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The Deal with Seal

  

Chloride ions' infiltration into bridge-deck concrete is one of the major factors impacting bridge-deck performance, as the ions play a key role in the corrosion of reinforcing steel. The Illinois Department of Transportation (IDOT) embarked on a multi-year research initiative to assess how effective various concrete sealer and laminate products are under specific conditions, including weather, construction practices, and maintenance practices, found in the state. Both penetrating sealers—chemicals sprayed onto the surface to penetrate the concrete—and film-forming sealers—chemicals spread onto the concrete surface with a squeegee—were considered in the study. The IDOT study's outcomes showed that sealers and laminates can significantly limit chloride ions' penetration of bridge-deck concrete in comparison to unprotected control structures. The findings prompted IDOT's improvement of statewide bridge-deck sealing policies in 2010, and the establishment of guidelines to help in the selection of structures to which concrete sealers would be applied. Sealing was directed for all existing concrete bridge decks with National Bridge Inspection Standards condition ratings of 6 or better. Sealers also would be applied to the decks and parapets of new bridges and rehabilitated existing bridges as a component of initial construction. Reapplication of concrete sealer every four years is recommended by the IDOT guidelines, based on the research findings.

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