Experimental Study on Mechanical Properties of Paste Backfill with Flue-Gas Desulphurisation Gypsum under Combined Action of Dry–Wet Cycles and Chloride Erosion

Abstract

Flue-gas desulphurisation gypsum—a solid waste from power plants—can be used to prepare paste backfill for reducing costs. Most paste backfills are exposed to dry–wet cycles and chloride salt-rich water in mines. Therefore, the mechanical properties and damage mechanisms of paste backfill with desulphurised gypsum under the coupling action of erosion due to chloride with different concentrations and dry–wet cycles were investigated using methods such as visual observation, mass measurement, uniaxial compression, acoustic emission, Fourier-transform infrared spectroscopy, X-ray diffraction analysis, and field-emission scanning electron microscopy. With an increasing number of dry–wet cycles, the mass, elastic modulus, and strength of the paste backfill exhibited the trend of increasing first and then decreasing. The failure mechanism changed from mainly vertical fractures to the alternating development of vertical and horizontal fractures. The surface denudation effect of the specimens in a solution with a higher concentration was more severe under the same number of dry–wet cycles. In this study, the laws governing the mass change, strength change, degree of surface denudation, and failure pattern of desulphurised gypsum-filled specimens under different concentrations of chloride salt and different numbers of dry–wet cycles were derived.

Changes in the Strength and Leaching Characteristics of Steel Slag-Oil Shale Residue-Based Filling Paste in a Complex Erosive Environment

“…Zhou et al [ 11 ] took cement-based composite materials as the test object, studied the changes in the physical and mechanical properties of specimens under the action of wet–dry cycles and found that long-term wet–dry cycles caused irreversible damage to cement-based composite materials. Wang et al [ 12 ] prepared a filling paste with cement, slag, desulfurized gypsum and other materials and studied the failure trends in the filling paste under the combined action of dry–wet cycles and chloride ions. Filling pastes remain immersed in mine water over long periods of time, and heavy metal ions present in the pastes may migrate to groundwater and cause environmental pollution [ 13 ].…”

Insight into Saturated Hydraulic Conductivity of Cemented Paste Backfill Containing Polycarboxylate Ether-Based Superplasticizer

“…Moreover, binder inclusion ensures that the backfill becomes self-supporting after a short period, making the excavation of adjacent ore body possible. To ensure optimum performance of CPB, its early-age and long-term behaviors have to be incorporated in the design [7][8][9][10]. Some of these properties are responsible for its environmental performance (e.g., leachability, susceptibility to acid mine drainage) and are largely associated with hydraulic conductivity [11,12].…”