United States Department of Transportation
i
Proposed testing of concrete sealers.
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2017-07-04
[PDF-1.34 MB]
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Abstract:Chlorides, in sufficient concentrations, will cause corrosion of steel reinforcement in bridge decks. Previous studies have shown that de-icing chemicals and practices used by the Kentucky Transportation Cabinet (KYTC) can result in problematic levels of chloride at steel reinforcing depths in a relatively short amount of time. With the advent of liquid applied pre-treatment deicing chemicals testing performed in Kentucky indicate chloride levels in bridge decks at a depth of two inches have increased significantly. The action levels for chlorides in concrete as related to reinforcing steel corrosion are: • Corrosion will initiate at 0.03% chlorides by weight of concrete. • Accelerated corrosion begins at 0.08% chlorides by weight of concrete. • Major section loss of steel occurs at 0.18% chlorides by weight of concrete. Concrete sealers have proven effective in arresting chloride penetration into bridge decks resulting in lower incidences of cracked and spalled concrete. Concrete sealing is a relatively inexpensive and durable treatment. In 2013 Kentucky Transportation Center (KTC) conducted a study (1) to determine the ability of a number of concrete sealers to resist chloride penetration into concrete. KYTC chose four of these products to be used on an experimental basis on the bridge that carries I 471 over 6th Street in Newport, KY. Results from the previous study and this one were combined and sorted by performance at a depth of ½ inch (Appendix 1). The application method varied between the two projects. For the previous study the recommended usage, from the manufacturer’s data sheet, was calculated for the surface area of each specimen and spray applied. The specimens for this study were flooded, as described below. Key properties of concrete sealers are resistance to chloride migration into the concrete and good penetration of the sealer into the concrete. Depth of sealer penetration would help offset wheel path wear and enhance the durability of the treatment. However, when a concrete deck has minor cracking, the performance of penetrating sealers will be limited. Recently several products have been promoted by manufacturers for potential use by the KYTC to seal bridge decks. The Kentucky Transportation Center (KTC) was asked to test and evaluate some of these products. For this study KTC focused on four of these products (Table 1). The process included specimen preparation, application of material, testing, and evaluation.
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