Bridge Deck Performance

Principal Investigator:

Ben Dymond, Assistant Professor, UMD-Civil Engineering

Project Summary:

Concerns about long-term corrosion of bridge deck reinforcement and degradation of the surrounding concrete have led to innovative approaches to protect steel rebar and reduce concrete cracking in Minnesota. First, a population of approximately 661 bridge decks was built between 1975 and 1989 with an epoxy-coated rebar top mat and uncoated black bar bottom mat to protect the top layer of steel reinforcement from corrosion. Most of these structures are still in service and have not been re-decked. Second, approximately 20 bridge decks have been constructed in the last five years with polypropylene fibers in the concrete mix to reduce the width and amount of deck cracking. To determine if the use of epoxy-coated top mat rebar or polypropylene fibers has affected the rate of deck deterioration, the objectives of this project include answering the following questions: 1) How are fiber-reinforced bridge decks performing compared to control group twin structures constructed without fibers? 2) How are the epoxy-coated top mat and uncoated bottom mat bridge decks performing compared to control group twin structures constructed without mixed rebar decks (e.g., epoxy-coated top and bottom mat rebar or uncoated top and bottom mat rebar)? 3) What type of deterioration is being observed (e.g., spalling of underside of deck concrete or unsound concrete on the top wearing surface)? 4) Should a preventative maintenance plan be developed for bridges built with epoxy-coated top mat and uncoated bottom mat rebar? Should this plan be different depending on the feature under the bridge? To achieve the objectives, researchers are evaluating bridge inspection reports to identify variation in different types of condition ratings and rate of deterioration between bridges built with mixed rebar decks, fiber-reinforced deck concrete, and control group twin structures. Furthermore, researchers are conducting on-site visual inspections to determine if bridges built with epoxy-coated top mat rebar or fiber-reinforced deck concrete have more/less visual degradation when compared to control group visual inspection results. Inspection report data is being used to determine if the deck condition ratings are better/worse for the epoxy-coated top mat bridge decks compared to the accompanying control group twin structures. If condition ratings are worse, researchers will work with the Minnesota Department of Transportation to determine if a preventative maintenance plan should be developed.

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