concrete in order for the reaction to take place: - Reactive aggregate, mostly in the form of opaline or chalcedonic chert, must be present. - Alkali ions, primarily in the form of Na+ and K+, must be present in the pore solution of the concrete. The alkali ions, originating from the cement or migrating from the exterior, will react chemically with the reactive silica of the aggregates. - Moisture must be present as well, as reactions take place only at high relative humidities. If the relative humidity is below 80–85% in the pores of the concrete reactions will cease. When all of these components are present reactions might take place. If they do, an expansive alkali silica gel will be formed, causing internal stresses to develop. These stresses can result in the forming of micro-cracks around the reactive grains. In severe cases these cracks will develop into a coherent system, and at this point the concrete is seriously deteriorated. 2.2 Preventive measures The damaging effects of AAR can be prevented by limiting one or more of the necessary components of the reaction. In Denmark AAR is usually prevented by using non-reactive aggregates. Furthermore the Danish specification for concrete durability [4] sets a limits to the total amount of alkalis in concrete to be placed in an aggressive environment. The adding of puzzolans like fly ash and microsilica can prevent reactions from occurring in two ways: 1) The puzzolans make the concrete less permeable to alkalis and humidity from the outside and thereby make it more difficult for the reactions to develop. 2) The puzzolans will react with the alkalis in a innocuous reaction leaving less alkalis for the damaging reaction. If necessary attention is given to the problem, and the correct preventive measures are taken, deleterious alkali-aggregate reactions can be avoided, even under severe and aggressive conditions.

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3 Recycled concrete with reactive aggregate It is a fact that most Danish aggregates have a high content of silica. It is also a fact that these aggregates have been used in most of the concrete structures built in Denmark until 1985. Therefore it is evident that a very large proportion of the concrete available for recycling in the years to come will be reactive to some extent. Under special circumstances it will be necessary to use crushed, reactive concrete as aggregates for concrete that is to be used under aggressive conditions. The substitution of sound natural aggregates with recycled concrete is only relevant for particles greater than 4 mm, as strength and workability properties are poor when using recycled concrete as fine aggregate. 3.1 Composition of reactive concrete The majority of damages due to AAR in Denmark are caused by reactive particles in the sand fraction. Of course also the original coarse aggregate can be reactive, but this is not very common. The recycled aggregate concrete, also referred to as new concrete, is then composed of new non-reactive mortar and recycled coarse aggregate. The recycled coarse aggregate will consist of an old mortar containing reactive grains and some original, coarse aggregate which is supposed to be non-reactive. This situation with reactive particles concentrated in lumps is shown in Fig. 1.

Fig. 1. Composition of concrete containing reactive recycled concrete.

3.2 Reactivity As the original coarse aggregate is assumed to be non-reactive, attention must payed to the reactivity of the original mortar contained in the recycled coarse aggregate. Based on its residual reactivity, the original mortar can be divided into 4 different types:

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Type 1: Mortar containing no reactive particles. Type 2: Mortar where the reactions have finished, as all of the silica has been consumed by the reactions. Type 3: Mortar containing reactive particles where the reactions are still ongoing, that is expansions are still developing. Type 4: Mortar containing reactive particles where no reactions have taken place yet due to lack of moisture or alkalis. Obviously mortar of the first two types will show no residual reactivity. The types 3 and 4 will show residual reactivity to some extent and thereby be potentially reactive when placed in a new concrete. When recycling concrete in an aggressive environment it is important to know which of these types the concrete that is to be recycled belongs to, in order to be able to take the necessary precautions and diminish the risk of damaging reactions. 4 Experimental programme In order to investigate the consequences of recycling of concrete containing reactive particles a series of tests have been carried out. The test method used is an accelerated expansion test based on the Danish mortar bar method. Test specimens were made as cylinders of length 200 mm and diameter 100 mm. The specimens were cast with various types of crushed concrete as coarse aggregate and an inert sand as fine aggregate. The cement used had a low content of alkalis. After initial hardening for 28 days at 20°C, the specimens were moved to a saturated sodiumchloride solution where they were stored at 50°C. During the test period of one year the length and weight of the cylinders were measured regularly. The changes in length were taken as a measure of the development of reactions. The recycled concrete was made with four different types of crushed concrete as coarse aggregate. It was the intention, that the four concretes should represent each of the four types listed earlier. Two of the concretes, type 1 and 4, were designed and cast specially for the experiments. The other two concretes, types 2 and 3 consisted of old concrete. A description of the four concretes used as coarse aggregate is given in table 1. Two different maximum grain sizes of the crushed concrete were used: 16 and 32 mm.

Table 1. Description of the four types of concrete used as coarse aggregate.

Name Type Description R-0

1

New concrete cast with non-reactive aggregates (dummy).

R-1

(3)

R-2

2

Old concrete from cores taken out of a pavement severely damaged by AAR.

R-3

4

New concrete cast with a highly reactive sand and non-reactive coarse aggregate.

Old, mixed concrete from a demolition site.

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The influence of the quality of the new mortar was examined by using two water/cement ratios: 0.45 and 0.55. The effect of adding puzzolanes was examined by making concrete with a fly ash content of 0 and 35%, taken as a percentage of the total amount of fly ash and cement. 35% was chosen as this is the maximum amount allowed according to the Danish specification for concrete durability [4]. Partial substitution of the coarse aggregate with recycled concrete was also submitted to examination. Test specimens were made containing only 20% of the highly reactive aggregate. It was supposed that this would prevent damages from occurring. 5 Results Some of the significant results from the expansion tests will be presented in this paragraph. More results can be found in [5]. 5.1 Reactivity In Fig. 2 the time-expansion relationship is illustrated for three of the four types of recycled aggregate, which were examined. When assessing whether or not a given expansion is critical in terms of concrete durability, it is essential to know at what level of expansion visible cracks are formed on the surface of the cylinders. During the test period this critical expansion was observed to be approximately 0.5–1.0%. From the figure it is evident that the aggregate designed to be highly reactive (R-3) has given rise to extensive cracking of the concrete cylinders. After one year the magnitude of the expansions is about 8%, and the concrete was observed to be severely deteriorated.

Fig. 2. Time-expansion curves for concrete made with three of the examined

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aggregate types. Dmax denotes the maximum grain size of the recycled coarse aggregate.

The expansions caused by the aggregate consisting of the partly reactive old concrete (R1) are somewhat delayed, and the final expansion is limited to about 2%, but this expansion still must be considered damaging to the concrete. The use of aggregate consisting of concrete severely deteriorated by AAR (R-2) resulted in very small expansions. This is probably due to the fact that most of the reactive silica has been used up during the earlier reactions. As could be expected the aggregate with practically no reactive silica (R-0) did not cause any expansion, and it is therefore not shown in Fig. 2. 5.2 Fly ash As mentioned earlier the adding of fly ash (FA) is expected to prevent the damaging effects of the reactions. This is illustrated in Fig. 3 and 4 with maximum grain sizes of the crushed recycled concrete of 16 and 32 mm respectively. The recycled aggregate used in these and the following concrete mixes are of the highly reactive type (R-3).

Fig. 3. Expansions with and without fly ash. Maximum grain size 16 mm.

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Fig. 4. Expansions with and without fly ash. Maximum grain size 32 mm.

From these two figures it can be concluded, that the adding of 35% of fly ash delays the development of expansions significantly. Furthermore it is evident that the maximum grain size of the crushed reactive concrete has a great bearing on the effectiveness of the fly ash. With a maximum grain size of 16 mm and water/cement ratio of 0.45 practically no expansion is measured after one year, while the expansion with a maximum grain size of 32 mm and w/c=0.55 is approaching the value obtained without fly ash. 5.3 Partial replacement By using only 20% of the highly reactive recycled coarse aggregate the expansions are reduced markedly compared to the expansions with 100% of recycled coarse aggregate. This is illustrated in Fig. 5. From the figure it is apparent that when the content of reactive silica is reduced to 1/5 the expansions reduces to about 1/25. In other words a positive dilution effect can be established.

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Fig. 5. Expansions with 20% and 100% recycled coarse aggregate.

6 Conclusions Based on the test results the following conclusions can be drawn: - Deleterious expansions and cracking can be the result when reactive recycled aggregate is used in concrete ir an aggressive environment. - The adding of fly ash to the recycled concrete delays the expansions markedly when a very reactive recycled aggregate is used. - The effectiveness of the fly ash depends on the water/cement ratio and the maximum grain size of the recycled aggregate. With a w/c ratio of 0.45 and maximu grain size of 16 mm no expansions were measured after one year in a very aggressive environment. - With only 20% of recycled coarse aggregate, the expansions obtained are so small that they do not lead to cracking in the concrete. Hopefully these results combined with further investigations will make it possible to recycle a greater amount of concrete, also under severe environmental conditions. 7 Acknowledgement The research program was financially supported by the Danish Environmental Protection Agency.

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8 References [1] Såbye-Hansen, E. et al. (1990) Recommendations for the Reuse of Recycled Aggregate for Concrete in Passive Environmental Class, Danish Concrete Association, Copenhagen, Denmark. [2] Yrjason, W.A. (1989) Recycling of Portland Cement Concrete Pavements, Transportation Research Board, Washington D.C., USA. [3] Puckman, K. et al. (1987) Genbrug af betonbelæninger, Statens Vejlaboratorium, Copenhagen, Denmark. [4] Anon. (1986) The Basis Concrete Specification for Building Structures, Danish National Building Agency, Copenhagen, Denmark. [5] Gottfredsen, F.R. and Thøgersen, F. (1992) Genbrug af alkalireaktiv beton i aggressivt miljø, Building Materials Laboratory, Lyngby, Denmark.

29 MODIFYING THE PERFORMANCE OF CONCRETE MADE WITH COARSE AND FINE RECYCLED CONCRETE AGGREGATES P.J.WAINWRIGHT Department of Civil Engineering, University of Leeds, UK A.TREVORROW Department of Building, Nottingham Trent University, UK Y.YU and Y.WANG Department of Civil Engineering, University of Leeds, UK Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. ABSTRACT Tests have been performed on concretes made using recycled concrete as both the coarse and fine aggregate. The recycled concrete was obtained from two laboratory made source concretes of different strengths. Tests were made on the recycled aggregate concrete to measure compressive strength, permeability and porosity up to an age of 168 days. The strength of the concrete made from only recycled coarse aggregate was between 11 to 20% below that of the control; when the natural sand was replaced by recycled fines the figures increased to between 21 and 38%. There was no clear relationship between the strength of the source concretes and the strength of recycled aggregate concretes. The differences in porosity and permeability between the control concrete and the recycled aggregate concretes are far greater than those for strength. There appears to be some correlation between the permeability of the source concretes and those of the concretes made from the coarse fraction of the recycled material. Tests were carried out on concretes made using recycled coarse and fine

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material in which modifications were made by using a superplasticiser and by partially replacing the fines with pfa or natural sand. The use of pfa leads to significant improvements in strength but the results of porosity and permeability were not so good; partial replacement with natural sand produced far better improvements in permeability and a combination of pfa and natural sand is suggested as the best possible solution to improved performance.

1 Introduction The use of recycled demolished concrete as an aggregate for new concrete began as far back as the end of world war two. Much research work has been undertaken to look at the properties of the recycled concrete aggregates and of the properties of the concrete in which they are used. The results of most of the work have been comprehensively summarised and reviewed in three state-of-the-art reports Nixon (1978), Hansen (1986, 1992). The majority of the work has concentrated on the mechanical or engineering properties of the concrete and it has been shown that good quality concrete can be produced using the recycled concrete to replace the coarse fraction of the natural aggregate. When the recycled fines is used in combination with the recycled coarse there is often a significant reduction in the quality of the resulting concrete due largely to the highly porous nature of this fine fraction. As the fines can often account for up to 40% of the total weight of the recycled concrete aggregate it is obviously desirable to use as much of this material as possible. Little work has been published on the durability of recycled aggregate concrete and most of that reported has concentrated on the frost resistance of the concrete. As with strength the durability of the concrete appears to be somewhat impaired by the use of recycled coarse aggregate but there is a significant reduction in durability when both recycled coarse and fines are used. The work reported by the authors seeks to provide further data on the durability of the recycled aggregate concrete, though unlike most previous workers durability is assessed in terms of the fundamental properties of porosity and permeability. The work also concentrates on trying to utilise more effectively the fines fraction of the recycled material. 2 Experimental Work Details of the experimental work have been given in a previous publication by Wainwright (1992) and it is only proposed here to summarise the most relevant points. 2.1 Test Details Concrete performance was assessed largely in terms of its strength, porosity and permeability. Strength was measured on 100 mm cubes in accordance with BS1881 (1983), and porosity was determined by measuring the weight of the specimens in

Modifying the performance of concrete made with coarse and fine recycled concrete aggregates saturated and dry conditions using a vacuum saturation technique. Permeability to oxygen was performed using the equipment and procedure developed by Cabrera and Lynsdale (1988). The specimens used were 25.4 mm in diameter by 48– 50 mm in height cored from 100 mm cubes. After coring the specimens were placed in an oven at 105°C±5°C for 72 hours. They were then placed in an air-tight container until they reached room temperature before the start of the test. 2.2 Production and Properties of Original Concretes Two different grades of source concrete were produced in the laboratory to provide the source material for the recycled concrete aggregates. The mix proportions were designed to provide concrete mixes with nominal cement contents of 380 kg/m3 and 220 kg/m3; both mixes were made to a nominal slump of 50 mm and the resulting water/cement ratios were 0.41 and 0.78 respectively. Cubes and slabs were cast from each mix and specimens were kept in a mist room at 20°C±2°C for 28 days. The slabs were broken down to provide the aggregate for the new concrete and the cubes tested for compressive strength the values of which were 43.0 and 78.0 N/mm2 for the low and high cement content mixes respectively. The corresponding values of porosity were 12.5 and 10.0% and the coefficients of permeability were 3.85 and 2.41 (×10–7 m2). 2.3 Production of Concretes with Recycled Aggregates A number of different mixes were made with the recycled concrete aggregates and their properties compared with that of a control mix made with natural aggregates from the same source as those used to make the original concretes. All mixes were made to a nominal cement content of 280 kg/m3 using a computer package to proportion the mixes. In the first instance three mixes were chosen for investigation:- one in which only the coarse aggregate was replaced with the recycled material, one in which only the fine aggregate was replaced and one made completely from recycled material; these three mixes were repeated for the recycled aggregates made from both source concretes. In addition a number of mixes were later made to assess ways of improving the performance of concrete made with the recycled fines. Using the mixes made from all recycled materials as the controls modifications were made to the mix proportions in the following ways: 1. Replacing 25% and 50% by weight of the recycled fines with natural sand. 2. Replacing 10% and 30% by weight of the recycled fines with pulverised fuel ash (pfa). The pfa used was an unclassified ash obtained from the Drax power station in North Yorkshire. 3. Use of a superplasticiser to enable the water/cement ratio to be reduced to achieve constant workability. The specimens cast from all mixes were stored in a mist room at 20°C±2°C until required for testing. Information on the mix designations and proportions are given in Table 1 and the properties of the hardened concrete are given in Table 2.

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Table 1 Mix Details for Recycled Aggregate Concretes

Mix Designation

Mix Description

Source Concrete (see Table 2)

Plastic Density (kg/m3)

3A, 3B

RC/100%NF

1, 2

2390, 2360

4A, 4B

RC/100%RF

1, 2

2250, 2290

5A, 5B

RC/50%RF/50%NF

1, 2

2320, 2320

6A, 6B

RC/75%RF/25%NF

1, 2

2290, 2315

7A, 7B

RC/90%RF/10%PFA

1, 2

2290, 2331

8A, 8B

RC/70%RF/30%PFA

1, 2

2290, 2328

9A, 9B

NC/100%RF

1, 2

2310, 2350

10A, 10B

RC/100%RF+SP

1, 2

2290, 2320

9E

Control all natural aggregates

2450

RC=Recycled coarse; RF=Recycled fines; NC=Natural coarse; NF=Natural fines; PFA=Pulverised fuel ash; SP=Superplasticisers

3 Concrete Properties

Table 2 Hardened Properties of Recycled Aggregate Concretes

Mix

w/c

Comp, Str (N/mm2)

Porosity %

Permeabilrty coef.(10–7 m2)

7d

28d

56d 168d 7d 28d 56d 168d

7d

28d 56d 168d

3A

0.62

32.5

44.2

46.5

50.0

32

14

14

14

12.6

5.7

5.1

4.2

3B

0.69

32.2

42.3

44.0

44.7

17

14

13

14

9.7

3.9

3.2

2.8

4A

0.65

22.9

30.0

32.0

34.6

39

22

22

21

17.4

10.5

8.2

6.7

4B

0.66

29.6

37.0

40.3

44.0

19

19

17

16

16.3

10.0

7.0

5.0

5A

0.60

26.2

35.2

37.4

40.9

36

18

18

18

13.4

6.4

5.6

5.2

5B

0.62

31.1

38.6

44.2

46.4

19

16

16

13

10.2

5.2

4.2

2.2

6A

0.69

27.4

35.0

36.4

39.1

37

21

20

20

14.1

9.4

9.3

4.8

6B

0.65

28.5

38.9

39.1

45.1

21

18

17

15

9.2

6.9

7.6

5.9

7A

0.61

29.6

39.9

47.4

55.0

21

21

20

17

31.6

10.5

8.6

6.6

7B

0.63

32.4

53.7

51.9

63.4

19

15

16

13

16.0

7.8

7.0

6.4

Modifying the performance of concrete made with coarse and fine recycled concrete aggregates 8A

0.58

32.7

48.3

59.3

62.7

23

17

20

14

5.9

5.4

6.7

5.0

8B

0.57

37.5

55.9

65.9

76.0

16

13

13

11

8.2

4.8

5.7

4.7

9A

0.71

28.0

36.3

37.8

39.5

17

19

16

15

13.3

8.8

6.3

5.5

9B

0.71

37.9

38.9

42.6

44.2

16

15

15

12

15.4

7.3

7.0

3.3

10A

0.58

32.3

39.1

41.7

42.9

22

19

19

18

9.0

6.3

5.5

4.7

10B

0.56

35.6

47.5

51.5

53.2

19

17

16

14

8.5

8.6

5.7

3.1

Cont.

0.62

40.8

49.8

52.7

55.9

11

10

9

8

5.5

4.3

2.4

2.1

3.1 Compressive Strength The compressive strengths for all mixes at four different ages of testing up to 168 days are shown in Table 2. The rate of strength development is similar for all concretes regardless of whether or not they contain recycled concrete aggregate (coarse or fine). Compared with the control mix made from all natural aggregates and made to nominally the same workability the use of recycled aggregate leads to a reduction in compressive strength of the concrete at all ages of testing. For concretes containing natural fines and recycled coarse aggregates made from the low and high strength source concretes the strength reductions at 168 days were 11% and 20% respectively. For concretes containing both recycled coarse and fines the corresponding strength reductions were 38% and 21%. Such strength reductions are in line with those of previous workers Hansen (1992). It is somewhat surprising to see that the strength of the concrete (mix 3A) containing the recycled coarse aggregate from the low strength source concrete is slightly higher than that made from the higher strength mix (mix 3B). However when looking at Table 2 it can be seen that this is largely due to the higher water/cement ratio of mix 3A reflecting the higher water demand to achieve the same workability. One possible explanation for this is that the coarse aggregate produced from the high strength source concrete contains a higher proportion of “old mortar” than that from the lower strength mix as reported previously by Wainwright (1992). The strength difference between the two mixes in question (i.e. 3A and 3B) though is only about 10%. This is to be expected because the quality of the coarse fraction of the recycled material is more dependant on the quality of the aggregate from which the source concrete was made rather than strength of the source concrete. In addition the strength of concrete is known to be influenced more by the strength of the cement paste than the strength of th aggregate itself. It is likely then that the strength of concretes containing the recycled fines will be more influenced by the strength of the source concrete than those made from just the recycled coarse. When making comparisons on the basis of an equal water/cement ratio (see Figure 1) it can be seen that the concretes made with aggregates from the stronger source concrete (i.e. mix 2) are approximately 5.0 N/mm2 stronger than those made from mix 1. It can also be seen (Figure 1) that mix 3A containing only the recycled coarse does not follow this trend which supports the argument made previously regarding the influence of the source concrete on the strength of the new concrete containing only recycled coarse material.

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Figure 1 Influence of source concrete on compressive strength

This trend with compressive strength, and in particular that relating to the two mixes made with recycled coarse and natural fines (i.e. mixes 3A and 3B), is repeated in further test carried out by the author (not reported here) using limestone coarse aggregate instead of quartzite to produce the source concretes. 3.2 Porosity and Permeability The results of porosity and permeably for all concretes are presented together with those of strength in Table 2. The trends are what might be expected; i.e. decreasing porosity and permeability with age for all mixes and an increase in both properties with the inclusion of the recycled aggregates. As with strength the inclusion of the recycled fines has a much greater adverse effect on porosity and permeability than the inclusion of recycled coarse alone. However, the presence of the recycled aggregate has a far greater effect on permeability and porosity than it does on strength. The most sensitive property appears to be that of permeability which in the case of the concrete containing the recycled coarse and fine material from the lower strength source concrete is more than twice as permeable as the control mix. It is also interesting to look at the influence of the source concrete on the porosity and permeability of the new concrete by comparing mixes with similar proportions (i.e. 3A. v 3B; 4A. v. 4B etc). Compared to strength there is a bigger difference in both porosity and permeability at any given age but particularly so in the case of permeability. Indeed with permeability, and unlike strength or porosity, there are significant differences even between those mixes made from recycled coarse and natural fines (i.e. 3A. v 3B). In fact

Modifying the performance of concrete made with coarse and fine recycled concrete aggregates the ratio of the 28 day permeabilities mix 3B to mix 3A is 0.68 which is very similar to that of 0.63 for the two source concretes. This is also true for the tests carried out with limestone aggregates referred to earlier but not reported here. No explanation can be given for this trend at present and further tests are required to establish its significance and verify its cause. 3.3 Tests to Modify the Performance of the Fine Fraction Results of those tests in which attempts have been made to improve the performance of concretes containing recycled fines are presented in Table 2. Some of these results are also presented in graphical form in Figures 2, 3 and 4 but for clarity only selected results are presented in this way.

Figure 2 Strength Development of “Modified” Recycled Fines Mixes

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Figure 3 Porosity/Age Relationship of “Modified” Recycled Fines Mixes

Figure 4 Permeability/Age Relationship of “Modified” Recycled Fines Mixes

3.3.1 Partial Replacement of Recycled Fines with Natural Fines In practical terms the partial replacement of recycled fines with natural fines was thought to be the simplest technique to employ. Replacement levels of 25% and 50% were chosen in the first instance and the results show that, compared to the mixes containing all recycled fines, there was an improvement in all properties at all ages. Increasing the proportion of natural fines results in an improvement in all three properties measured (with the exception of the permeability of specimens made with aggregates derived from

Modifying the performance of concrete made with coarse and fine recycled concrete aggregates the lower strength source concretes) although the improvement in strength is much less significant than that of porosity or permeability. In general more significant improvements are achieved with concretes made from the recycled aggregates produced from the higher strength source concrete. Table 3 summarise these trends by making comparisons with the two mixes containing all recycled coarse and natural sand (i.e. mixes 3A and 3B). On this basis it can be seen that the mix containing a 50/50 blend of natural and recycled fines (derived from the higher strength source concrete) actually performs better than the control mix (mix 3B) made from all natural sand. The improvements in strength and porosity though are not really significant at 4% and 7% respectively but the 21% improvement in permeability is. There is no obvious reason why there should be any improvement in any of the properties unless it is related in some way to the “old mortar” contained in the recycled fines possessing some hydraulic properties. The reason for the poorer relative performance of the mixes made with aggregates derived from the lower strength source concrete (See Table 3) could be because there is less “old mortar” in this material due to the lower cement content of the source concrete.

Table 3 Modifications to fines and their influence on Concrete Properties

Modification

Mix No’s (See T.1)

% Change Strength

Porosity

Permeability

Addition of natural sand

6A.6B 5A.5B

−22, +1 −18, +4

+42, +43 +29, −7

+14, +111 +23, −21

Addition of pfa

7A,7B 8A,8B

+10, +42 +25, +70

+17, −1 0, −21

+57, +129 +19, +68

Superplasticiser

10A, 10B

−14, +19

+28, 0

+12, +11

Note: Results above have been used obtained mixes 3A & 3B as controls, the % change is the differences as a % of control

3.3.2 Partial Replacement of Recycled Fines with pfa As explained in 2.3 in this particular series of tests the recycled fines was partially replaced by 10% and 30% by weight of pfa. The results presented in Tables 2 and 3 and Figures 2, 3 and 4 show that in most cases the addition of pfa results in a significant improvement in all the properties measured and the greater the proportion of pfa the greater the improvement. In addition and relative to all other concretes the properties of the concretes containing pfa improved with age. The reasons for this improvement are well known and are related firstly to the particle shape of the pfa and secondly to its pozzolanic properties. The spherical particle shape aids workability which in turn leads to a reduction in water/cement ratio for a constant workability (see Table 2). This reduction in water/cement ratio combined with the pozzolanic nature of the material leads to the improved performance. Of the three properties measured that of strength appears to be the one most affected by

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the addition of the pfa. As Table 3 indicates, compared with concretes made from all natural fines, replacement of only 10% of the recycled fines with pfa results in an increase in strength at 168 days of between 10 and 42%. With replacement levels of 30% the respective figures are 25 and 70%. The improvements in porosity follow a similar trend although the magnitude of the improvement is less significant. With 10% pfa the porosity (at 168 days) is equal to or 17% greater than that of the all natural fines mixes and with 30% it is equal to or 21% lower. (Note: As before the better performance is achieved with aggregates derived from the higher strength source concrete). The trend shown by permeability is not quite so clear; permeability is reduced with the addition of pfa and the higher the proportion the greater the reduction. Also when comparing similar mixes (i.e. 7A. v 7B, 8A. v 8B) those made with the aggregates from the higher strength source concretes had lower permeabilities. However, in relative terms the magnitude of the reduction in permeability is not as great as one would have expected considering the improvements achieved in porosity and strength. When comparing results with those of the mixes containing all recycled fines (i.e. Mixes 4A and 4B) the most significant improvement is with the mix containing 30% pfa made with aggregates from source Mix 2; (Mix 8A) this had a permeability 25% below that of Mix 4A. But mix 7B (i.e. 10% pfa, source mix) had a permeability 28% greater than that of the all recycled fines mix (Mix 4B). When making comparisons with the natural fines mixes (Mix 3 A and Mix 3B) it can again be seen (Table 3) that the reductions in permeability are far less than those for porosity and strength. It can also be seen from Table 3 that mixes containing 10% pfa perform better in terms of strength and porosity than even those containing 50/50 blend of recycled and natural fines. Yet when looking at permeability Mix 8A (30% pfa, source mix 1) is only marginally better than mix 5A (50% natural sand, source Mix 1) and Mix 8B (30% pfa, source Mix 2) is significantly more permeable than mix 5B (50% natural sand, source mix 2). No explanation can be given for this apparent anomaly in trend and further tests are being carried out to try and substantiate this. 3.3.4 Use of Superplasticisers The use of a superplasticiser as a water reducer enabled reductions to be made in the water content of mixes 10A and 10B to achieve a constant workability. The reductions were however only in the order of 10–15% (see Table 2) which were not as great as might be expected and in fact were similar to those for the mixes containing 30% pfa (Mixes 8A and 8B). Comparing mix 8A with 10A and mix 8B with 10B it can be seen that at early ages the mixes are very similar in terms of strength and porosity which is obviously a result of the similarity in the water/cement ratios. Because of the pozzolanic reactivity of the pfa, the rate of improvement with age, in strength and porosity is greater in these mixes than it is in the superplasticised mixes. Ultimately then the pfa mixes have a significantly higher strength and lower porosity than the superplasticised concretes. When making a similar comparison with permeability the results do not follow the same trend. At early ages the superplasticised mixes have a higher permeability yet ultimately at 56 days and over the reverse is true although the differences between mixes 8A and 10A are only very small. Infact when comparing all the concretes looked at in

Modifying the performance of concrete made with coarse and fine recycled concrete aggregates this phase of the work the superplasticised concretes performed better than most in terms of reducing the permeability (Table 3). However, when looking at the results of strength and porosity the mixes containing pfa showed the greatest improvement and one would have expected the same to be true for permeability. As explained earlier in 3.3.2 further tests are being carried out to establish the validity of some of the results particularly those of permeability. 3.3.5 Comparison of Methods of Modification Of the modifications made to the mix designs of those concretes made from all recycled aggregates the one using pfa to replace part of the fines appears to be the most encouraging. Not only is pfa itself a waste material but the results achieved by its use were in general the most favourable. In the previous discussion comparisons have been made with mixes containing recycled coarse and either recycled fines or natural fines. Compared to the mix made with natural sand the pfa mixes showed significant improvements in strength (i.e. between 10 to 70%) and generally some improvement in porosity (see Figures 2 & 3). However the results for permeability give some cause for concern; compared to the mixes made with all recycled fines there was some improvement but compared to the mixes made with natural fines the pfa mixes were between 19% and 129% more permeable at 168 days. The mix that performed best in terms of permeability was the 50/50 blend of natural and recycled fines (see Table 2 and Figure 4). If comparisons are now made with the control mix made from all natural aggregates and those mixes containing pfa then as far as strength is concerned the pfa mixes are superior. Based on results at 168 days the mixes containing 10% and 30% pfa are between 0% to 13% and 12% to 36% respectively stronger than the control. However both porosity and permeability are significantly higher, permeability by as much as two to three times. According to the data presented greater improvements in permeability can be achieved by using a blend of natural and recycled fines which suggests that a triple blend of pfa, natural and recycled fines would lead to an all round improvement in strength, porosity and permeability. It can be concluded from the results presented here that the use of pfa will lead to significant improvements in the strength but that the durability of such mixes would be suspect. The durability may be improved by further blending with natural sand but further tests need to be carried out to substantiate to what extent this is true. The use of superplasticiser leads to improvements in strength, porosity and permeability. The results though are not significantly better than the combined effects of pfa and natural sand and this together with the relative high cost of the material suggests that its use in this context is not worth pursuing. 4 Conclusions The following conclusions can be drawn from the tests carried out using coarse and fine recycled concrete aggregates in new concrete mixes.

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1. The properties (i.e. strength, porosity and permeability) of hardened concrete made with recycled coarse aggregates are inferior to those of a control mix made with all natural materials. The situation is made worse when the natural fines is replaced by recycled fines. Of the properties measured permeability is the one most affected by the use of the recycled material. 2. The strength of the concrete made with recycled coarse and natural sand is between 11%–20% weaker than the control at 168 days. When natural sand is replaced by recycled sand the figures are 21% to 38%. 3. There is no obvious relationship between the strength of the concretes made with the recycled aggregate and the strength of the original (source concretes). On the basis of equal workability and with concretes made from recycled coarse only those made from the weaker source concrete were the stronger; the reverse was true when recycled fines was used. For an equal water/cement ratio concretes containing recycled fines from the stronger source concrete were approximately 5.0 N/mm2 stronger. 4. There is a significant increase in both the porosity and permeability in concretes made using recycled concrete aggregates compared with the control made from all natural materials. 5. There is a good correlation between the permeability of the source concretes and the permeability of new concretes made using the coarse fraction of the recycled material from these source concretes. 6. The use of pfa as partial replacement of the recycled fines leads to significant improvements in strength. At 168 days mixes containing recycled coarse aggregate and recycled fines with 10% and 30% of the fines replaced by pfa were up to 30% stronger than the control mix made from all natural material. 7. Improvements in porosity and permeability were not as good; the same mixes were one and a half to two times more porous and two to three times more permeable than the control. 8. The replacement of recycled fines with up to 50% natural sand lead to improvements in strength, porosity and permeability. The improvements in strength and porosity were not as good as those achieved with pfa but the reverse was true for permeability, 9. The use of a superplasticiser to reduce water demand resulted in increased strength and reduced porosity and permeability in mixes containing all recycled aggregates. The improvements were not as great as the combined effects of the addition of pfa and natural sand. 10. In mixes made from all recycled materials 28 day compressive strengths of up to 55.0 N/mm2 were achieved by replacing 30% of the fines with pfa. However because of the high permeability of these mixes their durability is in doubt. Durability may be improved by the combined use of pfa, recycled and natural fines.

5 References British Standards Institution. (1983). Method for Determining Compressive Strength of Concrete Cubes. BS1881, pt. 116. 1983, London. Carbera, J.G. and Lynsdale, C.J. (1988). A new gas parmeameter for measuring the permeabilityofmortarandconcrete. Magazine of Concrete Research, 40, 144, 177–

Modifying the performance of concrete made with coarse and fine recycled concrete aggregates 182. Hansen, T.C. (1986). Recycled aggregates and recycled aggregate concrete—2nd state-of-art report. Materials and structures (RILEM), Vol. 19, No. 111, pp 201– 246. Hansen, T.C. (1992). Recycling of Demolished Concrete and Masonry. RILEM, Report No. 6. Published by E&FN Spon. Nixon, P.J. (1978), Recycled concrete as an aggregate for concrete—a review. RILEM TC-37-DRC. Materials and Structures (RELEM), 65, (1977), pp 371–378. Wainwright, P.J., Yu, Y. and Wang, Y (1992). Durability of concrete made with recycled concrete as an aggregate. Proceedings International Conference Fracture and Damage of Concrete and Rock. Vienna, Austria, November 1992.

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30 BEHAVIOUR OF REINFORCED CONCRETE BEAMS CONTAINING RECYCLED COARSE AGGREGATE F.YAGISHITA and M.SANO Department of Civil Engineering, Kinki University, Osaka, Japan M.YAMADA Department of Civil Engineering, Osaka City University, Osaka, Japan Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract This paper describes the experimental study of the feasibility of reusing the aggregate reclaimed from concrete masses which resulted from the demolition of concrete structures. Three types of recycled coarse aggregate which were produced in deferent processes were used. The characteristic features of failures under the Influence of shear and flexure are distinguished. The behavior of the beams is described in terms of deflection, failure modes, reinforcement strains, and crack patterns. Due to static loading, the experiment clarified the following points: The use of recycled aggregate concrete for structural members dominantly subject to bending moments resulted in the development of cracks with marginally larger openings. However, the use of recycled aggregate had little affect. In contrast, structural members dominantly subject to shear forces developed cracks along the longitudinal reinforcement which were indicative of a deteriorated bond. This showed a certain degree of difference, in the mode of failure, from structural members composed of natural aggregate. As well, the rigidity of the beams undergoing a fatigue loading test obviously decreased depending on the low-grade recycled aggregate was used. This tendency was more noticeable when beams were given a shear loading test. Bond tests, using the Schmidt-Thro test method, clarified the interrelated bond properties involving the type of recycled coarse aggregate, the direction of placing concrete, the thickness of cover, and the strength of the concrete. Keywords: Recycling, Concrete, Recycled coarse aggregate, Flexure and Shear, Fatigue, Crack, Concrete cover, Bond stress.

