Prestressed Bridges and Marine Environment

Abstract

A study was made of the corrosion of prestressing steel in bridge components exposed to a marine environment using analytical procedures and available techniques developed for conventional reinforced concrete structures. Four bridges were examined. Based on results of the study, it appears that in a marine environment the seawater and the seawater spray are major carriers of sufficient chloride salts to cause corrosion of prestressing steel. The atmosphere surrounding a bridge is not aggressive enough to cause any noticeable corrosion‐related distress in bridge members. The primary pathway for the ingress of chloride ions is through a concrete cover, sheathing, and grouting. Chlorides may also be deposited on the surface of a deck slab by vehicle tires and later washed down through deficient expansion/contraction joints to anchorages and tendons in end areas of pre‐ and posttensioned girders. Among major factors affecting the extent of corrosion‐related distress in prestressed bridge members are the following: time of exposure to direct action of the seawater, concentration of chlorides at the level of reinforcement, condition of expansion/contraction joints, permeability of concrete, thickness of concrete cover, quality of grouting, as well as the type of sheathing in prestressing tendons.