Performance of recycled aggregate in concrete from demolishing waste

Abstract

Demolition of old structures to make way for new and modern ones is common features in metropolitan areas due to rapid urbanization. However, very little demolished concrete is recycled or reused. The strict environmental laws and lack of dumping sites in urban areas on one hand are making the disposal of demolition wastes problematic while on the other hand the quarrying of raw materials is becoming difficult. The present research work is an experimental investigations carried out to evaluate the effect of partial replacement of cement, fine aggregate and coarse aggregate by different parts of demolished wastes on strength and workability of concrete made. For the study, design mix concrete of grade M25 (Referral concrete) was prepared using IS: 10262-2009. Thereafter, the replacement of different constituents of concrete, one at a time was carried out by replacing these with the different sieved fractions of crushed demolition waste. The compressive strength at 7, 14 and 28 days, and workability in terms of slump value were measured. The compressive strength of these mixes was measured on 150mm cubes. The compressive strength of recycled concrete (FAR concrete) with Demolition Waste in Concrete 20% fine aggregate replacement by demolition waste fine aggregate at 28 days is comparable to that of referral concrete. The compressive strength of recycled concrete (CAR concrete) made using 30% of demolition waste coarse aggregate is almost like referral concrete. Further, the results indicate that still higher replacement of the constituent materials is possible without much compromising the 28 days strength and workability.