Factors Other Than Chloride Level Influencing Corrosion Rate of Reinforcement


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Title: Factors Other Than Chloride Level Influencing Corrosion Rate of Reinforcement

Author(s): A. Castel, R. Francois, and G. Arliguie

Publication: Special Publication

Volume: 192


Appears on pages(s): 629-644

Keywords: chlorides; corrosion; damage; reinforced concretes; steel construction

Date: 4/1/2000

To evaluate the degree of corrosion, reinforcements of a fourteen-year-old concrete member were completely bared. The 3-meter long beams were stored in 3-point flexion in an aggressive environment made by sequences of drying and wetting by a salt fog (35g/l). The total chloride content was also measured at the level of all reinforcements. Because of the small concrete cover (10 mm for the stirrups and 16 mm for the longitudinal reinforcement), the chloride content appears to be significantly greater than the threshold usually used to evaluate the initiation of corrosion. Carbonation front was also measured and was only about 4 mm. Nevertheless, the degree of corrosion (mass loss calculation) shows no correlation with chloride content, as some large parts of reinforcement are not affected by corrosion. As a result, corrosion damage seems to be linked to a degradation of the steel-concrete interface. For tensile reinforcement, it corresponds to a mechanical degradation whereas for compression reinforcement it corresponds to the bleeding. This observation leads us to question ourselves about the relevance of a single value for the corrosion threshold. The nature of the interface between the steel and the concrete must be considered.