High ferrite Portland cement: Synergistic influence of Q phase and gypsum on hydration kinetics

High ferrite Portland cement (HFPC), a low-carbon alternative to ordinary Portland cement with reduced C₃S and C₃A alongside elevated C₄AF and C₂S, exhibits insufficient early- and mid-term strength development due to sluggish hydration kinetics. To address this limitation, the synergistic effects of Q phase (Ca₂₀Al₂₆Mg₃Si₃O₆₈) clinker (0–12 wt%) and gypsum (0–8 wt%) on the hydration regulation, mechanical properties and microstructure evolution of HFPC were systematically investigated. Results demonstrate that a hybrid formulation containing 6 wt% Q phase clinker and 4 wt% gypsum achieves a 1-day compressive strength comparable to pure HFPC while significantly enhancing the 28-day strength to over 90 MPa. Gypsum addition was found to mitigate the early-stage hydration retardation induced by Q phase, primarily by promoting the nucleation and stabilization of ettringite. This synergy elongates C-(A-)S-H chains and enhances chloride binding than HFPC, with concurrent porosity reduction and pore size distribution homogenization collectively boosting mechanical and durability performance.