Effect of Voids in Grouted, Post-Tensioned Concrete Bridge Construction: Seminar Slides (0-4588-P2)

This product gives the slides from the seminar presented February 26, 2009, about the research project; it discusses research motivation, research objectives, research methods and findings, and conclusions and recommendations. Recent investigations of post-tensioned (PT) concrete bridges and buildings have indicated a link between poor grout and/or voids and observed tendon corrosion. Because corrosion damage to post-tensioned tendons can result in high replacement costs, an evaluation of the corrosion susceptibility and impact of tendon corrosion on the performance of post-tensioned systems was needed. The research tasks included (1) assessing environmental conditions at PT bridge locations in Texas; (2) identifying critical environmental, void, and stress parameters affecting corrosion and tension capacity of PT strands; (3) developing methods to detect and assess the void, water, and corrosion conditions in PT systems; (4) assessing the structural reliability of PT bridges during their service life and when exposed to various environmental and tendon conditions; (5) identifying critical material parameters affecting void fillability of PT grouts and, if needed, recommending modifications to PT grout specifications; and (6) developing a repair grouting procedure. Researchers found that bridges in Texas are in severe, moderately severe, and moderate exposure conditions. Performing soundings on PT tendons can help locate voids, and the pressure-vacuum grouting procedure was better than the pressure and vacuum grouting methods in filling voids. Not all Class C grouts exhibited good fillability, and researchers recommend a change to the existing specification. The researchers also provide recommendations for assessment and treatment of PT bridges.