Experimental Study on Diffusion Process of Sulfate Ion in Cemented Gangue Backfill Material

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 (SO42−) in CGBM. Soluble salt solutions with different concentrations are prepared to simulate various mine water. The SO42− 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 SO42− concentration increases in CGBM when the external sulfate solutions concentration increases. With the increasing of magnesium ion (Mg2+) concentration and bicarbonate ion (HCO3−) concentration in the external corrosion solutions, the diffusion coefficient of SO42− was increased, and HCO3− has more significant effects than Mg2+. SO42− 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 SO42− can contribute to predicting the service life of CGBM.

Numerical Simulation of the Ion Transport Behavior in Concrete under Coupled Axial Loading and Sulfate Attack

“…These studies mainly focus on the experimental study of the sulfate ion transmission law, degradation of macroscopic mechanical properties, and theoretical model of sulfate attack based on mechanical and mathematical methods. Guo et al [9] tested the sulfate ion concentration in the cement gangue filling material by chemical analytical method and analyzed the degradation law via scanning electron microscopy (SEM) and X-ray diffraction (XRD). However, the transport law of sulfate ions under the influence of various environmental factors was not studied in detail.…”

Experimental Study on the Physical and Mechanical Properties of Cemented Gangue Backfill under Acid Mine Water Erosion

“…It has demonstrated that the initial sulfate content in the interior of the CGB significantly reduces its long-term UCS, implying that one of the factors contributing to the structural deterioration of the CGB is an internal sulfate attack. Guo et al [15] studied the diffusion process of sulfate ions in cemented gangue backfill material. The results showed that the diffusion rate of sulfate ions was affected by the internal pore structure, and the changes in the internal pore structure were related to the reaction products at different times.…”

Influencing Factors for the Instability and Collapse Mode of the Goaf Structure in a Gypsum Mine

“…Gypsum is an important mineral resource and widely used in various fields [1][2][3]. At present, gypsum is mined with the room pillar method, with multiple pillars supporting the working space and isolated pillars supporting the isolated mining unit [4][5][6].…”