Chloride profiles in two marine structures―meaning and some predictions

摘要

Interpretations of chloride profiles as well as prediction issues have been two of the more interesting topics when investigating corrosion of concrete structures. Chloride profiles from the oldest concrete pier with stainless steel as reinforcement (Progreso, Mexico) as well as the oldest pretensioned bridge (Maracaibo, Venezuela) have been measured in order to compare penetration mechanisms and to predict future behavior of the whole structures. Some of the results seem to indicate that the penetration mechanism is similar independently of the exposure environment and concrete quality. Besides, these results are compared with a newer construction (a bridge built 17 years ago in USA but exposed to a similar environment as the Progreso pier). The results are discussed in terms of concrete quality, internal amount of chlorides (time of exposure) and environmental variables. Some predictions for maintenance were performed based on the reported chloride thresholds for corrosion onset of black steel and 304 stainless steel. The predictions for both structures were in agreement with the physical and electrochemical evidences, indicating the need of immediate maintenance to avoid further deterioration.