Feasible techniques for valorisation of construction and demolition waste for concreting applications

Considering that the production of concrete is a resource and energy intensive process, the utilisation of recycled aggregates is one of the approaches that can be adopted to circumvent the issue of high extraction of natural aggregates (NA). In addition, construction and demolition (C&D) wastes are dumped in landfills, resulting in social, environmental and economic difficulties. The present study focuses on the use of recycled concrete aggregates (RCA) from C&D waste as coarse aggregates for concreting applications. A low-cost and simplified treatment method was used for valorise waste generated from demolition of concrete structures. Crushed RCA were placed in a drum type concrete mixer and rotated with water at a speed of 10 rpm for 30 min. Results showed that the remaining adhered mortar adversely affects aggregate properties, with a reduction in density and increases in porosity, aggregate impact value, Los Angeles abrasion value and water content compared with those of NA. The complete substitution of coarse aggregates with RCA reduced slump, density, dry and wet compressive strength by 47%, 1.8%, 28% and 27%, respectively, but enhanced water absorption by up to 5.6%. Results showed that proposed technique provides feasible and cost-effective way for valorisation. The manufacture of quality RCAs is essential and the removal level of adhered mortar will determine RCA quality, and consequently, the quality of concrete. To meet standard requirements for structural concrete, RCA can be used to replace NA by implementing proper control of the proposed valorisation technique, subsequently conserving natural resource for sustainable future.