Experimental investigation of strength, durability, and microstructure of red-mud concrete

Recent trends in the construction industry involve the use of industrial by-products as building materials to improve waste management and reduce excessive CO2 emissions from the cement industry. Red mud (RM) is a by-product of alumina refinery plants. When improperly disposed, red mud harms the surrounding area, owing to its highly alkaline nature. In the current work, up to 15% of the cement in concrete was replaced with red mud, in increments of 2.5%. In addition, to enhance the pozzolanic reaction, metakaolin was used as a ternary mineral; it replaces 10% of the cement. A slump cone test was conducted to evaluate the workability. Compressive, flexural, and split tensile strength tests were conducted to observe the mechanical properties. A rapid chloride penetration test and water absorption tests were conducted to determine the durability properties of the concrete. X-ray fluorescence analysis was conducted to determine the chemical composition of both the red mud and the metakaolin. A scanning electron microscope analysis was conducted to characterize the microstructure of the RM concrete. The 12.5% red-mud replacement mix showed the greatest improvement in mechanical properties among all the mixes. As the red-mud replacement increased, the chloride-ion passage was reduced. Moreover, a denser microstructure formation was observed with the red-mud replacement, as compared to standard concrete.