Sustainable utilization of fly ash for phase-change geopolymer mortar reinforced by fibers

The utilization of geopolymer mortar (GPM) made from fly ash (FA) as a sustainable construction material with minimal carbon footprint is a viable option. Incorporating microencapsulated phase change materials (mPCM) into GPM presents a promising solution to reduce the energy consumption of buildings. In this study, phase-change GPM (PC-GPM) was manufactured using FA as the main raw material. The thermal conductivity and latent heat of PC-GPM were improved through addition of mPCM, and the mechanical properties were enhanced through inclusion of basalt fiber (BF) and polypropylene fiber (PF). The mineral components and microstructural characteristics of PC-GPM reinforced by fibers were also investigated. The results indicate that an increase in the mPCM content led to a reduction in the dry density and compressive strength of PC-GPM. The addition of mPCM contributed to an increase in water absorption and a reduction in thermal conductivity. The physical-mechanical properties of PC-GPM were dependent on the content, length and type of fibers. The latent heat of PC-GPM was observed to be approximately 0.77 kJ/kg. The formation of sodium-alumina-silicate-hydrate (N-A-S-H) and calcium-alumina-silicate-hydrate (C-A-S-H) gels was found to enhance the mechanical properties of PC-GPM. The PC-GPM sample achieved a maximum compressive strength of 36.86 MPa, associated with a thermal conductivity of 1.198 W/(m·K) when the mPCM and BF contents were 25% and 0.75%, respectively. The experimental findings can offer valuable contributions to the advancement of environmentally friendly and sustainable phase-change building materials.