Abstract:Gas extraction drilling and sealing technologies are essential measures for controlling mine gas and ensuring safe production. However, the high demand for sealing materials in mines necessitates more cost-effective alternatives to existing materials. Coal gangue, the most abundant solid waste in coal production, can be used as an admixture to modify gas sealing materials, thereby promoting their large-scale utilization and reducing grouting costs. Therefore, this study systematically investigates the effects of coal gangue content, particle size, and water-to-cement (w/c) ratio on the working performance of gas sealing materials, as well as the composition and structure of their hydration products. The results show that the addition of coal gangue affects the material′s hydration process. Specifically, it inhibits the transformation of ettringite (AFt) to monosulfoaluminate (AFm), thereby promoting the net generation of AFt. This results in an increased expansion rate and compressive strength of the material. However, increasing the coal gangue content raises the silica concentration and reduces the amount of hydration products in the modified material system, leading to higher porosity and lower compressive strength. Changing the w/c ratio significantly impacts the properties of the coal gangue-modified materials. A higher w/c ratio leads to increased structural porosity and decreased compressive strength. It also improves fluidity and extends the setting time, which is beneficial for engineering applications, albeit at the expense of reduced material strength. When the w/c ratio reaches 1.2, the material experiences severe water bleeding. The particle size of the coal gangue has a relatively minor impact on the properties of the modified materials. At low w/c ratios (0.8 and 1.0), increasing the coal gangue particle size reduces the material′s fluidity and shortens its setting time. However, changes in particle size do not significantly affect the material′s expansion rate or mechanical properties. At a given w/c ratio, materials with coal gangue particle sizes between 100-300 mesh exhibit the shortest setting time and lowest porosity, resulting in the highest compressive strength. Overall, the performance of the modified gas sealing material is optimal when the w/c ratio is 0.8, the coal gangue content is 40%, and the particle size ranges from 100 to 300 mesh. Under these conditions, the material demonstrates good fluidity, a setting time of 30 minutes, and a 4-hour compressive strength of nearly 4 MPa. This formulation can significantly increase economic benefits while ensuring effective gas control. Close-