Abstract:Gas extraction drilling and sealing technology is a necessary measure for mine gas control and ensuring safe production. However, the high demand for sealing materials in mines requires existing materials to be more cost-effective. Coal gangue, the most abundant solid waste in coal production, can be used as an admixture to modify gas sealing materials, which promotes their large-scale utilization and reduces 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 on the composition and structure of their hydration products. Results show that adding coal gangue affects the material′s hydration process. Specifically, it inhibits the transformation of ettringite (AFt) to monosulfoaluminate (AFm), thereby promoting net generation of AFt. This leads to an increase in both the expansion rate and compressive strength of the material. However, an increase in coal gangue content increases the silica concentration and reduces the quantity of hydration products within the modified material system, resulting in increased porosity and decreased compressive strength. Changing the w/c ratio has a significant impact on the properties of the coal gangue-modified materials. Increasing the w/c ratio leads to higher structural porosity and lower compressive strength. It also increases fluidity and extends the setting time, which is beneficial for engineering applications, but at the cost of reduced material strength. However, when the w/c ratio reaches 1.2, the material experiences severe water bleeding. The particle size of the coal gangue has a relatively small 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, the change in particle size does 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 exhibits good fluidity, a setting time of 30 minutes, and a 4-hour compressive strength of nearly 4 MPa. This formulation can effectively increase the economic benefits while ensuring the effectiveness of gas control. Close-