Research on the performance and application of nano-MgO modified ultrafine cement-based sealing materials
Jiajia Zhao, Shixiang Tian, Cheng Chen, Xuan Zhang, Tengfei Ma, Qican Ran, Xinbo Luo
Abstract
The gas tightness and strength of cement-based sealing materials are critical factors influencing coalbed methane (CBM) extraction efficiency. However, ordinary cement-based sealing materials tend to lose water, shrink, and develop cracks, which results in poor gas extraction performance. Therefore, modifying cement-based sealing materials with nano-expansion materials is one of the effective solutions to this problem. This study utilized a range of experimental techniques and a coal mining case study to systematically explore the impact of nano-MgO content on the performance of ultrafine cement-based sealing materials, and to clarify the mechanism through which nano-MgO improves the properties of the modified materials. The results show that as the nano-MgO content increases, the setting time, flowability, and water bleeding rate of the modified materials decrease, while the expansion rate increases. Uniaxial compressive tests indicate that the material with 0.7 wt% nano-MgO content achieves the best compressive strength improvement. Nano-MgO significantly improved the material’s density and surface morphology, enhanced the pore structure, and strengthened the material’s strength and stability. Additionally, nano-MgO promoted the formation of hydration products such as Mg(OH)₂, and the degree of reaction of nano-MgO increased with curing time, showing an active role in promoting hydration reactions. A coal mine case study found that the 0.7 wt% nano-MgO modified material increased the maximum gas extraction concentration from a single hole by about 24 %, and the gas extraction volume by about 47 %. This study provides reliable technical support and theoretical basis for the application of new drilling sealing materials. • The study integrated physical experiments with a coal mine case study. • The performance of nano-MgO modified sealing materials was evaluated. • The optimum amount of nano-MgO to be incorporated is 0.7 wt%. • The modification mechanism of the sealing material is elucidated. • Modified materials significantly enhanced gas extraction efficiency.