Mineralogy and properties of cement clinker calcined with spent cathode carbon as an alternative fuel

Spent cathode carbon (SCC) is a hazardous solid waste generated from aluminium electrolysis, which poses challenges for safe disposal and resource recovery. In this study, the use of SCC as an alternative fuel in cement kiln co-processing and its effects on clinker mineralogy, hydration kinetics and mechanical performance were investigated. The results showed that SCC incorporation enhanced clinker burnability, promoted the formation of alite (C3S) and tricalcium aluminate (C3A) over belite (C2S) and ferrite (C4AF), and induced a progressive M1→M3 transformation of C3S. Higher substitution ratios enlarged alite crystals while reducing belite crystal sizes. Regarding hydration, SCC substitution prolonged the induction period and led to a non-monotonic variation of the reaction rate during the acceleration stage. Compressive strength was improved with SCC substitution ratios below 20% (with the optimum being 20%), whereas a marked decline occurred at 30% substitution. These findings confirm that controlled SCC substitution enhances clinker performance while offering a sustainable route for hazardous waste management.