The influence of the initial moisture content of lightweight aggregate on internal curing

► Details of internal curing are discussed regarding LWA moisture condition. ► LWA that is not presoaked can absorb fluid from the cement paste prior to set. ► This absorbed water can return to the system as internal curing (IC) water. ► When LWA is vacuum saturated it is harder for some IC water migrate into paste. ► When properly adjusted, all mixtures showed good internal curing performance. This paper explores the potential for manufacturing internally cured concretes with lightweight aggregate (LWA) that has different initial moisture contents prior to mixing: oven-dry, 24h pre-wetted, and vacuum saturated. Results show that when LWA is used in an oven-dry condition it can absorb water from the paste prior to set which will be returned to the system as internal curing water. When mixture proportion adjustments are properly made to account for the water absorbed by the aggregate before setting, the mixture can provide internal curing benefits. These beneficial aspects include increased hydration which leads to higher compressive strength, reduced water absorption, and reduced electrical conductivity (permeability). Further, these benefits include reduced autogenous shrinkage and a lower propensity for early-age cracking.