Study on properties of magnesium phosphosilicate cement using different reactive magnesia

Magnesium phosphosilicate cement (MPSC) is generally composed of magnesium oxide, phosphate and silicate, and the admixture is generally borax to extend the setting time. In the preparation of traditional magnesium phosphate cement (MPC), reburned magnesium oxide is generally used. In this study, light-burned powder calcinated with borax will be used instead of reburned magnesium oxide to prepare MPC. The calcination temperature range is 1000–1200 °C and the holding time is 2 h. This paper explores the influence of magnesia reactivity at different calcination temperatures on the performance of MPSC, including setting time, electron microscope, heat of hydration, phase composition and strength development. The results show that borax can significantly reduce the reactivity of magnesia. Experimental data shows that as the reactivity of magnesia increases, the mechanical properties of MPSC cement become better, and the porosity will also decrease. However, when the reactivity is too high, the cement cannot be formed because of the early setting time.