Study On The Pozzolanic Activity And Rheological Properties Of The Burnt Rocks Fluid In Coal Fire Fields

Coal fire disasters are seriously menacing the colliery's safety and ecological environment.Grouting engineering as a significant coal fire management is often used for seal the underground cracks to isolate the contact between coal and oxygen.Loess is the most common grouting material at present.Focusing on the current situation that loess resources are scarce in some coal fire fields in Northwest China,burnt rocks,one of the common waste,are studied and developed into a new grouting material as a substitute of loess slurry for coal fire prevention and extinguishing in this paper.The main research and results are as follows:(1)XRF,XRD analysis and Frattini test are applied to study the pozzolanic activity of the burnt rocks.The test results indicate that the burnt rocks possess pozzolanic activity.The larger the particle size of burnt rocks and the stronger the burning effect in the process of diagenesis is,the greater the pozzolanic activity is.Pozzolanic activity can be used as one of the criteria for classification and discrimination of burnt rocks(2)Basing on the comprehensive consideration of economy and material performance,sintering rock is selected as the raw material of grouting material,and its processing standard is determined as crushing and sieving to less than 100 mesh.The results of static water separation test of mixed slurry show that the water separation rate of slurry will increase with the increase of the proportion of burnt rocks and the water cement ratio of slurry.When the water cement ratio is 0.45:1 and the water cement ratio is 0.6:1(the mixture rate of burnt rocks is 0%,20% and 40%),the mixed slurry is stable and not easy to separate.(3)The viscosity of the pure burnt rocks slurry is relatively low,its shear stress basically increases linearly with the increase of the shear rate,and its viscosity is basically unchanged.The addition of cement will greatly ameliorate the rheological properties of pure burnt rocks slurry.The viscosity of the mixed slurry will reduce with the raise of water cement ratio.When the ratio of water to cement is lower than 0.6:1,the viscosity of the mixed slurry rises with the ascent of the ratio of burnt rocks;when the ratio of water to cement is higher than 0.6:1,the change rule is opposite.Under the condition of low shear rate,the mixed slurry tends to be pseudoplastic fluid,while under the condition of high shear rate,it tends to be Bingham fluid.Combined with the comprehensive analysis of slurry stability and rheological properties,the best water cement ratio and burnt rocks ratio of slurry is determined as 0.6:1 and 40% respectively.