Improving the fluid transport properties of heat-cured concrete by internal curing

Heat curing accelerates cement hydration, leading to a coarse pore structure. This undermines the transport properties of concrete, which is essential in evaluating concrete durability. In this study, effect of saturated lightweight fine aggregate (LWFA) on the mechanical and transport properties and the microscopical characteristics of heat-cured mortar was investigated. Results show internal curing by LWFA promotes cement hydration and benefits the formation of denser hydration products and the interfacial transition zone (ITZ). This is evidenced by a reduced water absorption and chloride diffusion coefficient and an improved compressive strength at later ages. Moreover, the long-term performance of heat-cured mortar with internal curing is similar to and even better than that of the mortar cured at ambient temperature, which can be explained by the combination of the denser hydration products formed at heat curing period and the efficiency of internal curing at the subsequent curing period.