Performance evolution of high ductility cementitious composites under different curing regimes: Hydration kinetics, microstructure development, and mechanical behavior

High ductility cementitious composites (HDCC) exhibit exceptional strain-hardening behavior and multiple cracking capabilities, making them highly promising for engineering applications. However, the high mineral admixture content leads to slow early-age strength development under standard curing. Steam curing effectively accelerates hydration and pozzolanic reactions, enhancing mechanical properties, refining microstructure, and increasing production efficiency. Despite these advantages, the absence of standardized steam curing regimes results in inconsistent performance outcomes. This study systematically examined the performance evolution of HDCC under steam curing and standard curing conditions through a multi-scale approach, encompassing microscopic hydration processes to macroscopic mechanical properties. The findings revealed that: (1) Increasing steam curing temperature accelerates hydration kinetics by shortening the nucleation and growth phase while prolonging the diffusion-controlled stage. Rapid FA dissolution releases Al^3 + , destabilizing AFt and promoting its transformation into AFm. Excessive temperatures further induce AFt decomposition, SO₄^2- desorption, and DEF formation, resulting in microstructural damage and compromised long-term durability. (2) Steam curing significantly influences fiber-matrix interfacial properties. High-temperature exposure weakens fiber bridging by increasing interfacial friction and reducing chemical bonding, thereby compromising tensile ductility and multiple-cracking behavior. (3) A curing regime of 60 °C for 5 days achieves comparable strength and ductility to 60–90 days of standard curing, meeting engineering demands while considerably shortening construction timelines. This research deepens our understanding of the mechanisms underlying HDCC performance evolution under different curing conditions, providing a robust theoretical foundation for material design. Furthermore, it offers scientific guidance for optimizing HDCC steam curing regimes, balancing performance and time efficiency, and fostering broader adoption in engineering applications.