Investigation of the effect of phosphate agent type on setting time, flowability, hydration and dehydration of magnesium phosphate cement.

Magnesium phosphate cements (MPC) are the most developed kind of chemically bonded ceramics which form through the reaction of magnesium oxide and soluble phosphate salts. Therefore, study of different magnesium phosphate cement systems is considered important according to the type of phosphate agent used. In this study, effect of mono-ammonium phosphate (MAP), di-ammonium phosphate (DAP), and sodium dihydrogen phosphate (MSP) on the properties of magnesium phosphate cement paste including setting time, flowability, bulk density, apparent porosity, and pH were investigated. The type and amount of hydrated phases and how the cement is dehydrated are also determined by phase analysis (XRD) and Simultaneous thermal analysis (STA). The results showed that the setting time and flowability of cement containing di-ammonium phosphate is higher than the other two types. In addition, the XRD results indicated that the type of hydrated phase was the same for ammonium phosphate salts, while the use of monosodium phosphate would not lead to the formation of a crystalline hydrated phase.