Repassivation of steel in carbonated concrete induced by cathodic protection

The paper discusses the peculiarities of cathodic protection applied to steel in carbonated concrete, which are strictly connected to the production of alkalinity at the steel surface. Results of a research on the application of cathodic protection to specimens with steel bars in carbonated concrete are discussed. A thin layer of concrete was realkalized within a period of 4-5 months by applying a current density of 10 mA/m 2 and steel could repassivate even in the presence of small contents of chlorides. A lower current density of 5 mA/m 2 could only maintain steel passive when the concrete in the vicinity of the steel had been previously realkalized through the application of a start-up current density of 70 mA/m 2 for one month. Protection mechanisms are investigated and design of cathodic protection of steel in carbonated concrete is outlined. The possibility of obtaining protection on deeper rebars is also considered.