Impact of Microencapsulated Phase Change Materials on the Thermal and Mechanical Behaviors of Silty Soil: Applications for Energy Geostructures

Microencapsulated phase change materials (mPCM) are advanced materials capable of absorbing and releasing heat through phase transitions, making them well-suited for enhancing the thermal performance of energy geostructures. Despite significant advances in the integration of phase change materials (PCM) into building envelopes, research on the use of PCM in soils remains limited. This study addresses this gap by investigating the impact of mPCM on the thermal and mechanical properties of silty soil, with a focus on geo-energy applications. Experimental investigations, including Differential Scanning Calorimetry (DSC), thermal conductivity measurements, and direct shear tests, were conducted on silty soil mixed with varying mPCM contents (0%, 8%, 1 Métral, November 5, 2025 and 12%). The results demonstrate that incorporating mPCM significantly increases the soil's energy storage density due to its high latent heat and specific heat capacity. However, the addition of mPCM also leads to a substantial decrease in thermal conductivity-over 50% in samples with 12% mPCM content-due to the low intrinsic thermal conductivity of organic PCM. This reduction poses challenges for ensuring adequate heat transfer in energy geostructures. Importantly, the mechanical properties of the soil are not negatively impacted by the integration of mPCM. The results demonstrate that mPCM contents between 8% and 12% are optimal for use in silty soils, enhancing energy storage density while maintaining mechanical integrity.