Chloride Induced Steel Corrosion in Concrete: Part 2—Gravimetric and Electrochemical Comparisons

This is the second of a two-part paper covering research into chloride-induced steel corrosion in concrete. The work focused on relationships between electrochemical data on chloride-induced reinforcement corrosion and gravimetric steel weight losses. Data were collected on a series of reinforced concrete slabs that were partially immersed in 3% NaCl solution for a period of 5 years. Slabs were made with a range of water-binder ratios (w/b) with portland cements having high and low C3A contents, slag-blended cement, or fly ash-blended cement. Data focused on measurements over time of concrete resistivity, corrosion rates, and gravimetric weight losses of steel taken at the end of the exposure period. Rates of corrosion of steel in concrete were measured using potentiodynamic anodic procedures. An analysis of estimated corrosion currents (I sub c) and the area under the I sub c versus time envelope for reinforcement within the concrete slabs is described. Measurements of weight loss of steel through corrosion in concrete are analyzed and related back to the electrochemical measurements taken. It was found that concrete w/b highly influenced the corrosion rate of steel in concrete. Quantitative links between steel weight loss, the electrochemical data, and concrete resistivity have been found. Under high-chloride conditions, the blended cement concretes having low w/b were found to perform better than other concretes investigated. The data suggest that such concretes had higher resistivity characteristics, had lower corrosion rate characteristics, and were likely to result in lower reinforcement weight losses when compared with equivalent portland cement concretes. Reinforced concrete performance under high-chloride conditions did not reflect concrete strength data from the materials considered. Results provide some guidelines for the design of durable concrete structures.