Thermal, mechanical, and durability performance of self‐compacting mortars incorporating recycled aggregate‐based composite phase change materials

Composite phase change materials (CPCMs) were developed using recycled concrete aggregate (RCA) via a vacuum impregnation method and incorporated into self‐compacting mortars as a partial replacement for fine aggregate at substitution levels of 15%, 30%, and 45%. Additionally, silica fume (SF) was partially substituted for cement, and 20 different mortar mixtures were produced. The performance of the prepared mortars was comprehensively evaluated in terms of their mechanical, thermal, and durability properties. Mechanical behavior was assessed through flexural and compressive strength tests, while thermal performance was characterized using differential scanning calorimetry (DSC) and thermal conductivity measurements. Durability was further investigated by examining sulfate resistance under MgSO 4 exposure conditions. The results indicated that CPCM‐integrated mortars exhibited a latent heat storage capacity of up to 20.88 J/g, enabling passive thermal energy storage within the cementitious matrix. Increasing the CPCM content resulted in reductions in both flexural and compressive strengths. The incorporation of SF, particularly at a 10% replacement level, resulted in the highest strength values among the tested series. The greatest reduction in thermal conductivity was observed in mixtures containing 15% SF, decreasing from 0.270 to 0.210 W/m K with increasing CPCM content, corresponding to a 22.2% reduction. After sulfate exposure, mixtures without SF exhibited lower flexural and compressive strength losses, indicating better mechanical performance under sulfate conditions. The use of RCA as a carrier for PCM provides a dual benefit by combining thermal functionality with material recycling, thereby contributing to sustainable construction practices. Overall, the findings highlight the potential of CPCM‐modified mortars as multifunctional cementitious materials with passive thermal energy storage capability.