On the influence of Mg/P ratio on the properties and durability of magnesium potassium phosphate cement pastes

This paper investigates the influence of magnesium to phosphate molar ratio (Mg/P) on the properties of magnesium phosphate cement pastes (MPPC). The aim of the present study is to investigate the durability of these materials. The results show that excess potassium dihydrogen phosphate (KH2PO4) has a negative impact on overall properties. High quantities of KH2PO4 lead to poor water resistance, as the anhydrous phosphate remained unreacted in the microstructure is highly soluble and generates important values of open porosity when samples are immersed in water. Another drawback to excess KH2PO4 is the appearance of an efflorescence phenomenon, confirmed by XRD analysis. Finally, samples having a high Mg/P molar ratio show important swelling, especially when water is present in the system (autogenous conditions).