Cement producers are increasingly adopting alternative fuels (AFs), e.g., plastic waste, used tires, biomass, and sewage sludge, to reduce the environmental footprint. These introduce additional components into the kiln, impacting the mineralogy and performance of Ordinary Portland Cement (OPC) clinker by the formation of specific polymorphs or new compounds in the product. Leveraging the Calculation of Phase Diagrams (CALPHAD) method, this study evaluates existing commercial thermodynamic databases, including FactSage’s FTOxid and GTOX. Additionally, it assesses their applicability to OPC clinker mineralogy predictions by a two-step model based on raw materials chemical composition and considering minor element insertion (MgO, Na₂O, K₂O, SO₃, MnO₂, P₂O₅, TiO₂, SiO₂, Al₂O₃, and Fe₂O₃). The output of the model, as main mineralogical phases (C₃S, C₂S, C₃A and C₄AF), is benchmarked with experimental mineralogical compositions from literature that used Laboratory XRD and Synchrotron XRD Rietveld analysis. Results show that FactSage’s FTOxid database performs poorly, showing no Alite (C₃S) for all simulated cases; whereas GTOX database yields a better outcome, achieving a similar overall performance with Bogue’s equations in clinker mineralogical prediction leaving significant room for refinement to improve accuracy and applicability. This study demonstrates that an optimization of clinker composition and process control is feasible via CALPHAD-based models with their improved Gibbs energy datasets. This supports the cement industry efforts to reduce AF-induced variability directly lowering CO2 emissions and energy consumption in clinker production.
Bandak et al. (Fri,) studied this question.