Effects of Dosage and Type of GGBS on the Mechanical Properties of a Hybrid Red-Mud Geopolymer

Bayer red mud (RM) is made from aluminum ore using the Bayer process and is considered an industrial waste. The storage of unused RM can cause environmental and geological problems. Although several studies have focused on RM geopolymers, the amount of RM consumed by these synthetic geopolymers is small (usually < 50%). Therefore, in this study, a hybrid geopolymer material with more than 90% RM content was developed and made it possible to apply in engineering construction. The consumption of a considerable amount of RM would reduce the massive accumulation of RM and address the shortage of natural construction materials. Experiments were conducted with ground granulated blast-furnace slag (GGBS) as the activator. Two different active GGBSs were selected to stabilize the RM by geopolymerization. The effects of dosage and type of GGBS on the mechanical properties of RM were investigated by conducting unconfined compression tests and disintegration and compression experiments. The experimental results indicated that the type and dosage of GGBS had a significant effect on the mechanical behavior of RM. Based on the unconfined compressive strength (UCS) values and the results of the disintegration and compression experiments, the optimal RM-GGBS mixed geopolymer was determined by orthogonal analysis. Microscopic analysis showed that under optimal conditions, the amorphous phase participated in the geopolymerization process, forming an amorphous geopolymer that improved the mechanical properties of RM.