Factors Influencing Mitigation Strategies for Autogenous Shrinkage

This research aims to answer several outstanding questions that must be addressed before internal curing materials can be commonly used in structural concrete. The wide range of possibilities for internal curing material properties can dramatically alter the effectiveness of internal curing. The research presented here investigates some of the more important material properties, such as desorption rate, absorption capacity, and distribution/protected paste volume, and the synergistic relationship between properties as related to reductions in autogenous deformation and the effects on mortar compressive strength. The estimated degree of hydration is an effective method to evaluate the efficiency of an internal curing material. However, effects on mechanical properties are not considered. Thus, in addition to the degree of hydration measurements, the relative changes of compressive strength that are due to internal curing material incorporation should always be investigated. The desorption rate of an internal curing material should match the self-desiccation profile of a high-performance cementitious mix as much as possible. Perlite lightweight fine aggregates had a prolonged desorption rate (up to 14 days), such that the aggregate’s effectiveness at mitigating autogenous shrinkage was minimized. In this case, the quantities of internal curing materials added to a particular mixture should be adjusted to account only for the water desorbed within the self-desiccation period (approximately 5–7 days). Expanded shale lightweight fine aggregates appeared to be the most effective internal curing material investigated in this research based on improvements to the degree of hydration and negligible effects on compressive strength.