Shrinkage mitigation strategies in cementitious systems: A closer look at differences in sealed and unsealed behavior

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.