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1 Introduction In recent years the amount of waste concrete which ensues from the demolition of concrete structures has been increasing more than ever before. The status quo is that both urban areas and their corresponding suburban areas are considerably short of waste disposal space. The difficulty in acquiring disposal areas as well as increasing disposal costs has resulted in the frequent, illegal disposal of waste. Consequently this has posed serious social problems. As well, the concrete aggregate supply has gradually decreased due to the limitation of its production resulting from quality control and environmental factors. Thus, the future of the aggregate supply is not optimistic. As a solution to these problems, extracting of concrete aggregate, for reuse, from waste concrete, or in other words, the recycling of aggregate, has been considered. In Japan, this type of study1) began in 1974. Crushers which were used then for the reclamation of aggregate were undeveloped, therefore the quality of the concrete composed of aggregate then reclaimed became the cause of critical problems. Later, The General Technology Development Project (1982~1986)2) was conducted under the supervision of the Ministry of Construction. An exclusive plant was studied and developed, which helped to improve the quality of recycled aggregate, and consequently led to the prospect that recycled aggregate would be able to be used for concrete. However, development has been delayed due to problems such as production costs. The applications are limited to the area of low-strength structures and secondary concrete products, because of many pending problems such as production costs. With the aim of breaking through this barrier, we conducted flexural and shearing tests, involving reinforced concrete beams in which three types of recycled coarse aggregates which were produced by different processes were used. The applicabi1ity of these coarse aggregates to concrete structural members was evaluated. Furthermore, with the aim of assessing the interfacial bond properties between recycled aggregate concrete and deformed steel bars, bond tests were conducted. The results were compared with the bond properties of the concrete composed of natural coarse aggregate. 2 Test program 2.1 Materials Used and Test specimens Table 1 shows the types of recycled coarse aggregates used and the physical properties. Three types of recycled coarse aggregates produced with varying production processes are described as follows. Low-grade recycled coarse aggregate (R3) is one which is produced by crushing concrete masses by using an impact crusher alone. Medium-grade recycled coarse aggregate (R2) is one which is produced by only impacting the aggregate R3 by using the roll crusher. High-grade recycled coarse aggregate (R1) is one which is produced by crushing the aggregate R2 once again by using the roll crusher. Mix proportions for 1 m3 of the concrete and the original concrete are presented in Table 2. The design strength of concrete was set at 280 kgf/cm2. High-early-strength

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Portland cement was used. The grain sizes of recycled coarse aggregates were similar to natural coarse aggregate. One qualitative characteristic of recycled coarse aggregate is that its coefficient of water absorption becomes greater than of a naturalaggregate’s. The coefficient of water absorption of the high-grade recycled coarseaggregate used for the experiments was 1.03 times that of natural coarse aggregate, on the average while the coefficient of the low-grade recycled coarse aggregate was 3.44 times as much. Test specimens were rectangular cross section 120 mm by 180 min. The shear span ratio a/d was set at 3.17 against the series of

Table 1. Properties of natural and recycled coarse aggregate

Type of coarse aggregate

Specific gravity

Coefficient water absorption (%)

mortar attached to natural aggregate (% v/v)

Natural (A)

5) 2.69 6) 2.67

5) 0.69 6) 1.45

————

High-grade (R1)

5) 2.64 6) 2.62

5) 0.80 6) 1.29

5) 9.9 6) 7.3

Medium-grade (R2)

5) 2.59 6) 2.56

5) 1.74 6) 2.22

5) 26.0 6) 16.7

Low-grade (R3)

5) 2.53 6) 2.49

5) 3.02 6) 3.64

5) 40.2 6) 35.2

5): Grain size 10~20 mm (Coarse aggregate) 6): Grain size 5~10 mm (Fine aggregate)

Table 2. Mix proportions of recycled and original concrete

Mix composition (kgf/cm3) Mix designation

Water Cement

Aggregate

Water-cement ratio (%)

Sand Fine Coarse

Natural and recycled aggregate concrete

186

306

743

Original concrete

160

356

745

753

323 1118

61 45

flexural test, and 2.29 against the series of shearing test. The flexural reinforcement D13 (yield strength of 3,300 kgf/cm2) along the beams and the web reinforcement such as stirrups D6 (yield strength of 3,200 kgf/cm2) were used for all beams.

Behaviour of reinforced concrete beams containing recycled aggregate

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2.2 Test procedure (1) Flexural static tests The test set-up shown in Fig. 1(a). Loading was applied to simple beams, at three points respectively. Loading was repeated in one direction, with three cycles each, up to the maximum strength of 0.25 Pu, 0.5 Pu, 0.75 Pu and 1.0 Pu, in which Pu is the ultimate strength determined by using the actual strength of a material based on an equation established by the Japan Society of Civil Engineers. In addition, after the maximum strength of each beam was confirmed, loading was incrementally repeated while controlling the displacement of the beam, until the rotation angle of the member amounted to 1/25. The deflection of the beam was measured directly beneath the point at which the beam was supported, and in the center of the test beams. In line with this, the axial strain of the reinforcement, the crack widths, and the crack patterns, were measured or observed from time to time.

Fig. 1 Test set-up for beams

(2) Flexural fatigue tests

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The range of loads applied for flexural fatigue test was set in ways in which the maximum load is 50% of the maximum load achieved through flexural static test, and the minimum load is set at 0.5 tf. The loading speed was 3 Hz. On completion of the given cycles (0, 10,000, 20,000, 30,000, 40,000, 50,000, 75,000, 100,000, 200,000 and 300,000) of loading, the measurement and observation of the Items thesame as those in static loading tests were conducted at the maximum load. Following completion of the 300,000 cycles of fatigue loading, loading was incrementally repeated while control1ingthe displacement of the beam, until the angle of the member amounted to 1/25. (3) Shearing static tests The test set-up is shown in Fig. 1(b). Loading was applied to a continuous beam by using the antisymmetric loading method. Loading was applied in one direction while controlling the displacement of the test beam. This was repeated for three cycles at the shear displacements of 1, 2, 3, 4, 6, 8, 10 and 12 mm, respectively. The measurement and observation of crack width was conducted on the first cycle of each step of displacement. (4) Shearing fatigue tests In the shearing fatigue loading, the setting of the range of loads to be applied, the loading speeds and the cycles of loading were all equal to those adopted in the flexural fatigue test. After the completion of 300,000 cycles of fatigue loading, incremental loading was repeated while controlling the displacement of the test beam, until its shear deformation amounted to 14 mm. (5) Bond tests The purpose of this test is to examine the bond properties of deformed bar and recycled coarse aggregate concrete. Test parameters include the recycled aggregate type, concrete strength, the direction of concrete placing, and thickness of the concrete cover. The recycled coarse aggregate which was used is the same as the one used for the test of the beam previously mentioned. There were three types of mix proportions of concrete in terms of water cement ratio; 65% (Mix proportion A), 53% (Mix proportion B) and 44% (Mix proportion C). As illustrated in Fig. 2, tests were conducted with the SchmidtThro test method3). Steel bar was a D16 high-strength deformed type (nominal yield strength of 6,500 kgf/cm2). All bars were provided with the embedment length of 100 mm. Concrete was placed in parallel (longitudinally as shown in Fig.3-a) and perpendicular(transversely as shown in Fig.3-b) to the axial direction of the bar. As shown in Fig. 3-b, the thickness of concrete covering to the bar was 4 cm, 6 cm, 8 cm. Loading was applied incrementally in one direction, and was terminated when the slippage of the free end of the bar amounted to about 0.3 mm. Six concrete cylinders 100×200 mm for each specimen were cast and testedat the same time as the specimens to measure the actual compressive and tensile strength of concrete.

Behaviour of reinforced concrete beams containing recycled aggregate

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Fig. 2 Details of Schmidt-Thro test method

Fig. 3 Direction of placing concrete for specimens

3 Test Results and discussions 3.1 Flexural static tests Table 3 shows the load at which the initial crack in each beam occurred, and the ultimate strength. Based on the data shown in the table, a comparison between the ultimate strength of each beam and the load at which the beam began cracking, was made. The results indicated that the ultimate strength of the test beam composed of low-grade recycled coarse aggregate was about 12% less than that of the beam composed of natural coarse aggregate. This percentage was common to all other beams, and the ratio of the experimental value to the design value was equal as well. Fig. 4 shows the loaddisplacement relationship of each beam subjected to cyclic flexure, in which there is no noticeable difference. This is due to the use of recycled coarse aggregate, in the initial stiffness, maximum strength and ducti1ity of the beam. Next, the effects of the cycle of rotation of the cross section of each beam wi11 be discussed below. Fig. 5 shows the moment-average curvature relationship of the beam in the constant bending moment zone. In the range in which the maximum strength was reached, the rotational stiffness of the beams composed of low-grade recycled

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Table 3. Results of test beams (flexural static tests)

Cylinder Cylinder tensile compressive strength strength Beam (kgf/cm2) (kgf/cm2)

Initial cracking moment (tf·m)

Ultimate moment (tf·m) Meas. Calc.

Meas. Calc.

BA

300

24.2

0.400

1.213

1.250

0.97

BR1

309

28.4

0.375

1.225

1.260

0.97

BR2

320

24.3

0.425

1.265

1.265

1.00

BR3

332

24.9

0.325

1.240

1.262

0.98

BA: Natural aggregate concrete beam BR1~3: Recycled aggregate concrete beam

Fig. 4 Load-displacement curves for specimen BA and BR series with flexure

Fig. 5 Moment-average curvature curves for beams

Behaviour of reinforced concrete beams containing recycled aggregate

391

Fig. 6 Crack patterns at δ=20 mm

coarse aggregates tended to be proportionally smaller. Fig. 6 illustrates the patterns of cracks that occurred in each beam when its displacement amounted to 20 mm. In all of the beams, the development of flexural cracks and flexure-shear cracks were noticed, but there was little difference in their patterns. However, in the test beams composed of lowgrade recycled coarse aggregates, the formation of a tied arch occurred in a slightly upward location. 3.2 Flexural Fatigue tests Fig. 7 plots the relationship between the cycles of loading and the decreasing stiffness for beams BA and BR2. There were similar reductions in their stiffness. Thus, the effect of the use of recycled coarse aggregate on flexural fatigue loading was scarcely noticed. Fig. 8 exemplifies a comparison between the patterns of cracks which occurred on the initiation of loading and on the completion of 300,000 cycles of loading. In the case of test beams composed of recycled coarse aggregate, a large number of minor cracks occurred on the initiation of loading. However, there was little difference noticed between both beams involving the patterns of cracks which occurred on completion of 300,000 cycles of loading, and the maximum widths of those cracks.

Demolition and reuse of concrete and masonry

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Fig. 7 Stiffness ratio versus cycles of loading

Fig. 8 Flexural crack pattern for beams BA and BR2

3.3 Shearing static tests Test results are summarized in Table 4. Based on these data, a comparison between the ratio of the shear stress of each beams observed on the occurrence of first cracks, to the maximum shearing stress was made. This indicated that the ratios of beams composed of low-grade recycled coarse aggregates were lower, and that the concrete composed of low-grade aggregate was about 8% lower in ratio than the concrete composed of natural coarse aggregate. All of the beams indicated almost the same maximum shearing stress. Fig. 9 shows the shear stress-shear displacement curves for test beams subjected to cyclic loading. No considerable difference due to the use of recycled coarse aggregate was noticed concerning each beam’s initial stiffness, maximum strength, and the stiffness at each step of displacement. Fig. 10 illustrates the maximum crack widths of the test beams. Up to the shear displacement of 4.5 min, about same crack widths were noticed regardless of the types of coarse aggregates used. Thereafter, the shear displacement

Behaviour of reinforced concrete beams containing recycled aggregate

393

obviously caused the larger widths of cracks to occur in the beams in which recycled coarse aggregate was used. Fig. 11 illustrates the patterns of cracks which occurred when the displacement of each beam due to shearing amounted

Table 4. Results of test beams (shearing static tests)

Cylinder compressive strength Beam (kgf/cm2)

Cylinder tensile Initial cracking strength Disp. Shearing (kgf/cm2) (mm) stress (kgf/cm2)

Maximum shearing stress (kgf/cm2)

SA

339

28.4

0.61

17.51

47.92

SR1

284

24.5

0.62

14.62

46.54

SR2

303

26.5

0.60

13.84

46.51

SR3

324

30.4

0.43

13.70

48.50

SA: Natural aggregate concrete beam SR1~3: Recycled aggregate concrete beam

Fig. 9 Shear stress-shear displacement curves for specimen SA and SR series

Demolition and reuse of concrete and masonry

394

Fig. 10 Maximum crack width versus shear displacement

Fig. 11 Crack patterns just before failure

to 12 mm. In the case of the beam composed of low-grade recycled coarse aggregate, cracks which were indicative of a deteriorated bond occurred along the longitudinal reinforcement in the tensile region. This was due presumably to the effects of the destruction of the original concrete’s mortar which adhered to the surface of the recycled coarse aggregate, as well as the drying shrinkage of the concrete on the underside of the reinforcement. 3.4 Shearing Fatigue tests The damage suffered by the beams as a result of the fatigue loading is illustrated in Fig.

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395

12. The stiffness degeneration is defined by the slope ratio (ki/kinit), in which kinit is the stiffness at initiation of loading. In all of the beams, the stiffness of those composed of natural coarse aggregate were reduced in a certain extent. while the stiffness of the beam composed of natural coarse aggregate showed little reduction in subsequent loading, the stiffness of those composed of recycled coarse aggregate were gradually reduced with the increasing cycles of loading. Fig. 13 illustrates the patterns of

Fig. 12 Stiffness ratio versus cycles of loading

Fig. 13 Crack patterns along the test span for beams

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Fig. 14 The increase of stirrup stresses during fatigue loading for specimen SA and SR series

cracks which occurred during initial loading and on completion of 300,000 cycles of loading. In all beams, cracks due to diagonal tension occurred at several places before the loading amounted to 300,000 cycles. Additionally, in the beam composed of mediumgrade recycled coarse aggregate and in that composed of low-grade coarse aggregate, small cracks which were indicative of a deteriorated bond occurred along the reinforcement in the tensile region. This led to the confirmation that no noticeable deteriorated bond would occur by this extent of loading. This is also obvious from the distribution of strain in the stirrups in each beam as shown in Fig. 14. Namely, strain in the stirrups located in and around the central inflection point of each beam was little increased, and no observable change in the bond properties of the reinforcement was noticed. 3.5 Bond Tests Fig. 15 shows the relationship between the bond stress and end slip in the test specimen of concrete which was placed in longitudinally. In all specimens, the end slip when the maximum bond stress was gained, were in the range of 0.25 mm to 0.3 mm. The maximum bond stress of aspecimen with mix proportion C (28-day design strength of concrete Fc=400 kgf/cm2) and of a specimen with mix proportion B (Fc=320 kgf/cm2) was greatest with those using natural aggregate, and those using less-treated rec-ycled

Behaviour of reinforced concrete beams containing recycled aggregate

397

coarse aggregate indicated smaller values. This tendency wouldresult from minor voids in the surface of the original mortar bonded to the recycled coarse aggregate. In other words, it is inferable that bond failure occurred inside the original mortar orin the interface between the preceding mortar and the succeeding mortar. On the contrary, with regard to the maximum bond stress of concrete with mixproportion A (Fc=240 kgf/cm2), coarse aggregate type created no noticeable difference. This would be due to the fact that the strength (Fc=400 kgf/cm2) of original concrete bonded to recycled coarse aggregates exceeded by far that of new concrete, therefore theoriginal mortar bonded to therecycled coarse aggregates barely affected the bond failure. Fig. 16 shows the relationship between the bond stress and end slip in a specimen with the concrete covering thickness of 8 cm, which was placed in transversely. From the figure, the difference between the quality of aggregate and the strength of concrete created little variation in terms of the relationship between bond stress and end slip. The possible factors which govern the results would include the affect of the water membrane formed on the underside of the bars which was generated due to breeding, and also the precipitation of the concrete bonded to the underside of the bars, which occurred due to the drying shrinkage of the concrete. Fig. 17 shows the results of tests in which the effect of the concrete covering thickness in the specimens of the concrete which

Fig. 15 Bond stress-end slip relation (longitudinally series)

Fig. 16 Bond stress-end slip relation (transversely series)

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Fig. 17 Bond stress-end slip relation (comparison of cover thickness) , Mix: A (w/c=65%)

was placed in transversely. This series of tests were conducted for mix proportion A. In the figure, it is indicated that an increase in the concrete covering thickness was very effective strengthening the bond of concrete to the steel bar. However, only less-treated recycled coarse aggregate indicated a considerably drop in the bond stress. In highertreated coarse aggregates, no difference was observed for the type of coarse aggregate used. For each of the aggregate types used, the specimens with the concrete covering thickness of 4 cm were 30% to 50% less in bond stress than those with the covering thicknessof 8 cm. 4 Conclusions Study of the results obtained in this investigation led to the following conclusions. (1) If the concrete composed of recycled coarse aggregate above the medium-grade is used for a structural member dominantly subject to a flexural moment and a uniaxial compressive stress, the effects of the aggregate on the strength, ductility and the mode of failure of the concrete member would be very slight. (2) If the concrete composed of recycled coarse aggregate is used for a structural member dominantly subject to a shearing force, it should be perceived that cracks which are indicative of a deteriorated bond tend to occur long the longitudinal reinforcement in the tensile region. Therefore, the arrangement of reinforcement may require an appropriate plan. In particular, when a structural member will be easily subjected to a shearing fatigue load, the potential of occurrence and existence of small cracks not only on the surface but also in the concrete would be high. (3) The void in the mortar of the original concrete which adhered to the surface of the recycled coarse aggregate would directly affect the reduction of the bond strength. However, if the longitudinal steel bar exists in a horizontal direction, the drying shrinkage or breeding of the concrete adjacent to the underside of the bar could possibly deteriorate the bond. (4) In the case that the strength of original concrete was in excess of that of new concrete, the original mortar bonded to recycled coarse aggregate barely affected the bond failure.

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References 1) Contractors Association Committee (1978) “Study on concrete composed of recycled coarse aggregate” Concrete Journal, Vol. 16, No. 7, pp. 18–31. 2) S. Kobayashi (1986) “The present status of waste concrete and a technology to use waste concrete” Civil Engineering Journal, Vol. 27, No. 15, pp. 99–102. 3) Gerfirend Schmidt-Thro etc. (1988) “EinfluB einer einachsigen Querpressung und der Verankerungalange auf das Verbundverhaltenla Heia Von Rippenstahlen im Beton” Deustcher Ausschuss Fur Stahlbeton. HEFT389, pp. 99–174.

31 MECHANICAL AND PHYSICO-CHEMICAL PROPERTIES OF CONCRETE PRODUCED WITH COARSE AND FINE RECYCLED CONCRETE AGGREGATES J.D MERLET and P.PIMIENTA CSTB, Paris, France Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract The aim of this study is to identify the influential parameters upon mechanical and physico-chemical properties of concrete made of crushed concrete as coarse and fine aggregate and determine solutions providing the most suitable concrete characteristics. Laboratory experimental tests have been carried out with different mixing proportions to study the properties of recycled-aggregate concrete In the fresh and hardened states and the results have been compared with those of concrete of similar mixing made with natural aggregates. The following properties were analysed: compressive and tensile strength, modulus of elasticity, drying shrinkage, moisture movement, freeze-thaw resistance and carbonation rate. Influence of pre-moistening and the use of plasticizers were quantified. Keywords: Concrete, Recycled aggregates, Compressive strength, Tensile strength, Modulus of elasticity, Drying shrinkage, Moisture movement, Carbonation rate, Water/cement ratio, Coarse/fine aggregate ratio, Premoistening, plasticizer.

1 Introduction Out of the 600 million tonnes of waste of all kinds produced annually in France, from 20 to 25 million are due to the demolition sector. The production of aggregates made from such waste has been increasing continually in recent years. By 1990, it had reached 3 million tonnes a year, i.e. 0.75% of French consumption of aggregates. Most of it (65%) is produced in Paris area, which is very short of natural aggregates (SNPGR-ANRED,

Mechanical and physico-chemical properties

401

1991; Charlot-Valdieu, 1993). The potential amount of recyclable construction materials is currently estimated at between 10 and 15 million tonnes a year. The economic interest of concrete recycling has recently been analysed (SNPGR-ANRED, 1991). The use of recycled aggregates near the work-site appears to be profitable when natural aggregates are transported over distances in excess of around 20 km. In France, concrete made of recycled aggregates has been studied for about ten years (Coquillat, 1980; Bernier, 1983; Karaa, 1986). This work, the intensity of which had slowed in the late eighties, has increased over the last two years owing to growing environmental concerns and through the impetus of national and European public authorities. Our study focused on the mechanical and physico-chemical properties of recycled aggregate concrete from a demolition waste crushing and processing plant. The origin of concrete used for crushing was known and its properties were analysed. Thus, this study differed from certain previous studies (Coquillat, 1980; Bernier, 1983; Ravindrarajah et al., 1987), which focused on various kinds of recycled aggregate concrete obtained from concrete made, stored and crushed in laboratories. A preliminary study was undertaken first to determine the influence of the following parameters: cement content, coarse/fine aggregate ratio (C/F), natural fine aggregate percentage.From thirty-six compositions tested and analysed, we defined the bestperforming compositions which were then studied in more detail. Compressive strength, splitting tensile strength, modulus of elasticity, drying shrinkage, moisture movement, freeze-thaw resistance and carbonation rate were measured. In particular, the influence of pre-moistening and use of plasticizers were quantified. 2 Materials The cement used throughout this study was Portland CPJ 45 conforming to the NF P 15– 301 standard (AFNOR, 1981) containing 5% of slag and 25% of fly ashes. Its Blaine fineness was equal to 2980 cm2/g. This cement was chosen because: it is used very much in France, it contains 30% of industrial by-products and therefore it serves one of our purpose, i.e. to study the development of recycling. Several mixes were made using fine and ultra-fine natural aggregates. Table 1 shows their fineness modulus and density. Reference concrete was made using coarse aggregates with a maximum size of 25 mm and bulk specific gravity of 1.49. The recycled aggregates were produced by a demolition waste processing plant which crushed an old industrial building floor. The mechanical properties and the specific gravity of this original concrete were : compressive strength

:

49–57 MPa

flexural strength

:

2.2–2.9 MPa

Demolition and reuse of concrete and masonry

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static modulus of elasticity

:

46–53 MPa

Specific gravity

:

2.31–2.35

The shape of recycled aggregates depends on the crushing technique. In this case, aggregates composed of natural aggregates immersed in mortar gangue had sharp edged very irregular shapes. The maximum size was 30 mm, the bulk specific gravity was 1.19, the water absorption was 6.5%. In this respect, owing to the mortar gangue, the recycled gravel occupied an intermediary

Table 1: Fineness modulus and apparent density of fine aggregates used during this study.

Aggregates properties

Natural aggregates

Fine recycled aggregates

Fine

Ultra-fine

Fineness modulus

2.34

0.98

3.55

Bulk specific gravity

1.44

1.41

1.35

position between traditional aggregates ( 4%) and light aggregates (5 to 15%). The shape of fine recycled aggregates was irregular too. Their water absorption was between 8 and 9%. Fineness modulus and bulk specific gravity are shown in table 1. 3 Experimental procedure Slump tests were carried out with the Abrams cone consistently with the French NF P 18–451 standard (AFNOR, 1981). The specimens were demoulded about 24 hours after casting and were either air-cured at 20°C, 50% RH or water-cured at 20°C. Each test was carried out on three samples. The results reported in this paper are the mean values obtained. Compressive and splitting tensile strengths were determined after 3, 7, 28 and 90 days according to NF P 18 406 (AFNOR, 1981) and NF P 18 408 (AFNOR, 1981) standards on cylindrical samples (ø=160mm, L=320mm). Static modulus of elasticity was measured during compressive strength tests. Diying shrinkage, moisture movement, freeze-thaw resistance and carbonation rate were measured on 70×70×400 mm3 prisms. Dimensional variations during drying at 20° C, 65% RH were measured on two opposite faces. The samples for measuring expansion by immersion in water had, prior to this, been cured for 90 days at 20°C, 65% RH and quick-dried in an oven at 70°C until stabilisation. The samples for freeze-thaw resistance testing were cured for 110 days at 20°C, 65% RH. They were then subjected to the following cycles :

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16 hours in water at 5 °C, 8 hours of freezing at −15°C. Carbonation rate tests were carried out on samples kept at 20°C and 15, 65 and 90% RH. Measurements were taken after 28 and 90 days. 4 Preliminary test The object of these preliminary tests was to analyse the best-performing compositions, which were subsequently studied in more detail. Table 2 summarises the compositions and the properties of the concrete mixes studied. Concrete with four different percentages of fine natural

Table 2: Compositions and properties of the preliminaiy tests recycled concretes.

Natural fine aggreg. (%)

0

C/F (%)

Cement Recycled coarse aggreg.

W/C Compressive (%) strength Recycled Natural Water (MPa) fine fine aggreg. aggreg.

250

880

817

-

220

0.88

12.5

1.08 300

833

703

-

200

0.67

15.5

350

845

781

-

213

0.61

21.8

250

1069

666

-

214

0.86

13.5

300

1031

641

-

213

0.71

17.5

350

1031

626

-

205

0.59

23

250

1143

598

-

245

0.98

14

300

1069

550

-

234

0.78

24.3

350

1044

582

-

210

0.60

24

1.6

1.8

50

Mix composition (kg)

250

827

378

378

231

0.92

20.7

1.08 300

820

378

378

222

0.74

23.3

350

795

362

362

237

0.68

26

250

987

308

308

214

0.86

18

300

1025

317

317

243

0.81

28

350

971

294

294

245

0.70

31

250

1015

281.5

281.5

223

0.89

23.6

300

1010.5

280

280

223

0.74

28.4

1.6

1.8

80

Demolition and reuse of concrete and masonry

404

350

984

274

274

234

0.67

32.7

250

827

152

605

205

0.82

23.3

1.08 300

820

152

605

214

0.71

20.2

350

795

145

579

218

0.62

25.5

250

987

123.2

492.8

208

0.83

17.5

300

1025

128

506

213

0.71

26

350

971

117.6

470.4

234

0.67

31.5

250

1015

112.6

450

216

0.86

21.8

300

1010.5

112

448

218

0.73

28.2

350

984

109.6

434.4

221

0.63

33.4

250

827

-

757

189

0.76

15.3

1.08 300

820

-

757

186

0.62

25.2

350

795

-

724

189

0.54

31.5

250

987

-

616

205

0.82

18

300

1025

-

634

192

0.64

26.2

350

971

-

588

222

0.63

31

250

1015

-

563

216

0.86

22.3

300

1010.5

-

560

210

0.70

30

350

984

-

548

219

0.63

30.6

1.6

1.8

100

1.6

1.8

aggregates were analysed (0, 50, 80 and 100%). Thus, the first series was devoid of natural aggregates and the last one was devoid of fine recycled aggregates. For each of these series, we selected three values of coarse/fine aggregate ratio: 1.08, 1.6 and 1.8. C/F=1.08 was obtained at by using the “Dreux-Gorisse” method (Dreux, 1981). C/F=1.6 or 1.8 are values commonly used for traditional kinds of concrete. Finally, for each combination, three values of cement content were tested (250, 300 and 350 kg/m3). In order to limit the number of compositions and to be able to compare them on a common basis, we decided to carry them out at constant plasticity, and thus to vary the water content in consequence. The chosen degree of plasticity corresponded to one commonly found in traditional concrete, defined by a slump at the Abrams cone of between 50 and 70 mm. Table 2 shows that the use of recycled aggregates requires larger quantities of water (0.59<W/C<0.98) than for traditional kinds of concrete (0.4< W/C<0.6). This is due to the greater absorption of water by recycled aggregates. We can also see that an increase in cement content permits reduction in water content and therefore increases the workability of recycled aggregate concrete. Compressive strength at 28 days is shown in the table. We can see that, for the three

Mechanical and physico-chemical properties

405

C/F values studied, resistance to compression increases with C/F value. Comparison of the first series with the three following ones shows that the addition of natural sand results in a better-performing concrete. However, the performance levels obtained with 80 and 100% natural sand content hardly differs from those obtained with 50% natural sand content. From these results, two mix compositions seemed interesting enough for the study to be continued. They are shown in bold type in the table: one contains only recycled aggregates, and the other is composed of 50% of natural sand. 5 The mix compositions studied In this second phase, we studied in more detail the two best-performing formulations revealed by the preliminaiy tests. Mix composition 1 (table 3) contains only recycled aggregates. The six other mix compositions contained fine natural aggregates. Their granulometric curves were complemented by the addition of 20% of ultra-fine natural aggregates (mixes 2, 4, 5, 6 and 7) and ultra-fine recycled aggregates (mix 3) decreasing the C/F ratio from 1.8 to 1.44. Concrete mixes 4 and 5 were respectively obtained by prehumidifying the recycled aggregates using 30% of mixing water and by immersing them in water for 24 hours in order to saturate them. The W/C ratio of these two compositions was 0.7. We checked that their workability was greater than concrete with a similar composition but whose aggregates had not been pre-moistened. Mixes 6 and 7 were made using plasticizers. Mix 6 was made by using 0.3% of Plastinent BV 40 and mix 7 using 1% of Sikafluid. The use of plasticizers made it possible to reduce the W/C ratio by between 10 and 15%. References 1 and 2 were traditional concretes containing respectively 300 and 350 kg/m3 of cement.

Table 3: Compositions of the studied concrete mixes.

Mix Cement N° content (kg/m3)

Recycled fine aggreg. (%)

Natural fine aggreg (%)

Recycled ultra-fine aggreg. (%)

Natural C/F W/C Remarks ultra-fine (%) (%) aggreg. (%)

Mix 1

300

100

-

-

-

1.80 0.78

Mix 2

350

50

30

-

20

1.43 0.65

Mix 3

350

50

30

20

-

1.43 0.70

Mix 4

350

50

30

-

20

1.43 0.70

Premoistening: 0%

Mix

350

50

30

-

20

1.43 0.70

Pre-

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5

moistening: 100%

Mix 6

350

50

30

-

20

1.43 0.64

Plasticizer 1:0.3%

Mix 7

350

50

30

-

20

1.43 0.60

Plasticizer 2:1%

6 Results and discussion 6.1 Mechanical tests Figure 1 shows the development with age of compressive strength, splitting tensile strength and modulus of elasticity for water-cured and air-cured recycled aggregate concrete (mixes 1 and 2) and traditional concrete (references 1 and 2). Tests were carried out on 7, 14 and 28 day old samples of both types of concrete. Ninety-day old samples of recycled aggregates concrete were also tested. Table 4 shows the results obtained on all the compositions after 28 day ageing. Figure 1 shows that curves representing compressive and tensile strengths as a function of age for recycled aggregate concrete look the same as those for traditional concrete. However their values are lower. Table 4 shows that the strength of mix-1 samples made with 300 kg/m3 of cement is 20 to 25% less than that of reference-1 traditional concrete. The incorporation of fine natural aggregates and the increase in the cement content of mix-2 samples results in a significant increase in the mechanical properties of recycled aggregate concrete.

Table 4: Compressive strength, splitting tensile strength and static modulus of elasticity of 28 days water-cured and air-cured recycled and natural aggregate concretes.

Mix N° Compressive strength (MPa) Tensile strength (MPa) Static modulus (GPa) Water

Air

Water

Air

Water

Air

Mix 1

25.5

19

2.59

1.95

27.7

23.3

Mix 2

31.2

28.2

3.06

2.38

29.8

24.7

Mix 3

24.7

19.9

2.60

1.86

25.8

22.0

Mix 4

35.5

-

3.14

-

32.6

-

Mix 5

29.4

-

2.99

-

30.6

-

Mix 6

38.0

-

3.47

-

32.6

-

Mix 7

39.7

-

3.70

-

35.0

-

Ref. 1

36.9

28.4

4.01

2.51

35.9

31.3

Mechanical and physico-chemical properties Ref. 2

40.7

35.3

4.16

2.80

407 39.8

32.6

Figure 1: Compressive strength, tensile strength and modulus of elasticity with age for recycled aggregate concretes (Mix 1 and 2) and natural aggregate concretes (Reference 1 and 2). Results on water-cured and air-cured samples are shown on the left and right side of the page respectively

However, their respective strengths remain 15 to 25% lower than that of reference-2 concrete containing the same quantities of cement. Measurements of modulus of elasticity lead one to draw similar conclusions. The

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values obtained on 28 day old samples of recycled aggregate concrete are 25% lower than those for traditional concrete. Stabilisation of modulus of elasticity of recycled aggregates concrete after seven days of air curing is also to be noted. A comparison of results obtained on mix-2 samples with mix-3 samples shows that the replacement of ultra-fine natural aggregates by ultra-fine recycled aggregates results in a decrease in mechanical properties, which then become much the same as those of mix-1 concrete. Table 4 also shows that the pre-moistening of recycled aggregates with 30% of mixing water (mix 4) improves the mechanical characteristics of concrete. On the other hand, our results indicate that Mix-5 concrete made with saturated aggregates after a 24 hours immersion in mixing water have similar mechanical properties to mix-2 concrete. As indicated hereabove, the use of plasticizers makes it possible to reduce the W/C ratio by 10 to 15% while keeping the same workability. This decrease in water content considerably improves the mechanical properties of recycled aggregate concrete which become comparable to those of traditional concrete. These results corroborate results obtained elsewhere. Hendriks (1986) reports a diminution in compressive strength due to the use of recycled aggregates of between 0 and 35%. 6.2 Drying shrinkage Figure 2 allows to compare the variations in drying shrinkage between the seven types of recycled aggregate concrete. As shrinkage measured on both traditional concrete is similar, we have included in the figure only the values obtained for reference-1 samples.

Figure 2: Drying shrinkage of the recycled aggregate concretes.

We can see that until 90 days the overall pattern of all the curves is quite similar. The largest shrinkage values were recorded on samples of mix 1 (672 µm/m at 90 days) and mix 3 (730 µm/m). They are much higher than those of traditional concrete (500 µm/m). The incorporation of natural fine aggregates significantly reduces shrinkage (600 µm/m).

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On the other hand, pre-moistening of aggregates apparently does not have any influence on drying shrinkage : results obtained on samples of mix 2, mix 4 and mix 5 are quite comparable. The use of plasticizers is very beneficial. Shrinkage values measured on samples of mix 7 are comparable to those of traditional concrete. 6.3 Moisture movement Figure 3 shows the expansion of mix-1 and mix-2 samples during their immersion in water for up to 60 days. These values are considerably higher than those for traditional concrete. Up to 60 days, they are not stabilised and range from 700 to 750 µm/m. By way of comparison, expansion by immersion in water of traditional concrete stabilises itself at a value of around 100 µm/m. 6.4 Freeze-thaw resistance The recycled aggregate concrete tested showed a good freeze-thaw resistance. No apparent damage was observed. Similarly, the reduction in the mass of samples did not exceed 1%. 6.5 Carbonation rate Figure 4 shows the carbonation depths measured on mix 1, mix 2 and mix 3 recycled aggregate concrete after 28 and 90 days curing. For the three curing conditions studied (15, 65 and 90% RH), the carbonation rate increases with decreasing relative humidity. In particular, the values measured on 15% RH

Figure 3: Expansion in water of Mix 1 and 2 recycled aggregate concretes.

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Figure 4: Carbonation depth of recycled aggregate concretes after 28 and 90 days curing at 15, 65 and 90 % RH.

cured samples are two to six times greater than those obtained at 65% and 90% RH. This result is in contradiction with the results generally obtained with traditional concrete for which a maximum carbonation rate is observed at 50% RH. No explanation has been found to explain this discrepancy. The incorporation of natural fine aggregates and ultra-fine aggregates (mix 2 and mix 3) leads to a decrease in the carbonation rate. The depth of carbonation after 90 days of cure and with 65% RH is around 30% less than that measured on samples of mix 1. It is worth noting that the use of cement with larger specific surface and without fly ash and slag should reduce the recycled aggregate concrete carbonation rate (Venuat and Alexandre, 1968). 7 Conclusion The main conclusions from the present investigation on processing plant recycledaggregate concrete are the following : the values obtained for the mechanical properties of recycled aggregate concrete are lower than for natural aggregates ones, their drying shrinkage, moisture movement and carbonation rate are higher than for natural aggregate concretes, we did not observe any damage after freeze-thaw resistance tests, concrete properties are improved by partial subtitution of recycled fine aggregates by natural fine aggregates, recycled aggregates pre-moistening increases mechanical properties and decreases drying shrinkage, mechanical properties and drying shrinkage of recycled aggregate concretes made by using plasticizers are comparable to those

Mechanical and physico-chemical properties

411

of natural aggregate concretes.

