Effect of the Ferrite Phase on Phase Evolution and Hydration Properties in Quaternary Phase–Ferrite Phase (QF) Low-Carbon Clinkers

To promote the sustainable development and efficient utilization of high-alumina cement clinkers, this study designed a binary composite clinker consisting of the quaternary (Q) phase (Ca20Al26Mg3Si3O68) and the ferrite phase. The effects of ferrite content (10–30 wt %) on clinker synthesis, hydration kinetics, and mechanical properties were systematically investigated using multiple characterization techniques. The results indicate that the incorporation of ferrite facilitates the formation of the Q phase at lower temperatures, reducing energy consumption during sintering; however, it induces partial decomposition to C12A7 above 1300 °C, necessitating precise temperature control for phase stability. Hydration tests reveal that an appropriate ferrite content (10–20%) effectively optimizes the hydration process: it not only mitigates early stage rapid hydration, reducing the risk of heat accumulation, but also significantly enhances mid-to-late-stage hydration activity, contributing to sustained strength development. The low-calcium composition reduces limestone consumption, enabling over 30% theoretical carbon reduction compared to that of ordinary Portland cement. This discovery advances the sustainability-driven design of high-performance, low-carbon cementitious materials via ecofriendly phase engineering.