The reactive products and reactivity of modified red mud and ground granulated blast furnace slag at different alkalinities

Abstract

• The red mud was successfully modified into high-activity glass. • The reaction mechanism of MRM and GGBFS at different pH values was investigated. • The dissolution of MRM in NaOH solutions enhanced with increased pH values with main reaction products being C-S-H and C 2 ASH 8 . • Compared to GGBFS, the activity of MRM was limited by the content of Ca and the absence of sulfate in glass. Supplementary cementing materials are widely used for cement and concrete. In this study, red mud was modified as a supplementary cementing material. The composition and activity of modified red mud are reported. The reaction products were analysed by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG) and scanning electron microscopy (SEM). The obtained results show that red mud can be modified to glass with activity, and the composition of MRM determines the formation of glass and activity. The dissolution rate of MRM versus time increases with pH in NaOH solutions. The reaction products of MRM pastes in pH = 14 were C 2 ASH 8 and C-S-H. Compared to ground granulated blast furnace slag, the activity of MRM is lower. This is probably attributed to the specific surface area, the content of Ca and the absence of sulfate in glass. The results can be useful for industrial application of MRM.