Experimental Study of Freeze-Thaw Deformation in Soil Modified with Phase Change Materials

Abstract

Previous studies have confirmed the potential use of phase change material (PCM) in reducing temperature fluctuations in the soil. However, PCM’s impact on soil volumetric deformation due to freeze-thaw action remains understudied. The thermal properties of PCM-A and PCM-B, along with the thermal conductivity, Atterberg limit, permeability, and freeze-thaw deformation of both the control and modified soils, were investigated to address this gap. Compared with the control soil, the modified soil’s plastic limit (PL) increases and even exceeds the soil's initial moisture content of 18% with the addition of PCM, which indicates less free water changing phase during freezing. The modified soil's thermal conductivity and permeability coefficient decreases with the PCM content, restricting the water migration during the freezing process. The reduced phase change temperatures shorten the specimen's frozen-state keeping time, meaning that delayed freezing and advanced thawing cause less moisture migration inside the specimens. Based on the grey incidence method, the thermal conductivity, PL, and permeability have almost identical influences on soils’ freeze-thaw deformation, and the phase change temperature has minimum impact. Referring to PCM-B modified soil, the greater degree of grey incidences between frost heave and phase change temperature relates to the stronger restriction to the frost heave for PCM-A modified soil. In conclusion, PCM-A modified soil significantly reduces freeze-thaw volumetric deformation, and an optimal addition amount not exceeding 6% is recommended.

Keywords: phase change material, soil thermoregulation, freeze-thaw deformation, control mechanism, grey incidence