Effect of red mud substitution rate on the properties of ternary solid waste geopolymers

In order to further enhance the comprehensive utilization rate of red mud (RM), ternary solid waste geopolymer (TSWG) materials were prepared by incorporating red mud into slag-fly ash-based polymers. The effects of varying red mud substitution rates on the mechanical properties and workability of these TSWG materials were investigated. Combining X-ray diffraction (XRD) and scanning electron microscopy (SEM) tests, the influence mechanism of red mud with different substitution rates on the properties of TSWG was discussed. Furthermore, the cost-effectiveness and environmental impact of TSWG mortars were evaluated. The results indicate that a high content of red mud can stimulate the depolymerization process of aluminosilicate materials. Compared to the reference group (with 0wt% red mud content), the initial setting time of the TSWG containing 40wt% red mud is shortened by 113 minutes. As the red mud substitution rate increases, the degree of polymerization reaction in the geopolymer is improved, but an increasing number of crystals, such as dicalcium silicate and quartz, emerge in the system, disrupting the original structure of the geopolymer material and resulting in a gradual decrease in compressive strength. At a 20wt% red mud replacement rate, the compressive strength of the TSWG after 28 days reaches 34.2 MPa, and the initial fluidity of the slurry is 254 mm. Compared to ordinary Portland cement mortar, this TSWG exhibits superior economic and environmental benefits, as well as a more convenient preparation method.