Comparative Studies of Galvanized and Epoxy-Coated Steel Reinforcement in Concrete


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Title: Comparative Studies of Galvanized and Epoxy-Coated Steel Reinforcement in Concrete

Author(s): S. R. Yeomans

Publication: Special Publication

Volume: 126


Appears on pages(s): 355-370

Keywords: corrosion; epoxy resins; galvanized materials; pullout tests; reinforcing steels; tests; Materials Research

Date: 8/1/1991

Comparisons of the corrosion performance and pullout strength of black, hot-dip galvanized, and fusion-bonded epoxy-coated steel reinforcement in concrete have been undertaken. Accelerated exposure testing confirmed that zinc coating was able to delay considerably the onset of corrosion and that epoxy coating effectively eliminated corrosion, provided the coating was not damaged. Where coated reinforcement was left with cut ends unrepaired, the epoxy-coated bars showed early corrosion of the exposed steel, with corrosion progressing along the bar under the coating. Even where cut ends were repaired, the epoxy-coated bars showed many sites of breakdown of the repair and corrosion of the underlying steel. The sacrificial nature of the zinc coating provided positive protection to the underlying steel where the coating was damaged. Pullout testing revealed that there is no significant difference in the ultimate bond strength of black, epoxy-coated or galvanized deformed bars. For plain reinforcement, the ultimate bond strength of epoxy coated bars in some 17 percent less than that for black steel bars, while that for galvanized bars is some 31 percent greater than for black steel. The ultimate bond strength of deformed bars is up to 50 percent higher than that of plain bars. The passivation of galvanized plain bars by chromate additions to the concrete mix water in the range 15 to 150 parts per million could not be shown to significantly improve the bond strength. Further work is being done in this area with much larger sample populations to clarify this result.