Evaluation of the potential environmental impacts and benefits of producing alkali-activated concrete from bauxite residue

The disposal of bauxite residue is one of the most challenging issues facing the aluminum industry. The only alumina refinery in Canada, located in the province of Québec, generates around one million tonnes of bauxite residue annually. In response to this challenge, and the growing demand from the construction industry for concrete with a low environmental impact, the utilization of bauxite residue in alkali-activated concrete emerges as a promising valorization pathway. This study presents a life cycle assessment (LCA) of alkali-activated concrete formulated with bauxite residue and fly ash sourced from coal-fired power plants. The main objective was to identify the conditions under which alkali-activated concrete could offer environmental advantages over conventional concrete. The results indicate that, under the most favorable scenarios, characterized by the use of unpretreated bauxite residue, the proximity of aluminosilicate precursors to concrete production facilities, and the supply of low-carbon sodium hydroxide and hydrothermal sodium silicate, most environmental impact categories can be reduced compared to portland cement concrete. In the case of greenhouse gas emissions, the reduction ranges from 43% to 59%. However, these benefits are highly sensitive to the availability of low-carbon sodium silicate and sodium hydroxide, as well as the availability, location, and mode of transport of aluminosilicate precursors. These findings underscore the importance of supply chain configuration. A multidisciplinary approach is needed to assess the environmental, technical, and logistical feasibility of a bauxite residue-based alkali-activated concrete sector in Québec and other regions where such residues are generated.