Bond deterioration of corroded reinforcements in SFRC: Experiments and 3D laser scanning

The bond deterioration behavior of reinforcements in steel fiber-reinforced concrete (SFRC) subjected to chloride-induced corrosion has not yet been fully elucidated. This study investigates the corrosion characterization, resistivity, corrosion-induced cracking, and associated effects on the bond performance of reinforcing bars in SFRC with milled-cut steel fibers (M fibers), referred to as MCSFRC. Pull-out tests were performed following galvanostatic corrosion, with the M fiber, concrete cover, and corrosion level being the main variables. A closer look at the bar corrosion was conducted using 3D laser scanning technology, which allowed for estimating the spatial-domain corrosion pattern and bond index degradation that characterize the rib-concrete interaction. The results indicated that, with the increase in corrosion levels, the bond index decreased exponentially as a result of pits propagating from the rib root to the rib peak. The bond strength of the MCSFRC specimens deteriorated less than that of the control counterparts and hook-end fiber-reinforced specimens in the literature. It is further revealed that the crack opening and bond index reduction are the bond deterioration mechanisms under corrosion, reducing the contact area between the bar and concrete through the ribs. On that basis, a mechanics-based model for bond strength deterioration was developed. The proposed model considered the two aforementioned effects, as well as the fiber reinforcement effect on crack suppression, showing good agreement with the experimental results.