Effects of fly ash addition on the rheological characteristics of red MUD slurry: An approach to the sustainable mining waste management

The aim of this paper is to study the addition of fly ash in red mud slurry in the view of environmental sustainability, as a contribution to waste disposal methods. Three mixtures with red mud concentrations ranging from 400 g/L to 800 g/L and fly ash addition (maximum of 30% per mass of solid in the slurry) were studied. Textural and morphological aspects were analysed by Scanning Electron Microscope (SEM). Additionally, the chemical composition (major oxides analysis) was performed by ICP-OES. To evaluate the rheological behaviour, measurements using a MCR102 Rheometer were carried out. The addition of fly ash follows a similar rheological behaviour to that shown by the red mud slurry. After dewatering, red mud slurry with fly ash shows a stable framework formed by the interaction of red mud with the silica and silica-aluminium compounds that could be used as raw material, according to international standards.