Impregnation Technique Extends the Service Life of Post-Tensioned Bridges with Grout Defects

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Many bridges and other structures have been constructed using grouted post-tension (PT) tendons. Problems with grouting techniques and grout materials has resulted in grout voids, chloride contaminated grout, and segregated grout. Subsequently corrosion of the PT tendons can occur and some tendons have corroded to failure. Some of these failures have occurred within 6 to 17 years of construction.

This paper describes the problem and the development and implementation of a cost-effective corrosion mitigation technique used to mitigate the corrosion and extend the service life of post-tensioned bridges which have grout issues.

The technique utilizes the interstitial space between the wires to deliver a low viscosity impregnation material along the length of the PT tendon. Laboratory and field testing has confirmed the ability of the impregnation material to travel the full length of PT tendons in bridges.

When the corrosion resistant impregnation material is introduced into a PT tendon, it coats the tendon surfaces with a corrosion resistant film and soaks into the grout surrounding the strands providing additional corrosion protection. Testing shows that impregnation can reduce corrosion by over 90%.

This technique has been tested and used by the Florida Department of Transportation (FDOT) and Virginia Department of Transportation (VDOT) on a number of PT bridges. This paper will discuss the application of this technique on tendons of the I-95 / I-295 Interchange in Jacksonville, FL, the I-4 Connector in Tampa, FL, Ringling Bridge tendons (Sarasota, FL), Wonderwood over the Inter Coastal Waterway (Jacksonville, FL) and Varina-Enon Bridge, Richmond, VA.

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