CORROSION EVALUATION OF POST-TENSIONED TENDONS ON THE MID BAY BRIDGE IN DESTIN, FLORIDA

Several segmental box girder bridges in Florida have experienced corrosion and corrosion-related tendon failures. One of these is the Mid-Bay Bridge near Destin, where as many as 11 tendons were replaced. Additionally, many other tendons exhibited cracking of the polyethylene duct. Visual inspection of this bridge revealed: 1) corrosion of tendons and individual wires ranging from minimal to severe; 2) presence of broken wires; and 3) cracking of the polyethylene duct. Extensive cracking of the polyethylene ducts was not the main cause of tendon corrosion problems. However, it does serve as a corrosion promoter by providing greater moisture, oxygen, and chloride access to the steel. Based on the various field and lab findings, a mechanism of tendon corrosion is proposed. Susceptibility of a particular tendon to deterioration by this cause should vary depending on the extent to which deleterious conditions are present.