Synthesis and characterization of geopolymer from “In Natura” red mud and glass waste

Abstract

The use of red mud in the geopolymer production is an attractive method for managing this waste. However, the processing steps usually applied, such as drying and grinding, can significantly increase the material processing costs, and consequently increase the cost of the final product. In this study, geopolymers were developed using red mud “in natura” (non‐processed slurry) and glass waste powder. Parameters including SiO₂/Al₂O₃ ratio (4, 5, and 6), NaOH solution (6, 8, and 10 M) and curing duration (10, 28, and 56 days), were examined to understand the extent and degree of geopolymerization. Compressive strength tests were performed along with the analysis of their microstructural characteristics using quantitative x‐ray diffraction (QXRD) analysis based on Rietveld's refinement method, scanning electron microscopy (SEM), and thermal analysis (TG and DTA). As a result, higher SiO₂/Al₂O₃ ratios and NaOH solution concentrations generally lead to greater compressive strength, which ranges from 9.7 to 43.1 MPa. Microstructural and compositional analyses demonstrated that the final products consist of an amorphous geopolymer binder, crystalline phases originating from raw RM and a neoformed phase, Garronite. This study showed that the RM without any processing step displays a high potential in the geopolymer production.