Innovative cement replacement using calcined bauxite residue: Enhancing environmental sustainability in the construction sector

Cement production is responsible for up to 95% of CO2 emissions in the construction sector, making it a significant contributor to global greenhouse gas emissions. Therefore, developing sustainable construction materials, such as bauxite residue (BR), is essential due to its high alumina-silica content and availability. However, the low reactivity of SiO2 in BR necessitates thermal activation to initiate pozzolanic reactions, whereby siliceous or aluminous phases combine with calcium hydroxide (Ca(OH)2) in the presence of water to yield additional binding compounds that enhance strength and durability. This study investigates the potential of calcinated bauxite residue at 500 °C (BRC500) as a partial cement replacement to promote sustainable construction through waste valorization. Compressive strength tests were performed at 10-50% replacement levels, along with setting time tests. XRD analysis was carried out to determine the crystalline structure and phase composition of the synthesized materials. The optimal mechanical performance was observed at a 10% replacement level, with the formation of portlandite as hydration phases. In contrast, higher dosages led to decreased strength and longer setting times. The findings align with Sustainable Development Goals No. 9, 11, and 12 by promoting sustainable infrastructure practices and circular use of industrial byproducts.