Civil Engineering Association

Durability Evaluation of Post-Tensioned Concrete Beam Specimens after Long-Term Aggressive Exposure Testing

This report focuses on the forensic analysis and evaluation of large-scale post-tensioned beam specimens after nearly 8 years of extremely aggressive exposure testing. The research was funded jointly by both the Federal Highway Administration and the Texas Department of Transportation. The relationship between durability performance and the following variables was evaluated in this study: level of applied load and initial cracking, level of prestress, duct type, strand type, grout type, grouting method, use of encapsulated system for anchorage protection, and galvanized duct splice type. In addition, the applicability of half-cell potentials and chloride penetration tests for evaluating the likelihood of corrosion was examined. Major findings were: 1) Mixed reinforcement (also known as partial prestressing) performed poorly from a durability standpoint. Only fully prestressed beams offered better durability performance than those which were not prestressed at all. 2) Corrugated steel galvanized ducts performed very poorly. Large holes were found in the ducts, and in some cases several inches of the ducts completely corroded away. 3) Corrugated plastic ducts offer better performance as long as they are "robust." 4) Non-flowfilled epoxy coated strand and galvanized strand offered no significant improvement in long-term durability over conventional strand. 5) Installing plastic caps over anchorheads rather than just filling the anchorage pocket with nonshrink grout increases the long-term durability of the anchorage.