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Year:
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2007
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VTRC No.:
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07-R35
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Abstract:
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The Virginia Department of Transportation uses cathodic protection (CP) systems on steel-reinforced concrete structures to extend the life of these structures. The purpose of this study was to identify, categorize, and evaluate the performance of the CP systems that have been used on these structures. These systems included galvanic anode CP (GACP) systems and impressed current CP (ICCP) systems. Some of these systems are exposed to chloride ions because of their location in a marine environment; others are on structures located inland that are exposed to chloride ions through the use of deicing salts. The study showed that greater care needs to be taken to transfer the maintenance and monitoring responsibilities of CP systems that are installed as part of a research study once the study is concluded. Further, some of these CP systems have not been associated with favorable research findings. Moreover, evaluation of inspection reports indicates that procedures are not in place to qualify VDOT bridge inspectors to monitor or evaluate CP systems and to record important data to ensure sufficient CP protection is being achieved with each CP system. Finally, the CP system cannot be treated as a stand-alone appendage during the design and construction of a structure; it must be considered in conjunction with the other electrical systems on a structure. The initial cost of an ICCP system is not substantially different from the direct cost of a rehabilitative overlay that would be required should such a system not be installed. If properly maintained, a retrofitted ICCP system would be expected to extend the life of a rehabilitated deck an additional 35 years. However, even with the cost of routine monitoring, an ICCP system can provide substantial savings in maintenance and user costs. Similarly, if a GACP system can prevent the need for repairs on approximately 16% of a substructure surface over the life of the structure, the costs of the GACP system would be approximately equal to that of a single rehabilitative intervention. Based on the results of this study, by preserving the structure and extending the life of the initial structure with a CP system, a future rehabilitation can be deferred or prevented and fewer intermediate repairs will be necessary. This can have significant implications for users of a structure, particularly on congested urban or arterial routes. Further, some CP systems do not require a significant investment in monitoring or maintenance, thereby reducing long-term costs that have sometimes been associated with CP.
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