Using superabsorbent polymers (SAPs) to mitigate frost damage of cement mortar at early age

Abstract

In cold regions, air-entraining agents (AEA) have commonly been utilized to prevent concrete from frost damage. However, the robustness of applying AEA is significantly affected due to the fluctuations in concrete mix proportion, supplementary cementitious material quality, and curing temperature. This paper proposes superabsorbent polymer (SAP) as a promising substitute for AEA, especially for early-age frozen cement mortar. Two types of SAP, acrylic acid and acrylamide (S1) and polyacrylic acid (S2), were incorporated into mortars cured at −10 °C within 7d and 28d, and the mechanical properties, resistivity, pore structure, and microstructure of the mortar were evaluated. The results demonstrated that the incorporation of SAP can improve the mechanical properties of mortar at low temperature. After being cured at −10 °C for 7d, the strength of mortar containing 0.4% SAP was increased by approximately 30% compared to that of reference. The low resistivity exhibited by SAP mortar demonstrated lower free water content during freezing. Additionally, the air content and the spacing factor of the hardened SAP mortar can meet the requirements of frost resistance like AEA. Moreover, adding SAP also promotes the degree of hydration in the later stage. Finally, the present study elucidates the mechanisms through which SAP improves the performance of early frozen cement mortar by reducing the amount of freezable water, introducing air voids, and providing internal curing.