Fly Ash/Paraffin Composite Phase Change Material Used to Treat Thermal and Mechanical Properties of Expansive Soil in Cold Regions

Abstract

Phase change materials (PCMs) can store large amounts of energy in latent heat and release it during phase changes, which could be used to improve the freeze-thaw performance of soil. The composite phase change material was prepared with paraffin as the PCM and 8% Class C fly ash (CFA) as the supporting material. Laboratory tests were conducted to reveal the influence of phase change paraffin composite Class C fly ash (CFA-PCM) on the thermal properties, volume changes and mechanical properties of expansive soil. The results show that PCM failed to establish a good improvement effect due to leakage. CFA can effectively adsorb phase change materials, and the two have good compatibility. CFA-PCM reduces the volume change and strength attenuation of the soil, and 8 wt.% PCM is the optimal content. CFA-PCM turns the phase change latent heat down of the soil and improves its thermal stability. CFA-PCM makes the impact small of freeze-thaw on soil pore structure damage and improves soil volume change and mechanical properties on a macroscopic scale. In addition, CFA-8 wt.% PCM treated expansive soil has apparent advantages in resisting repeated freeze-thaw cycles, providing a reference for actual engineering design.