Investigation of Chloride Induced Corrosion of Bridge Pier and Life-Cycle Repair Cost Analysis Using Fiber Reinforced Polymer Composites

摘要

Bridges are the long term investment of the highway agencies. To maintain the required service level throughout the life of a bridge, a series of maintenance, repair, and rehabilitation (MRu26R) works can be performed. To investigate the corrosion deterioration and maintenance and repair practices in the bridge pier columns constructed in chloride-laden environment, a questionnaire survey was conducted within the 50 state Departments of Transportation (DOTs). Based on the survey data, two corrosion deterioration phases were identified. They were corrosion crack initiation phase and corrosion propagation phase. The data showed that the mean corrosion crack initiation phase for bridge pier column having cover of 50 mm, 75 mm, and 100 mm was 18.9 years, 20.3 years, and 22.5 years, respectively. The corrosion propagation phase starts after the corrosion crack initiation. The corrosion propagation is defined in a single term, corrosion damage rate, measured as percentage of area damaged due to corrosion cracking, spalling, and delamination. From the survey, the corrosion damage rate was found 2.23% and 2.10% in the bridge pier columns exposed to deicing salt water and exposed to tidal splash/spray, respectively. For this study, two different corrosion damage rates were proposed before and after the repair criteria for minor damage repair as practiced by DOTs. This study also presents the collected data regarding the corrosion effectiveness of using sealers and coatings, cathodic protection, corrosion inhibitors, carbon fiber/epoxy composites, and glass fiber/epoxy composites as maintenance and repair technique. In this study, the cost-effectiveness of wrapping carbon fiber/epoxy composites and glass fiber/epoxy composites in bridge pier columns constructed in a chloride-laden environment was investigated by conducting life-cycle cost analysis.As a repair work, externally bonded two layer of carbon fiber/epoxy and glass fiber/epoxy composites were installed by wet-layup method in full height of the bridge pier column stem. The damaged concrete surface was completely repaired before installing external wraps. Three different strategies were defined based on the consideration of the first FRP repair at three different corrosion deterioration phases. The strategies were to apply FRP as preventive maintenance during corrosion initiation period, to apply FRP during the corrosion damage propagation, and to apply FRP after major damage. For both composites, the strategy to repair bridge pier column at early stage of corrosion damage, which is at the age of 25 year, was observed optimum, and the use of glass fiber composite wraps resulted in lower total life-cycle repair cost. The use of carbon fiber composites in repair found to have lower total life-cycle repair cost for lower discount rate up to 6% when repair is considered at the age of 15 to 20 years.