8 References AFNOR (1981) Hydraulic binders—Definitions, classifications and specifications of cement. AFNOR, NF P 15–301. AFNOR (1981) Concretes-Compression test. AFNOR, NF P 18–406 AFNOR (1981) Concretes-Splitting test. AFNOR, NF P 18–408. AFNOR (1981) Concretes-Slump test. AFNOR, NF P 18–451. Bernier G (1983) Le recyclage de béton sous forme de granulats. ENSET thesis. Charlot-Valdieu C. (1993) Les déchets de démolition ou de chantier: Etats des lieux. OTEB Report, CSTB. Coquillat G. (1980) Recyclage de matériaux de démolition dans la confection des bétons. CEBTP—Plan Construction. Dreux G. (1981) Nouveau guide du béton. Edition Eyrolles. Hendriks Ir. Ch. F. (1986) Waste materials. Routes—Roads AIPCR, 63–71. Karaa (1986) Evaluation technique des possibilités d’emploi des déchets dans la construction: recherche expérimentale appliquée au cas de bétons fabriqués à partir de granulats de bétons recyclés. Université Paris 6 thesis. Ravindrarajah R.Sri, Loo Y.H and Tam C.T. (1987) Recycled concrete as fine and coarse aggregates in concrete. Magazine of Concrete Research, Vol. 39, 141, 214–220. SNPGR—ANRED (1991) Les matériaux de demolition en France : le recyclage de la fraction inerte. SNPGR—ANRED Report. Venuat M. and Alexandre J. (1968) De la carbonatation du béton. Revue des matériaux de construction. 638, 421–427, 639, 469–477.

32 SILICEOUS BY-PRODUCTS FOR USE IN BLENDED CEMENTS* H.H.BAHNASAWY and M.A.SHATER GOHBPR, Cairo, Egypt Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract For economic and technical reasons numerous industrial by-products are being used in blended cements and concrete industries. As example, cement plants generate cement dust from out giong gas by filters during the coarse of their operation. In this work, cement dust, was used with different percentages as paratial replacement of cement. Water reducer was used to improve the properties of cement paste. Different kinds of Egyptian blended cements were tested to make a comparison between them and cement dust. Conclusions cover the basic properties and their control for different cement pastes. Keywords: Blended Cements, Cement Dust, Water Reducer, Setting Time, Expansion, Compressive Strength Non, Evaporable Water.

1 Introduction The utilization of by-products is today concern the problem of energy. Cement plants generate solid waste which polluite the surrounding on during the coarse of their operation. The cement kiln exhaust gas contains a mixture of finely divided raw feed,calcined raw feed, clinker and volatile salts(1). About 73% of the klin dust is recycled to the cement making process(2). The rest of the dust has no significant value. In addition the cost of its removal, it introduces a space problem and causes pollution to the surrounding areas(3). Now researches began to study re-use of cement dust in building materials. Cement dust was studied as a paratial replacement of cement in cement-sand mortar(4). Also cement dust was studied as a paratial replacement for portland cement in hollow concrete blocks. In this work, cement dust will be re-use as a replacement of ordinary portland cement by weight to make a new blanded cement.

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2 Experimental Work Tests have been carried out to study the effect of cement dust partial replacement of cement weight on blended cement properties. The scheme of the experimental program in this research can be summurized as follows: Five different percentages of cement dust replacement were mixed by the ration 0, 10, 15, 20 and 30%. Four percentages of water reducer was used (zero, 0.6, 1.8 and 2.4%) to study the effect of them on the water needed for each mix. - Surface area, initial and final setting time, expansion, unit weight, compressive strength and non-evaporable water tests at 3, 7, 28 days age were studied. 2.1 Materials Used Ordinary portland cement was used. The physical, mechanical and chemical properties of this cement are in complete complia with the limits of the Egyptian standard Specifications 373, 1991. Cement filter dust was taken from the electrical precipitator during the dry process (by pass dust) in Portland Cement Helwan Company. Table 1 indicates the chemical and physical properties of both portland cement and filter cement dust. Water reducer with high range of reducing effect was used. The properties of water reducer are complying with ASTM C 494 Types A, B, G. 2.2 Test Details For each mix, cement and cement dust were mixed in a rotating pot containing porcelian balls for a certain period of time to be sure that they are completly mixed. Surface area was measured using Blaine apparatus. Penetration, initial and final setting time was obtained using automatic Vicat apparatus. Soundness was tested using Lechatelier apparatus to determine the volume change of cement paste. Cubes of 20×20×20 mm were used to determine unit weight and compressive strength of the different blended cement pastes at 3, 7, and 28 days age. Each value represents the average of three tested cubes. Non evaporable water was calculted by drying two representative cement specimens about 2 gm from each mix, weighted in porcelain crucibles, and ignited for one hour at 1000°C in a muffle furnace, cooled in a dissicator, then weighted. The chemicallycombined water content (i.e the amount of water retained befor firing) was calculated as

Wn using the following equation: Wn=non evaporable water W1=the weight of sample before ignition(g) W =the ignited weight of a specimen(g) 2 L=percent of loss on ignition of unhydrated specimen Non evaporable water is an indication to the combined water as a result of hydration process.

Siliceous by-products for use in blended cements

415

3 Test Results and discussion Different cement-dust mixes and physical and mechanical properties of cement-dust paste are given in Table 2 and Figs. 1 to 5b on which the discussion will be given. 3.1 Water Requirement for Constant Penetration To determine the water content needed for each mix, many trials had been done to obtain the water required for constant Vicats reading 5–7 mm. For cement dust replacement 0, 10, 15, 20 and 30% and water reducer percentages 0.6, 1.8 and 2.4 of weight of cement, the water (cement+dust) ratio ranges between 36 and 18.5%. 3.2 Effect of Cement Replacement Dust on Water Content The relation between percentage of- cement dust replacement and water/(cement+dust) ratio for different water reducer ratios are shown in Fig. 1. It can be noticed that increasing percentages of cement replacement, the water percentage required to maintain a constant consistance appears to be increase. This increase reached up to 33% for 30% cement dust replacement. It is increase may be related to the surface area of the cementdust which about three times the ordinary portland cement. Adding water reducer to the mixes by 0.6, 1.8 and 2.4% from the wieght of cement, decreased the percentage of water for constant consistence up to 31% as shown in Fig. 2. 3.3 Effect of Cement Dust Replacement on Surface Area and Expansion of Cement Paste From Table 2 it can be observed that cement dust replacement in blended cement by the ratios 10, 15, 20 and 30% increases surface area by about 15, 43, 48 and 72% respectively. It can be also observed that expansion of cement paste are less than the limits of Egyptian Standard Specifications for portland cement and ranged between 0.5 and 2.4 mm for different cement mixes. 3.4 Effect of Cement Dust Replacement on Initial and Final Setting Time. The test results for the relation between percentage of cement dust replacement and both initial and final setting time for different water reducer percentages are shown in Fig. 3. For different cement paste mixes, it was observed that increasing the percentage of cement dust replacement delayed initial and final setting time up to 36 and 29% for 30% cement dust replacement. It may be related to the increase of absorbed water in cement paste on the surface of the dust which is more than the needed water for the hydration of cement particles.

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3.5 Compressive Strength Development For all mixes of contained different percentages of cement dust replacement and different dosages of water reducer, compressive strength increases with age from 3 to 7 and 28 days. Also compressive strength increases with the increase of water reducer percentage as shown in Fig. 4. The maximum percentage of increasing compressive strength was at 2.4% water reducer. This percentage of water reduceeer increased compressive strength at 28 days age by about 9, 5% for cement dust replacement 10, 15% than control mix (without water reducer). 3.6 Relation Between Non. Evaporable Water and Compressive Strength The relation between age in days and both compressive strength and non-evaporable water is shown in Fig. 5a, 5b. For 10% cement dust replacement, water reducer decreased combined water and increased compressive strength. It may be related to that the mixes contains water reducer needs time more than 28 days to complete the hydration of cement.

Table 1 Chemical Composition and Some Physical Charateristics of Portland Cement and Filter Cement Dust

Chemical Properties (Weight percent)

Portland Cement

Filter Cement Dust

19.59

10.8

Alumina

6.4

3.6

Calcium oxide

60.5

46.8

Iron Oxide

4.1

2.2

Magnesium oxide

3.1

2.2

Sulphur trioxide

2.7

5.9

Loss on ignition

3.0

19.5

Others

0.61

9

97 cm3 hr. min

205 cm3 hr. min

Initial setting time

55

11 30

Final setting time

1 50

Soundness (mm)

0.5

5.5

2450

6100

Silica

Physical Properties Water required for Standard paste

Surface area (cm2/gm)

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Table 2. Blended Cement Mixes and Test Results.

Mix % Surface % Expan. Unit Weight Compressive Non-Evaporab No. cement area water sion Stre. ngth water g/g-Igni (gm/on3) at 2 dust cm /gm redmm. weight ages (days) (kg/cm2) at ucer Water ages (days) cement dust 1

–

2

–

3

–

4

–

27

3 0.6

7

28

3

7

28

3

7

2

2.26 2.26 2.29 464 502 550 11.68 12.29 13

0.6

24

0.8

2.23 2.30 2.38 480 538 584 13.03 13.16 13

1.8

21

0.7

2.29 2.35 2.38 529 581 618 11.55 11.84 12

–

2.4

18.5

0.6

2.28 2.34 2.36 566 622 665 11.12 11.16 11

5

10

–

30

0.6

2.95 2.26 2.30 309 424 476 13.66 14.62 15

6

10

0.6

28

1.2

2.23 2.24 2.26 321 452 512 13.53 14.24 15

7

10

1.8

26.5

0.8

2.23 2.14 2.26 378 375 565 13.15 14.17 14

8

10

2.4

24.5

0.7

2.22 2.23 2.26 419 539 601 12.70 14.10 14

9

15

–

32

0.6

2.22 2.23 2.28 252 365 421 13.63 13.82 15

10

15

0.6

30

0.8

2.20 2.20 2.24 296 402 476 13.44 14.12 14

11

15

1.8

28.5

0.8

2.17 2.18 2.23 321 436 510 13.07 14.15 14

12

15

2.4

26.5

0.8

2.17 2.18 2.23 358 498 578 13.42 14.09 14

13

20

–

34

0.9

2.13 2.13 2.24 219 296 398 14.33 14.60 15

14

20

0.6

32

1.1

2.18 2.21 2.23 264 356 361 14.22 14.44 16

15

20

1.8

30.5

0.8

2.10 2.21 2.23 288 392 496 13.85 14.30 16

16

20

2.4

28.5

0.7

2.13 2.14 2.21 316 458 532 12.71 13.0 13

17.

30

–

36

0.7

2.08 2.12 2.16 156 255 380 11.42 11.55 14

18

30

0.6

34.5

0.6

2.08 2.11 2.18 222 300 408 10.78 11.54 14

19

30

1.8

32.5

2.4

2.08 2.10 2.15 245 336 460 12.69 13.40 15

20

30

2.4

30.0

1.8

2.07 2.10 2.14 285 395 520 14.09 14.18 16

2450

2930

3650

3750

4370

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FIG. 1 RELATION BETWEEN THE PERCENT OF CEMENT DUST REPLACEMENT AND WATER CONTENT

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FIG. 2 RELATION BETWEEN PERCENT OF CEMENT DUST REPLACEMENT AND REDUCTION IN WATER CONTENT

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FIG 3 INITIAL AND FINAL SETTENG TIME FOR CEMENT DUST MIXES

FIG. 4 RELATION BETWEEN % OF CEMENT DUST AND COMPRESSIVE STRENGTH OF CEMENT PASTE

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FIG. 5A RELATION BETWEEN COMPRESSIVE STRENGTH, NONEVAPORABLE WATER AND AGE OF CEMENT PASTE

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FIG. 5B. RELATION BETWEEN COMPRESSIVE STRENGTH NONEVAPORABLE WATER AND AGE OT CEMENT PASTE

For cement dust 20% content, combined water increased more than 15% cement dust but the compressive strength did not increase by the same rate. For cement dust 30% content, the combined water increased more than 20% cement dust with decreasing compressive strength, which may be means that there will not be improvement of strength by using water reducer.

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4 CONCLUSTIONS The previous results leads to the following preliminary conclusions: 1. Replacement cement dust instead of portland cement to make a blended cement leads to increase of the water cement ratio, but it can be improved by using water reducer. 2. Cement dust replacement to 15 percentage, has a little effect on initial and final setting time than the higher percentages. 3. Compressive strength improved for 10 and 15 percentage cement dust replacement than ordinary portland cement by using water reducer with high percentage. 4. Blended cement contains cement dust and water reducer needs more time than 28 days to reach its full strength. The using of water reducer can be improve the decrease in the compressive strength in case of using the replacement of cement dust up to 15% by weight of cement. 5. Comparing test results of blended cement dust by other Egyptian blended cements as Karnak (sand mixed cement) and slage cement, it can be concluded that blended cement dust is near to them in properties. 5 References 1. Daugherty, K.E. and Wist, A.O., “Review of Cement ndustry Pollution Control, Bulltain”, American Ceramic. Soc. 54 (1975). 2. Smith, R., Levin, J. and Kearny, A., “Mieltimedia Assessment and Development Research needs of Cement Industry, EAP-600/2–79–111, U.S. Environmental Protection Agency, Cininnati, OHIO (1979), P. 44. 3. Abd El Wahed, M.G., El-Didamony, H., Galal, A.F., Shater M.A. “Cement Dust Binder for Autoclaved Cellular Concrete”, Conference on Building materials and silicates; June, (1982), Werman DDR. 4. Bahnasawy, H.H. “Economical and Strength Aspects of Cement Dust in Mortar Production”, Al AZHAR Engineering Second International Conference, December 21– 24, (1991). 5. Elwefati, A.M. et al, “Cement Klin Dust as a paratial Replacement for Portland Cement in Hollow Concrete Blocks”, First Alexandria Conference on Structural and Geotechnical Engineering, December (1990).

33 THE TOTAL EVALUATION OF RECYCLED AGGREGATE AND RECYCLED CONCRETE* M.KIKUCHI and A.YASUNAGA Department of Architecture, Meiji University, Japan K.EHARA Shimizu Corporation, Japan Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. ABSTRACT As recycling of demolition concrete discharged from concrete structures, it is very important to take into consideration of not only reuse but also life cycle of concrete structures. In order to reuse over again the recycled concrete that produced from recycled aggregate in the past as aggregate for new concrete works, both of new concrete and recycled concrete should be designed to be obtained high quality concrete. To raise the strength of concrete that produced in the near future is directly connected with circulating reuse of demolition concrete as aggregate resources. Key words: Original concrete, Recycled aggregate, Recycled concrete, Freshed concrete, Compressive strength, Tensile strength, Flexural strength, Drying shrinkage, Neutralization, Ability of isolate chloride ion.

1 Introduction The effective reuse and recycling of demolition waste is becoming a world wide problems from coservation of resources and environmental preservation. Durable years of houses and building in Japan is shorter than that of any foreign countries, therefore, the amount of construction waste discharged with demolition work is so much. In consequence, it is an important subject in Japan to grapple with not only reusing, but also reducing of demolition waste. In these circumstances, ‘Article 48, is known Recycle Act’ was established with a view to reduce of construction waste and to accelate reusing of waste in 1991. In consideration of the present situation in Japan, this investigation has been started on the premise as following.

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(1) By raising durable years of building and extending a period from completion to demolition, as a result of these factors, resources and energy going into construction are able to reduce. (2) For technique to raise durable years, compressive strength of concrete used for new construction should be higher than traditional one. (3) Thus high strength Concrete waste discharged with demolition work is reused for new concrete as high quality aggregate resources. Three types of recycled aggregate produced by crushing original concretes which had the compressive strength of 400 kgf/cm2, 600 kgf/cm and above 800 kgf/cm2 were used in this investigation. Properties of these recycled aggregates, strength and durability of concretes containing these recycled aggregate were tested, and the effects of qualities of recycled aggregates on recycled concretes were examined. Adequate results for total evaluation of recycled aggregates and recycled concretes were obtained in case of taking into consideration on life-cycle of concrete structures. 2. Recycled aggregates 2.1 Original concrete Three types of concretes were produced as original concrete in laboratory, one of these is generally used in Japan as structural concrete has the strength 200~400 kgf/cm2 at 28 days, and other two concretes expected to be used in the near future as high strength and high durability concrete have the strength 600~800 kgf/cm2 at 28 days. (Refer to Table 1) 2.2 Types of recycled aggregates Three types of original concretes were crushed by jaw crusher adjusted the openset to 25 mm. For the ages of original concretes at crushing, type R1 was within 14 months, type R2 was from 2 to 12 months and type R3 was within two months respectively. Crushed original concretes were screened and classified according by particle size into coarse and fine aggregate. (a) Coarse aggregate: The particles above 5 mm were used as coarse aggregate. Coarse aggregate were adjusted particle distribution to the prescribed value in JIS A 5005 (Crushed stone for concrete). (b) Fine aggregate: The particles passed 5 mm sieve were used as fine aggregate without any adjustment.

Table 1. The outlines of recycled aggregates prepared in this investigation

Types of Original concretes

Production process of recycled aggregates

The total evaluation of recycled aggregate and recycled concrete Notation R1 R2 R3

427

Compressive strength Above 800 Each types of original concretes were crushed by jaw-crusher, kgf/cm2 at 28 days and screened to divide into coarse and fine aggregate. Further, coarse aggregate was adjusted in order to suit to the specified 500~700 kgf/cm2 gradation. at 28 days 200~400 kgf/cm2 at 28 days

2.3 Physical properties Main properties of Various types of aggregates are shown in Table 2. (a) Fineness Modulus: Fineness Modulus of recycled coarse aggregates showed the similar value as crushed stone by adjusting particle distribution. For fine aggregate, quite differences are observed between recycled aggregates and river sand. (b) Specific gravity: For the range of Specific gravity in dry condition of recycled aggregates, coarse aggregates are from 2.32 to 2.35, fine aggregates are from 2.01 to 2.08, these values are smaller about 10 per cent comparing with the crashed stone and river sand. (c) Absorption: Absorption of recycled aggregate is considerably large amount, particularly, values of fine aggregates shows approximately ten times that of river sand. (d) Percentage of absolute volume: For percentage of absolute volume, values of recycled coarse and fine aggregates are smaller, respectively about 3 point and 7 point comparing with the crashed stone and river sand. (e) Strength of aggregate: Strength of recycled aggregates measured by B.S. 812 are showed Table 2 and Fig. 1. Values of crashing at 40 ton of recycled aggregates decrease from 12% to 27% as increase from 400 kgf/cm2 to 800 kgf/cm2. Regression equation in Fig. 1 is given by values obtained in this investigation and Nishibayashi et al1). As the results of the experiment on the effect of the variation in strength of original concrete on properties of recycled aggregate, it is considered that the numerical range of variation for properties of recycled aggregate is relatively small.

Table 2. Main properties of aggregates in this investigation

Percentage Specific Absorptio of absolute Strength Types of n Classification Notation F.M. gravity volume aggregate (%)*1 (in dry) (%) (%) RG1

6.71

2.35

4.0

55.6

18.4

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Coarse

Fine

428

Recycled aggregate (RG)

RG2

6.69

2.32

4.4

56.3

22.8

RG3

6.66

2.32

5.1

56.1

25.2

Crushed stone

NG

6.72

2.63

0.9

59.1

13.8

RS1

3.61

2.03

12.5

61.4

-

RS2

3.87

2.08

10.5

63.0

-

RS3

3.72

2.01

12.1

57.0

-

NS

2.92

2.61

1.2

67.6

-

Recycled aggregate (RS) River sand

*1. Value of crashing at 40 ton measured by B.S. 812

Fig. 1 Crushing values of recycled coase aggregate at 40 ton measured by B.S. 812

3 The outlines of experimental method 3.1 Materials (a) Cement: Ordinary portland cement (K28: 412 kgf/cm2) (b) Aggregate: Three types of recycled aggregate, crushed stone (hard sand stone) and river sand were used. (c) Chemical admixture: High-performance AE water reducing agent, water reducing agent and air entraining agent were used as chemical admixture.

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3.2 Concrete mixtures (a) Types of concretes: Four types of aggregates; R1, R2, R3 and crushed stone (GN), four steps of replacement ratio by recycled aggregate; 0 per cent, 15 per cent of both coarse and fine (notation: 15), 30 per cent of both coarse and fine (notation: 30) and 100 per cent only coarse, four steps of water cement ratio; 25, 35, 45, 55 and 65 per cent, by combining those factors, 49 types of concrete mixtures were prepared in this investigation. 3.3 Mix proportions As design of mix proportion of recycled concrete, considering items such as particle shape, fineness modulus and percentage of absolute volume relating to mix proportion, unit water and sand percentage of recycled concretes were increased 2~10 kg/m3, 1.1~3.3 point respectively than that.of sand-crushed stone concretes. The outlines of mixproportion of recycled concretes are shown in Table 3. 3.4 Examination items, specimens and curing methods (a) Examination items: Slump, air content and unit weight were measured at freshed concrete, compressive strength, tensile strength, flexural strength and drying shrinkage were measured as physical properties, neutralization, and ability of isolate chloride ion were measured as durability properties (b) Specimens: Shapes and size of each specimens are shown in Table 4. (c) Curing methods: Curing methods adopted are shown in Table 4.

Table 3. The outlines of mixproportion of recycled concrete

Types of concrete W/C S/A*1 Classification and (%) (%) Notation

Sand-crushed stone concrete

N

Combination of aggregate Coarse

Fine

NG RG NS RS

Unit content (kg/m3) Cement Water

Admixture (%)*2 WRA*3

AEA*4

25

37.5

688

172

2.25

0.0200

35

39.0

440

154

1.50

0.0200

45

40.5

409

184

0.25

0.0040

55

42.0

316

174

0.25

0.0045

65

43.5

277

180

0.25

0.0060

25

38.6

696

174

2.10

0.0180

35

40.1

446

156

1.50

0.0160

100

0

100

0

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15

Recycled concrete (R1) (R2) (R3)

30

10 0

45

41.6

55

85

409

184

0.25

0.0040

43.1

324

178

0.25

0.0030

65

44.6

286

186

0.25

0.0060

25

39.7

696

174

2.10

0.0180

35

41.2

451

158

1.50

0.0160

45

42.7

418

188

0.25

0.0040

55

44.2

331

182

0.25

0.0030

65

45.7

292

190

0.25

0.0060

25

40.8

728

182

2.10

0.0180

35

42.3

451

158

1.50

0.0160

45

43.8

418

188

0.25

0.0040

55

45.3

333

183

0.25

0.0030

65

46.8

292

190

0.25

0.0060

70

0

15

30

85

70

100 100

15

430

30

0

* 1. S/A: Sand percentage * 2. (%): Weight percent to cement content * 3. WRA Water cement ratio 25% and 35% [High-performance AE water reducing agent (Naphthalene type)] Water cement ratio 45%, 55% and 65% [Water reducing agent (Lignin type)] * 4. AEA: Air entraining agent to be adapted for each WRA

Table 4. Examination items, specimens and curing method

Items Compressive Tensile Strength

Shape and Curing method size 100ø×20 cm cylinder 10ø×20 cm cylinder

Flexural

10×10×40 cm prism

Neutralization

10×10×19 cm prism

Durability Isolate chloride ion

Cured in water through all ages.

Cured in water till at two weeks, after that, dried for two weeks, test was began at age of 4 weeks.

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3.5 Testing procedure (a) properties of freshed concrete: Slump, air content and unite weight were measured in accordance with method defined by JIS A 1101, 1128 and 1116. (b) Physical properties: Compressive, tensile, flexural strength and drying shrinkage were measured in accordance with method defined by JIS A 1108, 1113, 1106 and 1129. (c) Durability: • neutralization: Specimens were cured under CO2 5%, 30 °C, RH 60% in chamber for one month, after that, splitted and sprayed phenolphthalein on the cross section, the depth of penetration of carbon dioxide into concrete was measured. • Ability of isolate chloride ion: Specimens were immersed in salt water solution has a concentration of 3% for 12 hours, after that, dried under 30°C in oven for 12 hours, this process was repeated 40 cycles. Specimens were splitted and sprayed Solution of Fluoresein Sodium on the cross section, still more sprayed nitrate of silver. The depth of penetration of chloride ion into concrete was measured. 4 Experimental results 4.1 Properties of fresh concrete (a) Slump: Considering the characteristic properties of recycling aggregate, as a results of adjusting unit water, sand ratio and amount of chemical admixture were designed as showed in Table 3, the slump of almost types of concretes were in the region of 18±1.5 cm. (b) Unit weight and air content: Unit weight of recycled concrete decreased gradually as replacement ratio by recycled aggregate increased. The other side, air content increased gradually as replacement ratio by recycled aggregate increased. This tendency on relating the both was observed generally in every types of recycled concretes. 4.2 Physical properties of hardened concrete (a) Compressive strength at 28 days: Relationship between cement water ratio and compressive strength of various types of recycled concretes at 28 days are shown in Fig. 2. (1) The influence of original concrete: The compressive strength of recycled concretes containing RI as coarse aggregate showed similar values comparing with that of sandcrushed stone concretes, and particular influence caused by various of original concrete is not recognized. For the concretes containing R2 and R3, difference tendency was observed in compressive strength of new concretes. In case of new concretes had above 700 kgf/cm2, the compressive strength were higher than that of sand-crushed stone concrete, and in case of below 500 kgf/cm2, these were similar to sand-crushed stone concretes. It can be considered that there is no effect of types of recycled aggregate on compressive strength in case of new concrete having below 500 kgf/cm2

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(2) The influence of replacement ratio: The influence of replacement ratio is shown clearly in case of new concretes having above 600 kgf/cm2. (3) Coefficient of variation of compressive strength: Coefficient of variation of compressive strength is showed in Fig. 3. In so far as this results, the coefficient of variation of recycled concrete was less than 5 per cent in any water cement ratio, it is considered that the similar technique for quality control can be applied. (b) Tensile strength and flexural strength: Relationships between compressive strength and each strength of various types of recycled concrete are shown in Fig. 4 and 5. In case of tensile strength, it is observed that recycled concrete have higher value in the range above 500 kgf/cm2, and lower value in the range below that comparing with sand-crushed stone concrete. Flexural strength also shows a similar tendency, that border was about 400 kgf/cm2. (c) Drying shrinkage: Drying shrinkage of various types of recycled concretes is showed in Fig. 6. Drying shrinkage of recycled concretes was with in the range from 6 to 10× 10−4 it is observed that the values of drying shrinkage of recycled concretes were apt to increase as the strength of original concretes decrease and as the replacement ratio increase. It can be guessed that the relative smaller value on recycled concretes above 55 per cent of water cement ratio is due to the cracking. It can be consider that the influence of strength of original concrete on drying shrinkage is relatively large.

Fig. 2 Relationships between replacement ratio and Compressive strength on recycled concrete

The total evaluation of recycled aggregate and recycled concrete

Fig. 3 Relationships between Compressive strength and tensile strength on recycled concrete

Fig. 4 Relationships between compressive strength and flexural strength on recycled concrete

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Fig. 5 Relationships between types of recycled concrete and coefficient of variation on compressive strength

4.3 Durability (a) Neutralization: The depth of neutralization of recycled concretes cured under CO2 5%, 30°C and R.H. 60% for one month is showed in Fig. 7. (1) The influence of water cement ratio of new concrete: Even if using recycled aggregate, the velocity of neutralization of recycled concrete having below 45 per cent water cement ratio was very slow. Particularly in case of water cement ratio 25 per cent, the progress of neutralization was not observed. The otherhand, in case of water cement ratio above 55 per cent, the neutralization of concretes was progressed rapidly. (2) The influence of original concrete: It is considered that the influence of strength of original concrete on neutralization is very small. (3) The influence of replacement ratio: Any types of recycled concretes replaced 30 per cent with recycled fine and coarse aggregate showed the tendency that the progress of neutralization was faster than that of other replacement ratio, that of replacement ratio 15 per cent is second to this. It is guessed that the replacement ratio with recycled fine aggregate have an effect on the progress of neutralization. (b) Restrainability to penetration of chrolide ion: The penetration depth of chloride ion into concrete is showed in Fig. 8. (1) The influence of original concrete: Depth of penetration of chrolide on into recycled concretes containing R1 and R2 were rather smaller, but that of R3 were wagerer than sand-crushed stone concretes. (2) The influence of replacement ratio: As an entirely tendency, the depth of penetration of chrolide ion was decrease as replacement ratio increases. (3) The influence of water cement ratio: Water cement ratio influences considerably on depth of penetration of chrolide ion of new concrete. The restrainability to penetration of

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chrolide ion is a smallest one in the properties investigated in this research comparing with sand-crushed stone concrete.

Fig. 6 Drying shrinkage of recycled concrete at 13 week

Fig. 7 Neutralization of recycled concrete

Fig. 8 Restrainability to penetration of chloride ion

5 Conclusions The investigations on the evaluation of recycled aggregate and recycled concrete are summarized as follows. (1) As the results of the experiment on the effect of compressive strength of original concrete on recycled aggregate, that is influenced firstly on the value of crushing at 40 ton, and the other properties, such as specific gravity, absorption, percentage of absolute volume were not hardly influenced. (2) Compressive strength, tensile strength, flexural strength and drying shrinkage of recycled concrete are influenced directly by compressive strength of original concrete, but it can be considered that there is no effect of original concrete in case of compressive

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strength of new concrete below 400 kgf/cm . (3) The replacement ratio with recycled aggregate are influenced on drying shrinkage of recycled concrete. (4) Neutralization and restrainability of recycled concrete are influenced considerably by water cement ratio of new concrete. References 1 Nishibayashi, et al (1982) “Fundamental Study on Recycled Concrete” CAJ REVIEW OF THE 36th GENERAL MEETING 1982. Vol. 36 2 Kikuchi, Mukai, et al (1983) “A Study on the Properties of Recycled Aggregate and Recycled Aggregate Concrete” CAJ REVIEW OF THE 37th GENERAL MEETING 1983. Vol. 37 pp. 92–94 3 Kikuchi, Mukai, et al (1984) “The Effects of the Ratio of Replacement with Recycled Aggregate on Properties of Sand-Crushed Stone Concrete” CAJ REVIEW OF THE 38th GENERAL MEETING 1984. Vol. 38 pp. 236–239 4 Kikuchi, Mukai, et al (1988) “Properties of Concrete Products Containing Recycled Aggregate” Proceedings of Second International Symposium held by RILEM Vol. 2 pp. 595–604 5 Mukai, Kikuchi, et al (1988) “Properties of Reinforced Concrete Beam Containing Recycled Aggregate ” Proceedings of Second International Symposium held by RILEM Vol. 2 pp. 670–679

34 PHYSICAL PROPERTIES OF RECYCLED CONCRETE USING RECYCLED COARSE AGGREGATE MADE OF CONCRETE WITH FINISHING MATERIALS* K.YANAGI and M.HISAKA Japan Testing Centre for Construction Materials, Japan Y.KASAI College of Industrial Technology, Nihon University, Narashino, Japan Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract This paper deals with the effects of sort and contents of impurities in recycled coarse aggregate on the properties of recycled concrete. Recycled aggregates which were assumed producing from reinforced concrete structure of wall, slab and roof, with several sort of finishing materials. Sort of finishing materials for original concrete were plastic tile (PT), multi-layer wall coating (ML), gypsum plaster (GP), ceramic tile (CT), asphalt membrane water-proofing (AM) , lime plaster (LP), fibrous wall coating (FW) and synthetic resin emulsion paint (EP). The items of investigations for concrete were compressive strength, static modulus of elasticity, drying shrinkage, accelerated carbonation, and resistance to freezing and thawing of recycled aggregate concrete. From these test results, the allowable quantities of impurities contained in recycled coarse aggregate were clearly declared. The crushed stone aggregate with 20 mm maximum size were replaced by 100, 50, 30 and 0 percent of recycled coarse aggregate. The mix proportions of concrete was 0.6 in water-cement ratio, designed slump 18cm and air content 4%. Keywords: Concrete, Recycled Aggregate, Recycled Concrete Impurity, Finishing Materials, Compressive Strength, Modulus of Elasticity, Drying Shrinkage, Carbonation, Resistance to Freezing and Thawing.

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439

1 Introduction In 1974, “The Research Committee on Disposal and Reuse of Construction waste” was established by Building Contractors Society (BCS) in Japan. About 7 years later, the similar project team was started by Ministry of Construction to confirm the results of BCS and proposed four Guidlines on the recycled aggregate and recycled aggregate concrete for the Publick work and Building respective ly. In 1988, The 2nd International Symposium on Demolition and Reuse of Concrete and Masonry heled in Tokyo. The authors reported the test results of about 20 samples of recycled coarse aggregate from two different processing plants in the suburbs of Tokyo. In the paper, the amount of impurities and fine particles in recycled coarse aggregate were investigated. But we didn’t make it clear the relationship between the impurities of recycled aggregate and the several properties of recycled aggregate concrete. In this paper, the effects of sort and contents of impurities in recycled coarse aggregate on the properties of recycled concrete were tested. 2 Experimental method 2.1 Recycled aggregate (1) Base concrete Size of base concrete was 45×90×12 cm and made of ready-mixed concrete. Table 1 shows mix proportions of concrete. The base concretes were demolded after curing for 7 days in outdoor site. Thereafter they were cured for 21 days in air.

Table 1. Mix proportions of ready-mixed concrete.

Slump W/C S/a Water Cement Sand Gravel AEA Unit Air Comp.streng (cm) (%) (%) (Kg/m3) (Kg/m3) (Kg/m3) (Kg/m3) (C*%) weight (%) (N/mm2) (Kg/l) 18.5

60

44.8

168

280

813

1008

2.8

2.269

4

24.6

(2) Finishing materials Used finishing materials were as below; Plastic tile (PT), Multi-layer wall coating for glossy texture finishing (ML), Gypsum plaster (GP), Ceramic tile (CT) Asphalt membrane water proofing (AM), Lime plaster (LP), Fibrous wall plaster (FW) and Synthetic resin emulsion paint (EP). The finishing materials were worked on the base concrete at the age of 28 days. (3) Manufacture of recycled coarse aggregate

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At the age of 56 days, a none finished concrete and the concrete with finishing materials were crushed under 50mm size by use of hydraulic crusher. Further more they were crushed under 25mm size by use of jaw crasher,thereafter under 5mm fine particle were screened out by 5mm sieve and the remainders were the recycled coarse aggregates for test. 2.2 Making recycled concrete (1) Materials Ordinary portland cement was used for all the mixes. Physical properties of crushed stone coarse aggregate, river sand as fine aggregate and various recycled coarse aggregates are shown in Table 2. Vinsol resin was used as an air entraining agent. The blended recycled coarse aggregate was made by blending each recycled aggregates with different finishing materials in equal quantities. A crushed glass and a soil under 25 mm sieve were replaced by 1, 3 and 5 percent to crushed stone aggregate and blended recycled aggregate concrete. (2) Mix proportions of concrete and making of specimen Table 3. shows the mix proportions of recycled aggregate concrete. Aggregates were prepared in saturated surface dry condition to make concrete. Spacimens were made by the method of JIS A 1132. Specimens were demolded after 24 hours and thereafter cured as the methods shown in Table 4 2.3 Test program (1) Impurities in recycled coarse aggregate The composition of impurities in recycled coarse aggregate made of concrete with finishing materials were investigated by a visual inspection. (2) Fresh concrete Slump, air contents and unit weight of fresh concrete were tested and setting time and bleeding volume of 15 sorts of concrete were tested respectively. (3) Hardened concrete Properties of hardened concrete of about 43 sorts were tested for compressive strength, static modulus of elasticity, drying shrinkage, carbonation, resistance to freezing and thawing. These tests methods are shown in Table 4. 3 Results and discussions 3.1 Quantity of impurities Table 5 shows the quantities of impurities contained in recycled coarse aggregates.

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According to Table 5, impurities are classified into 3 types in visual form.

Table 3 Mix design of recycled coarse aggregate concrete

Symbol of concrete CSA (Crashed stone a.c.) NF (Recy.a.none impurities)

Replacement ratio Slump W/C S/a Water Cement Air (%) (cm) (%) (%) (Kg/m3) (Kg/m3) (%) 0 30, 50, 100

PT, ML, GP, CT, AM, LP, FW, EP, BL

18±2.5

60

43

181

302

195

325

205

342

BG-1, 2, 3, CG-1, 2, 3, CS1, BS-1

1

CS-3

3

CS-5

5

GS-3

3

201

335

GS-5

5

208

347

18±2.5

60

43

4±1

4±1

Note) In the case of CG-1, 2, 3 the figure S-1, 2, 3 mean the replacement ratio of crashed glass.

