The Effects of Hydroxypropyl Methyl Cellulose (HPMC) on the Workability, Mechanical Strength, and Thermal Conductivity of Microencapsulated Phase Change Material (MPCM) Mortar

To enhance the performance of microencapsulated phase change material (MPCM) mortar, hydroxypropyl methyl cellulose (HPMC) was incorporated. This study tested the mortar’s consistency, water retention, water absorption, compressive strength, and thermal conductivity under varying contents of MPCM (as an equivalent volume replacement of sand) and mass contents of HPMC. The results indicate that increasing both MPCM and HPMC contents reduces mortar consistency. Specifically, when HPMC content is 0.05%, 0.10%, and 0.15%, the mortar’s consistency decreases by approximately 24.38%, 35.34%, and 41.30%, respectively, in MPCM-free mortar, with a maximum combined reduction of 74% observed in the 0.15% HPMC and 4% MPCM formulation. MPCM shows a negligible effect on water retention, while HPMC positively influences this property, though not significantly. In contrast, HPMC has little impact on water absorption, whereas MPCM significantly increases it: as MPCM content rises from 0% to 1%, 2%, 3%, and 4%, the mortar’s water absorption increases by 22.55%, 58.82%, 121.57%, and 200.00%, respectively. Both HPMC and MPCM additions lead to reductions in the mortar’s compressive and bond strengths. Notably, a 0.10% HPMC content decreases thermal conductivity by approximately 12% compared to mortar without HPMC. Using the corresponding fitting formulas, predictive values for various performance indicators can be accurately derived.