Tendon Corrosion in Precast Segmental Bridges

Abstract

Tendon corrosion of grouted internal tendons in precast segmental bridges is reviewed, with an emphasis on the role of grouting in the corrosion protection of posttensioning. An analysis and compilation of the available information on the subject was conducted as part of an NCHRP research study (NCHRP Project 20-7, Task 92) with emphasis on those structures located in the United States and the United Kingdom. It was determined that the corrosion problems with precast segmental and posttensioned bridges in the United Kingdom principally were due to poor design choices and poor quality construction, not a significant intrinsic susceptibility to corrosion. The study found no evidence of corrosion or other durability problems with precast segmental bridges in the United States, although it must be recognized that this conclusion is based on reported information primarily gathered by visual inspection. Similar to the experience in the United Kingdom, the few reported problems with grouted posttensioned structures in the United States were due to poor quality construction. Additionally, laboratory research indicates that properly designed and constructed precast segmental and posttensioned structures are corrosion resistant. To ensure good future performance of precast segmental bridges, high-quality design details and proper construction practices must be continued, especially when using internal tendons. It is important to adopt more stringent grouting requirements and inspection procedures in the United States, similar to what has been done in the United Kingdom, to ensure that the tendons are completely encapsulated in a high-quality grout.