Abstract:

Magnesium potassium phosphate cement （MKPC） is prone to dehydration and decomposition of its hydration products under high-temperature exposure， which leads to strength degradation and volumetric shrinkage， thereby limiting its engineering applications in high-temperature environments. To address this issue， an orthogonal experimental design was employed to systematically investigate the effects of the water-to-binder ratio and the content of silica sol， expanded vermiculite， and glass beads on the performance degradation of MKPC under high-temperature. The underlying mechanisms were further elucidated through microstructural analyses using XRD， SEM， and TG-DSC. The results indicate that expanded vermiculite and glass beads can effectively mitigate strength loss and volumetric shrinkage under high-temperature conditions and are the key components for suppressing the performance degradation of MKPC under high-temperature. When the water-binder ratio is 0.25 and the dosages of silica sol， expanded vermiculite and glass beads are 5%， 15% and 12% （mass fractions）， respectively， MKPC exhibits excellent strength stability and volume stability at high temperatures. Microstructural analyses reveal that expanded vermiculite promotes the formation of refractory silicate phases to construct a stable high-temperature skeleton， while glass beads soften to form a glassy phase that enhances particle bonding. The synergistic effect of these two components effectively improves the high-temperature structural stability of MKPC from both phase composition and microstructural perspectives.

Key words: magnesium potassium phosphate cement, expanded vermiculite, glass beads, silica sol, high-temperature resistance, orthogonal experiment