Preparation, microstructure, performance and mortar application of paraffin/titanium-bearing blast furnace slag phase change aggregate

The application of phase change materials (PCM) in building energy saving is limited by the cost and performance of PCM carriers. Using solid waste as a PCM carrier can reduce cost and environmental impacts. In this study, lightweight and porous titanium-bearing blast furnace slag (Ti-BFS) was innovatively used as PCM carrier to prepare paraffin/Ti-BFS phase change aggregate (PTA) by vacuum impregnation, and then PTA was used to develop thermal energy storage cement mortar by replacing sand. The microstructure and performance of aggregate and mortar were also investigated. The results indicated that PTA has a paraffin loading rate of 21.9%, latent heat of 65.7 J/g for melting and 65.0 J/g for freezing, and good chemical compatibility. The microstructure reveals that PTA has good compatibility with cement matrix. Compared with ordinary cement mortar, a reduction percentage of 28-day compressive strength, dry density and thermal conductivity at 100% PTA substitution rate are respectively 39.8%, 29.1% and 52.5%. However, a significant capacity to weaken temperature fluctuation was observed.