The reduction and utilization of waste and by-products is one of many challenges facing mankind in the modern world. This paper consists of an overview of the handling of the world's concrete waste and is concerned with unbound applications of blended construction and demolition (C&D) rubble for pavement bases and sub-bases in road construction. The problems of recycling mixed wastes are considered and global perspectives are presented on the use of C&D rubble. The paper proposes that studies should be carried out in order to research the technical properties of blended C&D rubble, which the authors believe would be economically and environmentally justifiable in promoting the widest possible range of recycled products for road construction.

This paper addresses first the generation of construction waste in Japan, the extent of recycling, and the shortage of landfill capacity. Second, it chronicles the trend of recycling concrete rubble from 1970 until today. Third, it discusses methods of manufacturing recycled concrete aggregate and introduces the recently developed equipment and methods to produce good aggregate for concrete. Fourth, the problems associated with the use of recycled concrete aggregate are mentioned. Also, the utilization of concrete fines, eco-concrete, and slurries from ready-mix concrete plants are addressed. Land in Japan is very scarce and resources limited. These conditions are similar to those faced by Europeans and Scandinavians. Therefore, this paper should be of interest to those countries and their efforts to build closed-loop material cycles.

Three series of flowable slurry mixtures were made, each series with three different sources of wood ash (W-1, W-2, and W-3). The series of mixtures were: low-strength (0.3 to 0.7 MPa), medium-strength (0.7 to 3.5 MPa), and high-strength (3.5 to 8 MPa) mixtures. Tests were performed for flow, air content, unit weight, bleeding, settlement, compressive strength, and water permeability. Wood ashes W-1 and W-3 caused expansive reactions in CLSM mixtures resulting in little or slight (average 1%) net shrinkage of CLSM. Wood ash W-2 caused either significant net swelling (15% for Mixture 2-L, and 21% for Mixture 2-M) or no shrinkage (Mixture 2-H) of CLSM. The 91-day compressive strength of low-strength, medium-strength, and high-strength slurry mixtures was in the ranges of 0.38 to 0.97 MPa, 1.59 to 5.28 MPa, and 4.00 to 8.62 MPa, respectively. Overall, the slurry mixtures showed an average increase in strength of 150% (range: 25% to 450%) between the ages of 28 days and 91 days. This was attributed to pozzolanic and cementitious reactions of wood ash. In general, water permeability of CLSM mixtures decreased with age.

The paper consists of an overview of the development of techniques for recycling concrete. Demolition, processing and the recycling of the resulting materials are often analyzed separately. "High quality" recycling of concrete waste does not always correspond to production/use of the product with the highest value, but rather the most feasible product in a specific project or region. It is by analyzing the whole disposal/supply-chain, including the substituted material, that the best effects of recycling can be achieved. Overviews of methods for environmental evaluations as well as economic considerations are presented. Integrated demolition waste management in Kosovo and an analysis of the potential market in Hong Kong are presented as examples of the worldwide market for recycled materials. Issues regarding the handling of polluted materials will be discussed from a practical point of view. Moreover, some aspects to soncsider regarding future demolition when producing new concrete products are presented.0

This publication contains 11 papers which promote and encourage the use of recycled concrete and other materials in concrete construction, taken from presentations at the 2003 ACI Spring Convention in Vancouver, Canada. Specific subject areas include the global perspective, challenges and opportunities of concrete recycling, the barriers to recycling concrete in highway construction, and current practices in the European Union, Japan, and USA. This publication also contains research papers on the use of recycled glass as aggregates for architectural concrete, recycled scrap tire rubber, flowable slurry containing wood ash, recycled latex paint as an admixture, crushed stone dust in production of self-consolidating concrete, a new binder using thermally treated spent pot liners from aluminum smelters, and the durability of concrete containing recycled concrete as aggregates that had shown distress due to alkali-silica reaction. Note: The individual papers are also available as .pdf downloads.. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP219