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OCR for page 1
CATHODIC PROTECTION FOR LIFE EXTENSION OF
EXISTING REINFORCED CONCRETE BRIDGE ELEMENTS
SUMMARY Over the past three decades significant attention has been focused on the condition of the
nation's aging highway bridge infrastructure. As the cost of maintenance and replacement
continues to increase, many agencies are looking for materials and technologies to preserve
their infrastructure and extend their service life. To address the corrosion problem on rein-
forced concrete structures, a research and development effort was initiated by both the private
and the public sectors in the early 1970s. Numerous different technologies were introduced to
repair damage caused by corrosion and to prevent or minimize further damage from occur-
ring. During this time cathodic protection, one of the most effective technologies to stop cor-
rosion, was adapted for implementation on reinforced concrete structures. In 1982, an FHWA
Policy Statement reported that cathodic protection is the only technology that can directly
stop corrosion in reinforced concrete structures and this statement is still valid today.
Since its first application on a bridge deck in 1973, many different types of systems have
been developed and a significant amount of literature on their performance is available. Cer-
tain types of cathodic protection systems are projected to provide service-life extensions in
the range of 25 to 50 years, and presently there are systems that have been in operation for 20
or more years.
The primary goal of this synthesis is to examine the utility of this technology for controlling
corrosion on reinforced concrete structures and determine, if possible, why public agencies do or
do not use this technology and explore how to encourage expanded appropriate use of this tech-
nology. To accomplish the goals of this project a survey of state and provincial departments of
transportation (DOTs) and the industry was conducted. A total of 37 responses were received
from public agencies, 32 of which were from U.S. state DOTs and 5 were from Canadian provin-
cial DOTs. Responding states include all with 10 or more cathodically protected bridge decks,
according to the National Bridge Inventory. A literature survey was also performed to obtain
information on practices and experience with the use of this technology. The results of this exer-
cise are documented in this report.
Agencies that have adopted this technology as one of the tools for bridge preservation and
have developed in-house procedures, protocols, and acquired the technical skills to imple-
ment it have experienced reductions in maintenance frequency and costs and have achieved
significant service-life extensions. In some cases, service-life extensions of more than 20 years
have already been achieved, and those structures are not expected to have corrosion-induced
damage as long as the cathodic protection systems are functional. However, only three states
in the United States--Florida, Missouri, and Oregon and three Canadian provinces--Alberta,
New Brunswick, and Ontario, have adopted this technology and are actively implementing
it. Many other agencies have experimented or implemented the technology on select projects
and have not made a commitment to implement it on a larger scale.
Some agencies' experience with the technology has not been satisfactory. Often, these
agencies did not have the expertise or resources to evaluate, select, design, install, and mon-
itor and maintain the systems. Many of these systems were not properly selected, had defi-
cient design, substandard installation, and insufficient or no monitoring and maintenance. At
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least one agency has indicated that although they had actively installed cathodic protection
systems on their bridge structures in the 1980s, currently they do not have an inventory of
the systems or any information on the status of the systems; those systems have been for-
gotten. Some failures were simply a result of the expansive growth the industry experienced
in the late 1970s and the 1980s, and it took the marketplace some time to weed out the less-
effective and less-durable systems. The survey data suggest that insufficient or no monitor-
ing and maintenance is being performed by many agencies and it is the most important reason
for the disappointing performance of many of the systems.
There are many agencies that can benefit from this technology but have not adopted it pri-
marily owing to the high initial cost, inadequate resources to monitor and maintain the sys-
tems, lack of understanding of the technology, and lack of innovation and competition. Of the
agencies that have never used or have not used cathodic protection since 2003, 18 indi-
cated that they would consider it in the future. These agencies may need Standard Specifica-
tions for selection, design, and construction of these systems and protocols for monitoring
and maintenance. Their staff may need to be trained in the implementation of the technology.
The FHWA or the National Association of Corrosion Engineers may need to develop a doc-
ument that public agencies can use to properly implement the technology. The National Asso-
ciation of Corrosion Engineers and/or the National Highway Institute may need to develop
and conduct training classes to ensure that agencies have staff with the requisite skill sets. In
addition, innovation and competition in the marketplace is lacking and the industry needs to
determine a way to provide innovative products at competitive prices. Many agencies appear
to favor the galvanic systems that require comparatively less monitoring and maintenance
than the impressed current systems, and innovation in this area would be beneficial for the
growth of the industry.
