Value-added utilization of electric furnace nickel-iron slag to enhance the performance of magnesium sodium phosphate cement.

Electric furnace nickel-iron slag is an industrial solid waste obtained by cooling the molten slag after the production of nickel and iron. Its main chemical components are SiO2, Fe2O3, and MgO. This study explores the impact of nickel-iron slag on the properties of magnesium sodium phosphate cement (MNPC), with the objective of addressing the environmental pollution caused by nickel-iron slag and reducing the cost of MNPC. Through experimentation, it has been found that as the content of nickel-iron slag increases, the volume deformation of MNPC is improved. When 30 % nickel-iron slag is added, the water resistance of the cement paste is significantly enhanced, and the porosity after 28 days of air curing is the lowest. Moreover, the compressive strength of all experimental groups gradually increases with the extension of water curing time. Specifically, MNPC with 30 % nickel-iron slag exhibits the highest compressive strength, the lowest strength loss rate, and the smallest porosity at 1 day, 3 days, and 28 days under both air and water curing conditions. The hydration products of MNPC are amorphous MgNaPO4・7H2O, while distinct crystalline peaks of MgNaPO4・7H2O are observed in MNPC containing nickel-iron slag, and the intensity of these peaks gradually increases with the curing time. The compressive strength of water - cured MNPC progressively increases with the curing duration, without any strength decline, and the intensity of the crystalline peaks of the hydration products also continues to strengthen. The innovation of this study lies in the effective utilization of nickel-iron slag in MNPC, which not only enhances the performance of MNPC but also provides a novel solution for the treatment of industrial waste and the development of sustainable materials.