Researchers at Concordia have found a way to use red mud, a waste product of aluminum production, to help turn low-quality clay and dredged sediment into useful ingredients for lower-carbon cement. They estimate that the swap could reduce greenhouse-gas emissions by 25 to 50 per cent, depending on the formulation.
The study examined whether these difficult-to-dispose-of materials could replace part of the conventional Portland cement used in construction. The approach could reduce the need for both virgin raw materials and clinker, a superheated mixture of clay and limestone that is a major source of cement's carbon emissions, the researchers say.
Researchers first heated the red mud and dredged sediment at 800 degrees Celsius to make the materials more chemically reactive. One hour of heating produced the best overall results, increasing their ability to participate in the chemical reactions that give cement its strength.
The team then tested different mixtures containing the treated waste materials. The results showed that red mud could compensate for some of the limitations of the dredged sediment, helping promote the formation of compounds that strengthen cement. In several formulations, the combination produced stronger materials than mixtures made with dredged sediment alone.
The researchers also found that the amount of red mud mattered. Too much could reduce strength in some mixtures, while moderate amounts improved the material's structure and performance.
The study was written by Faber Chaparro, MSc 2026, Mohamed Osman, PhD 2026, Ahmed Soliman, associate professor in the Department of Building, Civil and Environmental Engineering, and Mohammad Almakhadmeh, PhD 2026. It was published in the journal Construction and Building Materials.
It received funding from the Natural Science and Engineering Research Council of Canada, the Fonds de Recherche du Québec - Nature et Technologies and the Canadian Standards Association.
Read the paper: "Physico-chemical performance of red mud/dredged-based LC3"
