Experimental Investigation on Physical and Mechanical Behaviors of Paraffin Microcapsule Phase-Change Energy-Storage Concrete

Phase-change materials (PCMs) are gradually being applied in the field of building energy conservation due to their ability to absorb and release heat through phase changes within a specific temperature range. This study prepared a paraffin-microencapsulated phase-change aggregate (PCA) and used the equal volume sand replacement method to replace standard sand with PCA under a fixed water–cement ratio and curing conditions. Five sets of concrete specimens with varying PCA content were designed and tested for their apparent densities, compressive strengths, water absorptions, thermal conductivities, and microstructures. The experimental results show that the apparent density, compressive strength, ultrasonic velocity, and thermal conductivity of phase-change energy-storage concrete (PCC) gradually decrease with the increasing PCA content. Its apparent density, compressive strength, ultrasonic velocity, and thermal conductivity all reach their minimum values when the PCA content reaches 40%; minimum values are 2.07 g/cm3, 42.461 MPa (56 days), 8.93 km/s, and 1.43 W/(m·K), respectively. The water-absorption rate of PCC specimens exhibits non monotonic response characteristics with the variation of PCA dosage. This study can provide a theoretical basis for the preparation of PCCs by the PCA method.