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Iowa State University--Becoming the Best

Impact of Deck Cracking, Phase II (TR-405)


Principal investigators:

Project status


Start date: 08/01/98
End date: 09/30/00


Report: Impact of Deck Cracking, Phase II (TR-405) (2.62MB pdf) March 2000



About the research

Abstract: Concrete bridge decks subjected to corrosive environment because of the application of de-icing chemical could deteriorate at a rapid rate. In an effort to minimize corrosion of the reinforcement and the corresponding delaminations and spalls, the Iowa Department of Transportation started using epoxy-coated rebars in the top mat of reinforcing around 1976 and in both mats about 10 years later. The overall objective of this research was to determine the impact of deck cracking on durability and estimate the remaining functional service life of a bridge deck. This was accomplished by conducting a literature review, visually inspecting several bridge decks, collecting and sampling test cores from cracked and uncracked areas of bridge decks, determining the extent to which epoxy-coated rebars deteriorate at the site of cracks, and evaluating the impact of cracking on service life.

Overall, 81 bridges constructed with epoxy-coated rebars were sampled. No signs of corrosion were observed on the rebars collected from uncracked locations. Rebars that had surface corrosion undercutting the epoxy coating were those collected from cores that were taken from cracked locations. In general, no delaminations or spalls were found on the decks where these bars were cored. The surface chloride concentration at 0.5 inches below the deck surface and the diffusion constant were found to be 14.0 lb/yd3 and 0.05 in2/yr, respectively. For a corrosion threshold range from 3.6 to 7.2 lb/yd3, the predicted service life for Iowa bridge decks considering corrosion of epoxy-coated rebars was over 50 years. This illustrates that epoxy-coated rebars can significantly extend the service life when compared with bridges constructed with black rebars.