Experimental investigation on the physical and mechanical properties of silty clay enhanced by microencapsulated phase change materials

Microencapsulated phase change materials (mPCM) can absorb or release heat by transforming their core phase. This study investigated the effect of mPCM on the thermal and mechanical properties of silty clay in seasonally frozen strata. It analyzed and researched the thermal and mechanical properties of silty clay blended with different contents (2%, 4%, and 6%) of mPCM, as well as its changing rules, using the DSC thermal cycling test, the specific heat capacity test, the freeze-thaw (F-T) cycling test, the no-limit compressive strength test, and the microscope observation test. In addition, this study utilized hyperspectral equipment to assess the applicability of improved silty clay soils in practical engineering on seasonally frozen ground. The results show that mPCM has no supercooling phenomenon and has stable and reversible transformation characteristics, which improves the thermal stability of silt. The specific heat capacity of silt increased with the increase of mPCM dosage. The unconfined compressive strength of silty clay increased to 162.5 kPa at 2% dosage, which was 16.8% higher than that of silty clay, while the unconfined compressive strength of silty clay at 6% dosage decreased to 119.1 kPa, which was 14.4% lower than that of silty clay after freeze-thaw cycles. Adding mPCM reduces the microscopic damage to the pore structure of silty clay soils caused by the freeze-thaw process and mitigates the macroscopic attenuation of their mechanical strength. The mPCM can effectively reduce the solar radiation reflectivity of silty clay, thus providing long-term utility for winter projects.