Volume change and cracking in internally cured mixtures made with saturated lightweight aggregate under sealed and unsealed conditions

Low water to cement ratio (w/c) concrete exhibits increased occurrences of early-age shrinkage cracking. These occurrences have spawned innovative developments in concrete mixture design that reduce the risk of cracking. One such development is internal curing, which utilizes the inclusion of saturated lightweight aggregate (SLWA). The SLWA supplies additional moisture to cement paste as it hydrates thereby counteracting the effects of self-desiccation. This paper presents results from a study that examined mortar systems with different volumes of SLWA under sealed and unsealed conditions. Specifically, the results indicate the influence of SLWA volume and type on the internal humidity, autogenous shrinkage, and restrained shrinkage cracking behavior. The performance of each system is shown to be related to the cavitation of vapor-filled space in the paste, the SLWA spacing, and the pore structure of the paste in relation to the LWA.