Through company-driven research and global partnerships, Alcoa is making strides in finding reuse opportunities for bauxite residue, a byproduct of the alumina refining process.
Alcoa has a goal to reduce bauxite residue land requirements per metric ton of alumina produced by 15 percent by 2030, from a 2015 baseline. A key driver in achieving the goal is finding reuse opportunities for bauxite residue, which consists primarily of red mud and coarse sand.
Alcoa is a founding member of the four-year ReActiv project, which is seeking to transform bauxite residue into a reactive material suitable for new cement products that have a low carbon dioxide footprint. The project consortium comprises major cement company LafargeHolcim, seven alumina refineries, two aluminum associations, six universities and research institutes, and five engineering companies from 12 European countries. The European Union has provided US$10.6 million (€8.8 million) in funding.
In addition, the Alcoa Foundation is supporting research at the University of São Paulo (USP) that is focused on using bauxite residue in the manufacture of cement.
“The USP research has demonstrated that it is technically feasible to replace a portion of the cement with bauxite residue for diverse types of cementitious products,” said Lance Myers, principal research scientist and program manager for Alcoa’s Continuous Improvement Centre of Excellence.
The team at the USP commenced the study by comprehensively characterizing bauxite residue to ensure the material properties most relevant to the civil construction sector were well understood. Results from this work identified opportunities for the successful use of residue with Portland cement – the most common type of cement in general use around the world – in compositions of mortars or concretes.
To understand the durability of the final products, a pilot plant produced some urban furniture components (benches, tiles etc.) that were exposed to environmental conditions. Some components have been exposed for more than three years while others are still being monitored. Results to date are promising.
The results obtained so far show that it is technically feasible to replace up to 20% of pure cement with bauxite residue, but this will be dependent on the type of Portland cement and of the composition of the residue, according to USP’s research.
Meanwhile, Alcoa is working with the International Aluminium Institute (IAI) to identify potential pathways for the adoption of bauxite residue in cement production and use. In November of 2020, IAI released its technology roadmap to maximize the use of bauxite residue in the cement industry.
We are also supporting an IAI project, led by the University of Western Australia, that could rapidly transform stored bauxite residue into a soil-like medium. The study has progressed to testing at field scale, with trial plots established at our Kwinana refinery in Western Australia.