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.

With population growth and urbanization, the space available for installation of civil infrastructure is rapidly decreasing. There is need for a more efficient use of underground space, which involves the construction of tunnels and other underground structures. Due to space constraints, many underground infrastructure projects in the future will be located in rock/soil with time-dependent behavior and/or under high overburden pressure. A deformable supporting system that can serve as a buffer layer for protecting tunnel linings and buried structures from time-dependant deformations of the excavated rock/soil will therefore be needed. This study investigates the possible use of cement mortars containing crumb tire rubber to develop a flexible interface material for such applications. The effects of the water/cement ratio (w/c) ratio, rubber content and particle size on the mechanical properties of the mortars were studied using uni-axial and tri-axial compression tests. A statistical factorial experimental was designed to obtain response surfaces for the parameters under study. The findings of this research suggest that cement mortars containing ground tire rubber have superior ductility and may be used to accommodate deformations around tunnel linings, pipelines, and other buried infrastructure.

The use of mineral admixtures as addition to or replacement of portland cement has been attracting a great amount of interest in recent years. Using suitable quantities of those minerals not only improves some properties of fresh and dry concrete, but also reduces portland cement demand and helps solve several environmental problems. Aluminium production in various parts of the world generates a considerable amount of waste which contains leachable cyanides and fluorides that cause a serious environmental problem. This paper presents a study of the effect of substituting a percentage of cement by a glass flit in mortar and in concrete. The term glass frit refers to spent pot liners resulting from the aluminium production process, that have undergone various treatments and have been ground to the fineness of a cement. The various results obtained in different tests conducted on mortar and concrete showed that glass frit has a remarkable reactivity potential and an interesting rheological behaviour. Replacing a percentage of cement by glass frit improves workability and strengths of mortar and concrete. For a given slump, concrete containing 25% of glass frit requires 50% less water reducer than that of control concrete. The compressive strengths developed in mortar or in concrete are very similar or even greater than those made with portand cement only or those incorporating blast furnace slag with equivalent cement replacement rate.

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

Crushed limestone dust is a waste material from the production of concrete aggregate by crushing quarried limestone rocks. The dust is usually less tan 1% of the aggregate production. Although it is coarser than common cementing materials such as as Portland cement, coal fly ash and ground blast furnace slag, it is fine enough to cause many problems during materials handling and disposal. Laboratory results have indicated that crushed limestone dust can be used to produce self-consolidating concrete (SCC) with properties similar to those of SCC containing coal fly ash. . Due to the differences in morphologies and particle size distribution, the mix design has to be modified when crushed stone dust instead of fly ash or ground blast furnace slag is used. Fresh SCC mixtures containing limestone dust loses its flowability and sets faster than the mixtures containing fly ash due to the acceleration of the hydration of Portland cement by the limestone powder. SCC containing limestone dust exhibited strengths similar to that containing fly ash during the first seven days, but the former exhibited lower strength than the latter at 28 and 90 days due to the contributions from the pozzolanic reactions between coal fly ash and lime released from the hydration of Portland cement. The former also have lower autogenous and drying shrinkages than the latter.