Mechanism of the Freeze–Thaw Deterioration of Clay Incorporating Phase Change Material

During winter construction of earthworks such as earth dams and embankments, the structural properties of the soil may deteriorate due to freeze–thaw cycles. A new measure to combat freeze–thaw damage, incorporating phase change materials (PCMs) into the soil to regulate temperature, has been verified and applied in roadbed and pavement engineering. However, the law of deterioration from freeze–thaw cycles for this novel construction material is not clear yet. This study investigated the characteristics and mechanism of deterioration of clay mixed with paraffin-based PCM (PPCM-clay) through freezing and thawing using freeze–thaw tests, unconfined compression tests, permeability tests, and macro-micro structural analysis. The results show that the freeze–thaw resistance of PPCM-clay is better than that of pure soil. The amount of PPCM added is proportional to the effect of inhibiting soil strength and permeability degradation. Under the same number of freeze–thaw cycles, the compressive strength of PPCM-clay is greater than that of pure soil. Micropore expansion and frost heave are also not significant in PPCM-clay. This indicates that the low initial water content, relatively large porosity, thermal hysteresis, frost contraction, hydrophobicity, and high viscosity of PPCMs are the main reasons for the improvement in PPCM-clay freeze–thaw resistance. These findings provide a theoretical basis for the potential application of PPCM-clay as a dam or embankment material for weakening soil frost damage in winter construction in cold regions.