In the case of CS-1, 3, 5 the figure S-1, 3, 5 mean the replacement ratio of soil.

Table 4 Test program

Test item

Standard

Curing Methods

Compressive Strength

JIS A 1108 (Method of Test for Compressive Strength of Concrete)

Standard Curing (in water of 20°C) for 4 weeks. Air dring (in the room of 20°C, 60% RH) for 4 weeks.

Static Modulus of Elastisity

C7103T-1992 (Method of Test for Standard Curing (in water of 20°C) for 4 Static Modulus of Elastisity of weeks. Concrete) Air dring (in the room of 20°C , 60%RH) for 4 weeks.

Drying Shrinkage

JIS A 1129 (Method of Test for Length Change of Mortar and Concrete)

Standard Curing for 1 week, thereafter started the test.

Accerelating Carbonation

AIJ Recommendations ions for Design and Construction Practice of High Durable Concrete (Method of Test for Accerelating Carbonation of

Standard Curing for 4 week, thereafter cured in the room of 20°C, 60%RH untill the age of 8 weeks, thereafter started the test.The spacimens were kept in an

Demolition and reuse of concrete and masonry

Freezing and Thawing

442

Concrete)

acceleretive carbonizing test room of 30° C, 60%RH and 5% carbon dioxide.

ASTM C666-90 (Test Method for Resistance of Concrete to Rapid Freezing and Thawing: Method A)

Standard Curing for 4 week, thereafter started the freezing and thawing test of 300 cycles.

; JSTM is the abbreviated fon for Standard of Testing Method for Japan Testing Centre for Construction Materials.

That is to say, Broken pieces of finishing material coming off the base concrete (PT, CT) Finishing materials adhered to recycled coarse aggregate and broken pieces of finishing material coming off from the base concrete (ML, GP AP, LP, FW) Finishing material has adhered to recycled coarse aggregate (EP) Characteristics of finishing materials were as follows; (a) PT and CT were easy to come off from base concrete and didn’t make fine particles at crushing of them, and consequently a lot of broken piece were contained in recycled coarse aggregate. (b) AM came off from base concrete in the shape of layers and which were picked off as small broken piece. And asphalt primer didn’t easy to remove from base concrete, a lot of recyeled coarse aggregate were contaminated by them (C) GP, LP and FW were easily to become smaller at crushing of them. There was a mixture of broken pieces of finishing material and recycled aggregate adhered them. GP become a lot of broken pieces, but FW become scarcely of them. (D) ML was broken to pieces of finishing material and adhered to recycled coarse aggregate, but broken pieces we re not so much. (E) EP didn’t come off from base concrete, therefore there was plenty of coarse aggregate with them.

Table 5 Impurities in recycled coarse aggregate

Symbol of finishing materials

PT ML

Impurities of recycled coarse aggregate Range of particle cize (% Impurities Impurities Symbol of weight) Measured Calcureted impurities 2.5 5¯10 10¯15 15¯20 20¯25 (% weight) (% weight) I) ¯5 mm mm mm mm mm 0

0

0

0

0

0

7.6

3.1

2.6

2.1

4.5

3.0

3.2

-

3.1

2.2

2.8

6.0

8.6

3.6

8.0

0

0

0

0

0

0

-

BPA F BPA F

Physical properties of recycled concrete GP CM AM LM FW EM

443

2.1

2.5

3.0

6.5

5.5

3.2

7.3

0

0

1.3

1.4

0.9

0.7

-

0

0

0

0

0

0

3.0

5.2

5.7

7.5

7.5

5.8

-

2.7

2.5

6.6

6.1

17.3

7.2

8.7

0

0.5

0.6

0.4

1.6

0.7

-

1.2

0.0

1.1

2.0

11.3

2.4

8.4

0

0

0.3

0

0

0

2.5

2.4

4.1

1.7

7.4

3.8

0

0

0

0

0

0

1.6

2.4

4.1

6.0

10.5

4.4

0

0

0

0

0

0

9.8

8.3

BPA F BPA F BPA F BP F BPA

-

F

7.9

A

-

F

1) Symbols of remaining state of impurities BPA: Broken pieces, adhere to aggregate, F: Fragment of finishing materials, BP: Broken pieces, A: Adhere to aggregate.

3.2 Properties of fresh concrete (1) Mix proportion Unit water content of recycled coarse aggregate concrete with impurities was almost the same as shown in table 3, even though the sort of finishing materials and replaced ratios of recycled aggregate were changed in the range of 0, 30, 50 and 100%. The slump and air content of fresh concrete were 18±2.5cm and 4±1% respectively. When the crushed stone aggregate and blended recycled aggregate were replaced by 3 and 5 percent of soil, the unit water contents of concretes were increased to get the required slump. Increased unit water contents for crushed stone concretes were 8 or 13% and these for blended recycled aggregate concretes were 10 or 15%. (2) Setting time and bleeding water Setting time and bleeding water of 15 sorts of conerete were tested. Test results are shown in Fig. 1 and Fig. 2 respectively. The symbols in these Figures are shown in Table. 2, that is; CSA means crushed stone aggregate concrete, NF3 (none impurity) and from PT3 to BL3 (with impurity) are concrete using 100 percent of recycled aggregate respectively . In the conerete of CG-5, BG-5, CS-5 and BS-5, a symbol C means crushed stone aggregate, B means blended recycled aggregate concrete, and G-5 means replaced 5% of crushed glass under 25mm and S-5 replaced 5% of soil to recycled aggregate respectively. Setting times of recycled coarse aggregate concretes containing several impurities were somewhat early to compare with control concrete (NF3), namely recycled concrete with no impurities. When crushed stone aggregate and blended recycled aggregate were replaced by 5 percent of glass (CG-5, BG-5) and soil 1 (CS-5 ,

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BS-5), both of initial and final setting time of them were early to compared with those of control concrete (NF3) by about 60 minutes. There are no difference between the bleeding volume of normal concrete and the every sort of recycled aggregate concretes, but the bleeding volume of concrete replaced soil decreased by about 30 to 40 percent.

Fig. 1 Setting time of recycled aggregate concrete

Fig. 2 Bleeding volume of recycled aggregate concrete

3.3 Properties of hardened conerete Table. 6 shows the list of test results. (1) Compressive strength a) Compressive strength of 7 days in water curing. The compressive strength of the concrete using several recycled aggregates were similar to that of normal concrete (CSA). Comparison with the strength of control concrete (NFS), the strength of concrete replaced by recycled aggregate with impurities by 30 and

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50 percent were the same or larger than that of the control concrete. In the case of 100 percent replacement, the compressive strength of concrete using recycled aggregate with several finishing materials were the same or larger than that of the control concrete, except that of asphalt (AM3) and ceramic tile (CM3). b) Compressive strength of 28 days in water curing. Fig. 3 shows the compressive strength of recycled aggregate concrete with impurities at the age of 28 days.The compressive strength of the control concrete using 100 percent of recycled aggregate (NF3) was about 80% of that of crushed stone concrete. Comparison with the strength of concrete replaced by recycled aggregate with impurities by 30 and 50 percent were larger than that of the control concrete. Those compressive strength were approximate ly equal to that of crushed stone concrete. Therefore the difference of the compressive strength by variety of impurities was not recognized. In the case of 100 percent rep lacement, the compressive strength of recycled aggregate with finishing materials were similar to that of the control concrete, excluding that of recyeled aggregate with asphalt (AM3) and plastic tile (PT3) Table 6 Test results of the hardened concrete

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Physical properties of recycled concrete

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Fig. 3 Replacement ratio of recycled coarse aggregate vs. compressive strength

c) Compressive strength of 28 days in air curing. The compressive strength of crushed aggregate concrete was 90% of that of the control concrete (NF3). In the case of replacement of recyeled aggregate of 30, 50 and 100%, the

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strength of the recycled aggregate concrete were 85 to 122 percent to that of the control concrete. These are lager than that of the concrete (CSA), except that of asphalt (AM3) (2) Static modulus of elasticity According to Fig. 4, the static modulus of elasticity of recycled aggregate concrete cured in water for 28 days has a tendency of decrease when replacement ratio of recycled aggregate increases. And the static modulus of elasticity of recycled aggregate concrete with impurities was a little lager than that of no impurities. The reasons are not obviously.

Fig. 4 Replacement ratio of recycled coarse aggregate vs. static modulus of elasticity

(3) Drying shrinkage The relation between the drying shrinkage and the age are shown in Fig. 5. The drying shrinkage at the age of 13 weeks of control concrete is 17% larger than normal concrete. The drying shrinkage of concretes replaced 30 and 50% of recycled aggregate with impurities were a little smaller than that of control concrete (NF3), except that of gypsum plaster (GP3) and plastic tile (PT3). When soil is replaced in recycled aggregate and crushed stone aggregate, the drying shrinkage is 10 to 25% larger than that of the control concrete (NF3).

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449

Fig. 5 Age vs. drying shringkage of recycled coarse aggregate concrete

(4) Carbonation The relation between the carbonation depth and the age are shown in Fig. 6. According to this result.the carbonation depth of control concrete (NF3) is 1.7 times more than that of the normal concrete (CSA), and the depth of carbonation became larger when the replacement ratio is increased. The carbonation depth of recycled coarse aggregate concretes with impurities are similar or smaller than that of the control concrete, except recycled aggregate concretes with plastic tile (PT3). And the carbonation depth of concretes with soil (CS-5, BS-5) tends to become large. From these results, it appears that the carbonation rate of the recycled aggregate concretes with impurities will be same or a little smaller than that of the control concrete .

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Fig. 6 Accelerated carbonation depth of recycled coarse aggregate concrete

(5) Resistance to f reezing ing and thawing Fig. 7 shows the re lation between the number of freezing and thawing cycles and percentage of relative dynamic modulus of elasticity. According to this results, the resistance to free zing and thawing of the recycled coarse aggregate concretes with impurities shows good results regardless impurities from various finishing materials. And the durability factor of blended recycled aggregate concrete with soil (BS-5) is shows less than 90%.

Physical properties of recycled concrete

451

Fig. 7 Number of freezing and thawing cycles vs. relative dynamic modulus of elasticity

4 Conclusions Various sorts of recycled coarse aggregates were made from base concrete with different finishing materials. Amount and form of impurities contained in them were investigated Thereafter recycled concretes were made by using them, and compressive strength, static modulus of elasticity, drying shrinkage, accelerated carbonation and resistance to freezing and thawing of the recycled conerete were investigated. The following conclusions are derived; (1) It became clear that the impurities contained in plastic tile (PT), asphalt membrane water proofing (AM), gypsum plaster (GP) and emulsion paint (EP) give negative affects on the properties of the recycled coarse aggregate concrete, when crushed stone aggregate is replaced by recycled aggregate with 4 sorts of impurities (PT, AM, GP and EP) by about 50 percent, the properties of the recycled concrete are hardly affected by the impurities. (2) When the crushed stone aggregate and blended recycled aggregate are replaced by soil, the unit water content of concrete is increased to get the required slump, setting time of them became early to compare with those of control concrete, and bleeding volume of them were decreased. Futhermore the drying shrinkage and carbonation depth of them tend to become large.

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5 References Building Contractors Society (1977), “The Recommended Practice for Recycled Aggregate and Recycled Concrete”. KASAI.Y. (1976), “Usage of Recycled Aggregate and Recycled Concrete”. Concrete Journal, JCI VOL. 14 No. 9, Sept. Building Research Institute Ministry of Construction (1986) “Report on Studies Concerning Recycling Technologies for Construction Waste”. YANAGI, K. et al. (1988) “Effect of impurities in recycled coarse aggregate upon a few properties of the concrete produced with it”. Proceedings of the 2nd RILEM Inter. Symp. on Demolition and Reuse of Concrete and Masonry, in Tokyo, pp. 613–622, Chapman and Hall KASAI, Y. et al.(1988) “Durabi1ity of Concrete Using Recycled Coarse Aggregate”. Proceedings of the 2nd RILEM Inter. Symp. on Demolition and Reuse of Concrete and Masonry, in Tokyo, pp. 623–632 YANAGI.K. (1991), “A Study on Concrete Using Recycled Aggregate”. Concrete Journal, JCI VOL. 29 No. 7, July. pp. 87–90

35 EXPLORATION OF CONCRETE AND STRUCTURAL CONCRETE ELEMENTS MADE OF REUSED MASONRY* A.PAKVOR, M.MURAVLJOV and T.KOVACEVIC Faculty of Civil Engineering, University of Belgrade, Belgrade, Yugoslavia Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract The paper presents the results of explorations of several kinds of crashed brick concrete. By modelling the structural characteristics of so made concrete, material of various densities, mechanical and insulation properties are provided. That is how the possibility has been created to produce various kinds of structural members and structures. Besides, it has enabled the obtaining of reinforced concrete girders which were subjected to experimental research work. Keywords: Crushed Brick, Single-Fraction Concrete, Cavity Porosity Concrete, Shrinkage, Bonding, Modulus of Elasticity, Strength.

1 Introduction When reconstructions in cities are made which frequently impose demolition of numerous old building, even the whole blocks, or when old structures are replaced by the new ones, the depositing of considerable quantities of scrap material makes a great problem. Such material can by no means to deposited in urban surroundings but its placement outside urban surroundings is not acceptable either, because of ecological problems it could create. Such circumstances have initiated world wide serious explorations of possibilities to reuse such scrap material a high percentage of which is used masonry. In this paper the authors present the results of their latest research work referring to the possibility to use concrete and concrete members obtained of the crushed, already used brick. The presented results refer to: – testing of all essential physical and mechanical properties of crashed brick concrete,

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– testing of models of structural members, – modelling of members. The authors have also presented their own explorations of optimum solutions of two kinds of structural members: blocks for the production of bearing and partition walls, the elements of prefabricated floor structures, etc. 2 Component materials and selection of concrete mixtures 2.1 Component materials characteristics All kinds of concrete that will be considered in this paper have been made using the cement which, according to Yugoslav standards, is marked PC 45. This is pure Portland cement the compressive strength of which is approximately 45 MPa when it is 28 days old. Crushed brick from a demounted old structure has been used as the aggregate for the production of concrete. The aggregate has been separated into fractions 0/2, 2/4, 4/8, 8/16 and 16/32 mm. For some kinds of concrete instead of fraction 0/2 mm of crushed brick, the same fraction of fluvial aggregate has been used (Quartz grains have had the dominant role in that aggregate). The following characteristics of the crushed aggregate have been established by tests: Specific density

2540 kg/m3

Water absorption—average value Density of the aggregate fraction:

Compressive strength for the fraction

41 % 0/2

mm

1150

kg/m3

2/4

mm

775

kg/m3

4/8

mm

770

kg/m3

8/16

mm

755

kg/m3

16/32

mm

750

kg/m3

8/16 mm

1.24 MPa.

It should be noted that the testing of compressive strength of the aggregate has been carried out following the corresponding Yugoslav standard which, first of all, refers to testing light aggregates base on expanded clay. Figure 1 shows the relationship between the obtained strength of the crushed aggregate of the grain size 8/16 mm and the strength of the same two light aggregates based on expanded clay of the Yugoslav production (“Polet” and “Kanjiza”). The concrete kinds which will be considered below have been made using the mixtures of aggregates the grain size distribution of which has been presented in Fig. 2.

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2.2 Concrete mixtures composition The total number of seven different concrete mixtures marked by symbols A, B, C, D, E, F, and G has been treated within the explorations conducted. Mixture A is a single-fraction concrete (cavity porosity concrete) made of crushed aggregate fraction 8/16 mm only, with the quantity of cement paste indispensable for good coating of the grains. Mixture B is the concrete of discontinuous grain size distribution made using crushed aggregate fractions 0/2 and 16/32 mm (see Figure 2). Mixture C and D are the kinds of concrete with continuous grain size distribution of the crushed aggregate against Figure 2. The difference between those two concrete kinds is only in the quantities of water and cement used. Mixture E is the concrete with the same grain size distribution as the concrete B but the fraction of the crushed aggregate contained by it has been replaced by the fluvial aggregate 0/2 mm. Mixtures F and G are the kinds of concrete with the same grain size distribution as in the kinds C and D. However, the fraction of the crushed aggregate 0/2 mm has been replaced with the same fraction of the fluvial aggregate. It should be noted that all grain size distribution curves of the aggregate mixtures are defined on the basis of volumetric relationships so that the mixtures containing sand and the mixtures obtained on the basis of crushed aggregate only can be represented by the same grain size distribution curves.

Table 1. Concrete mixtures

TYPE OF CONCRETE

QUANTTIE8 OF COMPOUNO MATERIALS (Kg/m3) WATER

CEMENT AGGREGATE CRUSHED

SLUMP TEST (cm)

GRAVEL

A

168

336

1200

/

/

B

488

280

1142

/

4.5

C

428

300

1100

/

6.5

0

400

400

1180

/

7.0

E

425

280

780

838

6.0

F

420

300

924

384

5.5

G

413

400

881

412

7.0

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Fig. 1. Compressive strength of different aggregates

Table 1 contains information regarding the composition of all kinds of concrete which have been the subjects of explorations. The quantities of water mentioned in that Table are the total quantities which means that a part of the water used has been the water absorbed by the aggregate while the other part has been the quantity of water providing the required consistency of the mixture

Fig. 2. Grain size distribution curves of the aggregates

3 The results of concrete explorations 3.1 Density and the structure By exploring the densities of the concrete kinds marked A, B, C, D, E, F, and G the curves shown in Figures 3 and 4 have been obtained. As it is obvious, there is the functional dependence between density and time which, with some kinds of concrete, can be rather significant, Figure 5, however, shows the structure of certain kinds of concrete

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which, no doubt, are in correlation with the densities obtained.

Fig. 3. Densities of various kinds of concrete

Fig. 4. Densities of various kinds of concrete

Fig. 5. Structural characteristics of concrete

3.2 Compressive strength By testing the specimens of cubes having 15cm long edges it has been established that the strength of concrete is time-dependent (Figures 6 and 7) whereat nominal strengths of

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the tested kinds of concrete after 28 days have been especially analyzed. Those strengths are shown in Figure 8.

Fig. 6. Time-dependent compressive strength of concrete

Fig. 7. Time-dependent compressive strength of concrete

3.3 Bending strength This property of concrete has been tested on prismatic specimens of the dimensions 12×12×36 cm. Two concentrated forces in the thirds of specimen spans (1=30 cm) have been taken as the loading. The obtained strength of all kinds of concrete examined after 28 days are shown in Figure 9.

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Fig. 8. Compressive strength of concrete at the age of 28 days

Fig. 9. Bending strengths of concrete at the age of 28 days

3.4 Modulus of elasticity Modulus of elasticity has been examined for all kinds of concrete after 28 days except for concrete A which, in principle, cannot be treated as structural material. The tests have been conducted on prismatic specimens, of the dimensions 12×12×36 cm in accordance with Figure 10. The results of the test are presented in Figure 11. 3.5 Stress-strain diagram The stress-strain dependence has also been tested using the prisms of the dimensions

Demolition and reuse of concrete and masonry

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Fig. 10. Layout of measuring deformations of loaded concrete

Fig. 11. Modulus of elasticity of concrete

12×12×36 cm, again in accordance with the lay out given in Figure 10. The obtainec dependencies for 28 days old kinds of concrete are presented in Figures 12 and 13.

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Fig. 12, 13. Stress-strain diagram of concrete

3.6 Shrinkage of Concrete Time-dependent shrinkage of concrete is presented in Figures 14 and 15. As it is obvious, this characteristics has been observed up to three months age of concrete. The explorations have shown that the final shrinkage of crushed brick concrete is somewhat higher compared with the shrinkage of ordinary concrete however, the regarded curves have slower increments within 28 days time interval. This can be explained by the presence of the “captured” moisture in the materials, first of all in the crushed aggregate, which is gradually lost thereby creating moist environment which influences the delay of the process.

Demolition and reuse of concrete and masonry

Fig. 14, 15. Shrinkage diagrams of concrete

462

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4 Testing of reinforced concrete members 4.1 Bond between reinforcement and concrete Having in sigh the fact that the possibility to use reinforced members made of crushed brick concrete depends, among other things, on the attained concrete—steel bond, the testing of the bond has been carried out with the specimens shown in Figure 16. The mentioned tests have been conducted for concrete G only which is a typical, structural concrete whereat smooth bars of the diameter 22 mm and the ribbed bars of the #14 mm have been used. The results of the tests are given in Table 2.

Fig. 16. Testing of bonding of steel and concrete.

Table 2. Results of bonding test

STEEL BARS LIMIT BOND STRESS

NOTE

(mm)

(MPa)

Ø22

436

BARS PULLNG OUT

#14

6.42

BARS PULLING OUT WITH CUBES BREAK

4.2 The conception of experimental reinforced concrete girders exploration In order to collect the information regarding the possibility to use reinforced concrete girders made of crushed brick concrete, the exploration programme has been adopted which included testing of four types of beam girders. Type I—Girders (2 specimens) reinforced by smooth reinforcing bars of the quality 240/360 so dimensioned that their failure takes place along the

Demolition and reuse of concrete and masonry

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reinforcement due to the action of the bending moment; Type II—Girders (2 specimens) reinforced with smooth reinforcing bars, dimensioned so that their failure takes place due to the action of transversal forces; Type III—Girders (2 specimens) reinforced by ribbed bearing reinfor cement of the quality 400/500, dimensioned so that their failure takes place along the reinforcement due to the action of bending moment; Type IV—Girders (2 specimens) reinforced by ribbed bearing reinfor cement, dimensioned so that their failure takes place due to the action of transversal forces. The reinforcement of the tested girders together with the method of load application are shown in Figure 17. All the girders considered are made of the concrete marked G, layout of the measuring points for the tested girders are shown in Figure 18.

Fig. 17. Reinforcement of test girders

Exploration of concrete and structural concrete elements made of reused masonry

Fig. 18. Disposition of measuring points on test girders

465

Demolition and reuse of concrete and masonry

466

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Fig. 19.–22. Exploration results of the test girders

4.3 The results of testing The testing of the above described girders has been carried out with the gradual increase of the load P, up to the point of failure. At each level of loading, deformations have been measured and the cracks have been recorded. Some of the measured deformations are shown in Figures 19–24 while Figures 25, 26 and 27 show photographs of two girders after the testing. Table 3 is a presentation of failure forces for all the girders obtained through calculation and experimentation.

Fig. 23, 24. Exploration results of the test girders

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Fig.25. The appearance of a girder after testing

Fig. 26. The appearance of a girder after testing

Table 3. Design and experimental failure forces

TYPE OF BEAM

CALCULATION

EXPERIMENTAL

ONE FORCE (kN) I

17.68

17.68

II

37.28

44.20

III

15.78

19.89

IV

36.12

48.62

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Fig. 27. Detail of the failure in the support zone

5 Analysis of the possibilities to use the explored kinds of concrete Following the results of the explorations conducted it can be concluded that crushed kinds of concrete can be used in a number of ways. The possibility for application, which is herewith being considered is, first of all, conditioned by the fact that the structure of concrete can be very efficiently modelled when crushed brick is used which enables attaining materials having significantly different physical and mechanical characteristics. For example, if through application of the corresponding technological procedure the possibility to obtain single fraction concrete (cavity porosity material) is achieved, such concrete with primarily be thermal insluator and as such it can be used for the production of various solid and hollow construction blocks. Beside their function as thermal insluators, such blocks, with regard to their mechanical characteristics, can have an important role in the bearing walls of buildings. Figure 28 shows the possible cases of such blocks. On the basis of reinforced concrete members exploitations it can be concluded that reinforced structures can be successfully made using crushed brick, all in accordance with the principles of reinforced concrete theory and practice. However, having in sight lower density of such kinds of concrete, precast members make the most important field for the application of such kinds of concrete. Figure 29 shows an example of possible use of small reinforced concrete beams produced of crushed brick for door and window lintels and similar small span structures. Floor structures make a very important field of crushed brick concrete application. Beside classical types of such structures, the so called semi-precast systems can be implemented on the basis of crushed brick concrete. With those systems, a part of the structures is prefabricated while the other part is cast on the site. As an illustration of such system,

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Figure 30 shows an example of the structure being composed of thin concrete members reinforced by special factory produced reinforcement assemblies. After the erection, such members make the formwork for concreting the second phase of the system—solid concrete slabs. Logically, such slab can be made of both ordinary concrete and of crushed brick concrete.

Fig. 28. Building block

Fig. 29. Precast door and window lintels

Fig. 30. Semi-precast floor structure

PART SIX REUSE OF CONCRETE AND MASONRY MATERIALS— EXAMPLES

36 A METHOD FOR TOTAL REUTILIZATION OF MASONRY BY CRUSHING, BURNING, SHAPING AND AUTOCLAVING H.HANSEN Danish Technological Institute, Building Technology, Masonry Centre, Hasselager, Denmark Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract This paper describes a method for total reutilization of masonry. The method takes advantage of the mineralogical composition of masonry (clay bricks and mortar). After a crushing the lime based binders can be reactivated by burning to above 900°C. From the crushed and burned material bricks can be produced in a calcium silicate process. The properties of these bricks are satisfying for most types of masonry. The bricks are less sensitive to changes in moisture content than normal calcium silicate bricks. Keywords: Reutilization, Recycling, Calcium Silicate, Clay Bricks, Mortar, Masonry, Crushing, Burning, Autoclavation.

1 Introduction Masonry as well as concrete can be crushed and reused as filling materials or aggregates. In these cases physical properties like strength and volume are essential. But nearly no attention is paid to the chemical and mineralogical compositions, and to the possibilities based on these compositions. Crushing will cause a wide grain size distribution, but normally only the coarser fractions are used. Masonry and crushed masonry may be looked at as well defined materials within certain limits according to the mineralogical composition.

Table 1.

Demolition and reuse of concrete and masonry Clay bricks (~appr. 80%)

474

Mortar (~appr. 20%)

yellow bricks

red bricks

aggregates/sand

lime/cement

quartz

quartz

quartz

calcite

calcium-aluminium-silicates

hematite

calcite

hydrated-cementminerals

glass fase

feldspar

feldspar

other minerals

glass fase feldspar

It is obvious that such well defined materials can be used for more than aggregates or filling materials. The Danish Masonry Centre has for The Danish Environmental Protection Agency conducted a project for total recycling of masonry. The principle of the method is shown in figure 1.

Fig. 1.

In principle the entire masonry is reutilized, nothing is removed, nothing is added, except for the energy used in the processes.

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2 Experiments Two experiments were conducted. In the first experiment masonry from a renovation and demolition site inside the city of rhus was used. The masonry was composed mainly of yellow clay bricks and lime mortar. The masonry was crushed in a plant normally used for crushing surplus red clay bricks for tennis courts (a well known way of recycling clay bricks). The maximum grain size after crushing was 4 mm. Analysis of the crushed material showed a lime content of 18.7% (w/w) CaCO3. For mortar and other purposes lime is burned to a temperature of minimum 900°C. During this burning calcination takes place: CaCo3 + energy

CaO + CO2

The burned lime can then be slaked: CaO + H2O

Ca (OH)2 + energy

In this case the potential binders in the crushed masonry (lime in mortar, limestone in mortar sand, lime in yellow bricks) were reactivated by burning to 950°C. This was done in a chamber kiln in the Masonry Centre, due to lack of suitable production kilns in the industry The burned material was used in two ways: I: Moulding of test specimens as normally for the testing of mortar properties. After hardening the specimens showed a low compressive strength, max. 1.3 MPa, and a low flexural strength, max. 0.6 MPa. II: Production of new bricks using the production technique of calcium silicate bricks. The production steps were as follows: - mixing with water, up to 20% - shaping with a pressure of 200–300 bar - autoclavation at about 15 kg/cm2 for 5 hours. The results were bricks with a light grey-yellow colour and densities, suction and compressive strength as shown in table 2.

Table 2.

Shaping pressure

Density

Suction

Compressive strength

bar

kg/m3

kg/m2·min

MPa

Demolition and reuse of concrete and masonry 210

1627

2.3

10

240

1664

2.1

12

250

1678

2.2

12

300

1730

1.3

15

320

1738

1.3

15

Calcium silicate bricks, reference

1771

1.3

29

476

A problem for calcium silicate bricks may be changes in dimensions with changes in moisture content. Testing showed that the bricks had a shrinkage value about 20% of the value for normal calcium silicate bricks, and a value corresponding to the value for clay bricks. The adhesion between bricks and mortar was similar to the adhesion between reference calcium silicate bricks and mortar. In the second experiment surplus material from a commercial plant crushing masonry followed by screening at 4 mm was selected. Normally the material coarser than 4 mm was recycled, while the material finer than 4 mm was discarded. In this case the latter fraction was used for experiments. Obviously the material had an origin as masonry with red clay bricks. The material had a lime content of 14.3% (w/w) CaCO3. It was used without further crushing for new bricks in the calcium silicate process. It was burned, shaped and autoclavated as described earlier. The results were comparable to the results obtained earlier, see table 3. The bricks had a red white appearance.

Table 3.

Shaping pressure

Density

Suction

Compressive strength

bar

kg/m3

kg/m2·min

MPa

200

1550

3.5

8

3 Conclusions These experiments show that a total reutilization of masonry is possible. The bricks produced by the calcium silicate process are suitable for masonry in buildings up to 4 storeys. Architects have pointed out that such bricks based on masonry with yellow bricks may be used in stead of sandstone in restoration projects. The bricks may be more resistant to acid rain than sandstone. The bricks can be made from demolished masonry which in many countries is

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abundant in huge amounts. Surplus material from screening of crushed masonry which normally is discarded may be used, too. The bricks can be produced using existing equipment in crushing plants and calcium silicate plants. But a suitable burning method still has to be found. The demand for energy in the burning process is a major ecological impact of this method for reutilization of masonry.

37 RECYCLING OF CLAY BRICKS P.KRISTENSEN Danish Technological Institute, Building Technology, Masonry Centre, Hasselager, Denmark Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract This paper describes the problems related to recycling of bricks. Among the problems are frost resistance of old bricks, demolition methodology and the different dimensions of old bricks. Most of the problems can be solved by reburning of the old masonry. In fact 100% of old masonry can be recycled to new masonry products. Keywords: Frost Resistance of Old Bricks, Demolition of Masonry, Different Brick Dimensions, Reburning, Recycling of Bricks and Mortar, 100% Recycling of Masonry Products.

1 Introduction Old storey buildings and single-storey buildings consist weightwise of 60–75% masonry and present thus by far the largest potential for recycling of materials in the building sector. Great efforts have in fact been made to find methods for reutilization of especially brick materials, while mortar on the whole has been almost neglected. In Denmark recycled clay bricks have in particular been used as concrete aggregates, as filling materials and as cushion courses as well as tennis court gravel. The Danish Masonry Centre has experimented with recycling of clay bricks as clay bricks and attention has especially been paid to cleaning of clay bricks as well as classification of the properties of old clay bricks. 2 Problems in relation to recycling of bricks Frost resistance Bricks for masonry exposed to the Danish climate must be frost resistant.

Recycling of clay bricks

479

In Denmark it has been a common rule to use halfburned bricks for backings and internal walls. Facing walls have normally been built with decent hardburned bricks at the outside of the facing wall and halfburnt bricks in the inner leaves. When the building legislation at the end of the nineteenth century prescribed that the upper storey should consist of min. a 1½-brick wall, the next 2 storeys downwards of a 2-brick wall, and below added by a ½-brick in thickness for each storey so that a 6-storey building would have a 3-brick thick wall in the lower storey and a 3½-brick thick wall in the basement it goes without saying that only 10–15% of the bricks in the building can be recycled as facing bricks. These circumstances involve great expenses in selecting the more attractive facing bricks from the other bricks. Demolition of masonry The demolition methodology of today is disadvantageous to reutilization of bricks. Normally buildings are demolished with heavy equipment which causes that the bricks are crushed and therefore not suitable for recycling. A subsequent selection of the whole bricks from the amount of brickbats will therefore be extremely time-consuming, consequently with heavy costs. If masonry is selected into facing bricks and common bricks the assignment will be even bigger, and the guarantee that facing bricks are in fact facing bricks is not that big because of the bricks being difficult to distinguish from each other due to demolition dust. Selective demolition has from several sides been suggested as the solution of the problem. The idea is in fact right from a recycling point of view, but a selective demolition will of course be slower and more expensive than the demolition methods used so far. Regardless of which demolition method is being chosen it will be necessary to select, and this process is so time-consuming that it will be difficult from an economic point of view to make ends meet. Brick dimensions In connection with different recycling projects attempts have been made to develop 2 different brick cleaning machines. The development of the machines was started on the recognition that if recycling of bricks was to be profitable the cleaning process of the bricks should be mechanical and rapid. When the machine had been completed it soon turned out that problems occurred by cleaning bricks being too curved or uneven according to size. The bricks were not cleaned sufficiently which caused that at the following attempts it turned out that the adherence between bricks and mortar was not sufficient according to the Danish codes of practice for structural use of masonry. Mortar In connection with the tests with the mechanical cleaning methods it turned out that the machine had to give up towards cement mortars or strong cement-lime mortars. Most brickbuilt buildings which are now fit for demolition have, however, been built with pure lime mortars which are easily removed from the bricks.

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3 An alternative method of cleaning and refinement of old bricks The Masonry Centre, having already been through all the above problems, has on the basis of the experiences already made developed a new basis of ideas for cleaning of clay bricks. The idea is to reburn clay bricks by which the following advantages are achieved: - the bricks are effectively cleaned - all bricks will be hardburned - the mortar can be recycled. Reburning will make it possible to reutilize old masonry 100%. The process of reburning The process is built on the following reactions: - hardened cement will be decomposed at appr. 500°C - hardened lime will be resolved at appr. 900°C - clay bricks will be hardburned at 1000–1060°C. At the Masonry Centre experiments have shown that bricks in masonry are separated and the mortar on the bricks is easy to remove—even by means of a soft brush. The process reminds a great deal of the normal brick burning process. The top temperature is the same, perhaps a little lower, and the critical phases during the course of burning will be the same. Therefore it will be natural to use normal brick kilns for the process. 4 Advantages of the alternative method Demolition The masonry can be demolished according to usual methods with heavy equipment. No selection will take place at the site i.e. no processes will delay the demolition. The demolished masonry can immediately be transported for reburning i.e. the site can be cleared for new buildings, if any. Selection and cleaning In succession to the burning whole-bricks, half-bricks as well as mortar must be selected. The mortar contains quicklime and must therefore be treated carefully because of the effect of etching. Probably it will be necessary to let the actual process take place in a closed room. The mortar has during the burning process lost its continuity and will therefore be removable from the bricks by very easy cleaning methods. The actual selection can take place on a shaking table with grates with different mesh sizes in several layers. It can be designed so that whole-bricks are being detained on the upper grate, half-bricks and brickbats on the middle grate and the mortar will end at the bottom.

Recycling of clay bricks

481

The remains of mortar on the whole bricks will then be removable by means of compressed air or flushing. Reburning products The products resulting from the process are: - whole, hardburned bricks - quicklime and sand - half-bricks and brickbats. Final products As the bricks are probably very uneven dimensionwise a selection according to size should be made. This can be accomplished by an automatic screening plant. The bricks can then be placed on pallets after which they are ready for use. Quicklime and sand will after slaking turn into a wet-set mortar which, after analysis and possible addition of lime or sand, is ready for use. Half-bricks and brickbats can after crushing be used as aggregates in concrete or by addition of lime be used as a calcium silicate like brick. The demolished clay brick building has subsequently been reutilized 100%.

