Study On Early Strength Performance Of Sealing Material For Activated Fly Ash/Cement Composite Mine

With China's increasing attention to coal mine safety issues,the solution of gas outburst problems is the top priority of coal mine safety production.Drilling and extraction is one of the solutions to the problem of gas outburst.The drainage efficiency of gas is directly related to the quality of sealing.Cement-based sealing materials are currently the most widely used sealing materials for gas drainage.However,cement-based materials still have some shortcomings,and it is difficult to meet the increasing underground water retention requirements.Therefore,this paper aims to study the early strength properties of cement-based materials and modify them by adding mineral admixtures and admixtures.Adding mineral admixture fly ash to cement-based materials can improve the performance of materials and reduce engineering costs.However,the“secondary hydration”reaction of fly ash mainly occurs in the late stage of hydration,and the early strength of cement-based materials decreases after the addition of fly ash.In addition to the small size effect of nanomaterials,nano-Si3N4 also has good mechanical properties and chemical stability.Therefore,by using nano-Si₃N₄ and fly ash to recombine,the filling effect and micro-aggregate effect of the two can achieve synergistic optimization.The paper first studied the effect of nano-Si₃N₄ on cement-based materials.The experiment selected a water-cement ratio of 0.4?W/C=0.4?,and the nano-Si₃N₄ with a content of 1%,2%,and 3%?by mass of the gel material?was respectively incorporated into the cement paste.The relevant physical properties of the cement specimens were tested.The results show that the compressive strength of the cement specimens after adding the nano-Si3N4 is greatly improved compared with the benchmark group,but the compressive strength tends to decrease with the increase of the blending amount.When the nano-Si3N4 content is 2%,the physical properties of the cement test piece reach the optimum state.At this time,the compressive strengths of the hydrated 1d,3d,7d,and28d specimens were 9.2 MPa,19.8 MPa,27.5 MPa,and 48.7 MPa,respectively,and the strength increments were 37.3%,25.3%,and 22.8%,respectively,compared with the baseline group.,19.1%.Based on the experiment of the effect of single-doped nano-Si₃N₄ on the performance of cement paste,nano-silicon nitride and fly ash were combined to study the effect of synergy on the performance of cement-based materials.On the basis of the nano-Si3N4 content of 2%,10%,20%,30%fly ash was replaced by cement,and the compressive strength test of the test pieces of the experimental group at different ages was carried out.Fly ash mixed with 10%,20%,and 30%?instead of the corresponding cement content?was used as a control group.It was found through experiments that the compressive strength of the experimental group was not significantly increased compared with the reference group due to the volcanic ash activity of the fly ash,but the compressive strength was greatly improved compared with the control group with the single fly ash.The compressive strength of cement specimens with 2%nano-Si3N4 and10%,20%,and 30%fly ash hydrated at 1d was 32.1%,26.4%,and 30.6%,respectively.After comparison,it was found that 10%experimental group,2%nano-Si3N4+10%FA,was selected as the optimal group.XRD,TG-DSC and SEM analysis were carried out on the optimal set of cement specimens to study its effect on cement hydration reaction.Based on the above experiments,0.02%,0.03%,and 0.05%TEA were respectively incorporated on the basis of 2%nano-Si₃N₄ and 10%fly ash.The optimum dosage of TEA was selected by experiment and its mechanism was studied by microstructure analysis.It was found that the compressive strength,fluidity and setting time of the cement specimens reached the optimum state when the TEA content was 0.05%.When2%nano-Si3N4+10%FA+0.05%TEA was added to the cement-based material,the compressive strength of 1d was 9.3 MPa,which was 38.8%compared with the reference group.Through microstructural analysis,it was found that the optimal group improved the hydration process of cement without affecting the type of hydration products of cement.Moreover,the effect of the composite excitation of nano-silicon nitride and triethanolamine on fly ash cement is better than that of single-doped nano-silicon nitride.Figure[62]Table[6]Reference[69]...