EVALUATION OF CATHODIC PROTECTION SYSTEMS FOR MARINE BRIDGE SUBSTRUCTURES
1998
Four different cathodic protection systems were installed and evaluated in the reinforced concrete tie beams and footings of four bents at the Queen Isabella Causeway which links South Padre Island to the mainland of Texas. The types of cathodic protection systems installed and evaluated were impressed current sprayed zinc, sprayed titanium, titanium mesh with overlay and sacrificial sprayed zinc. The primary objectives of this study were to monitor and evaluate the installation of the different cathodic protection systems, to evaluate performance of the cathodic protection systems, to establish recommendations for full-scale application of cathodic protection for the Queen Isabella Causeway and to establish recommendations for the implementation of cathodic protection systems for marine bridge substructures in Texas. As part of this study, a pre-installation condition evaluation for the Queen Isabella Causeway was conducted. The purpose of the pre-installation evaluation was to assess the condition of the structure and the feasibility of cathodic protection as a rehabilitation option. The installation of the different cathodic protection systems was described, and the installation of the anode systems was evaluated using constructability, productivity, safety and environmental concerns, and aesthetics as the evaluation parameters. The preliminary performance of the cathodic protection systems was evaluated through field and remote monitoring. The field monitoring evaluations comprised visual inspection, delamination survey, half-cell potential measurements, corrosion rate measurements, chloride content determination, concrete permeability determination, rectifier and system component evaluation and polarization decay testing. As part of the performance evaluation, the variability of the sacrificial sprayed zinc system was studied with the remote monitoring capability. A simplified cost analysis was performed for the installed cathodic protection systems, which consisted in calculating the equivalent annual installation costs for a range of anode service lives. On the basis of the pre-installation condition evaluation, the field installation, the performance and the cost analysis, a cathodic protection system type was recommended for the Queen Isabella Causeway. Guidelines for the design, installation, monitoring and maintenance of the recommended system were provided as well as recommendations for the implementation of cathodic protection for marine bridge substructures in Texas.
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