Influence mechanism of SAP voids on the damage behavior of cement-based materials at cryogenic temperatures

The anti-freezing effect of superabsorbent polymer (SAP) has been confirmed at −20℃, but it is still unclear whether SAP can improve the frost durability of cement-based materials (CBMs) at cryogenic environment. Here, the characteristics of the SAP affected zone are analyzed using nanoindentation. The icing process of the pore solution is investigated with differential scanning calorimetry and low-temperature nuclear magnetic resonance. The damage behavior of CBMs is analyzed using strength testing. Two main peaks are found on the heat flow curves. The freezing of the pore solution mainly occurs from 0℃ to −7℃ and −35℃ to −45℃. At −100 ℃, almost all of the pore solution freezes. The incorporation of SAP results in increased apparent and capillary porosity, a greater volume of freezable pore solution, and diminished compactness within the SAP affected zone. Reducing SAP particle size can mitigate the aforementioned adverse effects and optimize the material's freeze resistance. The key to SAP void improving the frost resistance of CBMs lies in its dual role in the uptake and facilitated transport of the pore solution. This article confirms that SAP voids may become a new option for enhancing the cryogenic resistance of CBMs. SAP voids can absorb some pore solution and promote the migration of pore solution • The water-release of SAP reduces the hardness of the affected zone. • Adding SAP and raising SAP particle size both enlarge the accumulated ice content. • The pore solution has almost completely frozen at −100°C. • SAP void can absorb pore solution and promote the migration of pore solution. • Adding SAP and reducing SAP size can improve the frost resistance of CBMs.