Methods of Corrosion Protection and Durability of Concrete Bridge Decks Reinforced with Epoxy-Coated Bars - Phase I

摘要

In this study, the results of an extensive field and laboratory investigation conducted to evaluate the corrosion performance of epoxy-coated reinforcement are reported. One hundred and twenty three concrete bridge decks containing epoxy-coated reinforcement, uncoated reinforcement, and various other corrosion protection systems were included in a field investigation. An initial visual inspection of these bridge decks showed that 44% had signs of distress from corrosion of the reinforcement. Six decks, representing 5% of the total sample, were selected for a second more detailed survey. Three of the six decks had epoxy-coated reinforcement. This number represents 11% of the total sample of bridge decks with epoxy-coated reinforcement. Corrosion of the epoxy-coated reinforcement was discovered in areas of cracking and shallow cover on two of these three bridge decks. New construction bridge sites were also visited to perform holiday testing on epoxy-coated reinforcement upon arrival to the site, after placement, and after casting. The results from the holiday testing showed that an average of 31 holidays per meter (9 holidays per foot) were created during the concrete casting operation. Increasing the coating thickness by 101.6 mm (4 mils) and lowering the hose used when pumping concrete to the level of the top mat of reinforcement reduced the holidays created to 11.5 holidays per meter (3.5 holidays per foot) after casting. The results of 16 specimens subjected to cycles of exposure in the laboratory evaluation indicated that if the mat to mat resistance was greater than 5000 ohms, then over the 77-week period no corrosion activity was observed. No corrosion activity occurred even though the chloride levels at the reinforcement location were well above 0.79 kg/m3 (1.3 lb/yd3), the threshold level for initiation of corrosion. A possible way to achieve a high mat to mat resistance would be by limiting the damage to the epoxy coatings.