Damage Behavior of Bauxite Superfine Tailings-Cement Filling Material in Halogen Corrosion Environment

The superfine tailings and cement filling material of bauxite was soaked with halide corrosion solution at different time. The change rule of mechanical properties and microstructure was studied by uniaxial compression test and computed tomography (CT) scanning, and the corrosion mechanism was analyzed by microscopic morphology. The results showed that with the corrosion time increasing from 0 d to 360 d, the compressive strength and deformation modulus of the filling material decreased gradually, and the change rate was first slow and then fast. After 360 d corrosion, the compressive strength and deformation modulus of the filling material decreased by more than 30%. In the process of corrosion, the microscopic cracks in the specimen expanded gradually, and the surface porosity increased exponentially. Increasing mass fraction of slurry in a certain range could improve the compressive strength of specimen, but the enhancement effect decreased with the increase of corrosion time. There was a negative linear correlation between compressive strength and surface porosity of specimens, and the correlation coefficient was more than 0.95, indicating that it was reasonable and feasible to use CT scanning results to predict the regulation of material strength reduction. Under the long-term corrosion action of brine solution in groundwater, the invasion of corrosive ions and chemical action made the microscopic morphology of cement hydration products evolved, the pores gradually expanded, the particle bonding degree decreased, and finally led to the mechanical properties of materials attenuation.