1、2001 FIFTH CANMET/ACI CINQUIME CANMET/ACI - INTERNATIONAL CONFERENCE 0 INTERNATIONALE RECENT ADVANCES IN CONCRETE TECHNOLOGY PROGRS RCENTS DANS LE DOMAINE DE LA TECHNOLOGIE DU BTON l i Fifth CANMET/ACI International Conference on Recent Advances in Concrete Technology Editor V. M. Malhotra internati
2、onal SP-200 DISCUSSION of individual papers in this symposium may be submitted in accordance with general requirements of the AC1 Publication Policy to AC1 headquarters at the address given below. Closing date for submission of discussion is October, 2001. All discussion approved by the Technical Ac
3、tivities Committee along with closing remarks by the authors will be published in the January/February 2002 issue of either AC1 Structural Journal or AC1 Materials Journal depending on the subject emphasis of the individua1 paper. The Institute is not responsible for the statements or opinions expre
4、ssed in its publications. Institute publications are not able to, nor intended to, supplant individual training, responsibility, or judgment of the user, or the supplier, of the information presented. The papers in this volume have been reviewed under Institute publication procedures by individuals
5、expert in the subject areas of the papers. Copyright O 2001 AMERICAN CONCRETE INSTITUTE P.O. Box 9094 Farmington Hills, Michigan 48333-9094 All rights reserved including rights of reproduction and use in any form or by any means, including the making of copies by any photo process, or by any electro
6、nic or mechanical device, printed or written or oral, or recording for sound or visual reproduction or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors. Printed in the United States of America Editorial production: Annett
7、e D. Pollington Library of Congress catalog card number: 2001090232 ISBN: 0-87031-029-1 PREFACE The Canada Centre for Mineral and Energy Technology (CANMET) of Natural Resources Canada, Ottawa, has played a significant role in Canada for over 35 years in the broad area of concrete technology. In rec
8、ent years, CANMET has become involved increasingly in research and development dealing with the supplementary cementing materials, high-performance normal-weight and lightweight concretes and alkali-aggregate reactions. As part of CANMETs technology transfer program, an international symposium on Ad
9、vances in Concrete Technology was sponsored jointly with the American Concrete Institute and other organizations, and held in Athens in May 1992. In June 1995, CANMET, in association with the Amencan Concrete Institute and other organizations in Canada and the USA sponsored the Second CANMET/ACI Int
10、ernational Symposium on Advances in Concrete Technology in Las Vegas, USA. For the Athens symposium, the CANMET publication “Advances in Concrete Technology” constituted the proceedings of the symposium; for the Las Vegas symposium, the proceedings were published by the American Concrete Institute a
11、s AC1 SP-154. In August 1997, CANMET, in association with the American Concrete Institute and other organizations in Canada and New Zealand, sponsored the Third CANMET/ACI International Symposium on Advances in Concrete Technology in Auckland, New Zealand. The main purpose of the symposium was to br
12、ing together representatives from industry, universities, and government agencies to present the latest information in the subject area of the symposium, and to explore new areas of neededresearch and development. Thirty-three refereed papers from 15 countries were presented. In addition to the refe
13、reed papers, more than 20 other papers were presented and distributed at the symposium. The proceedings were published as AC1 SP-171. In June 1998, CANMET, in association with the American Concrete Institute, Japan Concrete Institute, and several other organizations in Canada and Japan, sponsored th
14、e Fourth CANMET/ACI International Conference on Recent Advances in Concrete Technology in Tokushima, Japan. More than 80 papers from 20 countries were received and reviewed in accordance with the policies of the American Concrete Institute. Sixty-one refereed papers were accepted for presentation at
15、 the conference and for publication in AC1 SP-179. In addition to the refereed papers, more than 30 other papers were presented and distributed at the symposium. In July-August 2001, CANMET, in association with the American Concrete Institute and several organizations in Singapore, sponsored the Fif
16、th CANMET/ACI International Conference on Recent Advances in Concrete Technology in Singapore. More than 100 papers from more than 25 countries were received and reviewed in accordance with the policies of the American Concrete Institute. Forty-six refereed papers were accepted for presentation at t
17、he conference and are published here as AC1 SP-200. In addition to the refereed papers, more than 25 other papers were presented and distributed at the conference. Thanks are extended to the members of the CAIWET/ACI paper review panel which met in Torremolinos, Spain, in June 2000 to review the pap
18、ers. Without their prompt review and constructive comments, it would not have been possible to bring out the AC1 special publication for distribution at the symposium in Singapore. The cooperation of the authors in accepting reviewers suggestions, and in revising their manuscripts accordingly is gre
19、atly appreciated. Particular thanks are extended to H. S. Wilson, Consultant, Ottawa, and G. D. Brearley and M. Venturino, both of CANMET, for their help in the processing of the draft manuscripts. The help of Messrs. A. Bilodeau (Chairman), B. Fournier, and R. Chevrier (Members) of the Slide Review
20、 Panel is greatly appreciated. R. Hartford, Manager, Editorial carbon dioxide emissions; cement; concrete; recycling 1 2 Nagataki and lida AC1 Fellow, Dr. Shigeyoshi Nagataki is a Professor, Department of Civil Engineering and Architecture, Niigata University, Niigata, Japan. He is also Professor Em
21、eritus of Tokyo Institute of TechnoIoa. He has served as Vice President of JSCE, JSMS and JSDE and past chairman of committee on concrete at JSCE. He has written many papers on concrete technology. Dr. Kazuhiko Iida is a concrete specialist, Technology Center of Taisei Corporation, Yokohama, Japan.
