Comparison of the Corrosion Resistance of New and Innovative Prestressing Strand Types used in the 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 goals of this research were to:

i. Determine the mechanical properties including modulus information of the different strand types that were used in the large beam specimens. These mechanical properties were not determined before the strands were placed in the beam specimens.

ii. Establish the corrosive properties of the different strand and grout interactions. This included establishing an appropriate testing technique to compare times to corrosion.

These objectives were achieved in two stages. The mechanical properties of the strands were determined first. A test setup was designed for easy testing. This setup was used for all the mechanical testing done on the strand specimens. The corrosive properties of the different strand and grout interactions were then established. Different electrochemical testing techniques were employed to attain the corrosive properties. Most importantly was the use of the linear polarization resistance testing technique to compare the times to corrosion for each strand specimen.