Development of artificial geopolymer aggregates with thermal energy storage capacity

Integrating phase change materials (PCMs) into building materials has been widely used to improve the energy efficiency of buildings, in which microencapsulation and shape stabilization of PCMs are considered as two most effective solutions. In this study, artificial geopolymer aggregate (GPA) was employed as a novel PCM carrier for energy storage purposes. Detailed investigations were conducted into the physical, mechanical, and thermal properties of GPA-PCM, which can be engineered through different raw material selections (e.g., slag content, water/binder ratio, and incineration bottom ash (IBA) content). It was demonstrated that increasing the IBA content is an efficient means to increase the porosity of GPA, an index of the capacity to accommodate PCM. Up to 16 wt% PCM could be absorbed into the GPA through vacuum suction, resulting in a significant melting enthalpy of 24.74 J/g. Besides, GPA-PCM could achieve an excellent mechanical strength greater than 53.2 MPa and thermal conductivity of 0.510-0.589 W/mK. The time-temperature history curves of GPA revealed that up to 10.5 degrees C of thermal regulation was achieved due to PCM impregnation. The developed GPA-PCM composites facilitate an innovative and low-carbon solution for utilizing PCMs in construction for temperature-regulating and energy-saving purposes.