Sintered bayer red mud based ceramic bricks: Microstructure evolution and alkalis immobilization mechanism

Abstract Bayer red mud based ceramic bricks (RMCB) were produced by normal sintering and the effects of sintering temperature on their physical and mechanical properties, mineral composition and microstructure were analyzed. The water permeability and interconnected pores formation mechanism was also analyzed, as well as the pH and conductivity of RMCB leaching solution to evaluate environmental effects. The results show the RMCB to have excellent performances (compressive strength, 22.69 MPa; bulk density, 1.68 g/cm 3 ; total porosity, 47.12%; Linear shrinkage, 7.29%) when sintered at 1125 ℃. Nepheline and anorthite phases formed during sintering are felt responsible for the strength of RMCB. The excellent water permeability is attributed to the creation of a network of interconnected pores within the RMCB. The pH and conductivity of RMCB are greatly reduced compared to the raw Bayer red mud leaching solution due to the stabilized aluminosilicates formed during the sintering process, thus avoiding alkaline harm to the environment.