A mechanistic study of a novel self-healing concpet for cement enabled by large clinker particles: Recovery of transport properties and microstructure characteristics

Abstract

Self-healing cement holds considerable potential in enhancing durability and building low-carbon concrete structures. However, most existing self-healing strategies rely on external healing agents, which often raises compatibility concerns and compromises scalability and cost-effectiveness. Here, we propose a novel strategy by partially replacing cement with large clinker particles of varying sizes (40–60 μm, 60–90 μm, 0.5–1.0 mm), and evaluate the healing effects on transport properties (capillary water absorption and gas permeability), crack closure, and microstructure evolution. The results showed that the mixes containing the 40–90 μm particles exhibited pronounced healing effects within 56 days, with the recovery of initial/secondary water absorption, gas permeability, and crack-healing width reaching 67.0–67.6 %, 83.2–83.4 %, 78.6–82.6 %, and 203–225 μm, respectively, significantly outperforming the control mix (46.2 %, 49.5 %, 64.1 %, and ∼150 μm). The XCT results revealed improved sealing along the crack depth and refinement of crack-adjacent pore structures. The TG-DTG analyses indicated that the residual unhydrated clinker acted as a delayed reaction reservoir, sustaining hydration over time. The SEM-EDS results suggested more uniform and stabilized deposition of hydration products (e.g. suppressing C-S-H over-crystallization and excessive AFm formation). Collectively, these results support a mechanism-to-performance linkage in which sustained hydration of large clinker particles enables progressive densification of the near-crack matrix, reducing transport-path connectivity and promoting recovery of transport properties. This work suggests a simplistic, robust and readily scalable approach to transform self-healing of cement-based materials, leading to resilient and sustainable buildings and structures.