Experimental and Numerical Investigations on the Rate-Limiting Step for Macrocell Corrosion of Reinforcing Steel in Concrete

Abstract

Macrocell corrosion is a frequent and detrimental problem plaguing reinforced concrete structures exposed to chloride environments. This paper investigates the rate-limiting step(s) of macrocell corrosion of reinforcing steel bars in concrete by quantifying the respective contributions of anodic polarization, cathodic polarization, and ohmic subprocesses to the overall macrocell corrosion. Experiments were carried out to study the impact of the distance between active and passive steels, the active-to-passive steel area ratio (A/P), and the microcell corrosion rate of active steel. Numerical simulations were further performed to extrapolate experimental results to large-scale concrete structures. Results demonstrated that with a decreasing A/P, the contribution of the anodic polarization subprocess was increased, while that of the cathodic polarization subprocess was decreased. The macrocell effect that aggravated the total corrosion rate of active steel was weakened as the microcell corrosion activity increased or with increasing the relative humidity.