Shrinkage reducing admixtures (SRA) and saturated light-weight aggregates (LWA) are becoming increasingly utilized to reduce shrinkage cracking of concrete mixtures. While both of these 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. This paper discusses the 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 work presented here provides a theoretical and experimental demonstration of the differences in the shrinkage behavior of mixtures containing SRA and LWA. Data is provided from experiments that demonstrates the benefits of SRA and LWA under both sealed and unsealed conditions. Theoretical considerations are presented that explain the influence of boundary conditions on shrinkage and cracking of concrete. This has important implications on selecting an adequate shrinkage mitigation strategy. In addition, it is demonstrated that the experimental results are consistent with the theoretical predictions.
Abstract