U.S. Department of Transportation
Federal Highway Administration
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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
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Publication Number: FHWA-HRT-07-043
Date: July 2007
Chapter 5. Interim Conclusions
The following interim conclusions are based on the results and analyses presented in this report.
- In the short-term tests used in this study, the epoxy-coatings evaluated provide superior corrosion protection to the reinforcing steel. The results also indicate that the bars will continue to perform well in the longer term, although the tests performed to date do not evaluate the effects of long-term reductions in the bond between the epoxy and the reinforcing steel.
- The corrosion rate on the exposed regions of damaged epoxy-coated reinforcement is somewhat higher than the average corrosion rate on the surface of uncoated reinforcement subjected to similar exposure conditions.
- The use of concrete with a reduced water-cement ratio improves the corrosion performance of both conventional and epoxy-coated reinforcement in uncracked concrete but has little effect in cracked concrete.
- Increased adhesion between the epoxy coating and reinforcing steel provides no significant improvement in the corrosion resistance of epoxy-coated reinforcement.
- The use of corrosion inhibitors in concrete improves the corrosion resistance of the epoxycoated steel in uncracked concrete, but not in cracked concrete.
- The bars with the primer coating containing microencapsulated calcium nitrite provide improved corrosion performance in uncracked concrete, but not in cracked concrete.
- The corrosion performance of epoxy-coated reinforcement in concrete containing a corrosion inhibitor generally improves as the water-cement ratio decreases.
- The zinc coating on the multiple coated bars acts as a sacrificial barrier and provides some corrosion protection to the underlying steel in both uncracked and cracked concrete. The degree of protection, however, cannot be evaluated based on the results available to date and must await the conclusion of the Southern Exposure and cracked beam tests when the reinforcing bars will be inspected for the presence and type of corrosion products.
- The superior performance of conventional epoxy-coated reinforcement in the current study may be improved with the addition of a corrosion inhibitor to the concrete. This conclusion may be modified as additional data are obtained.