Effects of Concrete Mix on Initiation of Reinforcement Corrosion and Chloride Threshold Level

The time-to-corrosion initiation (T i ) of reinforcement and the chloride threshold content (C th ) of a series of G109 concrete slabs were experimentally investigated. Results indicate that T i is increased by decreasing water-to-cement ratio or increasing cement alkalinity. The effects of a superplasticizer on initiation of corrosion of reinforcing steel bars (rebar) depend on concrete mix. Measurements reveal that chloride contents at both active (anodic) and passive (cathodic) sites increase linearly with the logarithm of T i regardless of concrete mix, whereas chloride contents measured at anodic sites are always greater than at cathodic sites. Defects at or nearby corrosion anodic spots could facilitate chloride accumulation: rebar corrosion would occur earlier than if no defect were present. Further analysis reveals that the weakest-link theory is applicable to predict the probability of initiation of rebar corrosion, as indicated by the Weibull distributions of T i and C th .