The effect of aluminum-silicon glass phase in fly ash on the microstructure and properties of magnesium phosphate cement

The characteristics of magnesium phosphate cement, such as fast setting, high early strength, and good bonding properties, have led to its wide application. However, its poor water resistance is a common drawback, often addressed by adding materials like fly ash (FA) to improve it. In magnesium phosphate cement (MPC), FA undergoes a chemical reaction, but the influence of the aluminum-silicon glass phase in its composition on MPC performance is not yet clear. In this study, two different FA/MPC composites with varying aluminum-silicon glass phase contents in the FA were prepared to investigate the effects of the aluminum-silicon glass phase in FA on the setting time, early hydration heat, mechanical strength, hydration products, water resistance, and microstructure of MPC. The study results indicate that the differences in the glass phase do not significantly affect the setting of MPC. A higher aluminum-silicon glass phase content is advantageous for promoting early hydration reactions in MPC, enhancing the formation of later-stage hydration products, improving late-stage mechanical strength, and enhancing water resistance.