Geopolymerization of Red Mud and Fly Ash for Civil Infrastructure Applications

This paper presents a study that investigates the geopolymerization of red mud, a major industrial waste from alumina refining, and fly ash, also an industrial waste from coal combustion, using very limited non-waste materials. Different synthesis parameters (e.g., red mud to fly ash ratio, sodium silicate solution to solid mixture (red mud and fly ash) ratio, and different types of sodium silicate solution) were varied to assess their influences on the mechanical properties of final geopolymer products. The results of unconfined compression testing show that these factors have significant influence on the mechanical properties of the synthesized geopolymers. Depending on the synthesis conditions, the unconfined compressive strength ranges from 3 to 13MPa, and the high values are comparable with certain types of Portland cement. The process of geopolymerization was confirmed by the composition of the final products analyzed by X-ray diffraction. The findings suggest that the two major industrial wastes, red mud and fly ash, can be reused to produce geopolymers that may replace Portland cement and hence be applied in civil infrastructure construction.