Effect of new modified materials on the microscopic pore structure and hydration characteristics of sealing materials in coal seam boreholes

To improve the efficiency of coal mine gas extraction, it is necessary to optimize the performance of sealing materials. In this paper, fly ash, nano-silica, and triethanolamine was selected to optimize the pore structure of the sealing materials. The qualitative and quantitative analysis of the seal material was performed by low temperature liquid nitrogen adsorption experiments, scanning electron microscopy, and combined with fractal theory. The results show that the pores of common sealing materials are mainly mesoporous, accounting for 52.19%, and the volume of micropores is the smallest, accounting for 9.88%. The single doping of fly ash made the pore volume of the material decrease by 9.5%, and the percentage of mesopores increased by 1.3%, but the percentage of micropores decreased by 0.9%. Co-doping with nano-silica and fly ash increased the microporous percentage of the material by 0.77% and the peak stress by 17.43%. The synergistic effect of fly ash, nano-silica, and triethanolamine was most effective in optimizing the pore structure of the sealing material. The pore volume was reduced to 0.08198 cm(3)/g, and the fractal dimensions D-1 and D-2 were increased by 2.88% and 2.48%, respectively. The microscopic morphology of the material was also flatter and denser, and the hydration of fly ash was also more complete.