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Effect of chloride ions on the corrosion of galvanized steel embedded in concrete prepared with cements of different composition

Abstract:

The behavior of galvanized steel inside concrete prepared with different types of cement is of vital importance in the latest construction mega-projects, which demand durability in environments as aggressive as sea water. This paper presents the results of a year of study on the behavior of galvanized steel rebars against the action of chloride ions. The steel bars in question were used in reinforced concrete prepared with Standard Portland cement and Pozzolanic cement at a water/cement ratio of 0.45, and then exposed to a 2.6 M NaCl solution with cycles of 4 days semi-immersion and 3 days drying at 60°C. The state of the galvanized steel bars was monitored through measurement of corrosion potential and corrosion current over time. Chloride ion entry profiles were also studied. The composition and morphology of the corrosion products formed on the galvanized steel were analyzed by MEB-EDAX. Polarization curves were used to evaluate the behavior of the galvanized steel bars in alkaline solutions; these bars were taken from concrete specimens exposed to an artificial marine media. It was shown that the behavior of the galvanized steel bars varies with the composition of the cement used depending on tricalcium aluminate content and its interaction with the chloride ions. In both types of concrete the galvanized steel bar was found to be in a passive state at the end of the test period. © 2014 by ESG.