38 SPECIAL TECHNIQUES FOR THE RECYCLING OF CONCRETE BASE PLATES (RAILWAY “SLEEPERS”) K.KLÖPPER Technical University “Otto von Guericke” Magdeburg, Germany Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract Recycling of used building materials will be more important in the the future. One material group consists in concrete base plates. In connection with the recycling of base plates there are some special problems to solve. We have to distinguish between such plates which are contaminated and such without pollution. The contamination results from trains especially in the areas of switch and on the other hand from loading and filling places. Another problem consists in handling and charching the base plates at the recycling place. The aim is to charge them in such a way that after crushing the reinforcement can be collected in nearly straight shape. Keywords: recycling, base plates, concrete reusing

1 Introduction In Germany there are many activities in the field of recycling. This concerns the industrial field as well as research work and associations which organize every year a Symposium with the aim to bring together all those people who are active in the field of recycling building material. In November 1992 the 8th Symposium “RecyclingBaustoffe” was held in Nürnberg. It was evident that recycling of building material has a great chance in the future. The aims of the German government /1/ show that more material has to be recycled in the next years. One material group consists in concrete base plates.

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2 Situation of rails in east Germany Fitzke /2/ old at the 8th Symposium “Recycling-Baustoffe” that in the year 1991 there were 25 Million of concrete base plates in the east part of Germany. Every year more than 2 Million of these plates have to be replaced by new ones. Therefore st is of importance to bring these plates to recycling. A lot of base plates have lost their quality long before the life time is over. Sometimes there can be reached only a quarter of the life time. The main reason of this situation results from the use of aggregates which are not suited for this purpose. 3 Recycling of concrete base plates 3.1. Recycling process The starting point is the exchange of base plates by a special machine which collects the old plates and replaced them by new ones. The old base plates are loaded on freight cares (Fig. 1) and transported to a recycling place (Fig. 2).

Fig. 1: Concrete base plates on tranport

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Fig. 2: Base plates on the recycling place

In the recycling process we have to distinguish between such base plates which are contaminated und such one without pollution. Figure 3 shows the main stations in processing the two kinds of base plates. There are some kinds of contamination. The main part results from loading and filling places. There are different chemicals transported by goods trains and in the past time there was not a great care of this. On the other hand the engine fuel must be filled. When there is no contamination the main following steps are necessary: - conveying in such a way that after crushing the reinforcement can be collected in nearly straight shape - crushing in a suited machine which is able to work with reinforced concrete - separation of steel and wood - classification by means of screens according with specifications.

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Fig. 3: Main steps in the recycling process of base plates

Figure 3 shows that in the case of contaminated base plates there are much more steps to go in the recycling process. At first is a cleaning process of necessity. The method has to be selected in accordance with the kind of pollution. This step makes the process expensiver. There is research work to do in this field. Until now there are no methods which can fullfill the ecological

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and economical requirements, At this time these plates were collected because it will not be allowed to deposite them. 3.2 Unsolved problems If recycling materials shall be used then the consumer will be sure that he is able to fullfill the quality requirements /3/. On the other hand it must be of interest from the point of economical view. Therefore we started the research work in this field /4,5,6/. We started with investigations of crushing process. Until now there are the following problems to solve: - which methods are the best for cleaning process - which kind of control processes can be integrated to guarantee the quality - which kind of conveying equipments will be the best We are working together with specialist of several fields. 4 Outlook The next years will be characterized by a higher ecological sensitiveness. Therefore the recycling processes also will be of more importance. It is of necessity to research intensively on this field. The past has shown that it is impossible to live in the present time in such a way that all problems are to solve by the next generations. That is the reason why we shall think about the egolocical consequences of our work. 5 References /1/ Töpfer, K. Entsorgungspolitik in der Bauwirtsdchaft-Perspektiven für die Bau- und Recyclingbranche In: 8. Symposium “Recycling-Baustoffe”, Nürnberg, November 1992 /2/ Fitzke, H. Recycling im Bereich der Deutschen Reichsbahn In: 8.Symposium “Recycling-Baustoffe”, Nürnberg, November 1992 /3/ Pätzold, H. Anforderungen an Recycling-Baustoffe In: Symposium “Recycling von Baustoffen” November 1992, Magdeburg /4/ Helm, M; Klöpper, K. Projektierung eines Zerkleinerungslabors sowie Vorbereitung und Durchführung von Zerkleinerungsversuchen mit Beton. Forschungsbericht, Technische Universität Magdeburg 1990 /5/ Helm, M; Klöpper, K. Recent results in the Field of Recycling Materials CIB ‘92 World Building Congress, Montreal, Mai 1992 /6/ Klöpper, K.

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Anforderungen an die Maschinenbautechnik beim Recycling von Baurestmassen und anderen Feststoffen VDI-Konferenz “Recycling-eine Herausforderung für den Konstrukteur”, Magdeburg, September 1992

39 RECYCLING OF REINFORCED CONCRETE STRUCTURES AND BUILDINGS USING COMPOSITE CONSTRUCTION: APPROACH TO AN ENVIRONMENTAL-ECONOMIC ASSESSMENT K.RAHLWES Philipp Holzmann AG, Frankfurt a.M, Germany Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract This report describes the state of recycling of reinforced concrete from buildings in Germany. Furthermore, the effect of recycling on the total cost of reinforced concrete and composite structures as well as the consumption of primary energy is investigated. Finally, the requirements for environmentally adapted construction in concrete is discussed. Keywords: Buildings, Recycling, Concrete, Rebar, Structural Steel, Primary Energy Consumption

1 Demolition Concrete for the Use in Road Construction Since 1988 dumping costs, for building rubble have risen, with strong regional variations, from between 7 to 40 DM/t to between 80 to 200 DM/t and they still continue to rise, Willkomm, (1990). Transporting building rubble to neighbouring countries which might accept the rubble and have larger dumping potential is politically and ecologically undesirable, nor is it feasible in most cases due to the transportation costs. The German waste disposal law gives priority to utilising waste over other methods of disposal. The goals established by the German Government at the beginning of 1990 require separate collection of building rubble at the location where it is produced, an increase in the rate of reusing the material to 70% in 1994 and forbids the dumping of mixed components or reusable building elements. In some German states similar laws have been in force since 1990. Concrete steel scrap and non-contaminated concrete rubble are without doubt reusable

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raw materials. Where buildings are demolished it is already common practice to dismantle the interior elements and the supporting structure separately. The supporting structure is usually demolished with an excavator and a demolition ball using the potential energy in the building. Under certain conditions hydraulic pincers are used. Non-contaminated reinforced concrete rubble is shipped to and processed at mobile or stationary recycling plants. End products are rebar steel scrap and concrete ballast, concrete fragments and sand which are used in road construction. Regulations for quality and testing of material to be reused in road construction were established for example by the Gütegemeinschaft Recycling-Baustoffe e.V. and published as early as 1985 as RAL-RG 501/1. The RC-material is subject to internal and external control and has to meet the same requirements as natural materials. However the rules applied for testing and for the technical limitations in the ecological assessment are still diverging. The basic idea for these regulations is that demolition material from buildings which were not polluted can be reused without restrictions. The goal, to give adequate consideration in tenders and awards of contracts to the use of recycled material has sofar been a request to public clients and should be supported by federal laws, uniform all over Germany. The higher production costs of the RC-material must be lowered at least down to the current prices for natural gravel, by the transfer fee which the contractor responsible for the demolition pays to the recycling firm. This fee represents only a small portion of the savings of the dumping costs due to recycling. The savings on dumping space and natural resources are compensated by increases in other cost factors, however this is not true for the energy consumption. Even if energy costs are considerably higher the environmentaleconomical profit will still prevail. Taking transportation costs into account will be in favour of recycling since the distance from the demolition site to the dump will usually be longer than the distance to the next recycling plant. 2 Concrete Fragments for New Concrete Due to the present market situation, but also because no suitable general technical regulations have been established, concrete fragments are presently not used for new concrete constructions in Germany. Numerous scientific studies which go back to the times where rubble was utilised following the Second World War, show, that concrete can undoubtedly be produced from concrete fragments and sand obtained from a healthy base material, Ivány/Lardi/Eßer (1985 and 1987), Schulz (1986), Sommer (1990) . Attention needs to be paid to the concrete composition and the material needs to be processed properly. The achievable quality is almost as good or only or slightly inferior as the original concrete. A prerequisite is that if buildings of mixed construction are demolished the reinforced concrete needs to be separa-ted from other mineral materials. Results of tests at the Philipp Holzmann AG laboratory for building materials are shown in the figures 1 to 4. The demolition concrete came from a building with a

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reinforced

Fig. 1. Compressive Strength of Recycled Concrete (laboratory test)

concrete structure, built in 1962. The concrete used was a B 300. The structural frame was demolished separately from the interior elements of the building by standard methods. The reinforced concrete rubble was broken down and sieved in a recycling plant consisting of a jaw crusher, sieving plant and a magnetic separator.

Fig. 2. Flexural Strength of Recycled Concrete (laboratory test)

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Remaining foreign substances were removed by hand. The granulation obtained was in the range 0–45 mm and 80–150 mm. In a second cycle the rubble was broken down to the

Fig. 3. Modulus of Elasticity of Recycled Concrete (laboratory test)

granular groups 2/8, 8/16 and 16/32 and was used in tests with mixtures containing 0, 20, 40, 60 and 100% concrete fragments as coarse aggregate. The consistency was the same for all tests. For the specimens where the consistency was obtained by adding water the results confirmed the known decrease in compressive strength, tensile strength and of the modulus of elasticity with increasing percentage of concrete fragments. In the tests where a plasticizer was used to obtain the required consistency the percentage of

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Fig. 4. Depth of Carbonation (concrete age 56 days)

recycled material had no influence on the quality of the concrete. This is also true for the depth of carbonation and the frost resistance. Only the modulus of elasticity of concrete with 100% concrete fragments sank to about 77% compared to concrete containing no recycled material. The tests confirmed that it is possible to produce a concrete that can be used as a category B35, and which is still easy to process, by substituting the coarse aggregate with up to 100% concrete fragments. To achieve these values it is essential to have an effective quality control at every stage of the process. An assessment still has to be made of materials in demolition concrete which are damaging to concrete or are harmful to the environment. Their concentrations as well as their bond in new concrete after repeated recycling need to be investigated. In addition values must be established related to the effect of other mineral rubble in new concrete after repeated recycling. Since separate demolition has been enforced by law, there are factors in favour of using demolition concrete for producing new concrete in the medium term. This is true even though present amounts are small compared with the quantities needed. Demands to preserve the nature and therefore to reuse former sites in order to avoid further sealing of the soil together with the increasing technical requirements for buildings necessitate to demolish existing buildings which are difficult to convert for other uses, in an increasing way. Figure 5 shows an attempt to calculate the expected amount of demolition concrete from buildings for West

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Fig. 5. Estimated Quantities of Concrete Rubble (West Germany). (Calculated from 75% of the Cement Production using 330 kg/m3)

Germany based on the cement production of the past, Bundesverband der Deutschen Zementindustrie. The use of concrete fragments may already be economical, if natural aggregate has to be transported over a long distance, Ivány/Lardi/Eßer (1985), Schulz (1986). If road construction can not reuse the full amount of the expected concrete rubble together with the rubble from demolished roads and other suitable recycled material, the concrete rubble should be used as aggregate in the production of new concrete. However, due to the transportation costs, the quantities which can or must be used in road construction heavily depend on the location and on the market situation. In order to give the recycling market a wider basis and more flexibility and in order to decrease the grey market, technical requirements for utilisation of recycled concrete must be completed for the use in road construction and need to be established for recycled concrete. 3 Reinforced Concrete Structures and Composite Construction The recycling of reinforced concrete is new compared to steel structures which have traditionally been recycled for economical reasons. We used a parking deck with 7 floors located in Frankfurt as an example to examine the competitive situation of reinforced concrete and composite construction using natural gravel and to determine how it changes under the new conditions. In both cases precast concrete plates were used as forms for the floor slabs. The girders in the reinforced concrete structure were assumed to be precast elements. Figure 6 and 7 show construction and dismantling costs (VAT excluded) per m2 of usable floor space based on 1989 prices. Costs are split into costs for dumping, raw material, energy, depreciation, miscellaneous and wages/salaries and include all stages of

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the process. The different stages of the process are shown in Figure 8. Figure 9 shows an example of the subdivided cost matrixes. They were established using information from firms, organizations, from the literature, as well as from studies carried out by the Department for Concrete Structures at the RWTH Aachen and by us. For demolition and recycling information from a specialized firm were used, Strauch (1990). The figures are in the range of those given in literature, Kuhne/Osebold (1981). Transportation cost of aggregate are based on the rates used in local freight traffic, GNT (1990). The distances considered are the average transportation distances as they occur for the object in question. Figures for the primary energy consumption in kWh were taken partly from Marmé/Seeberger (1982). Other parts were

Fig. 6. Parking Deck, Reinforced Concrete Construction and Dismantling

calculated from fuel and energy consumption. The efficiencies were also taken from Marmé/Seeberger. Therefore the conditions listed there will apply as well. Since proved, recent data were not available, the primary energy needs for the production were assumed to be 8000 kWh for one metric ton of rebar and structural steel, and 1140 kWh for one metric ton of cement, Marmé/Seeberger. The costs are broken down in accordance to the method of the process-chain-analysis. Starting from the erection of a building at a construction site (process stage 0) the

Recycling of reinforced concrete structures and buildings using composite construction

Fig. 7. Parking Deck, Composite Structure Construction and Dismantling

Fig. 8. Diagram of the different Process Stages

495

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building materials are traced back to their origins (Fig. 9). The process stages −2 and −4 comprise the production of intermediate products, stages −6 and −8 include the production of the basic material. In the other direction expenses for demolishing the building and processing the material to reusable products are examined. Between each process stage a line (odd numbers) is reserved for transportation costs. Each line contains different types of costs. Environmentally relevant costs such as energy, water and dumping are assessed separately. The remaining costs are divided into wages and salaries, depreciation and miscellaneous. Following this scheme the costs for 1 t of natural gravel, natural stone fragments, recycled fragments, cement, reinforcement and structural steel were calculated.

Fig. 9. Cost Matrix for Reinforced Concrete Column B (DM/m2)

Taking this basic data and information from concrete processing firms the cost matrix of the higher process stages can be calculated step by step. That way matrices are compiled for 1 m3 of concrete (based on an average composition), 1 t of precast concrete elements, 1 m2 of precast concrete plates used as forms 1 t of reinforcement, cut and bent 1 t of structural steel The overall matrix, covering all process stages, is obtained by adding information about the construction site and about the demolition of the structure.

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The cost columns “Depreciation” and “Miscellaneous”, (Fig. 6 and 7) which were not examined in detail in this report, also contain costs for energy, raw material and wages. The actual share of these costs are therefore slightly higher than shown in the cost columns. The use of information from different sources and mixing of statistical data with object-related details result in inconsistencies in the figures. This was acceptable in order to obtain satisfactory complete data. The divergences lie within the acceptable limitations of accuracy. Partial and total matrices are available per request to the author. The cost columns A (Fig. 6 and 7) apply to traditional standard procedure, i.e. dumping the demolition concrete for a fee of 80 DM/t. For columns B and C recycling for the use in road construction was assumed. The comparison of A and B shows the influence of saving the dumping costs and of the proceeds from selling the RCmaterial. The reduction in costs is somewhat higher for reinforced concrete because of the higher savings in dumping costs. For the reinforced concrete structure the total primary energy consumption resulted to 488 kWh for column A and 498 kWh for column B per sqm used area, respectively 529 and 536 kWh per sqm used area for the composite structure. The costs for one kWh of primary energy are, depending on the process stage, between 2.5 and 12 pfennigs. In cost columns C, based on the columns B, the price for one kWh of primary energy is set at 12 pfennigs for each process stage in order to test the sensitivity. It shows that there is no clear difference in the sensitivity for the different building methods. The share of the costs for energy increases from about 9 to 22% and the costs for 1 m2 of usable floor space by about 17%. For reinforced concrete (column B) the production of aggregate uses 0.7%, the cement production 21% and the production of steel reinforcement 61% of the total primary energy. This adds up to over 82%. For composite structures the figures are 0.5%, 15% and 70%, which makes a total of about 85%. The transition from dumping to recycling material for the use in road construction leads to hardly any increase of the total energy consumption, but it saves costs for dumping and raw material instead. The use of concrete fragments for new concrete results in practically no increase of the primary energy consumption or the total cost. The results of this calculation are not shown in the graphics. Reinforced concrete therefore proves to be absolutely recycling-friendly. The use of concrete fragments for new concrete is also correct from an environmental-economical point of view. 4 Summary and conclusions 4.1 Existing Buildings It is well worth, while from an environmental-economical point of view, to recycle

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existing reinforced concrete buildings for the reuse in road construction. To a large extent the technical questions have been solved theoretically. The already highly developed demolition and recycling techniques are subject to market pressure and will therefore without doubt follow this development, Schulz (1986), Willkomm (1988). To develop a well functioning market for recycling it is desirable to finish the technical regulations for recycling material for the use in road construction and to establish similar specifications for the use in new concrete structures. 4.2 New Buildings The goal is to create reinforced concrete structures that are more compatible to the environment and are a source of valuable recyclable material and not additional waste at the end of their service life. Therefore the more difficult question is what should be done in addition to improve the design, the construction techniques and the operation of new reinforced concrete buildings and how to obtain the necessary funding, Drees (1989), Willkomm (1990). It is questionable whether to attempt to design reinforced concrete structures to be easier to demolish and to recycle. First of all the costs for the demolition and the recycling of standard buildings are relatively low and subject to market pressures. The example of the parking deck shows that demolition, transport and recycling, using the traditional method of the demolition ball, account for 17 and 13% of the total cost and 9 and 8% of the total primary energy. On the other hand the supporting structure could loose ductility and robustness, characteristics the developing European standards put considerable emphasis on. Technical restrictions will be of little help. “Intelligent” demolition methods will eventually be developed in case of a growing market. In the case complete elements of the structure are recycled, so called Demountable Structures, almost all the primary energy used in the thermal processes during the production of the building material and required for the demolition would be saved, Reinhardt, Bouvy (1985). However in view of limited adaptability and technical as well as legal reservations, the potential for such methods is limited. A long service life will lower the environmental-economical costs. The superstructure and the interior elements should therefore be constructed in a way that the building can be adapted, with minimal effort and possibly without alteration to the supporting structure, for other uses and demands. It should be an “intelligent building”. The most important factor in retaining the value of a structure is to ensure that the supporting structure and the interior elements are designed in a way that the concrete will not be contaminated. An easy and clean separation of interior elements from the supporting structure should be made possible, Willkomm (1990). In buildings which make up for the bulk of the volume constructed the combination of supporting structure and interior elements is of major importance for operating, maintaining and recycling the building, as well as for using it for other purposes. Within reasonable effort the interior elements should also be recyclable to a large extent. To achieve this goal new concepts are needed in regard to material and construction beyond the initial stages. Many suggestions have already been made by architects and engineers,

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Steiger (1989), Willkomm (1990). High costs for retrofitting after the building has been in use for a long time or high costs that may have to be expected for demolition and dumping at the end of its service life have little effect on investment decisions. On one hand because the costs will not necessarily have to be absorbed by those who make the decision. On the other hand because the amount for such costs is not known. The investor as well as the future buyers do not have a scale for the environmental-economical quality. Therefore technical rules for construction under environmental considerations are just as necessary as rules for safe construction. These rules will consequently have to affect the construction and need to minimize the total environmentaleconomical costs. A basis could be sensitivity studies which cover the complete building for its full service life up to demolition and will include the estimated effects resulting from future developments. This represents a new interdisciplinary field for study and research. Considerable parts of this report were prepared by Dipl-Ing. Klaus Kaiser from the Technical Department at the headquarters of the Philipp Holzmann AG. References Bundesvbd. Dt. Zementindustrie: Zementverbrauch von 1880 bis heute Drees: Recycling von Baustoffen im Hochbau, Bauverlag Wiesbaden und Berlin 1989 GNT 1990, Tarif für den Güternahverkehr mit Kraftfahrzeugen, H.Vogel Verlag, München 1990 Iványi/Lardi/Eßer: Recycling-Beton, Uni-GHK-Essen, Forschungsberichte aus dem FB Bauwesen, Sept. 1985 Iványi/Lardi/Eßer: Recyclingbeton. Recycling in der Bauwirtschaft, hrsgg. v. Thomé Koszmiensky/Pietrzeniuk, FE-Verlag 1987 Kuhne/Osebold: Verfahrenswahl beim Abbruch von Massivbauwerken, Baumaschinentechnik 1981 H. 10 Marroé/Seeberger: Der Primärenergieinhalt von Baustoffen, Bausphysik 4 (1982), H. 5+6 Reinhardt/Bouvy: Demountable Concrete Structures, Delft University Press 1985 Schulz: Recycling von BaurestmassenEin Beitrag zur Kostendämpfung im Bauwesen, Forschungsauftrag BMBau-B I 6–80 0184–8, 1986 Sommer: Beton aus Altbeton, Zement und Beton 1990, H. 4 Steiger: Recycling—ein falscher Trost, Der Architekt 1989, H. 3 Strauch: Angaben zu Abbruch und Recycling. Unveröffentlicht Willkomm: Baustoff-Recycling, RKW Nr. 1060, Eschborn 1988 Willkomm: Recyclinggerechtes Konstruieren, RG-Bau-Projekt 52301, Verl. TüV Rheinland 1990

40 RECYCLING OF CONCRETE FOR THE RECONSTRUCTION OF THE CONCRETE PAVEMENT ON THE VIENNA-SALZBURG MOTORWAY H.SOMMER Forschungsinstitut der Vereinigung der Österreichischen Zementindustrie, Vienna, Austria Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract In 1991 and 1992 45 km of carriageway were reconstructed on the motorway Salzburg-Vienna, re-using the old concrete pavement 100% on the job-site. The fine material (0/4) that resulted when crushing the old pavement was added to the old granular subbase which without would have been too coarsegrained to be stabilized with cement. The bottom layer (21 cm thick) of the new concrete pavement was made from natural sand 0/4 and the crushed concrete as the coarse aggregate. The cement requirement was about the same as for crushed stone, but the flexural strengths were better than they would have been with most natural aggregates; the reason being the very good bond between the new cement stone and the old highquality concrete. Asphalt particles originating from thin bituminous overlays did not exceed 10% of the coarse aggregate and had practically no harmfull effects. Keywords: Recycling, Concrete, Concrete Pavements, Reconstruction of Concrete Pavements

1 Introduction The motorway Vienna-Salzburg has a total length of 300 km. On roughly half that length the concrete pavement is older than 30 years and needs renewal. A motorway is, of-course, a good case for recycling since large quantities of a welldefined material are available; recycling of concrete is also a practice already well

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established; but two questions had to be answered: (1) According to available experience concrete made from old concrete may be inferior in strength and modulus of elasticity and it may also shrink more than concrete made from natural aggregates [1]. This might require changes in the design of the pavement. (2) The old concrete pavement is covered with a thin (2–3 cm) bituminous surfacing which was placed to fill the ruts produced by the studded tyres. Thus the crushed pavement material would consist of approximately 90% of con crete and 10% of asphalt and it was not known how this would effect the properties of the new concrete. 2 Laboratory Tests [2] 2.1 Old pavement concrete Requirements 30 years ago: concrete

aggregate≥8 mm

28-day-strength (N/mm2) compressive

flexural

top layer

chippings

≥40

≥5,5

bottom layer

gravel

≥35

≥5,5

total air-content ≥2,5% Properties at an age of ≥30 years: compressive strength 70–100 N/mm2, no durability problems. 2.2 Test programme In Austria two layer construction is usual; because aggregates that are resistant to polish and wear are expensive. Recycling concrete was only considered for the bottom layer of the new pavement. Concrete from 4 different locations in Salzburg, Vienna and Lower Austria and an asphalt overlay were obtained, crushed and sieved into fractions; natural sand, quartzitic gravel, and crushed stone (Granulit) were also used. 10 different concretes were made; cement content was 350 kg/m3 (crushed material) resp. 320 kg/m3 (gravel), w/c=0,40 (2% moisture absorbed by crushed concrete not taken into account) , air-content 3,5%) , max. aggregate size 32 mm, continuous grading (A 32+B 32) 1/2.

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The concrete specimens were tested for strength (compressive and flexural, central loading), modulus of elasticity, shrinkage, and frost-salt-resistance.

Fig. 1: Flexural strength and modulus of elasticity of pavement concrete made from natural aggregate and crushed concrete 4/32

Recycling of concrete for the reconstruction of the concrete pavement

Fig. 2: Flexural strength of pavement concrete made from crushed concrete 4/32 containing asphalt particles

Fig. 3: Shrinkage of pavement concrete made from crushed concrete 4/32 containing asphalt particles

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Fig. 4: Resistance against frost and de-icing chemicals; concrete made from crushed concrete 4/32 containing asphalt particles

2.3 Sand from crushed concrete If sand from crushed concrete was used, even if mixed 1:1 with natural sand, the concrete did not show adequate resistance against the combined attack of frost and deicing chemicals. 2.4 Compressive strength and modulus of elasticity About the same as for natural aggregate, see fig. 1. 2.5 Flexural strength Much better than for quartzitic gravel, see fig. 1. 2.6 Asphalt content Asphalt contents of up 20% did not reduce the flexural strength significantly, fig. 2; shrinkage and swelling did not seem to be influenced greatly, fig. 3. Asphalt contents of more than 20% did impair frost-salt-resistance, fig. 4.

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2.7 Summary In Austria, chippings produced from old pavement concrete are at least as good as natural aggregate; reasons for that are: high quality of the concrete, absence of durability problems (alkali-silica reaction is practically unknown in Austria), and the very good bond that develops between the old concrete and the new cement stone, fig. 5. (better than with quarzitic gravel and at least as good as with crushed calcareous high-quality stone). Asphalt particles will reduce the properties of the concrete somewhat, but if less than 20% the flexural strength will still be better than that of concrete made from quarzitic gravel. 3 Reconstruction of the concrete pavement [2, 3] 3.1 Concept The concept is shown in fig. 6. 3.2 Processing the old concrete The old concrete pavement was shattered (using f. i. a Wirtgen Guillotine), taken to an on site crushing plant, and processed into the fractions 0/4, 4/8, 8/16 and 16/32. These fractions contained between 2% (16/32) and 10% (4/8) of asphalt and bitumen (originating from thin bituminous surfacings or from slab-jacking with bitumen). 3.3 Upgrading the old subbase The fraction 0/4 was placed on top of the old gravel subbase which (in the worst places) contained up to 15% of particles smaller than 0,063 mm (the fines had worked up from the subgrade) and was stabilized mixed-in-place with cement 20–25 cm deep (f. i. using a Bomag machine). A typical

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Fig. 5: Aggregate from crushed concrete

Fig. 6: Concept for the reconstruction of the concrete pavement on motorway A1

cement content is 100 kg/m3, strength requirement is 3 N/mm2 at 7 days (Proctor cylinders).

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3.4 Placing an intermediate asphalt layer 5 cm of asphalt were placed on top of the cement-stabilized layer to provide the concrete pavement with a subbase resistant to erosion in the presence of brine. 3.5 Concrete pavement A concrete pavement 25 cm thick without reinforcement but with dowelled joints (distanced 5,5 m) was placed using slip-form pavers. Paving width was 11,50 to 12,25 m. 3.6 Recycled concrete The bottom layer was made using natural sand 0/4 and the crushed concrete as the aggregate 4/32 and placed 21 cm thick. Typical mix-design: 365 kg/m3

cement sand 0/4

645

crushed concrete

air-entraining agent 1,2%

4/8

210

8/16

365

16/32

560 0,44

plasticizer 0,3%

1,1

water (w/c=0,425 effective)

153

density

2300

3.7 Top layer The top layer was placed only 40 mm thick, consisted of a very fine-grained concrete with a high percentaqe of chippings 4/8 (natural stone resistant to polish and wear) sprayed with a retarder and brushed next day. The exposed aggregate surface is noisereducing and skidresistant [4]. 4 Practical experience 4.1 Extent of application In 1991 and 1992 5 job-sites in the provinces of Lower Austria and Salzburg with a total of 45 km of carriageway.

Demolition and reuse of concrete and masonry

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4.2 Crushing With rotary type crushers the reinforcement orcement can be regained without any concrete adhering to it. 4.3 Mixing It was important to use the crushed concrete in a wet state, fig. 7. Net mixing time was 60 seconds (in order to obtain a good air-void system).

Fig. 7: Consistency (v=Verdichtungsmaß)

Recycling of concrete for the reconstruction of the concrete pavement

509

Fig. 8: Frequency distribution of flexural strengths (example from job-site T)

4.4 Strength The flexural strength was as high as with the best of natural aggregates, fig. 8. Strengths were also quite uniform; typical example: 28-day-strength (N/mm2) flexural

compressive

X

6,5

40,7

s

0,41

3,39

f5%

5,9

35,1

requirement

5,5

35

5 Summary In 1991 and 1992 45 km of carriageway were reconstructed on the motorway SalzburgVienna, re-using the old concrete pavement 100% on the job-site.

Demolition and reuse of concrete and masonry

510

The fine material (0/4) that resulted when crushing the old pavement was added to the old granular subbase which without would have been too coarse-grained to be stabilized with cement. The bottom layer (21 cm thick) of the new concrete pavement was made from natural sand 0/4 and the crushed concrete as the coarse aggregate. The cement requirement was about the same as for crushed stone, but the flexural strengths were better than they would have been with most natural aggregates; the reason being the very good bond between the new cement stone and the old high-quality concrete. Asphalt particles originating from thin bituminous overlays did not exceed 10% of the coarse aggregate and had practically no harmfull effects. Literature

[1] Wesche, K.-H. und Schulz, R.-R.: Beton aus aufbereitetem Altbeton. Technologie und Eigenschaften. Beton, Heft 2/1982. [2] Sommer, H: Wiederverwendung von Altbeton für neue Betonfahrbahndecken. Bundesministerium für wirtschaf tliche Angelegenheiten, Schriftenreihe Straßenforschung, Heft 403, Wien, 1992. [3] Stinglhammer, H.: Betonfahrbahndecken aus Altbeton. Schriftenreihe der Forschungsgesellschaft für das Verkehrsund Straßenwesen, Wien, 1993. [4] Sommer, H.: Lärmmindernde Betonoberflächen. Bundesministerium für wirtschaftliche Angelegenheiten, Schriftenreihe Straßenforschung, Wien, 1993.

41 INERT WASTES FROM CERAMICS PRODUCTION AND CONSTRUCTION WORKS: RECYCLING EXPERIENCES IN SASSUOLO, ITALY* G.F.SAETTI, A.COCCONCELLI and G.FINELLI SAT, Sassuolo, Italy C.MEDICI Health Inspectorate, Sassuolo, Italy Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. ABSTRACT In Italy, every year we have a mass of inert wastes of about 80,000,000 m3 consisting of inerts and the like from industrial production. It is a quantity similar to that of inert materials dug yearly for concrete and other uses (such as foundations of roads, etc.). In particular, the ceramics district of Sassuolo is a zone of about 50 m2, with 150,000 inhabitants, and many activities in industrial and agrozootechnical fields. This high concentration of human activities created a dangerous situation for water pollution, and also the depauperation of alluvial beds and soils, caused by the extraction of materials, is a problem. Thus, the opportunity (and the necessity) of the recovery and reuse of the inert wastes from industrial production (ceramics refuse) and from demolition of buildings, and so on, means reducing the need for disposal sites, and a similar reduction in the quantity of stony materials yearly extracted. The local authorities have designed some strategic actions, such as: - reduction in the use of stony inerts; - their substitution with alternative materials. In the ceramics district we currently have a power of treatment from the recycling of inert wastes of about 300,000 m3/yr. We have also tested the use of recycled materials for the construction of road foundations, with excellent results, in the full respect of the environment. Thus, we have the chance to solve the problem of the disposal of industrial inert wastes, as well as that of hazardous ceramic sludges (testing the recycled

Inert wastes from ceramics production and construction works

513

material, after inertisation). Keywords: Ceramics District, Third Firing, Ceramics Inerts, Wastes, Scrap Material

1 Introduction The term “ceramic district of Sassuolo” refers to a territory situated at the beginning of the foothills within and near the Municipality of Sassuolo. This territory straddles the Provinces of Modena and Reggio Emilia, which are separated by the Secchia River, a tributary of the Po River. The total area is approximately 300 km2, with 150,000 inhabitants, including the Municipalities of Sassuolo, Fiorano Modenese, Maranello, and Formigine in the Province of Modena; and the Municipalities of Scandiano, Castellarano, Casalgrande, and Rubiera in the Province of Reggio Emilia. Up to right after the Second World War, the economy of this area was based predominantly on agricultural and zootechnical activities. Starting in the 1950s, it was transformed first of all into an area of cottage industry and then became increasingly industrialised. By the 1980s, the current level of over 200 ceramics manufacturers had been reached, in addition to over 100 “third firing” ceramic decoration companies, that is, the third firing of the ceramic wall tiles for adding hand-painted or silk-screened decoration. The prevalence of this type of economy led to direct employment of over 21,000 people in the sector, and consequently to the production boom that has characterised these last few years. Thus, it can be affirmed that the ceramics industry is still the strong point of the local economy. 2 Production of inert construction waste materials in the district A quantitative evaluation of this type of waste is made difficult by the little attention it has been given up to now due to its non-hazardous nature, as well as by the low economic value attributed to its recovery. As regards materials recovered from demolition, construction, and excavations, the available data on quantities of inert waste discharge in regions such as Piemonte and Lombardia, economically similar to Emilia-Romagna, give an estimate of the volume necessary for recycling at 0.3–0.5 m3/yr per inhabitant. Surveys carried out in certain municipalities in the Emilia part of the region have made it possible to estimate, as a reliable average per inhabitant, a total of between 0.1 and 0.5 m3/yr. Considering the urban and industrial situation of the ceramic district which, due to continuous technological evolution necessitates constant and regular renovation and even radical restructuring of industrial facilities, we can hypothesise a coefficient of construction waste production that is surely closer to the maximum levels found in the literature. Thus, with a coefficient of 0.5 m3/yr per inhabitant, the result would be a district-wide level of 0.5 m3×150,000 inhabitants, or a total of 75,000 m3 of construction waste, which corresponds to approximately 105,000 tons.

Demolition and reuse of concrete and masonry

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Up to a few years ago, the destiny of almost all construction waste was that of being systematically disposed of, uncontrolled, in river or high-water bed areas. This waste could at least have been used for construction land-filling, which in the majority of cases is normally done using river gravel, readily available on the market at relatively low prices. In the last five years, growing attention has been paid, by both the public authorities and public opinion in general, to the phenomenon of depauperation of river resources which has had serious hydro-geological consequences (lowering of river beds with the resulting lowering of the water table). Thus, the issuing of concessions for excavation of natural inerts has been restricted, even to the point of total prohibition of river bed excavations and considerable restrictions on excavations in alluvial fan areas. All this has led to a rapid reduction in the availability of natural inerts, resulting in considerable increases in market prices. The unavailability of large quantities of inerts, and prices often incompatible with construction costs, has led some companies already operating in the excavations sector to look for ways of recovering construction wastes, and inerts in general that derive from production processes. Currently in our Province, three inert grinding and recovery plants have been installed, one of which is permanent and already operative, and two mobile systems of which one is being prepared for operation. A fourth plant, permanent, is operating within the ceramic district in the Province of Reggio Emilia. The general outline of this operation is as follows: (a) Materials are received and checked for their suitability; temporary storage. (b) Materials are loaded into hoppers and ground by jaw crushers. (c) Isolation and separation of metallic particles by means of a special magnetic tape. (d) Secondary raw materials are stored and then sent out for reuse. Thus, from the initial demolition and ceramic industry waste materials, the destination of the secondary raw materials mainly includes road foundations, construction foundations and filling. The most highly valued materials, such as reinforced concrete, can also be recycled for formulating the concrete mixture. From the quantitative point of view, the crushing plants operating in the Provinces of Modena and Reggio Emilia have the production data shown in Table 1 below.

