Evaluation of corrosion characteristics and corrosion effects on the mechanical properties of reinforcing steel bars based on three-dimensional scanning

Non-uniform corrosion of steel reinforcing bars is the main cause of structural failure in civil engineering. However, the accurate measurement of the critically corroded cross-sectional area, or the pit shape, is difficult owing to conventional limitations on detection. To accurately represent the corrosion morphology and better understand the corrosion effects on the tensile responses of deformed steel bars, a three-dimensional model of a corroded steel bar was reconstructed using a three-dimensional (3D) laser scanner. Based on the elicited 3D profiles, the corrosion factors-including the corrosion uniformity-the average, and maximum cross-sectional areas and their relationships, were identified in this study. The statistical analyses indicated that the number of corroded pits and their depths increased when the corrosion rate increased, and that decreases of the critical cross-sectional areas were linearly related to the average mass loss. Axial tensile tests of corroded steel bars were also carried out. The tensile test results showed that both the yield and the ultimate loads linearly decreased with increases in corrosion loss. Corresponding decreases in ductility were also observed. Compared with the degradation in the strength, the non-uniform corrosion had a considerable effect on the loss of ductility. The relationships between the mechanical parameters and the corrosion factors were established on the basis of the experimental results, and compared with the available prediction models. It was found that fractures originated at the locations of the critically corroded pit, and brittle fracture gradually occurred at the weakest location of the corroded steel bar, evidenced by concomitant increases in corrosion loss. Numerical simulations were carried out to clarify the critical section, the effect of pit corrosion on the concentration of stress, and the tensile response of the corroded steel bar, based on the 3D model reconstructed using scanning.