WTI

Replacing Thermal Sprayed Zinc Anodes on Cathodically Protected Steel Reinforced Concrete Bridges

Primary Investigator Contact Information

External Project Contact(s)

Report(s)

There are no reports associated with this project.

Project Objective

The objectives of this project are to determine the most cost-effective method to remove existing zinc anodes from a concrete surface, and to develop a protocol to prepare the concrete surface for the new anode.

Project Abstract

Corrosion of reinforced concrete structures is a major and increasing problem worldwide. U.S. highway departments spend an estimated $5 billion each year to remediate chloride-induced rebar corrosion of concrete bridges. The Oregon Department of Transportation (ODOT) has historic reinforced concrete bridges along the coast that employ impressed current cathodic protection (CP) to greatly reduce the corrosion of the embedded steel reinforcement. The CP systems rely on passing an electric current into the concrete through zinc metal anodes that have been sprayed onto the surface of the concrete. Some of these zinc anodes are nearing the end of their design lives, while others are beginning to separate from the concrete prematurely. Anode sections that have debonded no longer protect the underlying steel reinforcement, and the natural rate of corrosion resumes. Currently, there is no procedure established by ODOT to remove old anodes, prepare the concrete surface, and install new anodes. Using both laboratory investigation (in the WTI Corrosion and Sustainable Infrastructure Laboratory at Montana State University) and field investigation (on an Oregon bridge), researchers will investigate various methods for each of these procedures. The main “product” expected from this research will be a final report that includes procedures and recommendations for old anode removal and surface preparation before new anode application, which can be incorporated into field specifications for CP systems.

Task Descriptions

1. Literature Review
   1. The research team will conduct a comprehensive literature review to gather existing information relevant to this project, including CP basics, concrete surface preparation, anode material options, methods of testing anode performance and predicting anode service life, methods of anode application/installation and replacement, methods of monitoring performance of CP systems, and other advancements in the CP technologies. Available literature will be synthesized to document the state of the practice relative to CP technologies, with particular emphasis on new materials, innovative methods, and recent advancements used by other states and other countries to protect bridge substructures in coastal environments.
2. Investigate methods of zinc anode removal and concrete surface preparation
   1. The research team will identify, investigate and compare the various methods used to remove existing thermally sprayed zinc anodes and to further treat the concrete surface prior to the new anode application, such as shotblasting, sandblasting, and flame cleaning. The team will test various methods in the WTI Corrosion and Sustainable Infrastructure Laboratory, and validate them in field tests on the Yaquina Bay Bridge. From this task, the most cost-effective methods for zinc anode removal and concrete surface preparation will be identified and documented in the format of a protocol for suggested practice.
3. Final Report and Presentation
   1. Researchers will prepare a final report that will incorporate background (literature review), methodology, findings, and conclusions (including suggestions for next steps). Researchers will give a presentation of the findings at ODOT and at least one conference.

Milestones, Dates, Schedule

Student Involvement

True

Relationship to Other Research Projects

False

Technology Transfer Activities

True

Transportation Research Board Keywords

Corrosion, reinforced concrete, cathodic protection

Partners

Oregon Department of Transportation, Research and Innovative Technologies Administration (USDOT)