Incorporation of self-healing of UHPC in structural design approaches through healable crack width threshold and kinetics: The case study of H2020 project ReSHEALience database

Ultra-high-performance concrete (UHPC) stands out as a crucial construction material, boasting outstanding mechanical properties and exceptional durability in its uncracked state. The distinctive strain-hardening tensile behavior of UHPC necessitates a consideration of material and structural durability in the cracked state, prompting a rethinking of structural concepts and design approaches. Consequently, various competing mechanisms, including material deterioration, self-sealing, and self-healing capabilities, require meticulous assessment. The autogenous nature of the self-healing capacity of the material, crafted with compositions tailored to specific mechanical properties, further underscores this evaluation. This study elucidates above concepts by compiling and analyzing an extensive database of crack closure data obtained and processed through image processing techniques. This research specifically delves into appraising the self-sealing capacity of UHPC under structural service conditions, encompassing challenges such as chloride and sulfate attacks. Additionally, it endeavors to distinguish the crack healing kinetics of diverse UHPC mix designs, calibrating them across varying crack widths (0–20, 20–50, 50–100, 100–300 μm) and diverse healing environments. These findings assume significance in establishing the "healable width threshold" and the "self-healing coefficients of the crack healing kinetics law" under "structural service conditions". •Cracks exposed to aqueous environments can effectively quantify the closure process through self-healing kinetic coefficients.•Narrow cracks (0–20 μm) appear to have an optimal closure efficiency in salt water, even exceeding that of tap water.•Exposed to corrosive environments, CA and nanomaterials only improved the closure efficiency of cracks up to 100 μm in width.•Sustained loading is favorable for crack closure, especially for narrow cracks.•Healable crack width thresholds of 100 μm in tap water and 20 μm in corrosive water environments.