Saturated Lightweight Aggregate for Internal Curing in Low w/c Mixtures: Monitoring Water Movement Using X‐ray Absorption

Abstract

Abstract: The susceptibility for early‐age shrinkage cracking in low w/c concrete has led to the development of new technologies that can reduce the risk of cracking. Internal curing, one of these new technologies, uses saturated lightweight aggregate to supply ‘curing water’ to low w/c pastes as they hydrate. While significant research has been performed to determine the effects of internal curing on shrinkage and stress development, relatively little detailed information exists on movement of water from the LWA to the paste. The details of when water moves and how far it travels has implications on the volume of aggregate and the aggregate gradation that should be used in mixture proportioning with internal curing. This study examines the timing of the release of water from saturated lightweight aggregate (LWA) and the distance that water can travel. X‐ray absorption is used to determine the time at which water is drawn out of the lightweight aggregate and the loss of water is traced over time. Further, it examines the travel distance of the water into the paste. Experimental details associated with the X‐ray technique are provided to describe the importance of specimen alignment. Further, in sealed specimens, the results indicate little water movement prior to set. After set however, the distance of water movement was as much as 2 mm. The importance of water movement is discussed in terms of mixture proportioning and its influence on shrinkage and stress development.