Effects of sulphoaluminate cement on the strength and water stability of magnesium potassium phosphate cement

To improve the poor water stability of magnesium potassium phosphate cement (MKPC), the hydraulic sulphoaluminate cement (SAC) was used. In this study, the effects of SAC and phosphate content on the strength and water stability of MKPC were studied. Furthermore, X-ray diffraction and scanning electron microscopy-energy dispersive spectroscopy were used to analyze the products of the reaction. The results show that the compressive strength and water stability were improved by partially substituting SAC for MgO. The highest compressive strength was obtained in the SAC content of 20-30 wt% and the increasing amount of SAC improved the water stability of samples. More phosphate could increase the compressive strength under air-cured condition but significantly decrease the water stability of samples. Mass amorphous hydration products generated by the hydration of SAC, having the cohesive effect on the residual unreacted MgO and K-struvite crystals, increasing the density of the hardened paste.