Influence of substitution of red mud on the properties of LC3 cement

In 2024, the Royal Swedish Institute of Technology introduced Limestone Calcined Clay Cement (LC3), which garneredglobal attention due to its significantly reduced carbon emissions. LC3 is formulated from clinker, calcined clay (metakaolin,MK), and calcium carbonate (CC). However, with the dwindling reserves of clay and limestone in countries like China andthe increasing accumulation of industrial waste such as red mud (RM), substituting RM for MK and CC in LC3 presents apromising alternative. This study investigated the influence of replacing MK and CC with RM on the properties of mortar,alkali penetration, and microstructure. X-ray diffraction (XRD) was employed to analyze mineral composition, scanningelectron microscopy (SEM) to examine microstructure, and energy-dispersive X-ray spectroscopy (EDS) to assess elementaldistribution and alkalinity. The results indicate that RM enhances fluidity, prolongs setting time, and increases compressivestrength, albeit at the expense of early flexural strength. SEM observations reveal denser composites attributed to theformation of C-A-H and C-A-S-H gels, while EDS analysis shows that ammonium carbonate mitigates calcium ion migration.