Physico-chemical performance of red mud/dredged-based LC3

Production of Ordinary Portland Cement (OPC) consumes substantial quantities of raw materials and energy, contributing to global carbon emissions. Limestone Calcined Clay Cement (LC3) is a promising low-carbon alternative binder that replaces a substantial portion of clinker with less energy-intensive materials. At the same time, red mud (RM) and clayey dredged sediments (CDS) pose significant environmental challenges for the aluminum industry and the maritime sector, respectively. Therefore, this study investigates the potential of incorporating RM and CDS to produce a more sustainable LC3. Initially, optimal thermal treatment conditions (i.e. calcination) were evaluated to maximize the reactivity of RM and CDS. Results showed that calcining for 1 hr at 800 °C increased the Strength Activity Index (SAI) for both RM and CDS to above 80%, along with a substantial increase in the dissolution efficiency of Al₂O₃ and SiO₂. RM/CDS-based LC3 performed comparably to OPC and outperformed commercial LC3, while reducing CO₂ emissions by up to 50%. Microstructural analysis, supported by thermodynamic modeling, highlighted the roles of Al₂O₃ and SiO₂ supplied by RM and CDS in facilitating the formation of additional C-S-H, Aft, and Afm phases. These findings offer a viable pathway towards greater sustainability for the cement industry while valorizing waste from other industries.