The effect of seawater curing on properties of magnesium potassium phosphate cement

This paper investigated the effect of early seawater curing on properties of magnesium potassium phosphate cement (MKPC) paste. First, the MKPC paste was prepared by mixing overburning MgO powders, KH2PO4, the composite retarder (CR) and water in a certain proportion. Then, we measured the compressive strength, drying shrinkage deformation, and mass change of it under different curing conditions. The results were as follows. For MKPC paste specimens under seawater curing condition, the hydration ages before they were soaked in seawater had a significant effect on their compressive strength, drying shrinkage and mass increase. For MKPC paste specimens cured in seawater after 3-day natural curing, their 28-day and 60-day compressive strengths were 112.8% and 105.4% of those of MKPC paste specimens with same hydration ages under natural curing condition, respectively. In addition, the 60-day shrinkage strain of them (0.82 × 10−4) was significantly less than that of MKPC paste specimens with the same hydration age under natural curing condition (5.14 × 10−4). Moreover, they had higher mass increase ratio (1.23%). These were due to higher production, higher degree of crystallinity and less defects of MKP crystals, and more perfect pore size distribution in MKPC specimens soaked in seawater after 3-day natural curing.