22、He received his doctor of engineering degree from Niigata University in 2000. He has 33 years experience in the research of concrete for offshore structures and dams. He is a member of JSCE, JCI and JSDE. INTRODUCTION The concept of sustainable development has been proposed for what has been called
23、our finite deteriorating planet”. This concept involves reducing the environmental burden to the greatest extent possible and building a society based on recycling. In the concrete industry as well, recycling is currently being studied for demolished concrete. This material is already being reused a
24、s road base course and foundation material. In the future, however, this demolished concrete must be recycled as concrete agregate, and recycling must also be exended to include the cement in the concrete as well. CONCRETE RECYCLING IN JAPAN According to the Ministry of Welfare, 400 million tons of
25、industrial wastes are produced in Japan each year (Fig. 1). The construction industry is a major source of these wastes. The industries are currently promoting waste reduction and recycling, and so the quantity of final disposal wastes now represents about 17% of the total. However, the capacity of
26、final disposal sites is currently limited to only three years. A survey conducted by the Ministry of Construction in 1995 found that Recent Advances in Concrete Technology 3 the total quantity of construction wastes produced each year came to nearly 100 million tons, and demolished concrete was the
27、leading component of these wastes, accounting for 37 million tons (Fig. 2). While 65% of concrete wastes are recycled, they are reused mainly as road base course and foundation material, and almost none is recycled back into concrete. Almost all of the concrete structures in Japan have been built ov
28、er the last 50 years. As a result, the quantity of demolished and discarded concrete is expected to increase dramatically in the coming years (Fig. 3) (i). For this reason, there are many ongoing researches aiming to recycle waste concrete as concrete aggregate. However, in many cases the characteri
29、stics of the original concrete are not well known, so that the properties of the concrete made with recycled aggregates are not predictable. Furthermore, even recycling of demolished concrete as concrete aggregte becomes possible, it would not be adequate for a closed recycling system to turn old co
30、ncrete back into new concrete. Accordingly, special types of fully recyclable concrete that use limestone aggregate (2) and recycling of the cement in demolished concrete as well (3) have been proposed. The objectives of the study are to clear the properties of recycled aggregate concrete and to pro
31、pose new recycling system that covers cement as well. RECYCLED CONCRETE AS AGGREGATE Onginal Concrete The original concrete prepared for this investigation contained normal portland cement, river sand, crushed stone and an air-entraining and water- reducing admixture. The properties of the original
32、aggregates are shown in Table 1. Original concrete cubes for producingrecycled aggregate, 300 mm by 300 mm by 300 mm in size, were made with three mixture proportions representing high, moderate, and low strength as shown in Table 2. After water curing the original concrete cubes were demolded at th
33、e age of 28 days and exposed outdoors. They were processed into recycled aggregate at the ages of 1 month, 1 year, and 2 years. 4 Nagataki and lida At the same time, cylindrical specimens 100 mm in diameter and 200 mm in length were fabricated. The properties of the original concretes are shown in T
34、able 3. The compressive strength of concrete specimen at 28 days under standard curing conditions were 60.7 MPa for HSC, 49.0 MPa for MSC, and 28.3 MPa for LSC, respectively. Production of Recvcled Agmegate The crushing was carried out in accordance with the flow chart shown in Fig.4. The original c
35、oncrete underwent primary crushing with a jaw crusher and secondary crushing with an impact crusher. This stage is referred to as crushing . level 1. Further crushing stages using an improved jaw crusher with a strong grinding effect once and twice are referred to as crushing level 2 and crushing le
