Influence of recycled fines on strength and alkali–silica reactivity in cement composites

Abstract

This study evaluated characteristics of mortars using recycled construction and demolition waste (CDW) from the industry as fine recycled aggregate in replacement of natural sand (NS). Mixes with replacements in volume of 20 and 100% CDW and a control mix with just NS were tested for their compressive and flexural strength and alkali–silica reactivity (ASR). For mechanical strength, experimental results showed satisfactory performance for 20% CDW content. Concerning the ASR test, mortars with CDW performed better than the control, demonstrating a general innocuous behaviour for ASR. Scanning electron microscopy and energy-dispersive X-ray analysis were performed on aggregate and mortar samples before and after the ASR test and confirmed the results, demonstrating that the attack was more severe in the samples with the greatest amount of siliceous material in the aggregate. The results demonstrate the viability of the use of CDW fine aggregate replacement in mortars, envisaging the possibility of its incorporation in concrete.