Recycling and reconstitution of construction and demolition waste

The annual production of construction demolition (C&D) waste in the UK amounts to 109 million tonnes. This accounts for over 60% of the UK's total waste. Rather than send C&D waste to landfill, increased environmental awareness has led to pressure to use these materials as a resource. There are two ways in which C&D waste can be developed for use in concrete; (i) as recycled aggregates (a commonly perceived approach) or (ii) as a cement component (a novel approach). This paper reports on recent research undertaken by the Concrete Technology Unit (CTU) at the University of Dundee to promote these methods for using C&D waste. Research, carried out since 1996, to show the suitability of coarse recycled aggregates in concrete is described, including a full-scale demonstration that used recycled concrete aggregate as the sole coarse aggregate in a concrete pavement designed for a XF4 exposure class. In addition, the paper reports on research to render C&D waste suitable for use as a cement constituent. The processing options examined are ultrafine grinding and thermal processing. Preliminary results of an ongoing study are presented, along with a discussion of their significance and of the environmental impact implications.