Effect of Electric Furnace Nickel Slag on the Water Resistance of Magnesium Sodium Phosphate Cement

Nickel slag can be applied in a magnesium sodium phosphate cement (MNPC) system to improve its comprehensive performance and reduce the cost of cement preparation. In this study, the optimum dosage of nickel slag is determined, based on which the effect of nickel slag on the water resistance properties of MNPC is investigated. Results show that 30% nickel slag resulted in the optimum compressive strength, setting time, and flowability of MNPC. Nickel slag refines the pore structure of MNPC paste, while its coarser, nonabradable particles act as microaggregates. MNPC paste containing nickel slag continues to hydrate in water, progressively forming additional MgNaPO4·7H2O. Because MgNaPO4·7H2O is water-stable, it preserves the internal framework of MNPC and promotes ongoing densification, thereby ensuring a consistently high compressive strength. Therefore, nickel slag endows MNPC with more hydration products, more stable hydration crystals, and the microagglomeration effect of coarse particles, which synergistically enhance the water resistance of MNPC.