Study on the Mechanical Properties and Mechanism of a Nickel-Iron Slag Cement-Based Composite under the Action of Sodium Sulfate

The accumulated amount of nickel–iron slag has increased with the rapid development of the nickel-iron industry. To determine a method for comprehensively utilizing nickel–iron slag, triaxial compression tests of nickel–iron slag cement-based composite materials under the action of sodium sulfate were conducted, and the effects of the sodium sulfate concentration on the stress-strain relation, shear strength, cohesion, and internal friction angle of the composite materials were analyzed. In addition, the influence mechanism of the nickel–iron slag content and sodium sulfate concentration on the composite was examined. The results revealed that the stress–strain curve of the nickel–iron slag cement-based composites reflected softening. With the increase in the sodium sulfate concentration, the brittleness increased, while the shear strength, cohesion, and internal friction angle decreased; the addition of nickel–iron slag slowed down the rate at which these parameters decrease. Scanning electron microscopy images revealed that nickel–iron slag can improve the internal structure of the cement composite soil, enhance its compactness, and improve its corrosion resistance. The optimum nickel–iron slag content of 14% can improve the cementitious composites’ resistance to sodium sulfate erosion in terms of solid waste utilization and cementitious soil performance. The results obtained can provide technical parameters for preparing and designing cement-based composite materials as well as certain theoretical significance and engineering reference value.