United States Department of Transportation
i
Investigation of field corrosion performance and bond/development length of galvanized reinforcing steel.
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2014-12-01
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[PDF-1.19 MB]
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Abstract:In reinforced concrete systems, ensuring that a good bond between the concrete and the embedded reinforcing steel is critical to
long-term structural performance. Without good bond between the two, the system simply cannot behave as intended. The bond
strength of reinforcing bars is a complex interaction between localized deformations, chemical adhesion, and other factors.
Coating of reinforcing bars, although sometimes debated, has been commonly found to be an effective way to delay the initiation
of corrosion in reinforced concrete systems.
For many years, the standard practice has been to coat reinforcing steel with an epoxy coating, which provides a barrier between
the steel and the corrosive elements of water, air, and chloride ions. Recently, there has been an industry-led effort to use
galvanizing to provide the protective barrier commonly provided by traditional epoxy coatings. However, as with any new
structural product, questions exist regarding both the structural performance and corrosion resistance of the system.
In the fall of 2013, Buchanan County, Iowa constructed a demonstration bridge in which the steel girders and all internal
reinforcing steel were galvanized. The work completed in this project sought to understand the structural performance of
galvanized reinforcing steel as compared to epoxy-coated steel and to initiate a long-term corrosion monitoring program. This
work consisted of a series of controlled laboratory tests and the installation of a corrosion monitoring system that can be observed
for years in the future.
The results of this work indicate there is no appreciable difference between the bond strength of epoxy-coated reinforcing steel
and galvanized reinforcing steel. Although some differences were observed, no notable difference in either peak load, slip, or
failure mode could be identified. Additionally, a long-term monitoring system was installed in this Buchanan County bridge and,
to date, no corrosion activity has been identified.
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