Studies on Performance of the Treated Recycled Concrete Coarse Aggregate in High-Strength Concrete

The rapid growth in population and urbanization is resulting in the ever-increasing demand for built infrastructure thereby the concrete across the world. Demolition of the old and deteriorated concrete structures has also been increasing day-by-day resulting in generation of enormous amounts of Construction and Demolition (C & D) waste posing severe threat to the environment urging for immediate action. Hence, there is a need to convert this waste into a useful material in order to reduce environmental impact caused by the C & D waste. Also, the use of this C & D waste in concrete can reduce the dependence on the natural materials like river sand for fine aggregate and crushed granite for coarse aggregate resulting in conservation of natural resources leading to sustainable construction. This present study focuses on effective utilization of the C and D waste in concrete. In order to overcome the deficiency of reduction in mechanical properties of concrete by using recycled aggregates, aggregate treatment techniques have been adopted in this present study focussing on improving the aggregate properties. In the present study, aggregate treatment techniques viz., acid treatment (using HCl), base treatment (using NaOH) and mechanical treatment techniques were employed for coarse aggregate. The aggregate properties like water absorption, specific gravity, bulk density, resistance to abrasion, impact, and crushing values were determined. When compared to the natural aggregates, the deteriorated properties of recycled aggregates were significantly improved upon treatment using the different techniques. The treated recycled coarse aggregates have been used in two different grades of concrete i.e. M30 (standard strength) and M65 (high-strength concrete) with 100% replacement for natural aggregate. With this treated recycled coarse aggregate, the concrete properties (hardened state) were also significantly improved when compared to that of untreated recycled aggregate concrete.