Abstract
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 of waste. Two types of SWs, including fly ash (FA) and desulfurized gypsum (DG), were used to prepare cementitious backfilling materials for underground mined-out areas. Ordinary Portland cement (OPC) was used as cement in mine backfill. To better investigate the feasibility of preparing backfill materials, some laboratory tests, such as uniaxial compressive strength (UCS), scanning electron microscopy (SEM), and energy dissipation theory, were conducted to explore both strength and microstructural properties of backfilling. Results have demonstrated that the main components of FA and DG in this study are oxides, with few toxic and heavy metal components. The ideal ratio of OPC:FA:DG is 1:6:2 and the corresponding UCS values are 2.5 and 4.2 MPa when the curing time are 7 days and 14 days, respectively. Moreover, the average UCS value of backfilling samples gradually decreased when the proportion of DG in the mixture increased. The main failure modes of various backfilling materials are tensile and shearing cracks. In addition, the corresponding relations among total input energy, dissipated energy and strain energy, and stress–strain curve were investigated. The spatial distribution of oxygen, aluminum, silicon, calcium, iron and magnesium elements, and hydration product are explored from the microstructure’s perspective. The findings of this study provide both invaluable information and industrial applications for the efficient management of solid waste, based on sustainable development and circular economy.
Highlights
The extraction of ore resources has promoted the progress of human civilization, providing critical raw materials for sustainable development and circular economy [1,2].it is irrefutable that resource mining has caused a series of complications, such as water and air pollution [3], geotechnical risks [4], environmental hazards [5], farmland occupation [6], and tailings dam failures [7]
The present study investigates the particle size distribution and chemical composition of fly ash (FA) and desulfurization gypsum (DG), strength and loading energy development, and cement-based backfills’ microstructural characteristics
Tap water was poured into the stirring tank, and the JJ-5 cement mortar mixer produced by Wuxi Jianyi Instrument Machinery Co., Ltd. was used to mix for 3 min again until the slurry was fully dispersed
Summary
The extraction of ore resources has promoted the progress of human civilization, providing critical raw materials for sustainable development and circular economy [1,2]. Tailings are called solid waste or hazardous waste after ore processing [23,24] They can be prepared concrete additives, backfilling, and construction materials [25,26]. Tailings containing toxic elements or heavy metal ions cannot be used for filling underground voids according to the related environmental protection standards [27,28,29]. Cement, FA, and DG are utilized to prepare the backfill materials for underground voids. The present study investigates the particle size distribution and chemical composition of FA and DG, strength and loading energy development, and cement-based backfills’ microstructural characteristics. This study’s main contribution is that it can provide a reliable reference for the feasibility of preparing mine backfills prepared with solid waste
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