High early strength magnesium phosphosilicate cement

The phosphate bonded cement was prepared by incorporating magnesia with different content and fineness with fly ash and the mechanical properties of cement mortars were investigated. It was shown that the cement set rapidly and had high early strength. The mechanical properties of cement were improved when fly ash content (mass fraction) was form 30%-50%, and the cement had the best strength when the fly ash content was 40%. The mortars with higher magnesia content and finer particle size resulted in higher compressive strength. The hydration products formed in hardened paste were crystalline of hexahydrate phosphate and amorphous species. There was also much unreacted magnesia in the hardened cement paste, which could be as the fine aggregate. The particles of fly ash filled in the voids of cement matrix and made it denser and fly ash might participate the hydration and formed rigid interlinks with hydrates, which improved the bonding of the cement.