Investigating and Resolving Bridge Grouted PT-Strand Corrosion Problems

Thousands of bridge structures rely on grouted post-tensioned (PT) tendons to economically improve their structural capacity. However, problems with grouting techniques and grout materials has resulted in bridges with grout voids, chloride contaminated grout and soft grout. These problems have promoted corrosion and failure of PT tendons, some within 6 to 17 years of service. As a result of these PT issues the Florida Department of Transportation (FDOT) has spent more than $55 million (USD) repairing 11 PT bridges. Vector Corrosion Technologies (VCT) has developed a cost-effective corrosion mitigation impregnation technique to minimize corrosion of PT tendons and extend the service life of PT bridges. This paper describes the development and implementation of the post-tension impregnation (PTI) system used on grouted PT tendons. The PTI system was demonstrated for FDOT on the I-95/I-295 Interchange in Jacksonville, FL and PT tendon samples from the Ringling Bridge, Sarasota, FL. The system uses an impregnation material to impregnate the cement grout and form a corrosion resistant film on the surface of the steel strands. Testing confirms the ability of the impregnation material to travel over 250 feet along the length of PT strands, to soak into the grout surrounding a strand and to reduce corrosion by over 90%. Laboratory testing and field demonstrations confirm the effectiveness of this new technology for mitigating PT corrosion.