Prestressed Concrete Bridges in Adverse Environments

A survey of failures of prestressing steel in the United States is discussed, and a Federal Highway Administration study which investigated the corrosion of prestressing steel in bridge components in adverse environments using analytical procedures is described. The causes of failure are discussed, and preventive and remedial measures are reviewed. The latter include sheathing, anchorage systems, grease for unbonded tendons, drainage, and miscellaneous corrosion control measures. The rate of corrosion in pretensioned and post-tensioned concrete components may be decreased by one or more of the following: plastic sheathing of high density polyethylene or polypropylene; epoxy resin compound or corrosion-inhibiitng grease to seal ends of the anchorage systems; plastic lid or screw cap to prevent displacement of the protective coat on anchorages; prefabricated concrete plugs to plug an anchorage pocket; encapsulation of anchorage systems; and water-impermeable corrosion-inhibiting grease free of harmful impurities to fill unbonded tendons.