Curing-induced hydration accessibility and pore structure evolution in solid-waste-based UHPC

Incorporating solid wastes into ultra-high performance concrete (UHPC) to reduce clinker consumption is an effective pathway toward sustainability. However, the intrinsic heterogeneity of solid wastes, combined with the extremely low water-to-binder ratio of UHPC, renders the material highly sensitive to curing regimes, while the underlying mechanisms remain insufficiently understood. In this study, solid-waste-based UHPC systems were investigated under a unified mix design with three representative curing regimes, including standard curing, steam curing, and steam–subsequent standard curing. The effects of curing on reaction processes and pore-structure evolution were systematically examined from multiple perspectives, encompassing hydration kinetics, pore-solution chemistry, phase assemblage evolution, and pore-network characteristics. Rather than focusing on individual performance metrics, this work emphasizes the coupled roles of curing in regulating reaction accessibility, gel formation behavior, and pore-structure redistribution. The results demonstrate that curing regimes reshape the early-age reaction environment and hydration progression, thereby governing gel deposition modes and driving a transition of the pore network from capillary-pore-dominated to gel-pore-dominated configurations. Meanwhile, early curing conditions impose pronounced constraints on reaction pathways and structural stabilization. The distinct responses observed among different solid-waste systems indicate that accelerated curing can simultaneously enhance reaction efficiency and alter the reaction–structure balance, potentially influencing subsequent structural evolution. A mechanism-informed framework linking curing regime–reaction accessibility–gel formation and pore-structure redistribution–structural stabilization is established, providing engineering guidance for optimizing curing strategies and improving reliability-oriented performance of sustainable UHPC systems.