Table 1. Crushing plant production data

System

Province

Capacity m3/yr

Production 1990

Production 1991

Production 1992

Forecast 1993

PLANT 1

MO

100,000

60,000

85,000

95,000

100,000

PLANT2

MO

80,000

55,000

37,000

30,000

30,000

PLANT3

MO

80,000

not operating

not operating

not operating

70,000

PLANT 4

RE

100,000

20,000

20,000

20,000

30,000

Inert wastes from ceramics production and construction works TOTAL

360,000

135,000

142,000

515

145,000

230,000

In relation to an estimated quantity of approximately 400,000 m3 of inert waste (1,000,000 inhabitants×0.4), the sum of that produced in the Provinces of Modena and Reggio Emilia, it is thus evident how these plants, in just their short lifetimes, have been able to absorb approximately half of the total inert wastes produced. In the next period (2 years), considering that the market conditions for natural inerts is bound to become increasingly critical, it can be seen that the search for recovered inert materials, from construction and other sources, will reach the level of totally reabsorbing the secondary raw materials produced through recovery and recycling. The amount of inert material to be disposed of that does not go through the circuit of “treatment centres” is similarly used in a direct manner by the individual Authorities for interior building works (filling, yards). However, these activities are at present largely uncontrolled and thus are missing from the evaluation of inerts deriving from treatment operations. In any case, the packaging of such typologies of waste at the authorised dumps of class 2.5 typa A is limited to 5% of the production. 3 District-wide production of ceramic inert wastes In order to quantify the district-wide production of inert wastes deriving from ceramic production, we use as reference point the total 1991 ceramic tile production, which was approximately 322,000,000 m2. The calculation of the percentage of discard and thus of waste must of necessity consider the different types of production, as illustrated in Table 2 below.

Table 2. District tile production 1991

Production type White single-fired

m2/yr in miliions

avg. wgt. in kg×m2

tons/yr

% waste~

waste tons/yr*~

130

17

2,210,000

1.8

39,780

Red single-fired

62

20

1,240,000

2

24,800

Double-fired

72

15

1,080,000

1.5

16,200

Vitrified ceramic stoneware

32

22

704,000

2.5

17,600

Red and coloured stoneware, rustic cotto, klinker, other products

26

20

520,000

1

5,200

TOTAL

322

5,754,000

103,580

* The weight of the finished product (glazed) is equivalent to the weight of the grinding mixture,

Demolition and reuse of concrete and masonry

516

as the clays have a relative humidity of approximately 5 which is lost in the subsequent drying and firing phases and compensated by the weight of the glaze applied.

Over the years, ceramic waste materials have been reused more and more within the same tile production cycle. Still now, they are an important integrating element for the clay mixtures used in forming and pressing the product that is subsequently glazed. Here, the technology for recovery of waste materials for production of chamotte has been consolidated. An outline of this type of technology is given in Table 3 (further on), which demonstrates the simplicity of this technology which has now become more or less generalised. As to quantities, the percentage of recoverable waste material varies according to the type of product, from a maximum of 18% in the case of red clay body single and doublefiring to a minimum of approximately 3% for white clay body and vitrified ceramic stoneware single-firing. The reduced percentage of recovery in the latter group does not depend so much on a lower absorption capacity of the respective production cycles, but rather on the greater difficulty in finding selected waste materials that derive from the same production cycle, due to the colorimetric characteristics of the product. The following block diagram illustrates the transformation cycle of waste material to chamotte for ceramic mixtures.

Inert wastes from ceramics production and construction works

517

Also taking into account the above-mentioned difficulties, it can be seen how the singlefiring production cycles for white clay body and vitrified ceramic stoneware are able to reabsorb all waste materials in the grinding process. In the other types of production, however, there is a net deficit between production of waste material and recycling potential, in favour of the latter. It is evident, in fact, how red single-fired and double-fired production alone, which district-wide reach 148,0000 m2, equivalent to a weight of 1,480,000 tons+1,110,000 tons=2,590,000 tons, would be able to reabsorb in clay grinding approximately 466,200 tons of ceramic scrap material (2,590,000×18%). In reality, not all of the ceramics manufacturers use chamotte as a leaner for the grinding mixture. This necessity can be reduced if raw materials with a high sand content are used. In other cases, chamotte can be substituted by feldspars and brick scrap (used rarely). In any case, the current situation is completely favourable to the total reabsorption during the production cycle of ceramic scrap materials, which only in isolated cases, often to due poor management of waste materials, are disposed of in dumps.

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Table 3. Sales Stucture Italy 1990

Product

Direct sales floor+wall

Dealer sales

Total

square metres White single-fired Porous white single-fired

72,124,378

6,336,081

78,460,459

1,259,013

1,259,013

Red single-fired, dry ground

16,598,356

465,117

17,063,473

Red single-fired, wet ground

17,269,085

1,917,055

19,186,140

8,955,873

154,753

9,110,626

116,206,705

8,873,006

125,079,711

Glazing firm double-fired

33,517,028

2,865,245

36,382,273

Complete cycle double-fired

13,787,887

1,121,100

14,908,987

Total double-fired

47,304,915

3,986,345

51,291,260

Vitrified ceramic stoneware

18,176,402

1,060,955

19,237,357

Red and coloured stoneware

5,477,394

113,198

5,590,592

12,069,076

1,232,432

13,301,508

Klinker

4,634,766

270,500

4,905,266

Other products (1)

3,323,489

714,787

4,038,276

207,192,747

16,251,223

223,443,970

2.227,831

2.227,831

18,479,054

225,671,801

Porous red single-fired Total single-fired

Rustic cotto

Partial total Corrective General total

207,192,747

(1) White double-fired, glazed stoneware, mottled stoneware, engobed stoneware, mosaic, skirting tiles, and other products not included in the previous categories. source: 11th National Statistical Survey, ASSOPIASTRELLE, October 1991

Table 4. PRODUCTION STRUCTUREITALY 1990

Product

Direct production floor+wall

Subcontractors

Total

square metres White single-fired Porous white single-fired

155,172,482 3,374,079

12,266,254

167,438,736 3,375,079

Inert wastes from ceramics production and construction works

519

Red single-fired, dry ground

37,588,789

7,568,023

45,156,812

Red single-fired, wet ground

29,722,845

3,893,266

33,616,111

Porous red single-fired

21,644,155

422,751

22,066,906

247,503,350

24,150,294

271,653,644

Glazing firm double-fired

59,456,927

7,701,131

67,158,058

Complete cycle doublefired

31,671,327

1,884,130

33,555,457

Total double-fired

91,128,254

9,585,261

100,713,515

Vitrified ceramic stoneware

39,868,152

313,500

40,181,652

Red and coloured stoneware

6,682,212

279,186

6,961,398

14,872,409

255,830

15,128,239

Total single-fired

Rustic cotto Klinker

5,991,166

Other products (1)

4,616,553

1,450,484

6,067,037

410,662,096

36,034,555

446,696,651

General total

5,991,166

(1) White double-fired, glazed stoneware, mottled stoneware, engobed stoneware, mosaic, skirting tiles, and other products not included in the previous categories. source: 11th National Statistical Survey, ASSOPIASTRELLE, October 1991

4 Disposal in dumps As the disposal of scrap material in dumps can now be considered closely controlled, we can attempt to further define the quantities recovered and/or recoverable, and of those disposed of. However, the quantity of waste material destined for “direct recovery” is more difficult to ascertain (e.g. filling of land depressions, formation of heaps, etc.). Tables 5, 6, and 7, which follow, provide information from the district dump for 1990 and the first ten months of 1991. It is important to note the subdivision of the materials into 9 different categories, not only for defining the fees, but also for a continuous control of the alternatives that can be supplied to the producers of the waste materials themselves. 5 Conclusion The action of the company managed by the municipality, which is not concerned

Demolition and reuse of concrete and masonry

520

exclusively with obtaining good economic results but also—with the contribution of certain private structures—tends to guarantee technical solutions that include not only disposal, but also recovery and recycling. The most important conclusion, then, is that the conservation and recovery of natural materials, from pit or river, can be guaranteed, with definitive disposal in dumps occurring only when it becomes absolutely indispensible.

Table 5. Inert wastes consigned to “IL DOSILE” dump—1990

Date

Loam Coarse Excav.Mat. Const./Demol. Lith.Const. soil Fine cotto cotto tons Mat. tons Mat. tons tons

Pit clays tons

Tot ton

01/90

791.20 1,984.400

32.2

568.680

0.0

0.0

120.00

3,49

02/90

627.70 1,292.300

234.2

542.000

5.0

36.0

593.30

3,33

03/90

941.02 1,003.300

20.0

1,468.580

0.0

24.0

3.90

3,46

04/90

791.50

451.400

4.5

1,015.700

0.0

0.0

0.00

2,26

05/90

1,271.74 1,417.460

122.00

300.00

1.0

0.0

727.90

3,84

06/90

1,629.44 1,945.500

95.0

25.000

0.0 230.0

0.00

3,92

07/90

893.78 1,658.670

28.0

251.160

0.0

0.0

0.00

2,83

08/90

1,261.01 1,240.743

15.0

222.620

0.0 310.0

8.50

3,01

09/90

1,771.32 1,038.914

0.0

614.970

0.0

0.0

211.14

3,63

10/90

862.18 1,231.180

647.0

130.00

0.0

0.0

0.00

2,87

11/90

1,065.38 1,254.180

167.0

192.845

0.0

0.0

163.02

2,84

12/90

1,605.99 1,165.900

32.0

183.000

0.0

0.0

30.00

3,01

Total: 13,467.26 15,683.947

1,396.7

5,514.555

6.0 600.0 1,857.76 38,52

Table 6. Summary of inert wastes consigned to “IL DOSILE” dump 2nd category type A (from 01/01/91 to 26/10/91) Summary by type of material (in tons) Fine cotto ceramic material

16,382.506

Coarse cotto cermaic material

12,066.575

Glass Rock and rocky construction materials

4.000 100.900

Material from excavations

6,306.960

Scrap and materials from construction and demolition

3,428.935

Inert wastes from ceramics production and construction works

521

Pit clays

2,710.540

Loam soil

910.000

TOTAL

41,910.416

Summary by fees Zero fee

3,634.200 tons

Lit. 0

Fee A

17,936.445 tons

Lit. 129,142,404

Fee B

20,339.771 tons

Lit. 325,436,336

TOTAL

Lit. 454,578,740

Table 7. Materials from demolition, construction, and civil works excavations

Planning area

Inhabitants (1984)

Inerts (m3/yr)

Piacenza

276,063

82,819

Parma

398,938

119,681

Reggio Emilia

414,676

124,403

Modena

596,505

178,951

Bologna

826,054

247,816

96,369

28,911

Ferrarra

376,561

112,968

Ravenna

355,530

106,659

Forlì

173,640

52,092

Cesena

176,921

53,076

Rimini

255,883

76,765

3,947,140

1,184,141

Imola

Regional total

42 RECYCLING POWDERED CONCRETE WASTE* M.SANO and F.YAGISHITA Department of Civil Engineering, Kinki University, Osaka, Japan M.YAMADA Department of Civil Engineering, Osaka City University, Osaka, Japan Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract This report concerns the technology of recycling the dust concrete generated from broken cement concrete lumps. Currently the broken concrete lumps resulting from the demolition of cement concrete structures are crushed for reuse as aggregate. In the process of crushing, an enormous amount of dust concrete is generated, and there is no effective method available for the treatment or disposal of it. In order to utilize this dust concrete, we tried to add it to waste pavement asphalt concrete at the rate of approximately 20%. This resulted in the asphalt contained in the waste asphalt mixture bonding to the dust concrete, and the aggregates were separated from the asphalt as well. Next, individually separated independent aggregates were divided from the dust asphalt, and were recovered one by one. After recovery, the aggregates can be reused as a component of such building material as a concrete or asphalt mixture. The dust asphalt can be reused as a pavement filler or a backfilling material for which waterproofness is required. Keywords: Waste Concrete, Dust Concrete, Waste Asphalt Mixture, Aggregate Re-materializatialization,

1 Introduction The preservation of the global environment and the effective utilization of valuable resources are significant issues. In Japan, a great deal of waste has been generated from building construction, therefore its recycling is particularly important. Of this waste, the broken cement concrete lumps generated in the course of building demolition are recycled for reuse as aggregate. Waste asphalt mixture generated from road construction

Demolition and reuse of concrete and masonry

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is crushed for reuse as a road subbase material, by means of an established recycling technology 1). But the treatment or disposal of large quantities of dust concrete being generated in the crushing process has given rise to a new problem. Barely 50% of such waste is recycled, thus it is still insufficient. This paper proposes a method of recovering aggregates from waste asphalt lumps by using dust concrete, for recycling.

Figure 1. Outline of major processing machines.

Table 1. Dust materials used.

Recycling powdered concrete waste Material

525

Specific gravity

Gradation(µ)

Dust concrete

(C)

2.352

4~1

Artificial zeolite

(Z)

2.150

80~2

Volcanic, sedimental dust

(S)

2.272

20~3

Mineral dust

2.700

30~1

Flyash

2.109

80~2

Sluge generated while ore is wasted

2.601

60~1

2 Dust and Waste Asphalt Concrete In 1990 the total amount of broken concrete lumps hauled out from building demolition sites amounted to 25.4 million tons. Of this, 12.2 million tons or approximately 48% was recycled 2). Such concrete lumps undergo several crushing processes as illustrated in Figure 1, before reuse as recycled aggregates. Dust concrete occurs everywhere throughout these processes, and finally is gathered through a dust collector. The grain size of dust concrete is very fine, in the range of 4 to 1(µ), and its recycling entails technical difficulty. Dust materials other than dust concrete, which we used for this study, were chosen from industrial by-products or industrial waste for which proper treatment or disposal has been demanded from various circles. Table 1 shows material types and their principal properties. Another case is that of waste asphalt which includes dense-grade waste asphalt or reformed waste asphalt generated

Figure 2. Method of recovering aggregate from waste asphalt concrete,

Demolition and reuse of concrete and masonry

526

from road improvement etc. This waste asphalt amounted to 17.6 million tons in 1990, of which, 8.9 million tons or approximately 50% was recycled 2). For this study, several types of materials in which recycling development is required were used. 3 Method of Recovering Aggregate Figure 2 illustrates the method in which aggregate can be recovered from waste asphalt lumps. Firstly, dust is charged into the heated mixture of waste asphalt, and well agitated for a period of two or three minutes. During the agitation, most of the asphalt will uniformly bond to the dust, thereby causing the waste asphalt to lose its adhesive power. This leaves the aggregates independently separated from each other. These aggregates are then classified through sieves into the prescribed sizes of coarse aggregate, fine aggregate, and, even further, to asphalt-coated dust (here in after referred to as dust asphalt). Thus, the recovery method we have developed is very simple. 3.1 Mixing Temperature The temperature at which waste asphalt can be mixed with dust, was determined from the quantity of residual asphalt bonded in the form of a thin film to the surfaces of aggregates, or the quantity of bounded filler asphalt. In other words, the amount of asphalt bonded to the surfaces of the recovered aggregates having the grain sizes of 2 mm or larger, was determined as the bonded amount by percentage of asphalt to the weight of aggregates. The minimal percentage observed was taken as the mixing temperature. Figure 3 shows the result achieved by adding dust concrete to waste asphalt at the rate of 20% by weight. From the objective of reuse of recovered aggregates or dust asphalt, a mixing temperature in the

Figure 3. Relationship between the amount by percentage of asphalt bonded to

Recycling powdered concrete waste

527

recovered aggregate surface, and the mixing temperature.

range of 140 to 160 (°C) is preferable since the properties of asphalt rarely change in this temperature range. 3.2 Charging Amount of Dust Figure 4 shows the relationship between the amount of dust added to waste asphalt and amount of asphalt bonded to the surfaces of recovered aggregates. With the addition of dust at less than 16%, the amount of dust was insufficient leaving the waste asphalt still agglomerate. Coarse aggregates formed by the asphalt mortar and filler asphalt were generated as well. On the contrary, with the addition of more than 24%, the dust was excessive, and surplus dust to which asphalt did not bond, occurred, making the handling of it more difficult. As well, problems rose due to the fact that the homogeneity of recovered dust asphalt cannot be achieved, for reuse. Based on these judgment factors, the addition of 16 to 24% may be the proper range. From the minimal amount of asphalt bonded to the recovered aggregates and the uniformity of the recovered dust asphalt, the optimal addition of dust was set at 20% for this experiment. However, the amount of the addition of dust depends on the grain size and the specific gravity of the dust, therefore it would vary by type as well. Subsequently, taking into account the properties and grain size of dust, a dust mix was manufactured. In other words, additive dust was manufactured using volcanic, sedimental dust with grain size ranging from 20 to 2(µ), artificial zeolite, 10 to 1(µ), and dust concrete, less than 4(µ), altogether blended at the mix proportion shown in Figure 5. Although the mix proportion of dust concrete containing zeolite would be most effective to bond asphalt to the recovered aggregates, this proportion would require a larger amount of zeolite. This in turn would generate such an amount of dust as it may impede the

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Figure 4. Relationship between the amount by percentage of asphalt bonded to recovered aggregate surface,

Figure 5. Relationship between the amount by percentage of asphalt bonded to recovered aggregate surface, and the mix proportion of added dust.

Figure 6. Relationship between the amount by percentage of asphalt bonded to recovered dust surface, and the mix propertion of added dust.

proportioning process, therefore oil-absorbent dust zeolite was added at rate of 10% to the total amount of dust materials. This led to the mix proportion of dust concrete 72 to

Recycling powdered concrete waste

529

volcanic, sedimental dust 18 to zeolite 10. The amount of asphalt bonded to this dust mixture was approximately 38 to 40% of the total weight of dust materials, as shown in Figure 6. 3.3 Aggregate Grain Size Distribution Depending upon the Method of Recycling Currently the reuse of recycling asphalt involves a few problems. Firstly,

Figure 7. Aggregate grain size curves.

the problem of the extent of change in the properties of decomposed asphalt, and secondly, the quantity of aggregates contained in the recycled asphalt, as opposed to aggregates formed by asphalt mortar and filler asphalt. In other words, the problem is the extent of the possible effect of false aggregates which are generated while recycled asphalt, when reused as a subbase material, is added to new asphalt concrete at the rate of several percent or several tens of a percent. In particular, in the latter case, both the optimal amount of new asphalt and grain size distribution of aggregates would be affected, creating the heterogeneous properties of the asphalt mixture after its being laid on the road base. This would be attributable to the method in which waste asphalt was recycled. To clarify the cause, the difference between the grain size distribution curves plotted in terms of recycled asphalt and our proposed method, was studied using the same material. Figure 7 shows the results. If additive dust is charged into a sample having the grain size curve of ordinary recycled asphalt, (A), and the aggregates recovered, then their grain size curve will be (B). Furthermore, if the asphalt still bonded to the surfaces of the recovered aggregates is removed using a solvent, then its curve will be (C). As is evident from this literature, grain size curve (b) closely resembles grain size curve of aggregates’ own, (C), but curves (A) and curve (B) greatly differ from each other, due probably to the affect of the false aggregates previously mentioned. With the proposed method, when reusing recycled aggregates as part of an asphalt material, these problem

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can be eliminated, and the conventional mix design method can be applied as well. 4 Reuse of Recovered Material as Parts of Asphalt Mixture Asphalt is bonded to the recovered aggregates at the rate of 9 to 0% by by weight, and filler asphalt is bonded to recovered dust asphalt at the rate of 38 to 0% by by weight. We manufactured an asphalt mixture using recovered aggregates. Since the thickness of the bonded asphalt barely affects the

Table 2. Kind material of Figure 8 and Figure 9

Figure 8. Reuse of recovered aggregates for asphalt mixture.

Recycling powdered concrete waste

531

Figure 9. Properties of the asphalt mixture in which recovered materials are used.

grain sizes of the aggregates, the mix proportion of the aggregates was designed per the Japan Road Association Asphalt Pavement Specification 1988 3). The content of dust asphalt used as a filler was designed so that it be volumetrically equivalent to the stone dust content generally designed. When only recovered aggregates were used, the OAC (Optimum Asphalt Content) was approximately 2% less than the ordinary case, or in the range of 3.5 to 4.0%. As well, when recovered dust asphalt was used only as a filler, the OAC was in the range of 5.5 to 6.0% of the ordinary case. From these facts, in the case of using recovered aggregates, the asphalt bonded tothese aggregates would affect the percentage of the OAC. However, a Marshall test can be conducted in terms of the OAC. Figure 8 shows the Wheel-tracking test results and Figure 9 shows the relationship between the Dynamic stability and the Marshall stability.In these figures, a moreeffective tendency is shown when recovered aggregates and dust asphalt were used concurrently. This gives great expectations for more than fourtimes the Dynamic-Stability value of an ordinary mixture. Also it was possible to easily apply the proposed recovery method to an existing asphalt mixing plant. The percentage of asphalt bonded to the recovered aggregates was low at 7% in the plant. This suggests the recyclability of broken asphalt lumps into aggregates even in regions which do not have recycling plants. 5 Conclusions The proposed recovery method is applicable to recycling asphalt, re-recycled asphalt, and waste reformed asphalt to be used as a principal material. It would be possible to choose the additive dust type for the intended objective of reuse. As well, recovered aggregates

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and dust asphalt would be able to be reused as aggregates or filler of an asphalt mixture. However, when asphalt which has been decomposed over a prolonged period during service is reused as bonded to the surfaces of the aggregates, it is a different case. A study must be conducted of how the decomposed asphalt will affect, according to the degree of composition, the durability of mixture re-manufactured using that decomposed asphalt. Furthermore, since dust asphalt will be generated in large quantities, further studies will conducted of the development of other uses as a dust material, by taking advantage of its waterproofness, which probably is the only special feature it has. 6 References 1) Japan Road Association: Guidelines for Recycling Technology of Waste Pavement Materials 1984 2) Japan Road Constructions Association: 7th Symposium for Road Construction Technology 1992 3) Japan Road Association: Manual for Asphalt Pavement 1988

PART SEVEN BUILDING WASTE MANAGEMENT

43 DEVELOPMENT OF INTEGRATED WASTE MANAGEMENT STRATEGIES FOR DEMOLITION WASTE M.NICOLAI, M.RUCH, Th.SPENGLER, S.VALDIVIA, J.HAMIDOVIC and O.RENTZ German-French Institute for Environmental Research, Karlsruhe, Germany Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract Major parts of the recycling of buildings are the dismantling procedures for different types of buildings, recycling techniques for the materials from dismantling and the reuse options for the recycled materials. They are interdependent in terms of costs, quality standards for materials and practical realisation so that the management of building waste has to consider the entire structure of the problem from dismantling to reuse. Thus, planning tools for the developement of integrated concepts for the recycling and reuse of buildings are required. The submitted paper presents a planning system for those concepts which has been developed for the region of the Upper Rhine Valley (Alsace, France and Baden, Germany) within a research project at the German-French Institute for Environmental Research (DFIU/IFARE), University of Karlsruhe. Domestic buildings in this region have been classified and several possible dismantling procedures for each type of building have been evaluated. Specific recycling techniques have been analysed and optimised in terms of achievable product qualities and costs as well as assigned reuse options. Reuse options for the recycled materials have been drawn up. By means of an operations research model cost minimal dismantling-recycling-reuse procedures for the different types of buildings have been evaluated and are discussed for different scenarios for the economic and legal frame (disposal costs, required recycling proceeds). Keywords: Demolition Waste, Dismantling, Recycling, Reuse, Waste Management, Integrated Concepts.

Development of integrated waste management strategies for demolition waste

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1 Introduction Although recycling and reuse is generally possible, in Germany only 16% of the building material was recycled in 1989. Construction waste was almost completely disposed. The objectives of the German legislation are to achieve a recycling rate of 60% for building rubble and 40% for construction waste for the year 1995. Initiatives in France aim at the direct reuse of materials from the dismantling of buildings. In reality reuse options are often limited to road construction or soundproof barriers which represent a downcycling and are therefore insufficient from an economical point of view. Only recycling-products of a high standardised quality level can compete with traditional materials and so contribute to the development of real recycling. The latter can be achieved by both dismantling procedures and recycling techniques, well suited to each other. Therefore environmental legislation aims at selective dismantling and recycling of buildings. Major instruments are higher disposal prices for demolition waste, the integration of dismantling schemes into pulling-down permits and fees on natural construction materials. But only effficient sets of these instruments promote technoeconomically feasible and ecologically reasonable concepts for the demolition and recycling of buildings. These integrated concepts and the effects of the above mentioned instruments are still very little examined. The target of the presented research project is the development and application of a planning system for such an integrated concept for the region of the Upper Rhine Valley. With this system, the costs and interactions of dismantling and recycling are evaluated and optimal combinations of demolition procedures, recycling techniques and reuse options are determined. The effects of external factors (e.g. Legislation, disposal costs) will be examined. 2 Characterisation of the examined region The examined geographical region, the Upper Rhine Valley, is composed of the German Regierungsbezirk Karlsruhe and Freiburg and the French Départements du Haut Rhin and du Bas Rhin. The region between the vosges and the black forest is characterised by 1.6 million inhabitants and 0.45 mln Mg/year of demolition waste for the French side and 4.5 million inhabitants and 2.9 mln Mg/year for the German side, whereby recycling capacities are at 0.4 mln Mg/year for the former and 2.5 mln Mg/year for the latter. The corresponding areas are 8 200 km2 respectivly 16 270 km2. Along the Rhine Valley, numerous gravel pits exist so that current prices for traditional construction materials and thereby prices for recycling materials are very low. However, for ecological reasons licenses for the pits are not extended and gravel prices are expected to rise within the next few years. Disposal capacities are scarce and expensive on the German side and the new TASiedlungsabfall will worsen this. On the French side disposal costs are still low, but will rise with the enforcement of disposal laws. A higher density of recycling plants on the

Demolition and reuse of concrete and masonry

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German side is presently the consequence. The amount and composition of materials from demolition depends on the types and number of demolished buildings. On the French side of the region domestic buildings which were constructed before 1915 predominate and have mostly only one dwelling unit, whereas on the German side, the major part of the buildings was constructed after 1949 and contain two or more dwelling units. By means of demolition rates the number of demolished buildings in the region during a given period can be estimated. Demolition rates of these buildings mainly depend on their year of construction and are given in the Table I for the Land Baden-Württemberg. However, the number of demolitions depends also on the economic situation of the construction industry.

Table I: Demolition rates for the Land Baden-Württemberg

Year of construction

Number of buildings

Number of demolitions

%

before 1918

386 229

1016

0,26

1919–1948

231 645

393

0,17

1949–1970

616 480

208

0,03

after 1970

597 490

22

0,003

Total

1831 844

1639

0,09

3 Development of an integrated dismantling and recycling planning system The total dismantling and recycling costs of domestic buildings are a function of the considered dismantling techniques, the sorting techniques and the transportation distances. Furthermore, the capacities of the different reuse options, like road construction or manufacturing of wall bricks, may be limited in the considered geographical region. In order to achieve cost-efficient dismantling and recycling strategies the goal of the optimization must be the minimization of the total costs subject to technical, environmental and capacity constraints. Due to the complexity of this planning problem for the region of the Upper Rhine Valley, a sophisticated Operations Research Model has to be formulated and implemented on a personal computer. Figure 1 shows the structure of the developed integrated dismantling and recycling planning system. Based on the detailed composition of the buildings, so-called bills of materials, the sequence dependent dismantling costs and the dismantling precedence relations the precedence-graph of the dismantling activities can be developed for every type of domestic building in the considered geographical region. The bills include weight, volume and number for all the construction elements.

Development of integrated waste management strategies for demolition waste

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Figure 1. Structure of the integrated dismantling and recycling planning system

In order to obtain recycling-cost-functions for the resulting building components and parts, the different reuse options will be analysed from a technical and environmental point of view so that techno-economically optimized sorting- and recycling techniques can be designed. The optimization problem Minimize

Total dismantling-, sorting- and recycling-costs

subject to

Capacity constraints Quality constraints Technical constraints Environmental constraints

is formulated automatically as a Mixed Integer Programming Model and suitable Operations Research algorithms are developed and applied. With the help of this optimization model optimal dismantling and recycling strategies will be computed for all domestic buildings in the region of the Upper Rhine Valley. The amount and composition of the resulting building rubble will be determined and the different materials will be assigned to the designed recycling techniques and reuse options. Non-reusable building components and parts will be identified such that guidelines for a recycling-friendly planning and construction of domestic buildings can be formulated. In order to analyse the sensitivity of the proposed recycling strategies, a variety of different scenarios concerning the types and numbers of buildings, the transportation distances, the available recycling techniques, the environmental standards introduced by the governments and the environmental economic instruments such as waste duties or taxes on natural resources will be considered.

Demolition and reuse of concrete and masonry

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Due to the complexity of the integrated planning model, it will be decomposed into a dismantling planning model which will be formulated in the next chapter and a recycling planning model which will be described later. 3 Dismantling planning As the amount and composition of the materials from demolition shows important variation with the kind of building, the buildings have to be classified into different types. This can be achieved by the criteria - year of construction, - construction mode (skeleton or massive), - contruction material (wood, steel, concret, masonery) and - number of dwelling units. An analysis of the domestic buildings in the region showed, that eleven types of buildings predominate and can be classified as shown in the following Table II

Table II: Types of domestic buildings in the region of the Upper Rhine Valley

Skeleton construction

Massive construction

wood

concrete

steel

masonry

single multiple single multiple single multiple single multiple before 1930

X

1930–1960 after 1960

X

X

X

X

X

X

X

X

X

X

For each of these classes a representative building will be chosen and a detailed bill of materials will be prepared. On the basis of these bills of materials the different dismantling techniques will be analysed and aggregated into so called dismantling activities. For these dismantling activities the associated dismantling costs and the precedence-relations will be determined, so that precedence-graphs can be developed for each identified class of buildings. Figure 2 shows such a graph for a single family masonry house. environmental aspects, capacity dependent recycling cost functions have to be developed for all relevant building components and parts. 4 Recycling planning The objective of recycling planning is to design sets of optimal recycling techniques for processing dismantled materials and building components into reusable materials.

Development of integrated waste management strategies for demolition waste

541

Depending on the stage of dismantling, the feed can be either a single material or a mix of all the building materials. For some materials such as glass and metals, classic recycling techniques already exist and recycling planning is a simple coordination or pretreatment. For other materials, techniques are not yet developed or have to be modified according to the composition of the specific feed, e.g. for plastic and composite materials. Toxics like asbestos require specific treatments which may also be a conditioning for disposal. The recycling of used materials can be split into two major parts: - recycling techniques to process used materials and - reuse options for the processed materials. Both are interdependant which means that the development of sophisticated recycling techniques requires reuse option for high quality products whereas standardised high quality levels for recycling materials can only be set if techniques to realise them already exist. The applied methodological approach therefore is the Simultaneous Development of Recycling Techniques and Reuse Options in order to achieve an optimal assignment of residues to reuse options via optimised specific recycling techniques. For the example of the mineral fraction, which represents the major part of a building, methods and required tools for the design of reuse options and recycling techniques will be shown in the following. 4.1 Reuse options Mineral fractions from the dismantling of buildings contain concrete, gravel, stone, sand, bricks and tiles, gypsum and others.Traditional reuse options for the recycled mineral fractions from buildings are road construction and soundproof barriers. New options for the reuse in the production of concrete and in stone production are in development. A great amount of experiences in this working field exists and has been published, but standards are not yet fixed. However, these products have to compete with traditional ones so that controlled standardised qualities are essential. Prices and the substitution potentials are major criteria. An overview of reuse options is given in Figure 3. Prices for recycled aggregates in the examined region range from 0 to 16 DM/t depending on the quality and the granulation.

Demolition and reuse of concrete and masonry

542

Figure 2: Dismantling-precedence-graph for a single family masonery house

Following the engineering industry, where the concept of the precedence-graphs is used in the Materials-Requirement-Planning, the precedence-graph is the starting point of the dismantling planning process. By the application of a set of dismantling activities the corresponding building is disassembled into building components and parts. The decision whether a certain dismantling activity will be applied or not depends on the comparison of the alternative recycling costs of the corresponding building component with the dismantling costs and the minimal recycling costs of the resulting building components and parts. Taking into consideration technical aspects as well as

Development of integrated waste management strategies for demolition waste

543

Figure 3: Reuse options for recycled aggregate

4.2 Recycling Techniques Recycling techniques for building rubble process mixed demolition waste into reusable mineral aggregates, wood, metals and residues. The development and operation of recycling techniques are characterized by the following specific frame conditions: - quantity and composition of input material, - realisable price for input material, - processing costs, - quality of products and - realisable product price. In order to answer to these requirements methodological tools for the design of optimised recycling techniques have to be developed and applied. In the presented planning system such a tool for the systematical configuration of recycling plants for building rubble is integrated. The recycling processes are abstracted and structured into so-called unit operations which represent the processing functions such as crushing, screening or sifting. Together

Demolition and reuse of concrete and masonry

544

with a sequential modular algorithm a flow-sheeting program has been developed and implemented. By means of systematical permutation and reduction of the structure the recycling plants and the determination of the best set of technical aggregates for each structure optimal configurations can be evaluated. An illustration of the permutation and reduction of the structures is given in Figure 4. The obtained characteristics of the techniques as a function of the above mentioned conditions are: - achievable product quality, - recycling rate (proceeds), - balances for hazardous components and - costs. Ranges of these characteristics and of the frame conditions of recycling plants can be fixed in scenarios as optimization restrictions and so the evaluation of the influence of environmental policies, the regional situation of disposal costs, etc. can be examined. In addition to the traditional techniques descending from classic mineral processing, new ones can be integrated aiming at the production of high quality materials. Capacity and costs of every optimized recycling technique enter into the global planning system as recycling cost functions. Ranked by increasing specific costs, the total capacities and costs for the recycling of one material or mix are cumulated in a function. The capacity limits are determined by the substitution potentials for the recycled materials in the considered region. Recycling cost functions can also be ranked by other criteria like the recycling rate of a technique, the emissions or the achieved product quality so that better techniques, from an environmental point of view, can be given preference to. However, in this case the convexity of the function is lost. 5 Conclusions The determination of cost optimal dismantling and recycling procedures requires integrated concepts covering dismantling procedures, recycling techniques and reuse options. The planning of optimal dismantling-recycling-reuse sequences can be realised by the aid of operations research methods.

Development of integrated waste management strategies for demolition waste

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Figure 4: Permutation and reduction of the structure of recycling plants

Recycling planning is an iterative process of developing recycling techniques and the determination of quality standards for recycling materials. This requires the simultaneous development of the techniques and the reuse options by means of process simulation tools. Prototypes for the above presented planning system are running on PC for simple problems. The models will be extended for complexer problems and solutions for the entire considered geographical region have to be generated. Sensitivity and influences of external effects will be evaluated by numerous scenarios. Guidelines for recyclingfriendly construction will be created, new recycling techniques and reuse options will be suggested. The generated knowledge could lead to expert systems for dismantling procedures and recycling techniques. 6 Bibliograghy Bundesregierung der Bundesrepublik Deutschland: Zielfestlegungen zur Vermeidung, Verringerung und Verwertung von Bauschutt, Baustellenabfallen, Erdaushub und Straßenaufbruch, (Entwurf), Bonn, 1991 Dörle, K.: Aufbereitung und Wiederverwertung von Recyclingbaustoffen in der Praxis, in: 3. internationales Baustoff-Recycling-Forum, Mayrhofen, 1992 Entwurf des Gesetzes zur Verwertung von Sekundärrohstoffen und Entsorgung von Abfállen Kreislaufwirtschafts- und Abfallgesetz, Bonn, 1992 Hammerschmid, R., Rentz, O,: Methodische Planung regionaler Entsorgungsalternativen Dargestellt für Reststoffe aus der Rauchgasreinigung für Baden-Württemberg, in: Müll

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und Abfall, 7/1990, S.44451–457 Offermann, H.: “Recycling von Bauschutt—Technische und ökonomische Kriterien bei der VerfahrenswahT, Dissertation, Essen, 1988 Reiling, W.: Prozeßoptimierung zur Minimierung der Umweltbelastung mit Hilfe der quasi-dynamischen Simulatiuon, Dissertation, Karlsruhe, 1992 Rentz, O.: Entsorgung von Reststoffen aus der Rauchgasreinigung, Teil 2, Umweltministerium Baden-Württemberg (Hrsg.), Stuttgart, 1990 Schulz, R.: Recycling von Baurestmassen—Ein Beitrag zur Kostendämpfung im Bauwesen”; Abschlußbericht, Institut für Bauforschung, 1986 Willkomm, W.: “Recyclinggerechtes Konstruieren im Hochbau”, RKW; Eschborn, 1990

44 BUILDINGS AS RESERVOIRS OF MATERIALS—THEIR REUSE AND IMPLICATIONS FOR FUTURE CONSTRUCTION DESIGN T.E.LAHNER and P.H.BRUNNER Institute for Water Quality and Waste Management, University of Technology, Vienna, Austria Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. 1 Introduction In the year 2035, the global population will have doubled, and 75% of the population will be living in cities. This means a tremendous growth in turban areas, an unprecedented concentration in the consumption of energy and material in certain regions, and a very intensive use of land and natural resources. The main material flux within this system, the Anthroposphere, goes into the process “construction of buildings and networks”. The urban infrastructure thus contains a large stock of materials; in the future, the efficient management of this stock may become crucial in terms of resources as well as environmental impacts. This paper focuses on the input/output/stock modelling of the infrastructure of the urban anthroposphere. The past and current use of construction materials is discussed in relation to waste and materials management First conclusions are drawn with respect to the future design and construction process as well as to waste management. 2 The Stock “Urban Infrastructure” The urban infrastructur (buildings, transport systems, communication networks and others) is constantly changing. New needs and new tachnologies, together with rising economic incentives such as increasing real estate value or more efficient systems, cause the lifetime of this infrastructure to decrease. During the last centuries, the stock of materials and active substances of the infrastructure has grown by several orders of magnitude (cf. Fig. 2). This reservoir is potentially a great source of raw materials for the

Buildings as reservoiers of materials-thier reuse and implications for future construction design future. In order to use it in an intelligent way for ecological or economìc purposes, we have to know the residence times and usage patterns of the goods and materials in the infrastructure. Also, the construction methods as well as the use of materials have slowly changed during the last century (Mettke, 1991; Wilson, 1990).

