Microstructure and property evolution of interfacial microregion of magnesium phosphate cement on mortar under various environments

Portland cement specimens repaired with magnesium phosphate cement were soaked in Ca(OH)(2) and Na2SO4 solutions for an extended period to test the bonding strength of the specimens. After the immersion, the fracture positions and surfaces of the specimens were observed and analyzed. Subsequently, the interfacial microregion of the specimens in different immersion periods was analyzed using an optical microscope and SEM. Besides, the microstructure and property evolution of the interfacial microregion of magnesium phosphate cement (MPC) on mortar under various environments were studied in erosion environment, which was compared with the interfacial microregion in natural environment. Results indicate that the bonding strength of the specimens is weaker in Ca(OH)(2) solution than in the natural environment. At first, the bonding strength initially increases and then stabilizes with time. Moreover, the bonding strength of the specimens is weaker in Na2SO4 solution than that in the natural environment. The bonding strength initially increases and then decreases with time. In the natural environment, the crystal morphology in the interfacial microregion changes slightly, and the crystal structure becomes compact. In Ca(OH)(2) solution, the crystal morphology in the interfacial microregion changes significantly, and the crystal structure becomes compact. In Na2SO4 solution, the crystal morphology in the interfacial microregion makes significant changes, and the crystal structure loosens.