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these materials to be used and specified more widely in Indiana. It is recommended that a training video be developed that highlights the benefits of this material, describes its use, and discusses important features associated with placement and testing

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.

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Shrinkage reducing admixtures (SRAs) and saturated lightweight aggregates (LWAs) are increasingly used to reduce shrinkage cracking of concrete mixtures. While both methods show great potential, to obtain the full anticipated benefits of either SRA or LWA the boundary conditions of the concrete element must be carefully considered and understood. Addressed are shrinkage and shrinkage cracking behavior of concrete with sealed and unsealed boundaries. The sealed concrete undergoes self-desiccation, while the unsealed concrete simultaneously experiences both self-desiccation and external drying. The research work presented provides a theoretical and experimental demonstration of the differences in the shrinkage behavior of mixtures containing SRA and LWA. Data are provided from experiments that demonstrate the benefits of SRA and LWA under sealed and unsealed conditions. Theoretical considerations explain the influence of boundary conditions on shrinkage and cracking of concrete. This has important implications for selecting an adequate shrinkage mitigation strategy. In addition, it is demonstrated that the experimental results are consistent with the theoretical predictions.

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