Abstract
In this paper, the cause of corrosion of steel bars in concrete, particularly carbonation of concrete and the effect of repair work are discussed acording to comprehensive investigation of existing reinforced concrete structures. A coefficient of carbonation rate (=α) which is calculated from the examination exceeds the usual value. Deviations of the coefficient of carbonation rate (=α) have a tendency to be smaller in the past few years. A depassivated critical value of the difference between cover and carbonation depth is nearly 10mm or less. When the difference between those values is 0mm, the steel bars are perfectly depassivated. When the half cell potential is nearly -120mV vs Ag/AgCl, the depassivation begins and if the potentials is -230mV vs Ag/AgCl, the steel bar is also perfectly depassivated. There is little influences of chloride on the corrosion of steel bars in existing carbonated concrete. The difference between cover and carbonation depth has the most important role in the corrosion of steel bars.
