Setting and strength development of magnesium phosphate cement paste

Abstract

Magnesium phosphate cement (MPC) paste is prepared by mixing dead-burned magnesia powder and potassium di-hydrogen phosphate with a proper proportion of water. The paste demonstrates superior performance such as fast setting, high early-strength, low shrinkage and good bonding which makes MPC suitable for applications in the rapid repair of infrastructures. However, it has been found that MPC easily sets in a few minutes and thus causes difficulties in manipulation. Therefore, how to retard and control the setting time of MPC becomes a challenging problem in both scientific and engineering fields. The setting time of MPC is greatly influenced by the reactivity of magnesia. A reliable, effective and economic test method has been developed to measure the reactivity of magnesia. In the present study, two kinds of magnesia, namely, high-reactivity magnesia and lowreactivity magnesia were blended in order to adjust the setting process of MPC. The effects of blending ratio and molar ratio of magnesia to phosphate and borax addition on setting time and compressive strength of MPC cement paste were investigated. Finally, the reaction product and reaction mechanism were examined and discussed.

Mechanical properties of micro-steel fibre reinforced magnesium potassium phosphate cement composite

“…Potassium dihydrogen phosphate (KH 2 PO 4 ) has recently been identified as a good candidate for replacing ammonium phosphate [16]. Previous research on MPC prepared with KH 2 PO 4 indicated that the performance of composite was mainly influenced by the reactivity of magnesia, the molar ratio of magnesia-phosphate (M/P), and the retarder and water content [17][18][19][20][21][22].…”

Reaction mechanisms of magnesium potassium phosphate cement and its application

“…Other than the raw materials which can strongly affect the setting course of MPC, the properties of cement paste can be significantly influenced by the mixture proportions including the molar ratio of magnesium to phosphate (M/P), water content, species and amount of retarder, and curing conditions, etc. [Yang and Wu, 1999;Ding andLi, 2005b and2005c;Paceagiu and Georgescu, 2008;Qiao, et al 2009a and2009b. ] Although the theoretical M/P value is 1 according to the Eq.…”

Thermal insulation and setting property of inorganic solidified foam

“…CaF 2 ) is added to an inorganic solidified foam system, aluminium oxide (Al 2 O 3 ), coming from the admixture, could react with gypsum to form ettringite crystals (AFt) immediately; these will adhere to the particle surface (Qiao et al, 2009). At the same time, the consumption of gypsum accelerates the pace of tricalcium silicate (C 3 S) hydration, forming a small amount of fibrous calcium silicate hydrate filling among the cement particles.…”