Coefficient of Thermal Expansion of RCA Concrete Made by Equivalent Mortar Volume

Abstract

Featured Application Coefficient of thermal expansion of RCA concrete prepared by the equivalent mortar volume mix design was over 6-7% lower than that of RCA concrete by conventional mix design, at the same RCA replacement ratio. Additionally, it was similar to or 1-2% lower than that of the natural coarse aggregate concrete. The present study was conducted to experimentally verify if the coefficient of thermal expansion (COTE) of recycled aggregate concrete is proportional to the volume of the original virgin aggregate in the total recycled aggregate concrete mix. Three types of recycled concrete aggregate (RCA) were crushed from: railroad concrete sleepers; precast (PC) culverts; commercial recycling plant. RCA concretes were mixed using two concrete mixing methods: conventional mix method and equivalent mortar volume (EMV) method. And by varying the replacement ratio, three test series were made. Test results showed that at the same RCA replacement ratio of 68%, the COTE of RCA concrete prepared by the EMV mix design was over 6-7% lower than that of RCA concrete made with the conventional mix method. It was also similar to or 1-2% lower than that of the natural coarse aggregate concrete. This may be because the conventional mix method does not take into account the residual mortar content attached to RCA. This results in a decrease in the volumetric ratio of the original virgin aggregate and a relative increase in the volumetric ratio of the mortar (or cement paste).