Abstract: Preparation process of activated alumina admixture by calcining bauxite was studied.Combining with the species of product,crystalline state,and specific surface area,the effects of calcination temperature,and time on activity of Al₂O₃ were studied.Species and crystalline state of calcined product were detected by XRD.Specific surface area was detected by laser particle size analyzer.Inhibition effect of the obtained alumina admixture on alkali-aggregate expansion reaction was examined by accelerated mortar bar test (AMBT).Results showed that the best calcination temperature and time were 500 ℃ and 1.0 h,respectively.Inhibition effect of the obtained alumina admixture under those conditions on alkali-aggregate expansion reaction was the best.Activated alumina admixture with mass fraction of 30% could reduce the expansion rate of mortar bar of 14 d from 0.32% to 0.087% and the expansion rate was lower than 0.1% and had been controlled within the safe range.

Key words: bauxite, calcination condition, activated alumina admixture