Effect of curing regime on water resistance of magnesium-potassium phosphate cement

In this paper, the effects of curing conditions (dry air, moist air and water), state of water (static water and flowing water) and initial air curing time (5 h, 3 d and 28 d) on the corrosion behavior of magnesium potassium phosphate cement (MKPC) paste subjected to water attack were investigated. The strength residual ratio and mass loss rate were used as deterioration indexes of MKPC paste in water. The pH value and leaching amounts of soaking liquid were also employed to evaluate the water corrosion behavior. X-ray diffraction (XRD), scanning electron microscopy (SEM), thermo-gravimetry analysis (TG) and mercury intrusion porosimetry (MIP) were used to investigate the microstructure of MKPC paste before and after water corrosion. The experimental results showed that the water environment lead to a lower compressive strength of MKPC pastes, but the strength loss of MKPC paste under the flowing water curing was higher. Furthermore, prolonged initial air curing time could improve the water resistance of MKPC pastes, the specimens cured in air for the first 3 days then in water showed the best water resistance among all specimens immersed in water for 60 days. The deterioration mechanism of MKPC paste derived from the strength and mass loss test results was also clarified based on microstructural observation. (C) 2017 Elsevier Ltd. All rights reserved.