Analysis of Strength and Microstructural Characteristics of Mine Backfills Containing Fly Ash and Desulfurized Gypsum

The utilization of solid wastes (SWs) as a potential resource for backfilling is not only conducive to environmental protection but also reduces the surface storage waste. Two types SWs, including fly ash (FA) and desulfurized gypsum (DG), were used prepare cementitious materials underground mined-out areas. Ordinary Portland cement (OPC) was in mine backfill. To better investigate feasibility preparing backfill materials, some laboratory tests, such uniaxial compressive strength (UCS), scanning electron microscopy (SEM), energy dissipation theory, conducted explore both microstructural properties backfilling. Results have demonstrated that main components FA DG this study are oxides, with few toxic heavy metal components. ideal ratio OPC:FA:DG 1:6:2 corresponding UCS values 2.5 4.2 MPa when curing time 7 days 14 days, respectively. Moreover, average value samples gradually decreased proportion mixture increased. failure modes various tensile shearing cracks. In addition, relations among total input energy, dissipated strain stress–strain curve investigated. spatial distribution oxygen, aluminum, silicon, calcium, iron magnesium elements, hydration product explored from microstructure’s perspective. findings provide invaluable information industrial applications efficient management waste, based on sustainable development circular economy.