The Way Concrete Recycling Should Be Fuminori Tomosawa1, Takafumi Noguchi2 and Masaki Tamura3
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Journal of Advanced Concrete Technology Vol. 3, No. 1, 3-16, February 2005 / Copyright © 2005 Japan Concrete Institute 3 Invited paper The Way Concrete Recycling Should Be Fuminori Tomosawa1, Takafumi Noguchi2 and Masaki Tamura3 Received 20 September 2004, revised 1 December 2004 Abstract Providing excellent performance as a structural material, concrete has long been deemed essential for modern civilization and recognized as a material that will continue to maintain and support the development of human society. Now that recycling of concrete in a completely closed loop has become technically feasible, concrete is being seen in a new light. This paper reviews the background to this development referring to changes in social systems and the introduction of new technologies. In view of the fact that consideration of the global environment will be required in the future at every step of the production of concrete and concrete structures, this paper goes on to overview the methods for identifying social needs related to concrete structures, the manner in which production systems of structures should meet such social needs, lifecycle design techniques for structures, and techniques for expressing the environmental performance of structures. The authors finally discuss the nature of true recycling and a truly recycling-oriented society, based on the above-mentioned discussions. 1. Introduction the establishment of a full-fledged recycling system, as the recycling process principally consisted of simply Concrete is a useful cast material that has a close affinity crushing the waste concrete, which inevitably entailed a to natural materials, consists of only common compo- degradation in quality. Nevertheless, the goal of technical nents, and hardens by itself just by being in contact with development shifted in the mid-1990s to recycling of water in a natural environment. After hardening, it turns concrete into a material having qualities equal to those of into a material with sufficient strength and durability to normal concrete, and recycling of concrete in a com- be applicable to various structures. Recent technology pletely closed loop has now become technically feasible. for high-strength concrete has realized a compressive This paper reviews this development and introduces strength exceeding 150 N/mm2 for reinforced concrete the new technology while discussing the meaning of true skyscrapers. recycling and a truly recycling-oriented society. Concrete has thus grown to be an essential material for modern society with great commonness, usefulness, and 2. Current status and problems of excellent performance characteristics as a structural construction waste material, and will continue to be vital for maintaining and developing human society. 2.1 Analyses of construction waste However, the sheer amount of concrete in use and in According to a White Paper on the Environment, the total stock compared with other materials brings up the issue material input of Japan ranged from 2.0 to 2.2 billion tons of the enormous amount of waste generated when con- annually in 1999 and 2000, of which 1.0 to 1.1 billion crete is disposed of. This issue has existed for a long time, tons (50%) were accumulated every year in the form of as concrete has conventionally been regarded as being buildings and civil structures. These figures indicate the difficult to recycle. Being a major user of concrete, the enormous consumption of resources by the construction construction industry has addressed this problem and car- industry compared with other industries. The production ried out research and development regarding the recy- of concrete, a primary construction material for forming cling of concrete since the 1970s in cooperation with the modern nations, amounted to approximately 500 million public sector. However, the uses of recycled products tons (including 300 million tons of ready-mixed con- have been limited to road bottoming, without leading to crete) in 2000 in Japan, accounting for nearly 50% of the annual resource consumption of the construction industry. In other words, concrete accounts for nearly 25% of 1Professor, Faculty of Science and Engineering, Nihon Japan's total material input. Incidentally, the construction University, Japan. industry's consumption of steel and wood, two other primary construction materials, amounted to 32,530,000 E-mail: [email protected] 3 2Associate Professor, Dept. of Architecture, Graduate and 17,000 tons (34,219 m volume, converted by as- School of Engineering, The University of Tokyo, Japan. suming the density to be 0.5), respectively, in 2001, both 3Research Associate, Dept. of Architecture, Graduate far less than concrete consumption. School of Engineering, Tokyo Metropolitan University, Furthermore, the amount of waste in Japan totaled Japan. approximately 458,360,000 tons in 2000 (general waste: 4 F. Tomosawa, T.Noguchi and M. Tamura / Journal of Advanced Concrete Technology Vol. 3, No. 1, 3-16, 2005 Non-industrial Other waste Output Input 7300 (16%) 5236 (11%) Chemical industry Elec.,Gas,Heat, Construction waste Output 1700 (4%) Water supply Input Steel industry Total waste Do Check industry Final disposal of 1280 (28%) 2700 (6%) in Japan Illegal dumping 9200 (20%) industrial waste Pulp,Paper 45836 of industrial Construction Other Other waste 2700 (6%) 10,000 tons 4500 waste Plan Action (Ratio) 3220 (72%) 10,000 tons 16.2 (40%) Output Input 40.3 24.1 (60%) (Ratio) 10,000 tons Construction Agriculture (Ratio) Input Output 7900 (17%) 9100 (20%) (a) (b) (c) Fig. 1 Construction waste analyses. 