Experimental Study on the Stress Corrosion Coupling Effect of Pitting Steel Bars

The exposure of reinforced concrete bridges to chloride induces a corrosion phenomenon, leading to pitting corrosion on the steel bars and subsequent stress concentration development within them. This process accelerates corrosion, resulting in structural degradation. The stress corrosion coupling effect of pitting steel bars was investigated in this paper. First, based on electrochemical theory, the stress corrosion correction factor (SCCF) was proposed for carbon steel bars to chloride attack, which was applicable throughout the elastic-plastic stage. Then, an electrochemical experiment of steel bars in concrete was conducted to obtain the parameters for the SCCF equation. Electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) measurements were performed at various strain levels to investigate the stress corrosion behavior of steel bars under simulated chloride ion intrusion conditions. Next, based on the experiment results, a time-varying stress corrosion model was established to examine the corrosion pits of the steel bars under load. Finally, a numerical model of stress corrosion in concrete-exposed steel bars subject to chloride erosion was developed. The impact of loading on the stress corrosion coupling effect and the relationship between the SCCF and the stress concentration factor (K) were discussed. The analyses confirmed an accelerated corrosion rate in steel bars under stress, particularly magnifying as the steel bar transitions into the plasticity phase. Furthermore, the stress corrosion coupling effect was amplified with increasing loads. Within the elastic range, the SCCF and K were basically linear.