Thermodynamic optimization of Portland cement clinkers for designing SCM-blended cements

The composition of Portland cement clinker is crucial for determining the hydration and phase assemblages of blended cement systems incorporating supplementary cementitious materials (SCMs). This study investigates the influence of cement clinker compositions on the degree of reaction of fly ash and slag, and the phase evolution in blended systems. Thermodynamic modelling was employed to calculate the mineralogical compositions of clinkers from simulated raw materials and phase assemblages of blended cements, while the reaction degrees of SCMs were predicted using a machine learning model. The results indicate that a C 3 S content of approximately 57% is optimal, as it maintains sufficient portlandite availability for SCM dissolution. Fly ash showed greater dependency on portlandite availability, whereas slag exhibited higher intrinsic reactivity even at lower C 3 S levels. These results highlight the impact of clinker composition and SCM replacement levels on hydration products, providing insights for optimizing cement formulations from production to hydration. • Optimized C 3 S content (∼57%) boosts SCM reaction and balances strength. • Slag shows higher intrinsic reactivity at low clinker levels. • Thermodynamic modeling results reveal phase evolution trends in blended cement systems. • C-A-S-H is stable in all blends, while phase stability varies with C 3 S and SCM type. • Porosity drops sharply up to 63% C 3 S, then plateaus, which is key for dense and durable cement design.