Structural investigation relating to the cementitious activity of bauxite residue - Red mud

The cementitious behavior of red mud derived from Bauxite-Calcination method was investigated in this research. Red mud were calcined in the interval 400-900 degrees C to enhance their pozzolanic activity and then characterized in depth through XRD, FTIR and Si-29 MAS-NMR techniques with the aim to correlate phase transitions and structural features with the cementitious activity. The cementitious activity of calcined red mud was evaluated through testing the compressive strength of blended cement mortars. The results indicate that red mud calcined at 600 degrees C has good cementitious activity due to the formation of poorly-crystallized Ca2SiO4. The poorly-crystallized Ca2SiO4 is a metastable phase which will transform into highly-crystallized Ca2SiO4 with the increase of calcination temperature from 700 degrees C moving to 900 degrees C. It is the metastable phase that mainly contributes to the good cementitious activity of red mud. This paper points out another promising direction for the proper utilization of red mud. (C) 2011 Elsevier Ltd. All rights reserved.