Effect of Temperature on the Physical Salt Attack of Cement Mortars under Repeated Partial Immersion in Sodium Sulfate Solution.

Physical salt attack (PSA) is one of the dominant durability issues of cement-based materials, where salt crystallization pressure is the driving force inducing damage. However, research on the temperature-related deterioration behavior of cement-based materials is limited. In this study, salt-contaminated cement mortars were rewetted at different temperatures. The assessment criteria were based on the visual appearance, weight evolution and size distribution of scaled materials, and the alterations in the microstructure were investigated by microscopy, thermal and mineralogical analyses. The results indicated that more severe damage developed at 5 °C than that at 20 °C due to the greater crystallization pressure caused by the conversion from thenardite (NaSO) to mirabilite (NaSO·10HO) at the lower temperature. No damage was observed at 35 °C, since the repeated dissolution and re-crystallization of thenardite were harmless for the specimens. In addition, two distinct damage patterns were observed for PSA performed at 5 °C and 20 °C, namely, granular disintegration and contour scaling.