Abstract
The influence of the interaction among water-cement ratio, content of expansion agent, water reducing agent, and retarder on the compressive strength of new sealing material was studied. The Design-Expert software was used to design experiments, establish a quadratic polynomial regression model, draw response surface, and optimize parameters. The microstructure morphology of the sample is explored by a scanning electron microscope (hereinafter referred to as SEM). The research results show that the interaction between the water-cement ratio and expansion agent content is the most crucial factor affecting the compressive strength of the new sealing material. Under the optimal condition of 0.4% water reducing agent, 0.04% retarder, 0.8 water-cement ratio, and 8% expansion agent, the compressive strength of the sealing material cured for 3 d and 7 d is 39.247 MPa and 41.044 MPa, with the maximum absolute error of 1.71% and 2.81%, which proves the high accuracy of the model. The main hydration products of the new sealing material are ettringite and C-S-H gel, interlacing each other to form a dense structure, which contributes to the high strength of the new sealing material.
Highlights
China is currently faced with the most severe gas disaster in coal mines in the world [1,2,3]
Tan et al [23] studied the waterproof performance of two kinds of water swellable pad materials: water swellable rubber (WSR) and water swellable polyurethane (WSP)
The results reveal that the interaction between the water-cement ratio, retarder, expansion agent, and water reducing agent in the composite sealing material system significantly affects the compressive strength of the sealing material cured for 3 d and 7 d
Summary
China is currently faced with the most severe gas disaster in coal mines in the world [1,2,3]. Fly ash was used as a base material and adding water-retaining agent, expansion agent This material, with a certain degree of expansion, is not easy to shrink and adheres tightly to coal and could significantly improve the mechanical properties of grouting materials [15,16,17]. The results reveal that the interaction between the water-cement ratio, retarder, expansion agent, and water reducing agent in the composite sealing material system significantly affects the compressive strength of the sealing material cured for 3 d and 7 d. The optimal ratio is determined by the verification test, and the mechanism of action of the new sealing material is revealed by SEM analysis
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