Brittle Fractures of Prestressed Bridge Steel Exposed to Chloride-Bearing Environments Caused by Corrosion-Generated Hydrogen Available to Purchase

Recent laboratory and field studies indicate many fractures of prestressed tendons in bridges exposed to deicing salt and to marine environments may be associated with embrittlement caused by cathodic hydrogen (H). This type of H originates from corrosion reactions inside occluded pits and results from the anodic oxidation of metallic iron (Fe) and the localized cathodic reduction of H ions. The primary factor influencing the hydrogen-induced cracking (HIC) is the concentration of H in the steel lattice, which is dependent on a variety of factors. Examination of these factors suggested cold-drawn pearlitic steels, which are used commonly to manufacture prestressed tendons, may be inherently susceptible to this type of failure. The danger of HIC would be reduced significantly if susceptibility could be evaluated using a routine quality control test with a clear-cut acceptance criterion. Although a variety of tests are used for this purpose, none has attained general recognition. The endurance axial test (based on the use of smooth specimens in ammonium thiocyanate (NH4CNS) and the fracture mechanics test (involving the use of precracked specimens exposed to simulated environments) appear promising.