Pull-out tests to evaluate the effects of crack healing on the steel-to-concrete bond on concretes exposed to chloride-rich environments

This paper presents an experimental methodology to evaluate the effects of the self-healing of cracks on the steel-to-concrete bond. Overall, 80 cylindrical concrete specimens with a coaxial steel bar were cast and subjected to pull-out tests. To this purpose, the experimental methodology envisaged the casting of two types of concrete specimens: one made with a reference concrete and the other type to investigate the effects of a crystalline admixture as a self-healing promoter. Through pull-out tests, the specimens were precracked and subjected, together with uncracked companion specimens, to wet/dry cycles in tap water or saltwater. To facilitate the evaluation of the self-healing of the specimens, indices relating to the physical-mechanical characteristics have been defined. The results show a better behavior of both, surface crack sealing and recovery of the bond performance, when specimens were subjected to wet/dry cycles in saltwater. Moreover, crystalline admixtures promoted a continuous recovery of the steel-to-concrete bond performance due the continuous generation of healing products inside the crack.