Comparative Study of the Corrosion Resistance of Different Prestressing Strand Types for use in Post-Tensioning of Bridges

Project 4562 was launched with support from the Texas Department of Transportation and the Federal Highway Administration. The project was designed to test the relative corrosion resistance of various post-tensioned systems. These systems have utilized new and innovative strand types not commonly used in current post-tensioning projects. The project consists of various parts including large beam exposures. These large beam specimens are currently being exposed to a salt solution cycle at the Phil M. Ferguson Structural Engineering Laboratory at the University of Texas at Austin. From a previous project that was similar in scale, it was noticed that there was a need to know the corrosive properties before the autopsy of the large specimens. The grouts and grouting techniques had previously been tested by various researchers. Therefore, it was important to establish the corrosive properties of the strands used in the post-tensioning of the large beam specimens. The goal of this research was to establish the corrosive properties of the different strand and grout interactions. This included establishing appropriate testing techniques to compare times to corrosion and relative corrosion resistance.

These objectives were achieved in two stages. The corrosive properties of the different strand and grout interactions were established through active and passive corrosion tests. Different electrochemical testing techniques were employed to attain the corrosive properties which consist of the active corrosion tests. Most importantly was the use of the linear polarization resistance testing technique to compare the times to corrosion for each strand specimen. The passive corrosion tests utilized exposing the bare strands to a salt water solution and determining relative corrosion properties by final weight loss and visual inspection. Another passive test has the strands encased in grout and exposed to a salt water solution full time causing the strands to undergo electrochemical processes. The specimens are monitored for potential and current created during these processes.