Thermal regulation and mechanical performance of cement mortars for building thermal energy storage applications

Abstract

This study investigated the effects of microencapsulated phase change material (mPCM) with a phase transition temperature of approximately 25 °C on the physical, mechanical, thermal, and microstructural properties of cement mortars. mPCM was incorporated into mortar mixtures at 2.5%, 5%, and 7.5% of the cement weight. The results showed that mPCM decreased consistency and unit weight while increasing porosity and water absorption. The 28-day compressive strength decreased from 49.9 MPa for the reference mortar to 46.7, 44.2, and 38.8 MPa for mortars containing 2.5%, 5%, and 7.5% mPCM, respectively. The 28-day flexural strength decreased by 9.7-26.6%. SEM analyses revealed that void content and microcapsule-matrix interface discontinuities increased with increasing mPCM content. During heating-cooling cycles (0–40 °C), the maximum temperature differences between the reference mortar and the mPCM2.5, mPCM5, and mPCM7.5 mixtures were 1.1, 1.2, and 2.1 °C during heating, and 1.0, 2.0, and 2.8 °C during cooling, respectively. Increasing mPCM content enhanced the thermal buffering capacity, delayed heat transfer, and reduced internal temperature fluctuations. The findings demonstrate that mPCM-modified cement mortars have potential for thermal energy storage and indoor temperature regulation in building applications. The highest thermal buffering effect was achieved with 7.5% mPCM, but this mixture also showed the greatest reduction in mechanical strength. Overall, the study provides valuable information on the combined thermal and mechanical performance of mPCM-modified cement mortars for building thermal energy storage applications.