Abstract
Given that normal filling technology generally cannot be used for mining in the western part of China, as it has only a few sources for filling gangue, the feasibility of instead using cemented filling materials with aeolian sand as the aggregate is discussed in this study. We used laboratory tests to study how the fly ash (FA) content, cement content, lime–slag (LS) content, and concentration influence the transportation and mechanical properties of aeolian-sand-based cemented filling material. The internal microstructures and distributions of the elements in filled objects for curing times of 3 and 7 days are analyzed using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The experimental results show that: (i) the bleeding rate and slump of the filling-material slurry decrease gradually as the fly ash content, cement content, lime–slag content, and concentration increase, (ii) while the mechanical properties of the filled object increase. The optimal proportions for the aeolian sand-based cemented filling material include a concentration of 76%, a fly ash content of 47.5%, a cement content of 12.5%, a lime–slag content of 5%, and an aeolian sand content of 35%. The SEM observations show that the needle/rod-like ettringite (AFt) and amorphous and flocculent tobermorite (C-S-H) gel are the main early hydration products of a filled object with the above specific proportions. After increasing the curing time from 3 to 7 days, the AFt content decreases gradually, while the C-S-H content and the compactness increase.
Highlights
Ground subsidence, water and soil loss, and the protection of the ecological environment are some of the primary challenges facing the coal mining industry [1,2,3]
After mixing the AS, fly ash (FA), cement, and LS in certain proportions, water was added to the mixture, which was subsequently stirred with a mechanical mixer into a fluidized slurry of cemented filling material
The proportioning tests were performed on Group A to investigate how the FA content affects the transportation and mechanical properties of the filling material
Summary
Water and soil loss, and the protection of the ecological environment are some of the primary challenges facing the coal mining industry [1,2,3]. A considerable amount of research has recently been conducted on filling materials (coal gangue, fly ash, and construction waste) and microstructural characteristics for coal mines [6,7,8]. Studied the mechanical properties of cemented filling materials in which gangue was partially replaced by waste concrete. They found that when the replacement ratio of waste concrete was 37%, the filled. Cemented filling material with aeolian sand—which largely covers the ground surface in the mining area of Western China—as the aggregate has not been studied yet. We conducted an analysis of the microstructure and macroscopic mechanical properties of AS-based cemented filling materials using laboratory proportioning. The feasibility of using such filling materials is discussed and the obtained optimal proportions of filling materials that are suitable for the mining region of Western China are demonstrated
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