Abstract: In order to find the activation mechanism of high alumina bauxite calcination at low temperature， the crystallization characteristics of bauxite calcined at different temperatures were studied and the effects of calcination temperature on the activity of the corundum crystals were investigated by combining the product type， crystal state and surface morphology. X-ray diffraction（XRD） was used to detect the type and crystal state of the calcined high alumina bauxite. The morphology of the calcined product was observed by scanning electron microscopy（SEM）. The results show that the high alumina bauxite calcined at 500 ℃ has the fasted dehydration speed， lowest crystallinity and the highest gelation activity， and is more suitable as a cementitious material admixture in the manufacture of alumina cement and grouting materials. During the calcination and heating process， the layered structure of diaspore is gradually bonded to form the granular structure of corundum， and the horizontal stripes on the surface of the particles are gradually clear， indicating that the crystallinity of the crystal is gradually increased and the reactivity is gradually reduced.

Key words: Bauxite, Calcining conditions, Cementitious material admixture, Crystallinity