Potential of Utilizing Form-Stable Phase Change Materials to Improve Freeze–Thaw Resistance of Mortar with Varying Water Content

There have been numerous reports that the incorporation of phase change materials (PCMs) in concrete, which act by the release of latent heat, is a promising solution for melting snow, deicing, and improved freeze–thaw durability. For an in-depth understanding of PCMs for future application in practical construction, in this study, the effect of PCMs on the thermal performance of mortar containing various proportions of water was further investigated in terms of the degree of saturation (DOS), based on longitudinal guarded comparative calorimetry (LGCC). The exothermic peak during the phase transition of PCMs with added water was quantitatively determined using heat flow curves. The results indicate that the freezing point of water was depressed with respect to the bulk liquid, and that a lower DOS contributes to a higher degree of depression. Ice formation was effectively inhibited when the heat released by the PCMs was larger than that released by water. The reduction in the amount of frozen water caused by the addition of PCMs can be seen as having a similar effect as increasing the critical DOS to trigger damage. Additions of 30% and 50% PCMs could equivalently increase the critical DOS to 90%–95% and 95%–100%, respectively.