Figure 1. Use of construction methods in the 20 th century in Germany (adopted from Mettke, 1991)

549

Demolition and reuse of concrete and masonry

550

Figure 2. Use of construction materials in the USA (adopted from Wilson 1990)

The major part of the used materials is still incorporated in buildings, networks and roads. Thus, large amounts of materials have been accumulated, and this accumulation is still going on. According to preliminary estimations, approximately 300 tons of material per capita are contained in the infrastructure (Baccini and Brunner, 1991). Most of the construction material consists of sand, gravel, stones and bricks, of wood and of steel. But due to the enormous increase in the use of metals and chemosynthetic compounds in the building process, the compositon of a single building as well as the composition of a whole city is not the same as it was hundred years ago.

Buildings as reservoiers of materials-thier reuse and implications for future construction design

Figure 3: The material fluxes for the processes building and network construction and operating and maintenance of buildings (Baccini and Brunner, 1991)

In order to reuse the urban infrastructure efficiently, information about its composition and expected lifetime is needed for various time periods. This data cannot be collected by the investigation into construction wastes alone, it has to be supplemented by information of the construction industry about the composition and mass of the goods used for construction. 3 Construction and Demolition Waste Thus, todays metabolism of the urban anthroposphere not only consumes more and more material and energy, but also produces more waste materials. There is an ever growing amount of materials added which do not correspond to the composition of the earth crust or the biomass. Their wanted impact on the quality of the construction materials is large. The resulting construction waste is increasingly contaminated by various hazardous ingredients. The mass of C & D wastes per capita are approximatly ten times more than the amount of municipal solid wastes, thus they are quantitatively more important than the MSW. According to the changes in their composition because of the growing use of new organic polymers and chemical additives, these wastes are becoming more similar to municipal solid wastes. Therefore the stock of materials in the infrastructure must be carefully controlled.

551

Demolition and reuse of concrete and masonry

552

Table 1. Comparison of the contents of selected elements in demolition wastes and a mineral fraction of the sorting plant with the average abundance of these elements in the earth crust (adopted from Brunner and Stämpfli, 1993)

Element

Demolition waste a)

Mineral Fraction b)

Earth crust

Matrix elements (g kg−1) SiO2

260

390

600

Ca

150

160

41

C total

93

48

0,2

S

5,8

3,9

0,3

N

1,1

1,4

0,02

Cl

0,84

0,17

0,13

Trace elements (mg kg -1) Zn

790

170

70

Cu

670

330

50

Pb

630

930

13

Cd

1,0

0,5

0,1

Hg

0,2

0,1

0,02

a) Mixture of various inert and reactive materials resulting from the “nondiscriminatory” demolition of structure, such as a building or a road. The mixture includes concrete, bricks, wood, plastics, metals and usually contains a significant fraction (>10 %) with a high energy content. b) Selected heavy fraction of a mechanical sorting plant, it resembles the earth’s crust, with some exceptions. The sorting product contains more calcium, carbon, sulphur and nitrogen and also more of some trace elements. Because of these differences it may not be a priori assumed that the chemical behavior of the earth crust and the selected fraction are the same. In many cases similar fractions are used again as construction materials.

Data about the C & D wastes show that more than 90 % consist of a mineral matrix. These mineral materials come close to the quality of the earth crust. First priority is to collect these mineral materials separately from other materials and to treat them in a way that makes it possible to use them again like a “virgin” construction material. Since separation of the demolition products requires a high input of energy and in some cases is not possible, the materials need to be kept “clean”. Decreasing the amount of wastes to be landfilled is not the only reason for recycling mineral materials. In some regions these resources are limitted; occasionally, this limitation is due to the lack of public aceptance for new resource extraction sites. Recently, the use of organics such as vinyls or concrete additives and metals such as aluminium and copper has increased greatly, making it more difficult to reuse demolition

Buildings as reservoiers of materials-thier reuse and implications for future construction design wastes. But not only the materials themselve, also the use of compounded and laminated goods as well as monolithic construction techniques or new fixation techniques which allow faster and more economic construction cause problems in handling the C & D wastes. The potential of mechanical sorting process to separate according to chemical properties seems to be limited. In many cases the sorting fractions are better suited for subordinate uses or landfilling than for the use as a construction material (Downcycling instead of Recycling).Thus, the chemical separation of the mechanical sorting process is limited to a few elements. The results of Brunner and Stämpfli (1993) showed that the sorting process is distinctly selective for chlorine, organic carbon, iron and copper only. Exept for iron and copper, the metals are not generally concentrated in the metals fraction: zinc, lead and aluminium are distributed over all fractions (see table 2). Organic materials, such as wood and synthetic polymers and additives, are of growing importance in construction wastes. In many cases it is possible to reuse construction woods directly. In the case of selective demolition it may be collected separately and examined for mechanical properties. At this time there is no effective materialy recycling of mixed polymers available. Thus, they have to be incinerated. Incineration is also well suited for the not recycable wood and the small amount of hazardous construction wastes. Facilities for the thermal treatment of these fractions have to be equipped with advanced air pollution control devices and residue treatment. Metals may not be in the same concentration range as the former groups, but the separation of this group is easily achievable with only few impurities in most sorted metal fraction.

Table 2. Transfer coefficients of a construction waste sorting plant (adopted from Brunner and Stämpfli, 1993)

Fraction a) Small pieces<80 mm Light fraction b) c)

Heavy fraction d)

Metals e) Rest

Mass

0,25

0,27

0,03

0,001

0,45

Matrix elements Fe

0,14

0,10

0,13

0,63

<0,01

C organic

0,16

0,80

0,04

n.d.

<0,01

C1

0,09

0,86

0,05

n.d.

<0,01

Al

0,42

0,21

0,34

0,03

<0,01

Trace elements Zn

0,31

0,44

0,05

0,20

<0,01

Cu

0,03

0,15

0,13

0,69

<0,01

Pb

0,14

0,37

0,40

0,09

<0,01

Cd

0,29

0,57

0,14

n.d.

n.d.

553

Demolition and reuse of concrete and masonry Hg

0,43

0,36

0,12

554 n.d.

0,09

a) The input material is a mixture of various construction wastes as described in table 1 b) Material which passed a rotary sieve<80 mm, containing small pieces of mainly inorganic materials c) Light product of low density, which is mainly produced by consecutive sieving, sorting, pulverising and air-classifying. A product of high heating value. d) Selected heavy fraction as described in table 1. e) Metals from hand sorting and two magnetic separators.

4 Implications for the Future In the future, models are needed to describe and forecast the changes in the urban anthroposphere (stock and increase in stock, fluxes of materials and wastes, composition of the materials). The consumption of materials in the construction businesss allows to estimate the future amounts and composition of C & D waste stocks by means of material balances. This method of early recognition helps to plan the treatment and recycling of waste in time. In the case of long-term products, such as buildings, it takes several decades until waste minimization measures show any results in waste management. The long-term goal must be a material balance of building types. Despite minimization additional plants for recycling and treatment will be required over the next years. In the long run strategies and procedures have to be developed to recycle not only the largest groups of materials but also the less frequent elements and compounds. The ultimate goal of the management of construction materials ought to be multiple recycling on the highest value level with known sources and sinks for all materials. Future construction materials and techniques should allow to selectively dismantle a building, to keep the materials as pure as possible so that it can be incorporated in many following usage-cycles, and to release only a minor amount of wastes which have to be treated and landfilled. One possibility to reach this goal may be to minimize the number of different materials within one construction as far as possible. The more materials are used, the more information, energy, and man power is needed to separate them. Another possibility is to design buildings, especially industrial buildings as large-panel constructions with reinforced concrete panels in a way which allows an easier deconstruction instead an demolition of the elements. There is not only the high energy demand for separating the concrete and the steel, but also the high energy potential of the reinforced concrete, approximately 1000 kWh/t, which argues against the simple demolition. Exampels have been given by Mettke (1992). In order to reach this goal, the design of the urban infrastructure has to include materials management, waste management and recycling aspects. If we succeed in building an infrastructure in which the individual materials can be separated and reused in an efficient way, the infrastructure will become an important future stock of material. On the other hand that means we will take more care of the ressource “landscape” outside our cities.

Buildings as reservoiers of materials-thier reuse and implications for future construction design

5 References Baccini, P. and Brunner, P.H. (1991) Metabolism of the Anthroposphere. Springer, Berlin. Brunner P.H. and Stämpfli D.M. (1993) Material Balance of a Construction Waste Sorting Plant. Waste, Management & Research (1993) 11, pp. 27–48 Mettke, A. (1992) Wiederverwendung von Bauelementen und Bauwerksteilen aus Beton. Baustoff-Recycling+Deponietechnik, 6/92, 9–13 Wilson, D.G. (1990) Recycling of demolition wastes. In Concise Encyclopedia of Building and Construction Materials (ed. F.Moavenzadeh). Oxford, U.K.: Pergamon Press, pp. 517–518

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45 THE IMPLEMENTATION OF ECONOMIC, FISCAL AND PRACTICAL INSTRUMENTS TO PROMOTE CLEANER TECHNOLOGIES L.SØBORG Danish Environmental Protection Agency, Denmark Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 26 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract When you enforce cleaner technology it is necessary to consider the type of instrument very closely. Traditional regulations will often be difficult to enforce towards industry and contractors. The reason is the fact that cleaner technology is a strategy. So it will change according to different branches. Key words: Clean technology; legislation; economics; incentives; audit.

1 Introduction Traditional environmental regulations set up the framework for what society will accept regarding emissions from industry. Waste production is usually not considered as an emission. Industry will, within this framework, decide the processes and the design of the product. When a product is designed the producer is not aware of the costs of handling the waste from the product. 2 Cleaner technology Cleaner technology is a strategy, where you are trying to optimize all the different phases in the lifecycle of the product and thereby try to minimize the environmental impact from the production process as well as from the consumption and disposal of the product. Traditionally, there are no problems in setting up guidelines for different types of emissions. Neither are there problems with the enforcement by the authorities. However, it is far more difficult from a legal point of view to make regulations based on what is considered to be a strategy. At least, this is the case if the regulation is to be enforced. That is the reason why there is a need for finding new ways to regulate, and at the same time give industry incentives to promote this new way of thinking.

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3 New regulations A new act on environmental protection was passed through Parliament in 1991 and new instruments were introduced. One of the considerations, when creating these new instruments was, as already mentioned, the fact that the producer of a material or product does not include costs of waste handling when calculating the product price. In order to make the producer more aware of these costs, and in order to make him internalize these costs the following instruments given in the new act will be interesting: - Agreements concerning environmental behavior between government and industry - Fees on specific products - Waste audit In denmark, negotiations have already been started concerning different products, and an agreement has been made as to collecting and recycling of PVC from demolitions. The government has newly started negotiations with the Danish demolition contractors in order to make an agreement on selective demolition. Within the community an ecolabel directive has already been passed, and a directive on ‘ecoaudit’ is being negotiated at the present time. A priority waste stream analysis on demolition waste has been started by the Commission in order to find out the need for regulation within this field. 4 Economical and fiscal instruments The reason for choosing these instruments is the fact—as we see it in the Agency—that the best incentive is money. When decisions are made in industry they should be economically beneficial. Industry wants to make money. This is of course a natural thing and nobody could in fact oppose this. The economical measures include the following: - Subsidies of development of research activities - Subsidies of full scale demonstration plants The fiscal measures include the following: - Charges on waste disposal - Charges on products in order to enforce recycling and cleaner technology In Denmark, there is a charge on waste disposal of DDK 195:- per ton. This is approximately USD 25:-. Materials sorted out for recycling purposes are free of charge.

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5 Practical instruments The practical measures include the following: - Regulation of products in order to enforce recycling and cleaner technology - “Green-label” systems - Consultancy arrangements - Traditional regulation

6 Conclusion The Danish waste strategy is based on an overall priority setting of waste handling: 1 Cleaner technology 2 Recycling 3 Incineration 4 Controlled landfilling It appears that recycling and cleaner technology rank very high on the list of priorities of environmental policy measures in the years to come. This high priority will show the need for these new instruments.

46 TRANSITION OF THE TECHNIQUE OF REINFORCED CONCRETE CONSTRUCTIONS MEASURED TO EARTHQUAKE DAMAGE IN JAPAN K.YAMABE, H.KUBOTA and Y.KASAI College of Industrial Technology, Nihon University, Narashino, Japan Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract Firstly, the development and the introduction of reinforced concrete (RC) technique will be described. Secondly, the earthquake damage to RC buildings will be mentioned through the Great Kanto Earthquake of 1923 to the Miyagiken-oki Earthquake of 1978, and in accordance with the results of investigation and experimental reserch after the great earthquakes, the transition of the technique of RC constructions is considered in relation to the earthquake damage. Finally, on the future prospects of RC construction in Japan, it will be touch from the stand point of the design and execution method. Keywords: Reinforced concrete (RC) buildings, Earthquake damage,Transition of construction technique, Earthquake resistant design method, Future prospects of RC construction.

1 Introduction Buildings in Japan have been damaged repeatedly through the great earthquake until now. A lot of the damage had happened to traditional wooden building, and they were weak against fires, so the central Edo area (Tokyo) of the Tokugawa Shogunate often had disastrous fires [T.Hisada (1977)). Therefore, the brick construction which had been popular in Europe at that time was introduced in Japan in the middle of the 19th century [A.I.J. (1972)]. The first building of a brick construction in Japan was constructed in Nagasaki (1857). A steel structure was introduced from France at the end of the 19th century. Shueisha Printing factory was constructed in Tokyo by a steel structure (1894) . Also, the technique of a reinforced concrete (abbreviate RC) construction was introduced

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in the early part of the 20th century, and a RC warehouse was constructed in Kobe (1906) . In the new constructions which were introduced into Japan, brick constructions were almost all destroyed in the Nobi Earthquake of 1891 (see Fig. 1). After that, masonry buildings were destroyed in a large extent in the Great Kanto Earthquake of 1923, although some buildings reinforced with band steel were remained with small damage. Due to the above reasons, after the earthquake, masonry were rejected completely in Japan. On the contrary, because the buildings of steel structures and RC constructions received only damage in the San Francisco Earthquake of 1906, both constructions were highly appreciated as the earthquake resistant constructions, and they were steadily introduced from about 1910. As the steel structure and RC buildings stood up well in the Great Kanto Earthquake of 1923, they became the main stream for new buildings. Incidentally, the seven-story Nihon Kogyo Bank Building was built using a steel encased reinforced concrete construction in 1921 which was the characteristic structural form originated in Japan. This building was highly appreciated because of no damaged in the Great Kanto Earthquake. After this, a large number of buildings of seven stories or more were built using steel encased reinforced concrete construction.

Fig. 1. Factory of brick construction which were destroyed by the Nobi Earthquake of 1891 (after Y.Fujii (1979) : “Earthquake by photographs and diagrams” Kokusho Kankokai Co. Ltd.)

2 Development and introduction of the reinforced concrete technique The techniques of RC construction were introduced from Europe into Japan. A small pump house designed by Dr. K. Majima in Sasebo Navel Port Dock in 1904, this house was the first constructed RC building in Japan [A.I.J. (1972)] . It was considered that the

Transition of the technique of reinforced concrete constructions measured to earthquake damage real building using the RC construction was the warehouse of Tokyo Warehouse Co., Ltd. in Wada Cape, Kobe completed in 1906. In this year, the San Francisco Earthquake occurred, as a result of the spot survey by Dr. T.Sano and other researchers, they decided that RC buildings were more of a fireproof and earthquake resistant construction, it was suggested the future guides of Japanese building. Building No. 1 of Mitsui Bussan Yokohama branch office (4 stories with a basement) which was the first office building with RC construction was built in 1911, and the rental office building of Mitsui (6 stories with a basement) of first American style office building was constructed in 1912. After RC constructions were introduced from Europe, it took only 10 years for them to completely take root in Japan. In 1905, a lecture on the “Reinforced Concrete Construction” was started by Dr. T.Sano of the Department of Architechture, University of Tokyo, and in 1906, “The Reinforced Concrete Construction Technique” was main subject for discussion at the 7th International Architects Meeting in London. The theories of RC construction were applied gradually in Japan from 1915 to 1917 and the theories of RC construction were published by Dr. T.Naito, Dr. T.Sano and Dr. K.Goto respectively. These theories became the basis of the “Standard for Structural Calculation of Reinforced Concrete Structure” published by the Architectural Institute of Japan in 1933. 3 The damages to RC buildings by the great earthquake and its techniques 3.1 Damages to RC buildings in the Great Kanto Earthquake of 1923 Regarding the Great Kanto Earthquake, the damage to RC buildings are shown in Table 1 by Y.Nagata. As shown in Table 1, the number of collapsed buildings in old Tokyo City were very little e.g. only the seven buildings: the number of buildings damaged due to total and partial destroyed and severe damage amounted to about 10%, 62 out of the 593 buildings. Damage to RC buildings was exceedingly low compared with damage to wooden buildings. Futhermore, RC

Table 1. Damage to RC buildings in old Tokyo City by the Great Kanto Earthquake of 1923 (after Y.Nagata)

Degree of damage

Total destroyed

Partial destroyed

Severe damage

Small Undamaged Total damage

Factory

3

4

3

8

42

60

Office

1

2

8

25

129

165

Store

2

–

6

7

47

62

Dwelling house

1

–

4

2

45

52

563

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Kind of buildg.

Total

564

Hospital

–

–

–

4

8

12

School

–

–

1

5

15

21

Warehouse

–

3

15

9

97

124

Theater

–

1

–

1

3

5

Public

–

1

–

5

13

19

Others

–

2

5

3

63

73

7

13

42

69

462

593

buildings of this period were not constructed with an earthquake resistant design, but most of the RC buildings were not damaged during the Great Kanto Earthquake. As a result stated above, the RC buildings were highly appraised due to their fireproof and earthquake resistance. From Table 1, the buildings received severe and medium damage were mostly warehouses and factories. The prime damage to RC buildings were as follows [Y.Nagata (1926)], (a) Buildings built with an irregular plan. (b) Some of the reinforced concrete construction having small amount of wall quantity were fell down. (c) The curtain wall type construction of brick were fell down. (d) Bar arrangements of RC construction were not suitable. (e) A RC building was damaged at joint of bars because the laps of joint of deformed bar which were designed by American method were short, and no bar hooks. (f) The joints of both beam and column were weak and no rigid joints were employed. (g) Concrete strength was small, and the execution of work of placing concrete at joints of structural members were not done property. (h) Foundations were not put in properly. Moreover, regarding damage of the Great Kanto Earthquake, it was reported that damage to the top of the column of RC buildings arose like an explosive fracture damages due to insufficienct hoop and the concrete strength (see Fig. 2)

Transition of the technique of reinforced concrete constructions measured to earthquake damage

Fig. 2. Damage to the top of the column of RC buildings arose like an explosive fracture damages due to insufficient hoop and concrete strength by the Great Kanto Earthquake of 1923 (after Y.Nagata)

[Y.Kasai (1982)] . In next year (1924) after the Great Kanto Earthquake, the seismic coefficient method was defined into the Building Structual Code in the Urban Building Law for the first time all over the world. Also, the “Committee on Reinforced Concrete Work” was founded by the Architectural Institute of Japan in 1926, and the basis of the earthquake resistant design method of RC buildings in Japan was established. 3.2 Damages to RC buildings in the Fukui Earthquake of 1948 Since this earthquake had a shallow forcal depth of 10km, and the local earthquake occurred directly under the alluvium plain, the size of the seismic intensity was very large, causing a great deal of damage. Particularly, the seven-story Daiwa Department Store (see Fig. 3, 4) [Y.Tsuboi (1951)] was collapsed. This RC building was broken like an explosive fracture at the foot of column. Thereafter, the Building Standard Law was promulgated instead of the Urban Building Law in 1950. The Fukui Earthquake became a turning point, and following this the allowable unit stress of material was upgraded two times so far, the value of the seismic intensity also increased over 0.2 from over 0.1 so far. Also a SMAC (Strong-Motion Accelometer Committee) strong motion seismograph was produced for trial in 1953, and observations of strong earthquake motion advanced rapidly. Due to investigations of the earthquake response analysis using a computer and vibration test investigations of large scale model buildings, the restriction of conventional building height

565

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566

Fig. 3. Daiwa Department Store (seven stories) was collapsed by the Fukui Earthquake of 1948 (after Y.Tsuboi)

Fig. 4. Damage to the foot of the columns of Daiwa Department Store (seven stories) (after A.I.J.)

of 31 meters and under was removed from the Building Standard Low in 1963, with an era of super highrise buildings, beginning from that time. 3.3 Damages to RC buildings in the Tokachi-oki Earthquake of 1968 Five story or so a RC buildings such as the school building of Hakodate University (see

Transition of the technique of reinforced concrete constructions measured to earthquake damage Fig. 5) which was four stories and Misawa Commerce High School with three stories were destroied by this earthquake. This damage gave a feeling of

Fig. 5. Hakodate University (four stories) was destroyed by the Tokachi-oki Earthquake of 1968 (after K.Ogura)

unrest to the people, building designer and construction companies who believed in safety of RC buildings. The principal causes of the damages were as follows [K.Ogura (1968)], (a) Average strength of concrete were substantial lower than the specified design strength. (b) Methods of bar arrangement and the placing of concrete were not satisfactory. (c) Differential settlements of the foundation. (d) Toughness and strength for shear force of columns were insufficient. (e) Design method to the two-direction stress of corner columns was insufficient. (f) Consideration to the torsional vibration was insufficient. (g) Seismic forces acted on the convex structures such as pent-house and chimney on the roof floor were underestimated. (h) Execution of work and structual design of both the expansion joints and concrete joints were not sufficient. (i) Characteristics of the earthquake motions were not clear at this stage. Soon after the Tokachi-oki Earthquake of 1968, the San Fernando Earthquake of 1971 occurred in the U.S. and Olive View Hospital which had just been completed was damaged by this earthquake (K.Muto (1971)]. The first stories of this building was severely damaged, but this building did not collapse, and no person was killed in the earthquake. The

567

Demolition and reuse of concrete and masonry

568

Fig. 6. Kuzyu Lake Side Hotel (four stories) was destroyed by the Central Oita Earthquake of 1975: Second story was completely destroyed (after M.Tomii) ,

reason was the column reinforced with spairal hoop having sufficient toughness. The importance of this hoop-type column was verified by the minimal damage occurring to this buillding. The lack of hoop was one of the reasons for the school building of Hakodate University being destroyed (see Fig. 5). After, the four-story Kuzyu Lake Side Hotel which had just been completed was damaged by the Central Oita Earthquake of 1975 (see Fig. 6) [M.Tomii (1976)]. 3.4 Damage to RC buildings in the Miyagiken-oki Earthquake of 1978 Damage to school and office buildings of RC constructions (three or four stories) were very noticeable in the center of Sendai City due to this earthquake (see Fig. 7). Damage of midium to severe and collapsed buildings amounted to about 30. This damage gave again a feeling of unrest to many people. The principle causes of damage were as follows [T.Shiga (1980)] , (a) Foot and top of columns were destroyed by shear and compression force, and could not support the axial force. (b) The number of columns and amount of structural wall quantity at first story were small. (c) The space of hoops were too wide. (d) The short columns were failed due to shear force, and the other were cracked by bending force. (e) Damage to expansion joints was conspicuous.

Transition of the technique of reinforced concrete constructions measured to earthquake damage

Fig. 7. An office building of RC construction in Sendai City was collapsed by the Miyagiken-oki Earthquake of 1978: Damage to the top of the column of this building arose like explosive fracture damages (after T.Shiga)

(f) The convex structures on the roof floor were broken off and damaged. (g) The school buildings which had a off barance plan. Because the buildings of RC construction and steel structure were damaged greatly from the Tokachi-oki Earthquake of 1968, the San Fernando Earthquake of 1971 and the Miyagiken-oki Earthquake of 1978, the urgency to establish a new earthquake resistant design method was emphatically demanded. Also the results of the Promotion of Cooperative Research and Development Project conducted by the Ministry of Construction incorporated into the earthquake resistant design method at the time, and the earthquake resistant design method of today came into effect in June of 1981. The principal features and contents are as follows [H.Umemura (1982)], (a) This method constituted two grade formula of primary and secondary design. The objective of primary design was that no cracks should occur during a moderate earthquake. The objective of the secondary design was that no building would collapse nor harm human lives during a severe earthquake. (b) The earthquake resistant design method with different height and structural requirements for buildings were incorporated. (c) In addition to the elastic design method, the ultimate earthquake resistant design method including the plastic region was enriched the contents. (d) The regulations on the structural planning of buildings such as the modulus of eccentricity (prevention plan of torsional vibration) and the story stiffness ratio (equality of stories stiffness) were established. (e) Because of prevention of segregation fracture and failure of the nonstructural elements, the regulations on the restriction of stories deformation of building were

569

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established. (f) This method should be effectively apply for future technological developments. In Japan, fortunately, the buildings constructed by the new earthquake resistant design method enforced since 1981 have never experienced a great earthquake until the present time. Whether the buildings designed by this method can endured a great earthquake or will only be able to seen in the future, but we hope that the RC buildings based on the new design method enacted by the newest technology, and the careful execution work are not damaged by any several earthquake. 4 Development on the further prospects of reinforced concrete construction The principle investigations of RC construction being advanced at present are as follows, (a) Development of both reinforcing bar and concrete with heigh-strength or super heighstrength. The earthquake resistant design method based on the ultimate strength concept including plastic zone are realized, and accoding with the construction of large size and highrise RC buildings the high strength reinforcing bar and high strength concrete are required. “Development of Super Light Weight and Super Highrise Technology for RC Buildings (so called as New RC technology)” of the Promotion of Cooperative Research and Development Project are conducted by the Ministry of Construction. In the final report the possibility of specified strength of concrete is suggested the turning into 1000 kgf/cm2 from 600 kgf/cm2 [H.Muguruma (1991)] . Moreover, investigations on heigh-strength reinforcing bars were studied to a great extent. From this study, reinforcing bars with a yield point of 7000~8000 kgf/cm2 were developed, and now practical applications are also being started slowly [H.Kato (1992)] . (b) Highrise building using the reinforced concrete. The new developments of RC construction are advanced so as to construct buildings being with “toughness and ductility”. Highrise buildings of the 20 to 30 story type are now constructing. (c) Hybrid structures of both reinforced concrete and steel structure. As the new structure with mutual merits of both concrete and steel, the investigations of the hybrid structure have been seriously researched lately [M.Wakabayashi (1992)]. Taking concrete examples, plans such as structures combining RC wall with a steel frame, structures with column of a RC construction and beams of a steel structure, and girders of both ends of RC construction and center of steel structure, are now being put into practice. These are still in the investigation stage, we hope the hybrid structures will become practical applications for highrise buildings based on the RC construction. (d) Prefabrication method of reinforced concrete construction effectively using PC panels. PC panels are already being used, and the development of PC panels and half made PC panels have been advanced due to its simplicity for use in the field, because of

Transition of the technique of reinforced concrete constructions measured to earthquake damage shortage of house and necessity of large quantity production of building [K.Nakano (1979)]. Regarding the HPC method for composites both PC panels and wide flange shapes were put into practical use in about 1970 [T.Hisada (1977)]. Today, the 30 story apartment buildings have been constructed using RC prefabricated column and half PC panels. (e) Development of the reinforced concrete construction appling vibration control and base isolation system. Investigations on vibration control and base isolation system in Japan has developed rapidly. Especially, using the base isolation system have been started for practical application by degrees, though the apprication for highrise building and the economy still remain respectively. We consider that this system will be improved in the future though the vibration control system is still in its investigation stage.

5 Conclusion The reinforced concrete (RC) buildings at present in Japan have been designed based on the data of buildings damaged by the past large earthquakes. Buildings in metropolitan areas have not experienced great earthquakes for a period of about several ten years, but we hope that earthquake resistant design method enforced since 1981 which incorporated the newest construction technology will effectively work considering the aseismic properties of RC buildings. Also, we hope that the investigations on the newest RC construction will be used to improve RC buildings in the future. References (All the references are written in Japanese) Architectural Institute of Japan. (1972) Development and history of architecture in modern Japan., Maruzen Co. Ltd., pp. 7–192. Hisada, T. (1977) Earthquake and architecture., Kajima shuppan Co. Ltd., pp. 25–193. Kasai, Y. (1982) Transtion of modern building construction looking at the stand point of a building material’s engineer., Buildg. Eng., 367, pp. 1–15. Kato, H. (1992) Development of tendon., Journ. Archit. Buildg. Sci., Archit. Inst. Japan, 107, 1330, p. 144. Muguruma, H. (1991) Concrete with super high-strength, high-durability., Journ. Archit. Buildg. Sci., Archit. Inst. Japan, 106, 1320, p. 48. Muto, K. et al. (1971) Los Angeles Earthquake., Journ. Archit. Buildg. Sci., Archit. Inst. Japan, 86, 1041, pp. 693–754. Nagata, Y. (1926) The report of the investigation on damage to the reinforced concrete structure., Rep. Imper. Earthq. Invest. Comm., 100, c, pp. 211–332. Nakano, K. et al. (1979) Precast concrete work., Kajima shuppan Co. Ltd., pp. 1–88. Ogura, K. et al. (1968) Reinforced concrete construction., Report on the damage due to 1968 Tokachi-oki Earthquake, Archit. Inst. Japan, Tokyo, pp. 39–589. Shiga, T. et al. (1980) Earthquake damage of reinforced concrete structures., Report on the damage due to 1978 Miyagiken-oki Earthquake, Archit. Inst., Japan, Tokyo, pp. 135–468. Tomii, M. et al. (1976) Damage to the Kuju Lakeside Hotel., A report on damage to

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reinforced concrete buildings during the Oita Earthquake of April 21., Archt. Inst. Japan, pp. 15–162. Tsuboi, Y. et al. (1951) General view of damage to the reinforced concrete buildings., Fukui Earthq. Damage Invest. Rep., Buildg. Sect., pp. 112–116. Umemura, H. et al. (1982) New earthquake resistant design., Building Center of Japan, pp. 1–373. Wakabayashi, M. et al. (1992) Hybrid structure., Journ. Archit. Buildg. Sci., Archit. Inst. Japan, 107, 1329, pp. 11–33.

PART EIGHT CLOSING SESSION

47 RETRIEVING MATERIALS—THE EFFECTS OF EC HEALTH AND SAFETY DIRECTIVES B.S.NEALE Health and Safety Executive, Bootle, UK Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract This paper discusses the requirements of some EC Directives where there may be conflicts in requirements between those which may contain environmental requirements for recycling of materials and those requiring a healthy and safe work environment. The need for technical methods and controls for selective removal of materials for re-use is discussed to prevent the clock from being be turned back as far as workplace health and safety in demolition engineering is concerned. This paper considers the integration of demolition and recycling operations and what it means to the materials recovery teams. The considerations apply to concrete and masonry, as well as other materials. The responsibilities of those involved, and the management approach strategy are mentioned. This paper is restricted to discussing the author’s views on these key health and safety issues. The broader view was discussed in a previous paper1. Keywords: Access, Demolition, Dismantling, Environment, Health, Materials, Recycling, Safety, Stability, Work.

1 Introduction Workplace activities in the demolition industry are known to experience higher accident statistics than other industry sectors. The industry has a desire to improve the health and safety record. There can be a dual benefit in that there can be improved efficiency and thus cost savings2. Evidence of a desire to improve the statistics, and efficiency, is seen in the industry by employers adopting the principle of removing people from the high risk locations with the greater use of machines. The desire, or requirement, however, to retrieve materials for re-use can lead to increasing hazards and thus people can become exposed to increased risks. As well as personnel on site, the health and safety of members of the public could be put at

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additional risk. General obligations on employers are given in the Council of European Communities (CEC) directive3 on the introduction of measures to encourage improvements in the health and safety of workers at work. This directive, which is commonly known as the Framework directive, states in Article 6, Clause 1: Within the context of his responsibilities, the employer shall take the measures necessary for the safety and health protection of workers, including prevention of occupational risks and provision of information and training, as well us provision of the necessary organisation and means. The employer shall be alert to the need to adjust these measures to take account of changing circumstances and aim to improve existing situations. The general principles of prevention are given in Article 6, Clause 2. A selected summary (in the same order as in the directive) is given below: • avoid risks; • evaluate risks that cannot be avoided; • combat the risks at source; • design work places to suit the individual; • adapt to technical progress; • replace the dangerous by the non-dangerous; • develop an overall prevention policy which covers topics that include technology, organisation, and the working environment; • give collective protective measures priority over individual protective measures; • give appropriate instructions to the workers. Evaluating risks can be understood as assessing risks. Within this context, risk is seen as the likelihood that harm will occur. Where the term hazard is used in this paper it means something with the potential to cause harm. 2 Initial approach When recovering materials for re-use two phases in removing any facilities need to be examined to help reduce the effects of possible conflict in requirements. This is to ensure that the potential hazards are recognised so that adequate standards for health and for safety are employed. The two phases are: • winning or removing the components and parts of the building or structure during demolition; and • handling and processing materials, once removed, in readiness for reuse. Methods employed to remove materials for reuse often involve deconstructing by dismantling or removing components individually so that they will not be damaged and can be re-used. This applies to individual items more than components which will be broken down or crushed, although components of structures, such as concrete beams and

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decks, may be removed prior to reduction or crushing. This deconstructing philosophy can mean that the work force will be put into close proximity with those components. They are likely to be potentially hazardous locations as hand demolition methods will often be used. The effects of which are that people will be put to work: • closer to materials where there may health hazards; and • at height on the structure where hazards, such as the risk of falling, are high.

