Investigation on hydration characteristics and microstructure development of low-carbon cementitious material blended with calcined phosphogypsum and steel slag

This research investigates the hydration characteristics, microstructure changes and mechanical properties of a low-carbon cementitious system composed of calcined phosphogypsum (CPG) and steel slag (SS). It systematically assesses how SS fineness and CPG-to-SS ratios affect water requirement, setting time, pH variation, hydration dynamics and compressive strength development. Results show SS fineness notably impacts hydration by regulating system alkalinity and hydration product nucleation/growth. CPG dominates early strength while SS contributes to long-term strength. Finer SS boosts strength and refines microstructure at low CPG dosage but inhibits performance at high CPG content due to elevated pH and particle aggregation. Analysis via isothermal calorimetry, XRD, TG, MIP and SEM verify the interactive hydration mechanism and pore structure modification, highlighting that optimizing SS fineness and CPG proportion is key to developing sustainable, high-performance low-carbon cementitious binders.