The role of calcium formate in supersulfated cement: A multiscale study on hydration mechanisms, pore structure and environmental benefits

This research investigates the role of calcium formate (CF) in enhancing the hydration, microstructure, and mechanical performance of supersulfated cement (SSC). The environmental impact of SSC-CF systems was evaluated. Hydration kinetics revealed that 3 wt% CF (SSC-3CF) shortened the induction period by 1.2 h and advanced the main exothermic peak by 1.3 h. Analysis based on the Krstulović-Dabić model indicated that CF primarily enhances the nucleation and crystal growth process, increasing the reaction rate constant K NG , with an optimum at 3 wt% CF. The addition of 3 wt% CF reduced total porosity by 33.27 % at 1 d, minimized large capillary pores and increased fine capillary pores, yielding a denser structure. SSC-3CF exhibited significantly higher compressive strength at all ages, with maximum enhancements observed before 7 d. Solid-state 29 Si NMR elucidated that CF accelerates slag dissolution and promotes C-(A)-S-H gel precipitation, correlating with a 98.0 % increase in hydration degree at 1 d. Critically, a preliminary carbon footprint assessment indicated that SSC-3CF achieved an estimated footprint of 158.76 kg CO₂/t, suggesting a potential reduction of approximately 76.9 % compared to PC. The findings demonstrate CF’s dual role in mitigating SSC’s early-strength deficit through optimized hydration kinetics and pore refinement while offering substantial carbon reduction potential for sustainable construction.