Feasibility study of red mud for geopolymer preparation: effect of particle size fraction

The storage of red mud has seriously damaged the ecological environment, and its utilization is urgent. The roles of particle size fraction of red mud on the geopolymer properties was investigated, to provide guidance for the preparation of red mud-based geopolymer. The composition variation, workability, mechanical strength, and microstructure of each red mud fraction were analyzed, and the results show that the chemical composition changed with the classification. The fluidity decreased first and then increased with the decrement of particle fraction, and all the specimens showed the rheological characteristics of Herschel-Buckley model. The specimens with coarser and finer particles both had excellent mechanical strength and lower porosity. The microstructure of red mud-based geopolymer with different red mud particle fractions was analyzed by FTIR, XRD and SEM-EDS. The results showed that the main hydration products were geopolymer gel (N-A-C-S-H). And the particle fraction has a little effect on the kinds of hydration products. Finally, the particle fraction of red mud was classified according to the properties of red mud-based geopolymer.