36、vel 3, respectively. The recovery ratios of coarse aggregate for crushing level 1,2, and 3 were 6O%, 45%, and 30%, respectively, with the mass of the original concrete being loo%, in which the mass ratio of original coarse aggregate was approximately 43%. The strength of the original concrete had no
37、 appreciable effects on these recovery ratios. The properties of the recycled coarse aggregates produced are given in Table 5. Generally speaking using higher strength concrete and a higher crushing level can produce recycled coarse aggregate of better quality. However, the aggregates did not satisf
38、y the Japanese Industrial Standard (4) for concrete aggregate in terms of density and water absorption. Strength Characteristics The materials used with recycled coarse aggregate comprised normal portland cement, river sand, and an air-entraining and water-reducing admixture. The river sand was the
39、same as used in the original concrete. The mixture proportions are given in Table 4. When the water-binder ratio was 0.35 or less, silica fume and an air-entraining and high-range water-reducing admixture were used. Fig. 5 shows the relationship between the binder-water ratio and the 28-day compress
40、ive strength of recycled concrete using aggregtes reclaimed at i month Recent Advances in Concrete Technology 5 with 3 levels of crushing. The compressive strength of concrete containing recycled coarse aggregate depends on the compressive strength of the original concrete. The compressive strength
41、of recycled aggegate concrete was similar to original aggregate concrete and retained a linear relationship with the binder-water ratio of up to 1.5 times the 28-day strength of the original concrete. The level of crushing had no appreciable effect on the compressive strength. Fig. 6 shows the relat
42、ionship between the binder-water ratio and the 28-day compressive strength of recycled concrete using aggregates reclaimed at 1 month, lyear, and 2 years with crushing level 2. The age of concrete at the time of crushing (crushing age) had no appreciable influence on the compressive strength of recy
43、cled concrete using aggregate made from the original concrete with high strength (HSC) and moderate strength (MSC). For the original concrete with low strength (LSC), the compressive strength of recycled concrete was somewhat influenced by crushing age. The concrete made with the recycled aggregate
44、reclaimed at 1 year or 2 years exhibited higher compressive strength in comparison to the recycled aggregate reclaimed at 1 month. Resistance to Freezing and Thawing The materials used were the same as those used in the test of concrete strength. The mixtures were proportioned to provide a slump of
45、8 +2.5cm and air content of 4.5f ISYO, with the water-cement ratio being constant at 0.55. The freezing and thawing test procedure was in accordance with ASTM C 666 Procedure A, though the test was initiated at an age of 28 days. Fig. 7 shows the changes in the relative dynamic modulus with freezing
46、 and thawing cycles for the recycled concrete using aggregates reclaimed at 1 month with 3 levels of crushing. Recycled aggregate concrete showed larger losses in the relative dynamic modulus than the original aggregate concrete. The losses were larger for aggregates made from low and moderate stren
47、gth concrete. Large losses were also found in the case where the crushing level was low. Though the resistance to freezing and thawing decreased, the durability factor was greater than 70 at 300 cycles, which is generally considered as satisfactory. 6 Nagataki and lida Fig. 8 shows the changes in th
48、e relative dynamic modulus with freezing and thawing cycles for the recycled concrete using aggregates reclaimed at 1 month and 1 year with crushing level 1. At crushing age of 1 year, the resistance to freezing and thawing of recycled aggregate concrete was improved and similar to original aggregat
49、e concrete. Fig. 9 shows the relationship between the mass losses by the soundness test (5) on coarse aggregate and the durability factor of the concrete using these aggregates at 300 cycles. For crushing age of 1 month, the mass losses correlated relatively well with the durability factor. Though the threshold value for mass losses is generally assumed to be 12%, a mass loss of as high as 60% of recycled coarse aggregate provided sufficient resistance to freezing and thawing for the concrete. For crushing age of 1 year, the durability factor was retained over 90 regardless of the soun
