Internal curing with superabsorbent polymers of different chemical structures

This study investigates the absorption behavior of superabsorbent polymer (SAP) with different chemical structures and their effect on cement hydration, early-age autogenous shrinkage and mechanical properties of cement paste. SAP with high density of anionic functional groups absorbed the cement pore solution quickly, and then released it because the anionic groups on the network of SAP complexed with multivalent cations in the pore solution (e.g., Ca2+). Much less release was measured for SAP with low density of anionic groups. Furthermore, SAP with either both anionic and cationic groups or with only non-ionic groups did not release the liquid. Despite their different behavior in solutions, all SAP were able to counteract autogenous shrinkage. SAP with either both ionic groups or high density of anionic groups showed excellent internal curing effect. The internal curing had no negative effect on the compressive strength of the paste when the total cement-to-water ratio was considered.