Mitigating autogenous shrinkage using a combination of superabsorbent polymer and magnesia-based expansive additive

Various strategies have been developed to mitigate the autogenous shrinkage of cement-based materials (CBMs), including internal curing and shrinkage compensation. However, the sole use of internal curing or shrinkage compensation is insufficient in many cases. In this study, magnesia-based expansive additives (MEAs) coupled with a superabsorbent polymer (SAP) were investigated as internal curing agents to mitigate the autogenous shrinkage of cement pastes. The internal relative humidity (RH), autogenous deformation and compressive strength of cement pastes containing two different types of MEAs and SAP were examined. The results showed that, with the incorporation of SAP, the RH in the cement paste was maintained at a higher level than that in cement pastes without SAP, and hence autogenous shrinkage was reduced. The combination of SAP and MEA provided very effective compensation for the autogenous shrinkage of cement paste. Moreover, the cement paste containing 8 wt% MEA and 0.2 wt% SAP produced a gentle expansion of 111 microstrain rather than shrinkage. This was attributed to the increased hydration degree of magnesia owing to the additional water supply provided by the SAP. This study provides a novel and efficient way to mitigate the autogenous shrinkage of CBMs.