Influence of mixed recycled aggregate on the physical - mechanical properties of recycled concrete

This article discusses the findings of a feasibility study on the partial replacement of natural coarse aggregate with a poor quality recycled aggregate from construction and demolition waste in the manufacture of concrete of 30 MPa strength grade. The mixed recycled aggregate used had a high asphalt and floating material content. Workability, density, compressive and tensile strength, water absorption and sorptivity were studied in a series of concretes containing 25 or 50% of the recycled aggregate with and without floating materials. The results showed that using up to 50% of the recycled aggregate had no adverse effects on fresh concrete workability. Most of the physical and mechanical properties of hardened concrete (strength, density, sorptivity and water absorption) were observed to decline with rising recycled aggregate replacement ratios and floating particle content. Overall, considering the strength and other properties achieved, the concretes containing the mixed recycled aggregates studied were found to be apt for housing construction. The technical, economic and environmental improvements stemming from the potential replacement of natural coarse aggregate with such recycled construction and demolition waste would contributed to the sustainability of the construction industry.