Potential to design magnesium potassium phosphate cement paste based on an optimal magnesia-to-phosphate ratio

摘要

Abstract Magnesium potassium phosphate cement (MKPC) is an important engineering material, and it has been attracting increasing attention. Properties of MKPC based materials depend largely on the magnesia-to-phosphate molar ratio (M/P) and the water-to-cement mass ratio (W/C). While the effect of W/C has been clear, experimental results of the effect of M/P in the literature seem to be inconsistent. In this paper, a model is developed to unify these experimental findings. The model hypothesizes that the strength of MKPC based materials is dominated by the volume ratio of magnesium potassium phosphate hexahydrate and space (MKP/space ratio), and the ultimate MKP/space ratio can be limited by the availabilities of the three reactants, i.e. magnesia, phosphate and water. It proves that, if the W/C of MKPC-based material is kept constant, there exists an optimal M/P that results in the highest compressive strength. It appears that the higher the W/C is, the smaller this optimal M/P will be. Graphical abstract Display Omitted Highlights • Microstructure of magnesium potassium phosphate cement paste is characterized by a reaction product-to-space ratio. • Degree of reaction of magnesium potassium phosphate cement is limited by amounts of magnesia, phosphate and water. • An optimal magnesia-to-phosphate molar ratio gives the highest strength in magnesium potassium phosphate cement paste. • Value of the optimal magnesia-to-phosphate molar ratio depends on water-to-cement ratio of paste.