Corrosion evaluation of post-tensioned tendons on the Mid-Bay Bridge in Destin, Florida

Corrosion and corrosion-related tendon failures have been disclosed on several segmental box girder bridges in Florida. One of these was the Mid-Bay Bridge near Destin where as many as 11 tendons were replaced. Additionally, many other tendons exhibited cracking of the polyethylene duct. The visual inspection of this bridge revealed (1) corrosion of tendons and individual wires that ranged 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 primary 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 upon the various field and laboratory findings, a mechanism of tendon corrosion is proposed. Susceptibility of a particular tendon to deterioration by this cause should vary depending upon the extent to which deleterious conditions are present.