SUSTAINABLE CONCRETE RECYCLING

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. The sheer amount of concrete in use and in stock compared with other building materials brings up the issue of the enormous amount of waste generated when concrete is disposed of. Besides, aggregate resources are beginning to be depleted at a high speed. Concrete has conventionally been regarded as being difficult to recycle. The construction industry has addressed these problems and carried out research and development regarding the recycling of concrete since the s. Recycling technology has been shifting from simple crushing into scrubbing with somepreparations to produce high-quality recycled aggregate for structural concrete, and recycling of concrete in a completely closed-loop has now become technically feasible. This paper profiles various concrete related problems from the viewpoint of resource recycling, reviews the development history of concrete recycling in Japan from the viewpoint of the properties of recycled aggregate concrete and the environmental impact caused in life cycle. Then the paper proposes a design concept for closedloop recycling and presents the outline of completely recyclable concrete, with which closed-loop circulation of component materials is realized. The paper also introduces a newly developed technology realizing sustainable resource recycling with low energy consumption in concretestructures.

Keywords:

Concrete waste , Aggregate resource depletion , Closed-loop recycling , Recycled aggregate , By-product powder , Completely recyclable concrete , Aggregate surface modification , Microwave heating , Energy consumption