FRP-Concrete Bond after 12-Year Exposure in Tidal Waters

The Friendship Trail Bridge linking St. Petersburg to Tampa, Florida, was demolished in 2016. This was the site of 13 fiber-reinforced polymers (FRP) repairs of corroding reinforced concrete piles undertaken in three separate demonstration studies completed in 2003-2004, 2006, and 2008. The repairs used carbon or glass fiber, wet layup or prepreg, and epoxy or polyurethane resins. Installation was by shrink wrap in the initial series and by pressure bagging in the next two. Residual FRP-concrete bond was evaluated in 2015-2016 through 120 pull-off tests conducted on 10 representative repaired piles. Results showed wide variation in the measured pull-off strength depending on the resin type, the number of FRP layers, the prevailing conditions at the time the epoxy was mixed, and how it was placed. Ambient conditions at installation influenced bond in epoxy-based systems. The highest residual bond was recorded in epoxy-based repair on piles that were installed by pressure bagging in 2008.