Calorimetric freeze-thaw response of superabsorbent polymers in a cementitious environment

Superabsorbent polymers (SAP) can protect concrete from frost damage but the mechanism behind their effect on the frost resistance of concrete, specifically on the freezing behavior of the pore solution in concrete, is not yet well understood. In this study, SAP exposed to demineralized water or synthetic pore fluid is subjected to freeze-thaw action and its calorimetric response during this process is registered. The results show that for liquids absorbed in SAP, the freezing and melting peaks occur at lower temperatures than for the bulk exposure liquids. The freezing and melting peaks of these liquids held in SAP may be further affected by various factors such as: the addition of ice-nucleating agents, the concentration of ions in the exposure liquids, the moisture state of SAP, repeated drying and wetting pretreatment of SAP, and cyclic freezing and thawing. With the decrease of the moisture content in SAP, the freezing and melting peak temperatures of liquids in SAP decreases. Moreover, there is a good correlation between the proportion of freezable water in SAP, and the temperature where ice formation and melting, respectively, occur. These observations have relevance for the understanding and use of SAP to improve the frost resistance of concrete.