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-indu ced steel corrosion in concrete. Work described in this paper focused on re lationships between electrochemical data on chloride-induced reinforcement corrosion and gravimetric steel weight losses. Data were collected on a ser ies of reinforced concrete slabs that were partially immersed in 3 percent NaCl solution for a period of 5 years. Reinforced concrete slabs investigat ed were made with a range of water-binder ratios (w/b) with protland cement s having high and low C3A contents, slag-bended cement, or fly ash-blended cement. Data in this paper focus on measurements over time of concrete resi stivity, corrosion rates, and gravimetric weight losses of steel taken at t he end of the exposure period. Rates of corrosion of steel in concrete were measured using potentio-dynami c anodic procedures. an analysis of estimated corrosion currents I-c, and t he area under the I-c versus time envelope A(cr) for reinforcement within c oncrete slabs used in the investigation, is described. Measurement of weigh t loss of steel through corrosion in concrete are analysed 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 lin ks between steel weight loss, the electrochemical data, and concrete resist ivity, have been found. Under high-chloride conditions, the blended cement concretes having low w/b were found to perform better than other concretes had higher resistivity c haracteristics, lower corrosion rate characteristics, and were likely to re sult in lower reinforcement weight losses when compared with equivalent por tland cement concretes. reinforced concrete performance under high-chloride conditions did not reflect concrete strength data for the materials consid ered. The results serve to provide some guidelines for the design of concre te structures for insuring durability.