Investigation on mechanical and thermal behavior of geopolymer phase change concrete

Phase change concrete (PCC) is gradually gaining traction in engineering applications owing to its superior thermal regulation capabilities. This study investigates the effects of varying paraffin microcapsule (PM) replacement levels on the mechanical and thermal properties of geopolymer-based phase change concrete (GPCC) and ordinary Portland cement-based phase change concrete (CPCC) through macroscopic physical and mechanical testing, complemented by microscopic characterization techniques. The results demonstrate that the compressive strength of both GPCC and CPCC decreases progressively with increasing PM content, accompanied by a continuous rise in porosity. Under identical PM replacement levels and curing ages, GPCC consistently exhibits higher compressive strength than CPCC, despite possessing a relatively looser microstructure. The incorporation of PM enhances the structural integrity and ductility of the failure modes observed in both concrete types. PM addition induces a concurrent increase in porosity and reduction in matrix densification for both GPCC and CPCC. While maintaining a compressive strength threshold of no less than 25 MPa, GPCC-20 achieved a latent heat of phase transition and specific heat capacity that were 2.0 and 1.1 times those of CPCC-10, respectively, with its thermal conductivity being 40.1% lower than that of CPCC-10. These findings provide a theoretical foundation for the further research and engineering implementation of phase change concrete.