Study and numerical application of bond properties between co-corroded rebars and concrete

To investigate the bond degradation caused by coupled corrosion (co-corrosion) of main rebars and stirrups in in-service reinforced concrete (RC) structures, an accelerated corrosion test and pull-out test were conducted on 43 RC specimens. The study focused on parameters such as the corrosion ratios of the main bar and stirrups (individually and in combination), rebar diameter, stirrup quantity, and cover thickness. The corrosion characteristics, failure modes, and key bond parameters of each specimen were analyzed and compared. The results showed that both the corrosion ratios and corrosion morphology of the main bars and stirrups exhibited uneven characteristics. A thicker cover, closely spaced stirrups, and smaller main bar diameter delayed the development of splitting cracks and improved the interface bond strength. The corrosion-induced crack morphology in specimens with corroded stirrups and co-corrosion was more complex. For specimens with co-corrosion, where the corrosion ratios of the main bar and stirrups were greater than 1.5 % and 3.2 %, respectively, the bond strength was significantly reduced. Compared to single corrosion, co-corrosion led to a more significant bond strength degradation. Finally, based on the bond test results, a bond stress-slip model was developed, which accounts for different confinement conditions and the effects of co-corrosion. The rebar stress-slip model was derived using the bond model and microelement method. By applying this model to a zero-length section element, a corrosion RC fiber model considering bond-slip effects was established. The predicted results showed good agreement between the bond-slip and fiber models and the experimental data.