Abstract
Cemented gangue backfill material (CGBM) is made of coal gangue, fly ash, cement, and water. The backfill body will be corroded by mine water that contains different kinds of corrosive ions. The paper mainly aimed to study the diffusion process of sulfate ion () in CGBM. Soluble salt solutions with different concentrations are prepared to simulate various mine water. The concentration was measured by layered sampling method and chemical analyzing method. The diffusion coefficient was calculated according to the second Fick’s law. Scanning electron microscope (SEM) and X‐ray diffraction (XRD) were used to analyze the degradation mechanisms. The experimental results showed that the concentration increases in CGBM when the external sulfate solutions concentration increases. With the increasing of magnesium ion (Mg2+) concentration and bicarbonate ion () concentration in the external corrosion solutions, the diffusion coefficient of was increased, and has more significant effects than Mg2+. reacting with CGBM produced ettringite and gypsum. The ettringite and gypsum changed the pore structure of hardened CGBM and affected the compressive strength of hardened CGBM. Studying the diffusion of can contribute to predicting the service life of CGBM.
Highlights
Backfill mining is taken to solve the problem of surface subsidence caused by underground coal mining [1]
E main objective of this paper is to study the diffusion process of SO24− and investigate the relationship between compressive strength and diffusion and analyze the products using XRD and SEM. e paper considers the time factor to establish a prediction model which is about Cemented gangue backfill material (CGBM)’s length of service, which can contribute to predicting the service life of CGBM
Based on the results presented in this paper, the following conclusions are offered: (1) e SO42− concentration increases in CGBM when the external sulfate solutions concentration increases
Summary
Backfill mining is taken to solve the problem of surface subsidence caused by underground coal mining [1] It has many benefits, such as reducing the accumulation of solid waste, and the occupation of cultivated land, developing and utilizing underground space [2], and protecting groundwater and environment [3]. Cemented gangue backfill material (CGBM), one of the common backfill materials, is made of coal gangue, fly ash, cement, and water [4]. Comparing to other backfill materials, the main raw materials of CGBM, such as coal gangue and fly ash, are plentiful and cheap, and its performance meets the workability and strength requirements of mining. Most of the mine water contains corrosive ions such as Mg2+, HCO−3 , and SO24− , and mine water varies greatly
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