Effect of thermal activation and particle size on cementitious activity of bauxite tailings.

To explore the influence of thermal activation and particle size on cementitious activity of bauxite tailings, in this study, the raw bauxite tailings were classified into coarse bauxite tailings (CBT) and fine bauxite tailings (FBT) by a powder separator, and then the effect of activation temperature on cementitious activity of CBT and FBT was investigated. XRD, TG, and FTIR were used to study the phase and structure changes of CBT and FBT during the process of thermal activation. The results show that the main mineral phases of CBT and FBT, diaspore and kaolinite, begin to remove a large amount of hydroxyl groups at 500 ℃ and convert into corundum and metakaolin, respectively. The diaspore and kaolinite have completely removed the hydroxyl groups at 600 °C and 700 °C, respectively. With the increase of activation temperature, the particle size of CBT and FBT are first gradually decreased, when the activation temperature exceeds 700 ℃, as the activation temperature continues to arise, the particle size of CBT and FBT are gradually increased due to the occurrence of sintering. The activity index of bauxite tailings is increased with the increase of fineness, and the optimum activation temperature of CBT and FBT is 700 °C. When the activation temperature is the same, FBT has higher pozzolanic activity than CBT.