A series of reinforced G109-type concrete specimens with cement of equivalent alkalinity (EqA) either 1.08 or 0.32 was cyclically ponded with a 15-wt% sodium chloride (NaCl) solution and time-to-corrosion initiation, Ti, was determined. The specimens were subsequently dissected, the steel-concrete interface examined and characterized, and concrete along the top of the upper rebar sampled and analyzed for Cl−. The results revealed greater Ti and Cl− thresholds for corrosion initiation, [Cl−]th, for the higher EqA specimens; however, the data were scattered for seemingly identical specimens. In many instances, corrosion initiated preferentially at entrapped air voids at the rebar-concrete interface provided the diameter of these was ≥2.5 mm. An explanation is proposed for the site specificity of corrosion initiation and scattered [Cl−]th that considers both entrapped air voids and the spatial distribution of coarse aggregates within the Cl− ingress path.

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NACE International
2008
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