Development of New Method for Corrosion of Steel Reinforcement in Concrete Using AC Impedance

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From the results of 5-year exposure test under a marine environment, it was confirmed that the fly ash 30% concrete and the silica fume 10% concrete performed better in corrosive behavior of the steel bar in concrete compared with the normal Portland cement concrete and the blast-furface slag 50% concrete, and that the results of the Rapid Chloride Permeability Test (RCPT,AASHTO T277) gave a reasonable estimate of chloride ion permeability of normal Portland cement concrete in service although the AASHTO T277 test was primarily a conductivity measurement. With the regard to the chloride ion permeability of concretes incorporating mineral admixtures, the results of the RCPT showed that both the surface and the interior of the concretes with mineral admixtures were much less permeable to chloride ions than the corresponding normal Portland cement concrete under all curing and environmental conditions. Furthermore, it was found that there was a good correlation between the charge passed in the RCPT,the initial direct current and the electrical resistance, which also correlated well with the chloride ion penetration depth into the concrete after the RCPT.With the regard to the diffusion coefficient for chloride ions calculated according to the Ficks second law, the coulomb values obtained from the RCPT also correlated well with both the diffusion coefficient for chloride ions and the depth of chloride ion penetration after the exposure to a marine environment.