Microstructure and hydration of interstitial in clinkers produced over molten steel

Abstract Scalable electrical production of clinker is possible under reducing conditions, and the reactivity of C 3 A produced in such conditions has only been superficially described. We examined electric clinkers made over molten steel with a range of fineness and compared them against commercial clinkers. Using x‐ray diffraction, calorimetry, and backscattered electron microscopy/image analysis, we investigated the roles of morphology, crystal structure, and phase interaction. Shortage of Fe 3+ ions in the interstitial in electric clinkers makes its C 3 A more reactive like white cements and synthetic systems. In the presence of ferric oxides, ferrite is formed and the concentration of dissolved Fe 3+ ions in C 3 A increases. The kinetics of C 3 A hydration are hindered both by the ferrite phases intermixing with the C 3 A phase, hence acting as a physical barrier for dissolution, and by Fe 3+ ions dissolving in C 3 A, thereby reducing its intrinsic reactivity. Although this higher reactivity of C 3 A requires more gypsum to ensure proper sulfation, this can be managed by controlling fineness and blending with supplementary cementitious materials.