Calcination Activation Of Bauxite Tailings And Its Influence On The Performance Of Cement

With the rapid development of the alumina industry,the accumulation of bauxite tailings is increasing day by day.Most bauxite tailings are accumulated in the tailing pond and the utilization rate is very low.The treatment and utilization of bauxite tailings is imminent.The use of bauxite tailings as auxiliary cementitious materials in building materials has become an effective way of utilization.Through experiments,this paper systematically studied the influence of calcination temperature on the activation performance of bauxite tailings with different particle sizes,and simulated the hydration of bauxite tailings as auxiliary cementitious materials in cement and cement using different kinetic models.The hydration process of the bauxite tailings composite cementitious material,and the hydration process is deeply explored from the mechanical properties and microstructure.The results show that the mineral phase and chemical composition of the coarse and fine tailings classified by the concentrator are basically the same.Through XRD and infrared spectroscopy analysis,the main mineral phase of the coarse and fine tailings,diaspore,is at 600℃It is completely transformed into corundum phase,and kaolinite is completely transformed into metakaolinite at 700°C.Below 700℃,with the increase of the calcination temperature,the particle size of the coarse and fine tailings gradually becomes smaller;starting from 700℃,with the increase of the calcination temperature,sintering occurs,and the coarse and fine tailings The particle size of the particles began to gradually become larger.When the calcination temperature is 700℃,the activity index of the coarse tailings and fine tailings reach the highest.When the content of gypsum in the ternary cementing system is constant,as the content of bauxite tailings increases,the end time of the induction period and acceleration period is shorter,and the time to reach the second exothermic peak is shorter.The larger the exothermic peak,the higher the reaction rate K in the acceleration phase,and the lower the value of n.When the amount of bauxite tailings in the ternary cementing system is constant,with the increase of the amount of gypsum,the opposite result is obtained.The hydration rate and the degree of hydration in the diffusion stage of the bauxite tailings-lime-gypsum ternary gelling system are extremely low.As the content of bauxite tailings increases,the degree of hydration of the ternary gelling system in the diffusion stage gradually decreases.With the increase of the content of bauxite tailings,the end time of the induction period of the cement-tailing composite cementing system is gradually extended,shortening the time to reach the peak of the second exothermic peak,and at the same time reducing the second peak of exothermic heat.The cumulative heat release of the entire composite gelling system is calculated.The hydration kinetic model can simulate the hydration process of the composite gelation system to a certain extent,can reflect the hydration trend of the composite gelation system and control the kinetic process of each hydration stage.With the increase of the content of bauxite tailings,the reaction rate constants k₁’,k₂’and k₃’in the composite cementing system decrease.When the content of bauxite tailings is the same,the values of k₁’and k₂’increase with the increase of tailings fineness.As the content of bauxite tailings increases,the degree of hydrationα1 decreases,andα₂ andα₂-α₁increase.There are 51 pictures,15 tables and 102 references in this paper...