3 Health hazards Health hazards are not always well known. Even when such hazards are known about in detail, it is often difficult to know where they exist because the potential dangers cannot always be seen. Some types of health hazards can be recognised more easily than others. Asbestos is an example. Plans can then be put in hand to implement appropriate measures to deal with the specific hazards safely. Those that are identified but not dealt with effectively can produce risks to people that otherwise would not have occurred if they were not in close proximity because of their recovery and recycling activities. All hazards should be identified, of course, but on occasions where this does not happen the workforce may be at risk because of their close proximity due to these activities. The post-closure strategy for a facility coming out of use needs to include a decommissioning strategy where such health hazards can be identified. The scope for safe removal of material, including proposed methods of work, together with appropriate phasing and timing can then be planned and managed. The risks to which people could be subjected because of this process include those as a result of: • being built into the building or structure; • the use of the facility (such as materials brought in, used , combined, products made, by-products, etc.) • external sources during use of the facility (ground-based, water borne, atmospheric and living creatures); • external sources during the post-closure phase (ground-based, water borne, atmospheric and living creatures). The hazards may be “locked in” until the effects of some action, either deliberate or unintentional, brings them “alive” during removal. Such effects could include vibration, fire, heating, percussion, cutting, sawing, sweeping. Some of these actions may have effects at locations remote from the application of the action and this will have to be taken into account and planned for. The health hazards could have effects which include being pathogenic, allergenic, toxic or carcinogenic. The health hazards to be managed can be grouped into the following categories :

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• biological agents—including micro-organisms such as spores, bacteria and those transmitted by infestations; • chemicals—chemical elements and compounds, including enzymes; • ionising radiations—although less likely, may be encountered. These may be introduced into the body by the respiratory mechanism, ingestion, adsorption through the skin or directly through an opening in the skin. The way in which the health hazards may be present in a facility can be by accumulation, deliberate impregnation of construction materials, inadvertent impregnation of construction materials and in the make-up of construction materials. Areas to consider in each of these categories include : Accumulation: • of deposits in areas not normally visible or accessible, such as under floorboards, in roof spaces and in basements; • on external surfaces; • on internal surfaces of the building or structure, such as walls and floors; • on internal surfaces of plant, equipment and other fixtures, including tanks and vessels; • on internal surfaces of movable elements, such containers. Inadvertent impregnation: • of porous or permeable materials used in the structure including concrete, bricks and plaster, by events such as: - spillages on floors; - physical contact in storage areas; and - adsorption from the atmosphere; • of non-structural materials such as thermal insulation, which may be present in ceiling voids, behind dry lining or as lagging; and • of walls due to rising damp and walls below ground level from contaminated ground. Deliberate impregnation: • for reasons such as timber preservation or fire retarding; • unrecognised as such, for example surface treatments (including paints) of timber and walls, which may include treatments that have deteriorated.

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Construction materials (inherent in make-up): • visible heavy metals, such as lead in piping or flashing; • invisible heavy metals, such as lead in paints; • fibrous materials in lagging, such as asbestos; • fibrous materials in boards or sheets, such as asbestos. Consideration will have to be given to the processing of recovered materials where exposure to hazards will produce risk not previously present, primarily because the processing would not have been undertaken. The risks will include well known ones, such as noise, but may additionally include health risks due to biological agents, chemicals and perhaps ionising radiations as mentioned above. 4 Safety hazards Safety hazards are usually better known, partly because the potential dangers can be seen and appreciated. The prime safety hazard and the single major cause of death or injury on sites is falling. The second highest cause of death or injury on sites is due to transport. As far as the removal process is concerned, the industry has seen a greater use of machines, in recent years. This reduces or removes the need for people to be in hazardous locations. The post-closure strategy for a facility coming out of use needs to include a decommissioning strategy where such safety hazards can be identified. The scope for safe removal of material, including proposed methods of work, with appropriate phasing and timing can then be planned and managed. The risks to which people will become exposed because of this process which need to be managed include : Falls of people. tools and materials (including materials being retrieved): • from the workplace; • whilst gaining access to, or egressing from, the workplace; • whilst transporting materials and tools through the building, or to the external perimeter of the structure; • at the external perimeter of the building or structure where the material is being collected; • due to collapse because of reduced structural stability during dismantling of: - the whole structure; - areas of the structure; - individual members. Stacking and storage: • unstable stacking of retrieved materials at any location; • temporary stacking, which may cause structural overload and collapse;

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• surcharging weak ground with stored material. Transportation and handling: • manual handling and lifting; • loading and unloading materials for onward transportation; • transporting material across site to: - on-site processing locations; - off-site locations; • misuse of plant. Processing materials (both on-site and off-site) • manual handling and lifting4; • machine guarding; • other factory based hazards. Where methods of preventing falls involves the use of temporary access systems, any risks in preparing them for use and removing them needs to be taken into account. 5 Managing the situation for health and safety Risk evaluations are required under the Framework directive3 as mentioned in Section 1 of this paper. In the UK, this has passed into national legislation with the requirement for risk assessments which are described further in the associated Approved code of practice5. It could be argued that it would be easy to provide for the lowest form of protection, that is, personal protection only. This would be unacceptable, and would, of course, contravene requirements for health and safety, depending on the results of assessments. Safe retrieval methods will need to be investigated, with alternatives examined. Those methods will need to be assessed by identifying the hazards and any resulting risks. A suitable method, or variety of methods can then be selected. They can be implemented by designing into the job, systems of work allow for a safe and healthy environment taking into account factors such as: • structural stability; • all places of work; • access to, and egress, from places of work • protection for those not connected with the project, such as the public; and • health surveillance. Controls such as effective site management, adequate supervision and a properly trained workforce will be required6. Desired safe methods can be identified at an early stage. “Early” can be at pre-tender stage where the client, possibly with a professional adviser, examine the options. It

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should, in any event, be early enough to planned into the job before work on site starts. 6 Conclusion This paper has explored some of the considerations to be made if the apparent conflict in EC directives is to be resolved. The conclusion is that there will have to be rigorous assessment of methods to be used. This should include realistic and meaningful investigation, planning, monitoring, training, supervision, with effective overall and detailed management. The legal responsibilities of all those involved, such as the clients and consultants, as well as the contractors needs to be realised. Cooperation, understanding and good working relationships between all concerned with the project will contribute to a successful job. 7 References 1. B.S.Neale, (1992), Health and Safety Management—EC Directives: First International Concrete Blasting Conference. Danish Federation of Explosives Engineers. 2. Health and Safety Executive, (1993), The Costs of Accidents at Work, HS(G)96. HMSO Publications, UK. 3. CEC, (1989), Council Directive number 89/391/EEC, Official Journal of the European Communities, Annex 3, 26 June 1989. CEC. 4. Health and Safety Executive, (1992), Manual Handling Operations Regulations and Guidance, L23. HMSO Publications, UK. 5. Health and Safety Executive, (1992), Management of Health and Safety at Work Regulations and Approved Code of Practice, L21. HMSO Publications, UK. 6. Health and Safety Executive, (1991), Successful Health and Safety Management, HS (G)65. HMSO Publications, UK.

48 THE GREAT BELT LINK PROJECT C.E.LOOSEMORE European Storebælt Group, Nyborg, Denmark Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract The Great Belt Link is Europes second biggest civil engineering scheme after the Channel Tunnel. Construction of the West Bridge, a combined road/rail bridge some 6.6 km long, was performed by precasting huge bridge elements on land and transporting them by floating crane to their final location. A 30 hectare land based site was required to prefabricate the elements but on completion of the permanent works the area had to be returned to a level surface with no obstructions within the top 1 m of the ground. During the construction phase the Contractor, European Storebælt Group, crushed the waste concrete and sold it to local contractors for the upgrading of local access tracks and roads. Demolition of the construction site is about to commence. Various means of disposing of the heavily reinforced concrete have been investigated including burying on site, breakwater core fill, bund wall sound barriers and transportation to approved areas. Keywords: Great Belt Link, Crushed Concrete, Breakwater Core Fill, Sound Barriers, West Bridge, European Storebælt Group.

1 Introduction The Great Belt fixed link consists of three major projects: the railway tunnel between Zealand and Sprogø, the combined road and railway bridge between Sprogø and Funen and the road bridge connecting Zealand and Sprogø. The railway tunnel under the Eastern Channel, the East Tunnel, is being constructed as a bored tunnel consisting of two single-track tubes each with an internal diameter of 7.7 m. The total tunnel length will be just over 8,000 m, of which the bored stretch of each tube will be approximately 7,400 m. The remaining stretches at each end of the tunnel will be two cutand-cover tunnels extending 227 m and 277 m onto Zealand and Sprogø, respectively.

The Great Belt Link project

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The combined road and railway bridge across the Western Channel, the West Bridge is an all-concrete bridge with separate bridge superstructures for rail and motorway traffic. The total length, which slightly exceeds 6,600 m, is mainly constructed of standardized 110.4 m spans. The bridge rests on two abutments and 62 bridge piers founded on the bottom of the Western Channel with water depths of up to 25 m. The motorway bridge across the Eastern Channel, the East Bridge, will be almost 6,800 m long, nearly 2,700 m of which will be a suspension bridge with a 1,624 m main span and two 535 m side spans. From the suspension bridge 14 approach spans totalling approximately 2,500 m will lead down to the coast of Zealand and 9 approach spans totalling approximately 1,600 m to the ramp on Sprogø. In addition to the bridge and tunnel sections, the Great Belt fixed link also includes new road and railway sections on land connecting the existing motorways and railways with the fixed link.

Fig. 1. The Great Belt Link

The Great Belt fixed link comprises considerable works on and around Sprogø. Major land reclamation works have thus increased the area of the island fourfold, and on the Sprogø East Reef comprehensive dredging has taken place to compensate for the blocking of the water flow caused by the fixed link. This article deals specifically with the demolition of the fabrication yard that was constructed at Lindholm to enable elements for the West Bridge to be prefabricated. The author is employed by the Contractor responsible for building the bridge and has been directly involved in the planning of the demolition work. The Contractors liability for reinstating the prefabrication yard was clearly defined in the Contract Specification produced by the Client Great Belt A/S. However, as the time for the demolition works approached meetings were held between Great Belt A/S and Nyborg Kommune (the local

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authority) to discuss in detail the reinstatement of the land and disposal of the waste. Because of the Contractors intimate knowledge of the site he was party to most of these meetings. This article has been written based on the information gained from these meetings. 2 The West Bridge The construction of the West Bridge between Funen and Sprogø was started in the summer of 1989 following the signing of a contract between Great Belt A/S and the consortium of Contractors European Storebælt Group (ESG) consisting of: Højgaard & Schultz A/S, DK Ballast Nedam Civil Engineering, NL Taylor Woodrow Construction Ltd, GB Losinger Ltd, CH C.G.Jensen A/S, DK Per Aarsleff A/S, DK

Fig. 2. Main elements of the West Bridge

The successful bid was an alternative concrete design based on precasting the various elements on land and subsequently transporting them by sea to their final position. Elements consisted of: 62 Caissons forming the bridge foundation—maximum weight of a unit 7000 tonnes.

The Great Belt Link project

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124 Pier Shafts (62 road and 62 rail). 63 Road Girder each 110 m long and weighing 5800 tonnes each. 63 Rail Girder each 110 m long and weighing 4800 tonnes each. To place these units a specially designed, self propelled, heavy lift vessel was constructed. The “SVANEN” is ranked as one of the worlds largest inshore floating cranes. 3 Lindholm—The Prefabrication Yard The advantages of a prefabrication construction technique for a bridge is that work can continue on land throughout the year with relatively little downtime due to inclement weather. One of the disadvantages however is that a large construction site is needed requiring many resources to establish it and ultimately to demolish it. Because floating vessels were to be used for the transportation of the bridge elements a quay wall with a minimum water depth of 6 m was required. Within the close proximity of the bridge no such facility was available and it was decided that a purpose made quay and construction site would be needed. Within the Contract Specification it was deemed that on completion of the Western Bridge contract, the “temporary” facility would be taken over by Nyborg Harbour. To ensure that the construction site could be of later use the specification required that the sheet piled quay wall be of at least 220 m continuous length, designed for a 25 kN/m2 surcharge and subsequent dredging to a depth of −12 m. All concrete and steel structures on the construction site were to be removed above a level of +1 m (ground level was +2 m) on completion of the work. Dredging to open water was permitted with the arisings to be deposited on Sprogø within an area protected by a stone revetment. The reclamation of the Lindholm Site required the dredging and pumping of 400,000 m3 of sand from Storebælt. This enabled an area of 30 hectare (75 acres—the equivalent of 60 football pitches) to be at the Contractors disposal for constructing the prefabricated bridge elements. To enable the prefabricated bridge elements to be lifted by the floating vessel, concrete jetties were constructed. The elements were pushed along these jetties by specially designed hydraulic machines enabling the vessel to then straddle the jetty and lift the elements (the floating vessel consisted of two pontoons jointed at the back making a U shape).

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Fig. 3. The Lindholm Prefabrication Yard

4 Disposal of Waste Concrete During Production The construction of the West Bridge involved the production and placing of some 480,000 m3 of concrete. During the peak construction period 7,000 m3 of concrete was produced per week. The concrete was distributed from the two site batchers using a fleet of concrete wagons each with a capacity of 6 m3. The main walls of the Caissons were slipformed, a process whereby concrete is placed continually within a shutter in layers approximately 200 mm deep and the shutter is mechanically raised at slow speed. Hardened concrete emerges from the underside of the shutter between 6 and 10 hours later depending on the type of mix used and the ambient air temperature. Slipforming, being a continual process, requires a concrete supply 24 hours per day. Most other pours on site involved large volumes of concrete ranging up to 1000 m3 and taking up to 16 hours to complete. It was necessary to run the concrete batching plants 24 hours per day to meet these demands and so a solution was necessary on how to process the waste concrete. Approximately 1% of the produced concrete had to be disposed of. This waste was generated from two sources: a) Over-ordered concrete (a small proportion). b) Mixed concrete that after testing, but before placing in the formwork, was found not to comply with the very stringent specification, ie. air content, etc. It can be seen that even with waste of only 1% this could still generate 70 m3 of concrete

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587

per week. Initially, investigations took place to see if the concrete could be used to prefabricate small temporary works items as used by most Contractors, ie. temporary bollards for use during road works. The idea was that prepared shutters could be set up on a part of the site with an electric vibrator permanently available. The concrete wagon driver could then fill the shutters with the waste concrete from his truck. This solution was not progressed because the supply of waste concrete was generally intermittent and, when available, usually in large loads (6 m3 per wagon). Estimates indicated that the cheapest solution would be to crush the concrete and then sell it to other Contractors to either make haul roads on their sites or to upgrade temporary roads on farmland. The concrete was ideal for crushing as it contained no reinforcement or encast items. An area approximately 50 m×40 m was designated as the official tipping area for waste concrete. The concrete wagons would drive into this area and deposit their waste concrete onto the ground in a layer approximately 300 mm thick. At least once a day a mobile mechanical digger would travel to the area of hardening waste concrete and using his excavator bucket “cut” the concrete into small sections and pile these into a heap. At times, especially in hot weather, the excavator had to be fitted with an hydraulic concrete breaker because the concrete had hardened too much to be “cut”. Once the storage area started to become full a mobile crushing plant was hired to crush the concrete. The crushed concrete was produced in two sizes, 0 to 32 mm and 32 mm to 60 mm. The crushing plant was hired approximately three times each year. The prime users of the crushed concrete were either local farmers who used it around their farms to make access ways or the local community who used it to upgrade or repair their roads in the forests. Material was sold for 30 DKK per m3 (loose) for the larger stone and 40 DKK per m3 for the smaller. In order to reduce costs the system for selling the crushed concrete was simple and unsophisticated. The haulage lorries that arrived on site to transport the material were measured by volume and then filled level. A gate pass indicating the volume that they carried was issued and this doubled as an invoice. The Contractors costs in hiring the crushing plant and loading the crushed concrete were almost covered by the income received in selling the material. The comparison shown below is based on information that was available in January 1991 and is based on 1,000 tonnes of concrete: a) Dumping at an approved dumping area DKK Fee

65 DKK/ton*

65,000

Tax on waste

130 DKK/ton

130,000

Transport

200 DKK/ton

200,000

Total cost of depositing Tax reimbursed by Client Net cost of depositing

395,000 90 DKK/ton*

90,000

Demolition and reuse of concrete and masonry

588 305,000

* The fee for dumping at an approved area is variable. Such dumping areas are run by private companies and they can charge up to 65 DKK/ton maximum. Their price is usually dependant on the quality of crushed and uncrushed concrete they have available. If their stocks are high then their dumping fees are high and vice versa.

b) Crushing on site using a rented crusher and selling DKK Mobilize crusher

8,000

Crushing including loading of material into crusher

40 DKK/ton

48,000

Total cost to crush concrete Net value of materials (based on 1.5 T/m3)

40,000

22 DKK/ton

Net cost of crushing

22,000 26,000

5 Demolition of Lindholm Prefabrication Yard Construction work on Lindholm will be completed in late May 1993 and it is the intention to complete all the necessary demolition work by December 1993. As stated earlier in this paper it is the Contractors responsibility to leave the site completely clean down to a level of +1 m, some 1 m below ground level. The demolition material quantities involved to clear the site are: Reinforced concrete

35,000 m3

Steel

7,000 tonnes

Asphalt

5,500 tonnes

The owner of the reclaimed land is Nyborg Harbour who are owned by Nyborg Kommune, the local authority. As the construction work on the prefabrication site came to a close, meetings were held between the Harbour, Kommune, Great Belt A/S and the European Storebælt Group to ensure that the area was left in a condition most suitable for future use. Such decisions had obviously to ensure that the relevant laws on these matters were complied with and that costs were kept to a minimum. At this moment in time final decisions have not been taken on how the reinforced concrete should be disposed but resolution is close at hand. The site contains some 35,000 m3 of reinforced concrete that can be split into four categories: 14,000 m3 of heavily reinforced foundations into which blasting pipes were

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inserted during construction to enable easy removal. 4,500 m3 of heavily reinforced beam foundations for the site cranes. 11,000 m3 of lightly reinforced ground bearing slabs. 5,500 m3 of heavily reinforced foundations situated over water. According to the relevant laws there is a charge of 195 DKK/t for depositing building material unless it is deposited in an approved area. The Lindholm Site is located on the island of Funen and the local approved area is Kommunens Genbrugsanlæg, Fjeldsted, some 50 km from site. The fee for depositing on an approved area is 20–40 DKK/t. Interpretation of the relevant laws is the responsibility of the Kommune but it is hoped that the ground bearing slabs can remain as they will undoubtable be useful when the site is developed by the Harbour. The Contractor has actively investigated the possibilities for the re-use of the remaining concrete and the following alternatives have been proposed: To use as the central core area for a proposed breakwater. To supply it to a local contractor in blocks of less than 1 m3 in volume. To supply it to the local approved area in blocks less than 1 m3 in volume. To extend one corner of the site. To form sound barriers. 5.1 Proposed breakwater This alternative would incur only the cost of demolition and transportation. Concrete was required in blocks not greater than 1 m3 and with the proviso that protruding reinforcement did not extend for more than 100 mm. However, the disadvantage was that the recipient required the material within a timescale that did not match the availability from site. 5.2 Supply to a local contractor A local contractor intended to crush the material and then resell it in a manner similar to that instigated by the site for the waste concrete produced during the permanent work operations. Once again the only costs involved would be the demolition and transportation. 5.3 Supply to the local approved area Within Denmark this is the usual method of disposing of waste. All builders material and specifically concrete, brick and asphalt is sent to the local approved area. A fee is charged for tipping and the material is prepared for re-use. From a contractors view-point this is an expensive alternative as material has to be demolished and transported on top of the deposit tax (tipping fee).

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5.4 Extension to the site or from sound barriers The future development of the Lindholm Site will be for industrial purposes. To the west, adjacent to the site boundary, is a residential area. There is a proposal that the demolished concrete be built up into a sound restraint bund on the western edge of the site and then covered and grassed. Such bunds require the planning permission of the Kommune but do not incur a deposit tax. Such a bund would improve the environment of those living close by. An additional proposal is to extend the south west corner of the site by depositing the broken concrete into the Fjord. Reclamation of land does not attract a deposit tax. Tenders for the demolition works were sent to 7 contractors and are due to be returned by Mid-May. The tender documents required the contractors to price three alternative disposal methods that would cover most of the proposals mentioned above, ie. depositing on site, bund wall construction and transport to an approved tip. Once the tenders have been assessed the Local Authority will be in a position to make a final judgement on how demolition work should proceed.

49 THE “RECYCLED HOUSE” IN ODENSE E.BITSCH OLSEN Axel Nielsen—Carl Bro A/S, Odense, Denmark Demolition and Reuse of Concrete. Edited by Erik K.Lauritzen. © 1994 RILEM. Published by E & FN Spon, 2–6 Boundary Row, London SE1 8HN. ISBN 0 419 18400 7. Abstract This paper describes briefly the construction of a block of flats where the use of recycled materials have contributed considerably both to reduce the consumption of new materials and to reduce the dumping from neighbouring demolition sites. When the house is completed all recycling activities will be evaluated both technically and economically. This evaluation is not yet prepared, but the experience gained proves already that recycling in the modern construction process is adaptable from a technical point of view. Keywords: Aggregates, Bricks, Concrete, Recycling, Slates, Steel, Tiles, Timber.

1 Introduction The “Recycled House” is a 2½ storey 2-wing building with 14 cooperative non-profit flats in the centre of Odense. A significant part of the structure is built from recycled materials such as crushed concrete and crushed tiles used as aggregates in concrete, used timber for structures and joinery, used bricks and used roof slates. It means that the house is a mile stone in the renewed efforts for large scale recycling of building materials—an old tradition in Denmark which has been forgotten for decades. It exhibits in full scale 1. the technical state of recycling building materials 2. the organisation when recycling techniques are introduced in cooperative housing schemes A considerable part of all housing schemes in Denmark are built as cooperative housing subsidized by the tax payers. This type of housing projects introduces restrictions such as limited unit costs, limited flat sizes, forced tender procedures etc. These restrictions have to be met in all ways if recycling should gain accept as a common activity in the Danish

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building industry. Therefore the achievements in the second above mentioned point are just as important as those in the first point. As the Danish system of subsidized cooperative dwellings is rather complicated it shall not be spelled out here, where we will emphasize the technical point of view. As this building is a prestige project all involved parties have been very conscious of the project and taken part in the decision making. In a positive way all parties have contributed to the successful completion. Financially responsible is the client: Hoeistrup Cooperative Housing Figure 1. The “Recycled house”

Procurement of the recycled materials has been managed by the Odense Urban Renewal Company while the architectural and the technical consultants are Architect M.A.A., Torkild Kristensens Tegnestue Ltd. Axel Nielsen · Carl Bro a¦s, Consulting Engineers FRI

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The Contractor is: Hoejgaard & Schultz Vest Ltd. Special recycling activities have been financed by the National Agency of Environmental Protection (N.A.E.P.) through funds from the Recycling Council in the Ministry of Environment. The project is one of three projects supported by the N.A.E.P, the other two are built in Horsens (Jutland) and Copenhagen. All special recycling activities are managed by Demex, Consulting Engineers Ltd., Copenhagen. Figure 2. Storey plan

Figure 3. Cross section

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2 The Recycled House 2.1 The house The recycled house was completed in August 1993 and the tenants moved in by September 1st. The house is a 2-wing building in 2½ storey (2 normal stories and penthouse flats in the roof structure) plus basement with bomb shelter, technique rooms and locker areas for the The living area includes 14 flats—2 3-room dwellings and 12 2-room dwellings. The street along the building falls approx. 3 metres from one end to the other. This of course influences the architects design of the facades and the lay out of the basement. Plans of the storeys are not exceptional and according to Danish practice, but in this demonstration project internal walls are made of bricks. This is an unusual high standard in cooperative dwellings.

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Further it should be mentioned that all construction work on subsidized buildings has to be awarded to the lowest bidder in a tender. This means that all specifications for and control of the works with recycled materials had to be described in tender documents and thus considered and defined before a lot of good experience was gained. To balance reliable specifications against the limited economy in the project was a great challenge for the architect and the engineer. 2.2 Components with recycled materials In the above section building components including recycled materials are described. As recycling at present is an unusual procedure in Denmark the major consideration for all the materials has been how to define and control a proper but not too high standard, as most of the standards for new material are not suitable for recycled materials. A recommendation for the use of recycled aggregates for concrete is the only authorized standard at present. For all other components existing standards for new materials were adapted. During the construction period, practical problems led to alterations. E.g. the prescribed steel profiles were not available as used members, and new profiles were accepted. In the figure 4 components and their recycled materials are listed together with the standards specified in the tender documents. Figure 4—Standards for recycled materials

Components

Recycled materials

Standards

Drainage layer

Crushed concrete

Specifications for granular curve, content of organic material and the max. capillary rise

Concrete aggregates

Crushed concrete and bricks

According to an authorized Recommendation

Steel reinforcement

Melted scrap iron

According to ISO 630 Fe 360 Re 510

(Structural steel

Used members)

According to ISO 630

Walls

Cleaned bricks

Strength: DS 438

Floors

Used floorboards

Shape: Visual control Strength: DS 413

Internal doors

Repaired used doors Visual control

Window frames

Cut timber

Visual decomposition control

Other joinery

Cut timber

Visual decomposition control

Roof structure

Cut timber

Visual decomposition control Strength: DS 413

Roof slates

Reused slates

Full shaped after cleaning

DS means Danish Standard.

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Visual decomposition control includes control against dry rot and fungus. 2.3 Production of recycled materials Crushed concrete and tile Part of the concrete material was taken from a demolished fly-over. The demolition of this rather new bridge included several full-scale tests concerning load-deflection, demolition and recycling. The rest of the concrete aggregates were taken from an old concrete air-raid shelter situated on the site. Crushed tiles were delivered from a municipal recycling plant. The standard for aggregates in new concrete was specified according to the Recommendation for the use of recycled aggregates for concrete in passive environmental class, class GP1 (in concrete grade 25 and 30 MPa) and GP2 (in concrete grade 5–20 MPa). The material was graded in 4–16 mm and 16–32 mm fractions and the 16–32 mm fraction was used in the drainage layer. Bricks Bricks for external and internal walls were selected from 2 demolition sites in Odense; one of them on the neighbour plot. The bricks were divided into 2 classes: 1 Bricks originally placed in external facades. 2 Bricks originally placed in other load bearing walls Class 1 is expected to have been proven frost-proof and was used in the external walls. Class 2 was used in internal walls. Preliminary tests proved very high variation in the strength and it was decided to specify a rather low compression strength: 10 MPa. 130.000 cleaned bricks were needed. They were cleaned by hand as no efficient machinery is found available for the cleaning of bricks. They where sorted, stocked on pallets, wrapped in plastic and stored outside. Timber Timber was collected from several demolition sites—even in Jutland. Both long full shaped beams—used in the Entrance house—and more simple beams and boards were used. The old sound wood has proved to be heavier and stronger than contemporary building timber. The selected timber was both tested visually and controlled for dry rot and fungus. Timber for structural components was then graded according to strength. Only existing major cuts or holes and great splits from seasoning caused rejection. Roof slates Roof slates were taken from several demolition sites in Odense; they were

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598

cleaned and laid up again. The quality of the old slates is higher than that of contemporary slates. 2.4 Working with recycled materials As working with recycled materials was an unknown (or revived) activity for the contractor and the craftsmen, many special aspects were brought up in the site meetings and during the control procedures. As all parties gave the construction a very high priority only a few things turned to be problems. A major problem was caused by the bricks. Firstly it was very difficult during the demolition to sort reusable bricks from the poorly fired bricks which often are to be found in old brick houses. Secondly the hand cleaning was very troublesome and expensive; and the following storage procedure was not sufficient. It meant thirdly that the cleaned bricks were very wet when they arrived on site. This caused trouble for the brick layers and also caused quality reduction. In some cases new bricks had to substitute the recycled bricks. For the other materials most troubles arose from the long chain of unusual procedures. Some links needed to be adjusted. E.g. the authorized strength control of the structural timber had to be adapted to take into account holes and cuts which are not allowed in new structural timber. Reused beams are often stronger than new timber beam even if they have holes for bolts or small cuts. Generally the craftsmen have handled the recycled material very professionally and they were able to incorporate recycled materials in their building process. 3 Conclusions At the time of writing construction is still going on and no general evaluation is prepared. Especially an economical evaluation is very important and such an analysis is not yet carried out. It must be emphasized that this project is a pilot project for recycling, completed before a sufficient recycling trade and industry is established in Denmark. That is the reason for the support from the Danish Ministry of Environment. The experience from this project will lead to more efficient handling methods for recycled materials such as timber and bricks. The production of crushed materials is now established professionally. But a question is, if the optimal way of using the crushed aggregates is in the building industry, or it is more profitable to use it in the road construction. In the planning process of this building it was considered, whether it was possible to recycle water (reuse of cleaned waste water) locally. The techniques are available but the economics (among other things the compulsory waste water duties to the municipality) made it impossible, and it was abandoned already in the planning stage. The achieved sum of experience on recycling—good and not so good—is very high from this project and this, combined with the evaluation from the “Recycled Houses” in Copenhagen and Horsens, will form a good foundation for increased recycling in the Danish building industry.

Author Index Bahnasawy H.H. 412 Barth H.P. 2 Bauchard F. 77 Belhadj A. 346 Bitsch Olsen E. 587 Brunner P.H. 545 Cocconcelli A. 510 Collins R.J. 52 De Pauw C. 130 Ehara K. 424 Finelli G. 510 Gallias J.L. 77 Gottfredsen F.R. 361 Hamidovic J. 533 Hanada M. 297 Haneda H. 297 Hansen H. 471 Hashizume K. 207, 251 Hayashi H. 268, 282 Henrichsen A. 128 Henderieckx F. 27 Hida T. 268, 282 Hisaka M. 437 Ishibashi J. 179 Ishikawa H. 144 Jannerup M. 38 Karibayashi M. 268 Kasai Y. 98, 179, 207, 235, 437, 557 Katsuyama K. 251 Kibert C.J. 89

Index Kikuchi M. 424 Klöpper K. 480 Kobayashi N. 193 Kobayasi S. 235 Kovacevic T. 451 Kristensen P. 476 Kubota H. 557 Kubota S. 220 Kurokawa K. 160 Lahner T.E. 545, Lauritzen E.K. 38 Loosemore C.E. 577 Mana F. 77 Matsunaga H. 220 Medici C. 510 Merlet J.D. 399 Momber A.W. 335 Morel A. 77 Mukugi J. 220 Muravljov M. 451 Nakagawa W. 307 Nakajiku M. 193 Nakamura S. 160 NakamuraY. 220 Neale B.S. 570 Nicolai M. 533 Ogata Y. 251 Ohhara T. 220 Ohtsubo S. 251 Okada T. 8 Pakvor A. 451 Pimienta P. 399 Rahlwes K. 486 Rentz O. 533 Rousseau E. 61, 77 Ruch M. 533 Saetti G.F. 510 Saito T. 160, 179 Saitou T. 235 Sano M. 383, 520

600

Index Sato T. 251 Sawada I. 193 Schulz R.R. 113 Seiki Y. 144 Seki Y. 179 Shater M.A. 412 Shibata H. 193 Shindo T. 193, 207 Simons B.P. 27 Søborg L. 553 Soeda K. 268, 282 Sommer H. 498 Spengler Th. 533 Sueyoshi K. 235 Thøgersen F. 361 Tomita K. 179, 235 Trevorrow A. 370 Tsuchiya K. 282 Tsuji Y. 297 Valdivia S. 533 Vyncke J. 61 Wada Y. 251 Wainwright P.J. 370 Waldron P. 346 Wang Y. 370 Williams G.T. 324 Yagishita F. 383, 520 Yamabe K. 557 Yamada M. 383, 520 Yamaguchi U. 193, 251 Yamamoto M. 160, 220 Yanagi K. 437 Yasunaga A. 424 Yokota M. 144 Yoshida T. 160 Yu Y. 370

601

Subject Index Abrasive 335 Accelerated tests 361 Access 570 Aggregate ratio 399 Aggregates properties 113 recycling 61, 77, 98, 128, 424, 437 rematerialization 520 Aggressive Environment 361 Alkali Aggregate Reactions 361 Alloy, shape memory 307 Appling current through rebars 307 Arc saw 144 Asphalt mixture 520 Audit 553 Autoclavation 471 Base plates 480 Blasting controlled 144, 220 delay 193 demolition 160, 207, 235 Bond 346 Bond stress 383 Bonding 451 Breakwater core fill 577 Brick clay 471 crushed 451 dimensions 476 frost resistance 476 reburning 476 recycling 476 Building 8, 486 Bulk density 113 Burning 471 Calcium silicate 471 Carbonation 437 Carbonation rate 399

Index Cavitation 335 Cement blended 412 dust 412 Ceramics district 510 inerts 510 scrap material 510 sludges 511 third firing 511 wastes 510 Charge holder 220 Clay bricks 471 Clean technology 38, 553 Coarse/fine aggregate ratio 370 Collapse 179 Collapse mechanisms 324 Compressive strength 399, 412, 437 Concrete aggregates 77, 113 cavity porosity 451 construction 207 cover 383 crushed 399, 577 demolished 98 dust 531 freshed 424 pavements 498 plain 335 post-tensioned 346 prestressed 346 recycling 89, 98, 128, 424, 437, reinforced 8, 160, 193, 235, 251, 335, 486, 557, reusing 38, 480 single fraction 451 technical specifications 61 waste 520 Construction industry 2 materials 78, 545 processes 545 techniques 558 Crack 383 Crushing 471 Cutting 335 Damage assessment 130

603

Index classification 130 Danish legislation 38, 128 Decommissioning 144 Demolition agent, non-explosive 268, 282, 297 blasting 160, 193, 207, 235, 251 environment 570 experimental 179 guidelines 27, 128 partial 220 prestressed concrete 346 selective 38 systems 130, 268 techniques 307 waste 27, 61, 533 water jet 335 Disaster relief, integrated 130 Dismantling 533 Drying shrinkage 399, 424, 437 Ductility 8 Durability 361 Dynamite 235 Earthquake damage 557 resistant design methods 557 Economics 553 Elasticity modulus 437, 451 Electric heating 307 Energy consumption 486 Environment 570 Environmental impact 89 Environmental legislation 61 European Storebaelt Group 577 Expansion 399 Expansive energy 297 Expansive pressure 268, 282, 297 Explosives 193, 207 Fatigue 36 Feasibility Economic 2 Financial 2 Finishing materials 437 Flexure 383 Fly ash 361 Fly rock 160, 193 Fragmentation 160, 235, 251

604

Index Fragmentations, spread 251 Frost resistance 437 Granular 282 Great Belt Link 577 Grout 346 Guideline 77, 98, 113 Gun phenomenon 282 Health 570 History 142 Hydration 282 Impact 346 Impurity 437 Incentives 27, 553 Induction heating 307 ntegrated concepts 533 Isolate chloride ion 424 JPDR (Japanese Pow Demonstration Reactor) 144 Laser beam 307 Legislation 2, 553 Market standardization 2 Masonry demolition 476 recycling 38, 89, 471 Materials construction 545 management 545 recovery teams 570 waste 98 Modulus of elasticity 399 Moisture movement 399 Mortar 471 Neutralization 424 Noise 160, 193 NEDA (Non-explosive demoliti agent) 297 Notched borehole 220 Pavements 498 Pilot projects 113 Plasticizer 399 Policy 2

605

Index

606

Preparatory work 179 Premoistening 399 Principals 2 Protection 235 Pulsating jet 335 Quality certification 61 Rebar 307, 486 Reburning 476 Recycling 533 concrete aggregates 52, 361 370, 383, 399, 424, 437, 486, 498 base plates 480 bricks and mortar 476 demolition waste 52, 77, 216 masonry 52, 471, 476 ratio 399 Regulation 2 Rehabilitation 8 Reinforced concrete buildings 557 Restraint 297 Reuse 113, 533 Re-utilization 471 Safety 570 Scrap material 510 Seismic capacity evaluation 8 Seismic strength 8 Setting time 399 Shear 383 Shrinkage 451 Site-clearing 130 Slates 587 Sound barriers 577 Stability 570 Standards 52, 113 Steel structural 486 pipes, restraint 297 Strength compressive 424, 437 flexural 424 tensile 424 Sulfur-coated anchor 307 Tall buildings 324 Technology 38, 553 Tensile strength 399

Index Third firing 511 Tiles 587 Timber 587 Vibration 160, 193 Waste asphalt mixture 520 ceramic material 510 concrete 520 construction 27, 61 demolition 27, 61, 533 materials 98 Waste management 533, 545 Water absorption 113 cannon 335 evaporation 412 jet 144, 335 reducer 412 Water/cement ratio 399 West bridge 577 Work 570

607