Effect of seawater for mixing on properties of potassium magnesium phosphate cement paste

This paper aims to study the effect of seawater mixing on the properties of potassium magnesium phosphate cement (MKPC) paste. Fresh water and seawater were used to prepare MKPC pastes, respectively. Then, the compressive strength, residual ratio of compressive strength, hydration temperature, phase composition and microstructure of the MKPCs prepared with seawater and fresh water were compared. Results showed that the MKPC pastes prepared with seawater had higher fluidity, longer initial setting time and lower compressive strength than those prepared with fresh water. Adding silica fume and limestone powders to MKPC pastes prepared with seawater can accelerate the early-stage hydration and make the pastes more compact, leading to significantly less loss of compressive strength. Thus, adding some mineral admixtures into MKPC paste prepared with seawater could lessen the negative effect of seawater for mixing on the properties of hardened body. This study might provide useful information for application of seawater in mixing MKPC for marine construction.