THE PERFORMANCE OF BENDABLE AND NONBENDABLE ORGANIC COATINGS FOR REINFORCING BARS IN SOLUTION AND CATHODIC DEBONDING TESTS: PHASE II SCREENING TESTS
This report is a continuation of the work reported in the January 1995 report FHWA-RD-94-103. That report presented coating adhesion performance data following cathodic debonding and solution immersion tests on 22 bendable and 11 nonbendable organic coatings applied to straight and 4D bent shape reinforcing steel bars. This Phase II report describes tests on 5 bendable and 5 nonbendable organic coatings, 7 of which were selected from the previous study on 33 coatings. These 10 coatings, 9 epoxies and 1 vinyl, also included the 3M 213 epoxy coating that was commonly used for many years in bridge construction. The 10 coatings were tested for adhesion performance on straight and 4D, 6D, and 8D bent bar shapes after cathodic disbondment tests and solution immersion tests. With straight bars subjected to solution immersion tests, deionized water is less discriminating than the OH ion solution as related to adhesion reduction. The best adhesion was generally achieved with the four nonbendable epoxy coatings; however, one bendable coating with a steel surface pretreatment also provided very good adhesion on straight bars. With bent or prebent bars subjected to immersion tests, the deionized water was also less discriminating than the high-pH solution. The best performance was also obtained using nonbendable coatings. Poor adhesion after testing was found with bendable coatings bent to 4D, 6D, and 8D. The use of steel surface pretreatments on bendable coatings did not solve these adhesion reduction problems. Prebent bars with nonbendable coatings did not generally maintain as good adhesion as coated straight bars with the same nonbendable coatings. When straight bars with bendable and nonbendable coatings were subjected to cathodic disbondment tests, all eight newer epoxy coatings maintained excellent wet or dry coating adhesion when tested away from the intentional drill holes. The same eight epoxies, when tested at the drill hole, generally provided much poorer wet or dry adhesion. With 8D bent or prebent bars subjected to cathodic debonding tests in the OH ion solution, the four nonbendable epoxies provided excellent adhesion at away-from-the-hole locations, either wet or dry. The five bendable epoxies provide much poorer adhesion at away-from-the-hole locations. With at-the-hole locations, all five bendable epoxies provided extremely poor adhesion. The four nonbendable epoxies generally provided poorer adhesion at the hole under wet or dry conditions when compared to the excellent adhesion at the away-from-the-hole location.
- See also FHWA-RD-94-103 (TRIS 00674239).
Wiss, Janney, Elstner Associates, Incorporated330 Pfingsten Road
Northbrook, IL United States 60062
Federal Highway AdministrationTurner-Fairbank Highway Research Center, 6300 Georgetown Pike
McLean, VA United States 22101
- McDonald, D B
- Sherman, M R
- Pfeifer, D W
- Publication Date: 1996-5
- Features: Appendices; Figures; References; Tables;
- Pagination: 121 p.
- TRT Terms: Adhesion; Bending; Cracking; Debonding; Epoxy coatings; Laboratory tests; Organic coatings; Performance evaluations; pH value; Reinforcing bars; Surface treating
- Old TRIS Terms: Bendability
- Subject Areas: Geotechnology; Highways; Materials; I35: Miscellaneous Materials;
- Accession Number: 00725001
- Record Type: Publication
- Report/Paper Numbers: FHWA-RD-96-021
- Contract Numbers: DTFH61-93-C-00027
- Files: TRIS, USDOT
- Created Date: Aug 29 1996 12:00AM