Effect Of Temperature On Properties And Structure Of Slurry Backfill Material

China is rich in coal resources and economic development is highly dependent on it.But the environmental problems are becoming increasingly prominent because of the over-exploitation of coal.At the same time,a large amount of fly ash is generated with the large-scale construction of thermal power plants,causing serious damage to the ecological environment.Green filling and mining has gradually become an important mining method for coal resources in order to achieve sustainable economic development.The Slurry Backfill Material is based on fly ash as the base material,mixed with cement,lime,gypsum and other accessories,having excellent mobility,water-saving,swelling,long-term stability,high strength,low cost and other characteristics,not only solving the problem of the using of fly ash,but also can be used for underground filling.Although the Slurry Backfill Material has been used for actual production,we do not understand the internal formation process which has restricted the further development of research.In this paper,the effect of temperature on the properties and structure of Slurry Backfill Material was discussed.The main research work is:(1)We calculate the enthalpy change,entropy change and Gibbs free energy change before and after the reaction from the thermodynamic analysis of the Slurry Backfill Material to determine the possibility of the occurrence of each reaction and the formation process of Slurry Backfill Material.(2)Build the hydration kinetics model of fly ash and cement,and the hydration process is divided into three processes: crystal nucleation and crystal growth,phase boundary reaction and diffusion.We can calculated the body of fly ash and cement hydration degree at different temperatures under different age filling through the model.So the coagulation time,compressive strength,ettringite content and microstructure of Slurry Backfill Material under different temperatures can be predicted.(3)The coagulation time and compressive strength of the samples at different temperatures were tested and analyzed by SEM,XRD and differential thermal analysis.The increase of temperature has a positive effect on the setting time and pre-strength of the slurry backfill material.But the free water inside the filling body will be lost when the temperature is too high,so that the r late of the reaction lost a good hydration environment,resulting in lower hydration rate decreased and the growth of the intensity is slower.The slurry backfill material is filled with ettringite structure as the skeleton,with silica gel,aluminum glue and other cementitious material as the main filler,is a porous structure consisted of solid-liquid-gas three-phase structure.