Modeling Corrosion Progress of Steel Wires in External Tendons

Abstract

When prestressing tendons are corroded, a bridge owner must decide whether to replace or repair them. If this decision must be based on a destructive inspection method, section losses in the steel strands must be estimated by measuring either the corrosion depth or the perimeter of the corrosion area. For this study, models for the determination of corrosion progress in corroded wires were investigated in a preliminary study of evaluating section losses in strands. Corroded strands were sampled from a post-tensioned concrete box-girder bridge that demonstrated external tendon failure due to chloride- and moisture-induced corrosion. The strands were cut into equidistant lengths, and the corroded areas of the cross sections were measured. Analysis showed that using models of existing corrosion progress routinely underestimated the section losses for maximum corrosion depth. Actual measurements showed that corrosion rapidly progressed along the perimeter in the earlier stages, and the result was a corroded surface with a convex shape. Herein, new corrosion-progress models that more-accurately reflect the actual corroded sections of wires are proposed. Although the measurements showed a large degree of dispersion, the proposed models were verified as more effective in estimating section losses.