A Depth-Dependent Fiber-Bridging Model to Predict the Tensile Properties Recovery Induced by the Self-healing of Strain-Hardening Cementitious Composites

The self-healing of strain-hardening cementitious composites (SHCCs) relies on the penetration of CO₂ (or dissolved CO₃²⁻) into the cracks; some SHCCs mixed with special binders, e.g., the reactive magnesia cement (RMC)-based SHCC, even rely on carbonation to harden in the first place. As the carbonation degree decreases with matrix depth, it induces depth-dependent fiber-to-matrix interface properties in these scenarios. In this work, we present a new analytical model that captures the effect of depth-dependent carbonation and self-healing of RMC-based SHCC. In this model, the fiber-bridging tensile stress vs. crack width curve is formed by summing the tensile load vs. displacement relationship of individual fibers. On the single-fiber level, the debonding and slip-hardening of the fiber-to-matrix interface induced by a tensile preloading as well as the recovery of the interface properties by self-healing are coherently quantified in a clear kinetic process. On the fiber-bridging level, the experimentally characterized carbonation vs. depth relationship is added to the model. The modeling results can well capture the single-fiber pullout behavior and the fiber-bridging behavior of the self-healed SHCC specimens.