United States Department of Transportation
i
Evaluation of Non-destructive Techniques for Corrosion Detection in Concrete Exposed to a Marine Environment
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2005-05-01
[PDF-15.21 MB]
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Abstract:A study was conducted to evaluate electrical tests and chemical tests of reinforced concrete specimens subjected to a cyclic laboratory simulated marine environment. The tests compared the electrical tests to visual inspections involving acoustic and optical microscopy. The specimens were proportioned using corrosion-inhibiting admixtures intended to slow the corrosion process. The corrosion-inhibiting admixtures included Darex Corrosion Inhibitor (DCI), Rheocrete CNI, Rheocrete 222+, FerroGard 901, Xypex Admix C-2000, latex, fly ash, and silica fume. Relevant tests such as pH level, air permeability, chloride content, macrocell current, and half-cell potential were performed. Both electrical test of macrocell current and half-cell potential proved effective in predicting moderate to substantial corrosion. When macrocell currents measured over 10 µA , substantial corrosion was found 94% of the time. Similarly, when the half-cell readings indicated 90% probability of corrosion, substantial corrosion was found 100% of the time. However, when the half-cell readings indicated less than 10% probability of corrosion, 65% of the specimens had signs of corrosion. Overall, the air permeability and pH values do not indicate any correlations to the various levels of corrosion. Using chlorides and half-cell values certain limits could be related to certain levels of corrosion. In all cases chloride values (mass of cement) above 3% and half-cell values over 90% probability of corrosion (-350mV) were all substantially corroded.
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