52,360,000 tons; industrial waste: 406,000,000 tons) as shown in Fig. 2, an enormous amount of demolished shown in Fig. 1 (a). Waste from construction accounted concrete lumps will be generated in the near future from for approximately 20% (79,000,000 tons) of the indus- concrete structures mass-constructed during Japan's trial waste. Moreover, in 2000, construction waste ac- rapid economic growth being, which are doomed to counted for nearly 30% (12,800,000 tons) of the demolition due to durability problems. Moreover, road 45,000,000 tons of industrial waste destined for final construction is decreasing and the method of repair is disposal sites as shown in Fig. 1 (b) and approximately expected to shift from replacing to milling and applying 60% (241,000 tons) of the 400,000 tons of illegally an overlay. These trends will lead to an imbalance be- dumped industrial waste as shown in Fig. 1 (c). As con- tween the supply of demolished concrete and the demand crete lumps account for approximately 42% (35,000,000 for road bottoming. Also, the volumetric reduction of tons) of total construction waste, approximately 8% of future infrastructures based on population estimation and total waste in Japan therefore consists of concrete lumps. the extension of the service life of the existing stock by As stated above, concrete accounts for large percent- increased succession, utilization, and conversion will ages of both resource input and waste discharge. Thus keep on reducing the amount of new construction of promotion of the recycling of demolished concrete is a structures and concrete production. Accordingly, this pressing social issue in Japan where the remaining ca- will culminate in the need to recycle aggregate into ag- pacity of landfill sites for industrial waste is diminishing gregate for concrete, and it is no exaggeration to say that every year. recycled aggregate can account for the greatest part of future aggregate for concrete. It is therefore vital to 2.2 Destinations of demolished concrete convert recycling from quantity-oriented to qual- With the aim of solving the construction waste problem, ity-oriented recycling as proposed in the Promotion Plan the Japanese Ministry of Land, Infrastructure and for Construction Waste Recycling 2002 formulated by Transport (MLIT, formerly the Ministry of Construction) the MLIT in 2002. In other words, it is necessary to find formulated an Action Plan for Construction Byproducts optimum recycling methods with due consideration to (Recycling Plan 21) in 1994, which called for halving the the material balance, while promoting the production and amount of final disposal of construction waste by 2000, supply of high-quality recycled aggregate. and a Promotion Plan for Construction Waste Recycling It should also be noted that a large discrepancy exists in 1997, which includes principles, objectives, and between the amount of demolished concrete generated at measures for further promoting recycling of construction waste. Thanks to such active and continual policies, 6 construction waste discharge began to decrease, with the Concrete production recycling ratio of concrete lumps and asphalt concrete 5 lumps exceeding 95%. In view of the still low recycling ratios of waste wood, slime, and mixed waste generated 4 by construction, the MLIT then enforced the Basic Law Demolished concrete for Establishing a Recycling-based Society, the Con- 3 struction Material Recycling Act, and the Law on Pro- From buildings moting Green Purchasing. 2 However, concrete lumps, which boast a high recy- cling ratio, are entirely destined for bottoming and 1 grading adjusters for arterial high-standard highways, From civil structures 0 urban expressways, and general roads designated by the 1950 2000 2050 year Road Bureau of the MLIT. The quality of recycling is therefore completely different from that of asphalt con- Fig. 2 Estimated amount of demolished concrete (Iida, K. crete lumps, for which level-cycling is accomplished. As 2000). F. Tomosawa, T.Noguchi and M. Tamura / Journal of Advanced Concrete Technology Vol. 3, No. 1, 3-16, 2005 5 450 produced the Standard for the Use of Recycled Aggre- Estimated generation of aggregate and 400 stone per unit input gate and Recycled Concrete (Draft) in 1977. This stan- Statics discharge of concrete lumps 350 from demolished concrete structures dard requires that the oven-dry density and water ab- sorption of recycled coarse aggregate be not less than 2.2 300 g/cm3 and not more than 7%, respectively, and those of 250 Potential generation recycled fine aggregate be not less than 2.0 g/cm3 and 200 not more than 13%, respectively.