Materials Recycling in Construction: A Review of the Last 2 Decades Illustrated by the WASCON Conferences

This paper reviews materials recycling in construction on the basis of the proceedings of the WASCON conferences that were organized every three years since 1991. To do so, (1) Environmental aspects; (2) Technical aspects of development and application of products; (3) Development of tools; and (4) Developments on industrial scale, are addressed. It is shown that the WASCON conferences and their proceedings allowed and encouraged worldwide exchange of information. Much attention was devoted at the consecutive conferences to assessment of the environmental impact of recycling in construction, mainly due to leaching. Two types of waste with a high annual production rate that received much attention at WASCON, construction and demolition waste, and municipal solid waste incineration bottom ash, are discussed in depth. It is shown that for recycling in construction of both types of waste significant progress was made. It appears from this paper that in the period considered (1991-2012) construction with alternative materials made much progress, that a lot of R&D, leading to technical development was carried out, and that also several developments at industrial scale were reported. Moreover, recycling is moving more and more from downcycling to high value use, to 'cradle to cradle'.