Development and sustainability assessment of red mud-based green bricks: Techno-economic and environmental performance

Red mud (RM) is an alkaline discarded hazardous waste for mining alumina from bauxite ore and thus has the potential to be used for geopolymerization. This work has been designed to couple RM with by-product waste to develop a green structural block, an alternative to fired clay or cement brick. Specimens were initially prepared at a lab scale for optimization and thus verified at an industrial scale. At the lab scale, the proportion of RM was optimized by using it in the range of 0-50 % at 10 % intervals and activated by the combination of NaOH and Na2SiO3. The physicomechanical performance was evaluated, and the specimen with 30 % RM performed best at ambient and hot curing conditions. Upon transitioning to an industrial scale, structural block/ brick measuring 225 x 113 x 75 mm was manufactured using uniaxial compression, resulting in a notable 202 % increase in strength compared to laboratory-scale specimens. Furthermore, blocks/bricks fulfilled the structural requirements outlined by ASTM and ACI, validating their suitability for industrial applications. Economic and environmental analyses of developed bricks revealed fewer costs and significantly lower CO2 emissions than conventional bricks and geopolymer-based bricks. The economic and environmental indices also made the RM the appropriate choice. Furthermore, the RM-based brick is sustainable and feasible based on the sustainability matrix.