Effect of recycled concrete powder on strength, electrical resistivity, and water absorption of self-compacting mortars

Abstract

The chemical composition of recycled concrete powder (RCP) and the physical properties of self-compacting mortar with RCP as supplementary cementitious materials (SCMs) were investigated in detail. RCP was obtained by crushing and sieving recycled concrete from demolished buildings; particles that passed No. 4 sieve (4.75 mm aperture) were then ground to a fineness such that 80% particles could pass through No. 325 sieve (45 µm aperture). The RCP partially replaced ordinary Portland cement (OPC) in varying ratios of 20%, 40%, and 60% by weight of powder in self-compacting mortars in which the water to powder ratio was maintained at 0.35. The compressive strength, electrical resistivity, porosity, and water absorption of the RCP self-compacting mortars were investigated. The results indicated that the RCP was reactive, having a strength-activity index of 89.4% and 87.2% at 7 and 28 days, respectively. The porosity and water absorption coefficient increased, and electrical resistivity decreased with an increase in the RCP content. Based on the results of this study, the optimum RCP replacement ratio with minimal negative effect on the compressive strength is up to 20%.