Adjust setting time and early-age strength of ferrite-rich calcium sulfoaluminate cement through different chemical admixtures

To regulate the setting behavior and early-age strength of ferrite-rich calcium sulfoaluminate (CSA) cement, this study employed amino trimethylene phosphonic acid (ATMP) in combination with citric acid (CA) or sodium gluconate (SG). The effects of these retarders on CSA were investigated through assessments of physical and mechanical properties, microscopic characterization, and hydration kinetics. The results show that ATMP improves paste fluidity and significantly prolongs the setting time by extending the hydration induction period. The compressive strength of CSA increased progressively with curing age. XRD analysis revealed that the addition of retarders promoted ettringite formation, thereby contributing to strength development. The highest 28-day compressive strength (48.9 MPa) was achieved when ATMP and SG were used together at a total dosage of 0.3%. Calorimetry further indicated that increasing the ATMP content delayed the main exothermic peak, with the most pronounced delay observed for the ATMP–SG combination.