A discussion of analysis approaches for determining time-zero from chemical shrinkage and autogenous strain measurements in cement paste

Early-age cracking in concrete has served as an impetus for research on early-age shrinkage. The majority of these studies have focused on the development of testing procedures to measure chemical shrinkage and autogenous strain [1]. Hammer et al. [2] and Boivin et al. [3] have demonstrated that at early ages the chemical shrinkage and autogenous strain are similar. However, when the cement suspension transforms from a fluid to a solid, the chemical shrinkage and autogenous strain measurements diverge. The time of divergence between these measurements has been referred to as ‘time-zero’ (‘t0’). It denotes the time when the material starts to behave as a solid and residual stresses can begin to develop in the material. While the general concept of using the divergence between these measurements is well known, the analytical determination of this time is not well defined. In this paper, the authors investigate analysis procedures aimed at providing a reliable automated method for determining ‘time-zero’ from chemical shrinkage and autogenous strain measurement results.