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".