Chloride-induced rebar corrosion and concrete cracking are complex processes driven by interacting multi-physics mechanisms and multiple contributing factors. This study proposes an innovative multi-physics modeling framework to comprehensively analyze the entire degradation process, from ionic transport to corrosion initiation and cracking induced by corrosion expansion. A multi-ionic transport model is developed to quantify the impact of electrochemical processes and crack propagation on ionic transport. Based on phase-field theory and corrosion kinetics, a corrosion model is then proposed to describe corrosion product loss, filling, and accumulation. A multiphase phase-field cracking model is hence developed to characterize fracture behavior and degradation induced by corrosion product pressure. Third-party data are used to validate the proposed models and framework. Results indicate ignoring multi-ion interactions overestimates pore-solution chloride, while neglecting electromigration distorts local ion distributions. Explicit crack representation generates preferential transport pathways, accelerates ingress, and increases peak current density and electrochemical potential by over 10%. Coupling the displacement field enhances crack-growth predictions and avoids premature or excessive cracking. This work offers a new perspective on cracking and durability deterioration in reinforced concrete by establishing a mechanistic framework that enables more reliable predictions in the cracked state, thereby reducing reliance on empirical formulations.

The article ‘Effect of matrix self-healing on the bond-slip behavior of micro steel fibers in ultra-high-performance concrete’, written by Salam Al-Obaidi, Shan He, Erik Schlangen and Liberato Ferrara, was originally published in volume 56, issue 9, article 161 without Open Access.

This study investigates the bond-slip behavior of micro steel fibers embedded into an Ultra-High-Performance Concrete (UHPC) matrix as affected by the self-healing of the same matrix in different exposure conditions. The UHPC matrix contains a crystalline admixture as a promoter of the autogenous self-healing specially added to enhance the durability in the cracked state. For the aforesaid purpose, some samples were partially pre-damaged with controlled preload (fiber pre-slip at different levels) and subjected to one-month exposure in 3.5% NaCl aqueous solution and in tap water to study the fiber corrosion, if any, and the effects of self-healing; after that, they were subjected to a pull-out test, to be compared with the behavior of analogous non-pre-slipped samples undergoing the same curing history. Moreover, some samples were cured in the chloride solution, intended to simulate a marine environment, to study the effect of marine curing on the pull-out behavior of steel fiber. The steel fiber corrosion and self-healing products attached to the surface of the steel fiber were analyzed via Scanning Electron Microscopy (SEM), and Energy -Dispersive Spectroscopy (EDS). The results indicate that the newly healed particles formed on the highly damaged fiber-matrix interface significantly enhance the friction phase of the bond-slip behavior and result in a significant residual capacity compared to non-pre-slipped specimens. On the other hand, the self-healing effect in specimens subjected to low damage pre-slip contributed more to the chemical adhesion region of the bond-slip behavior. Owning to the dense microstructure of the matrix, curing in 3.5% NaCl aqueous solution was not found to significantly affect the pull-out resistance as compared to the samples cured in tap water.