United States Department of Transportation
i
Bridge Deck Chloride Testing Protocols: Study of US-40 Bridges Over the Provo River, Utah
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2020-03-01
[PDF-16.37 MB]
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Edition:Sept 2019 to Feb 2020
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Abstract:A primary contributor to the degradation of reinforced-concrete bridge decks is chloride-induced corrosion, resulting from application of salts for anti-icing/deicing during the winter months. The purpose of this research is to evaluate different methods of chloride testing, including field sampling and laboratory testing methods, to conduct analyses to compare methods of testing for effectiveness and efficiency, and to recommend protocols to UDOT for future chloride testing in concrete bridge decks. Research methods included a chloride sampling and testing matrix to be executed by a team of four independent subconsultants. The chloride sampling and testing matrix included comparison of methods in three categories: concrete sample extraction, sample preparation, and chloride concentration testing. The concrete sample extraction methods included hammer-drill powder sampling and concrete wet-core sampling following either uniform 1-inch sample depth increments or a progressive range of ½-inch sample increments. Additionally, comparisons were made between powdered sampling using a constant profile of uniform bit diameter versus a tapered profile of progressively smaller bit diameters. The sample preparation method used was acid-soluble digestion of concrete powder according to similar procedures in either ASTM C1152 or AASHTO T260. The chloride-concentration testing methods included potentiometric titration and calibrated ion-selective electrode (CISE). Results showed that core sampling and subdivision by cutting and crushing, followed by acid-soluble digestion and potentiometric titration provide the most consistent and reliable determination of chloride concentration profiles. CISE results were highly variable and are not recommended.
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