Enhance the durability of heat-cured mortars by internal curing and pozzolanic activity of lightweight fine aggregates

Abstract

Heat curing is a technology that has been widely used for concrete employed in urban infrastructures since it allows to achieve both high production efficiency and a high degree of control on the concrete performance. Nevertheless, some limitations in the light of degraded microstructures and low hydration degrees of cement at a later stage hinder the durability of it. In this paper, a type of lightweight fine aggregate (LWFA) that has a porous aluminosilicate structure was employed to address this issue. The substitution of LWFA for a portion of the conventional sand to provide internal curing (IC) and pozzolanic reaction for the heat-cured mortars was examined with respect to its influence on the chloride penetration resistance. Experimental measurements of chloride ions absorption and penetration depths are combined with extensive microstructural characterization such as BSE, XRD and TG analyses to determine the synergistic effect of LWFA impacted on heat-cured pastes and mortars. For heat-cured mortars employing 53% LWFA and 47% conventional sand as aggregates by volume, the coefficients of rapid chloride migration were estimated to be reduced by 20.2% and 41.4% at 28 d and 60 d, respectively.