Half-cell potential testing has been recommended as a non-destructive method for assessing the corrosion potential of reinforcing steel in concrete bridge decks. The technique is particularly useful because it can be utilized to evaluate the probability of corrosion before damage is evident at the surface of a bridge deck. The specific objective of this research was to quantify the effects of age, chloride concentration, concrete cover thickness, spatial position, temperature, and presence or condition of epoxy coating on half-cell potential measurements of concrete bridge decks typical of those in Utah. The laboratory testing associated with this research followed a full-factorial experimental design. Nine rectangular concrete slab specimens were prepared, each containing three black reinforcing steel bars at three different concrete cover depths and four epoxy-coated bars each having different coating conditions. Three replicate slabs were created at each of three different chloride concentrations. Three repeated measurements were made at each of three locations along each of the seven bars in all nine of the slabs at three ages, with testing performed at three temperatures per age. In addition, compressive strengths of the concrete cylinders were measured at 7 and 28 days. Statistical analyses of the half-cell potentials were performed using analysis of variation and Tukey's method for multiple comparisons. Although American Society for Testing and Materials C 876 only specifies the measuring of half-cell potentials of uncoated reinforcing steel, credible half-cell potentials were also obtained for epoxy-coated rebar in this research. The results of the testing indicated that all of the factors except for cover thickness and spatial position have important impacts on half-cell potentials over the ranges of levels investigated in this research. Half-cell potential measurements became consistently less negative with increasing age and consistently more negative with increasing chloride concentrations and increasing temperature. With regard to the factor of treatment, the uncoated rebar had the most negative half-cell potential, followed by epoxy-coated rebar with rib scrapes, pliers strikes, end cuts, and full epoxy coatings, in that order. While these data indicate that a coating, even damaged, reduces the probability of corrosion when compared to uncoated rebar, the data also suggest that both the amount and distribution of the coating damage over the affected rebar influence corrosion. Given these research findings, bridge engineers and managers should have confidence in using half-cell potential testing for assessing the corrosion probability of reinforcing steel in concrete bridge decks. In decks with properties similar to those investigated in this research, variations in age, chloride concentration, temperature, and presence or condition of epoxy coating cause variation in half-cell potential readings consistent with the effects of these factors on corrosion. Therefore, the half-cell potential technique is recommended for assessing the probability of corrosion of reinforcing steel on bridge decks. Although the use of epoxy-coated reinforcement, even when damaged, reduces the probability of corrosion, care should still be taken to minimize any damage to the coating during shipping and field handling. Owners and contractors alike should establish appropriate inspection protocols and repair methods for epoxy-coated reinforcing steel used on bridge decks to ensure maximum service life.
| Identifer | oai:union.ndltd.org:BGMYU2/oai:scholarsarchive.byu.edu:etd-2257 |
| Date | 05 December 2007 |
| Creators | Pinkerton, Thad Marshall |
| Publisher | BYU ScholarsArchive |
| Source Sets | Brigham Young University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
| Rights | http://lib.byu.edu/about/copyright/ |
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