Federal Highway Administration State Planning and Research Funding
Iowa Department of Transportation
Brent Pharesbphares@iastate.edu email >
Bridge Research Engineer, BEC
Justin Dahlbergdahlberg@iastate.edu email >
About the research
For the past 13 years or so, the Kansas Department of Transportation (KDOT) has been using polymer-based overlays on primary highway bridge decks. Since the first trial application, more than 200 decks have been overlaid with primarily epoxy-based materials. Recently, however, KDOT has begun trials with overlays based on methracrylates and polyesters.
In general, anecdotal evidence suggests that the KDOT experience has been good. However, implementation has not been without problems and a commonly encountered learning curve.
Despite these problems, KDOT has started using polymer overlays on new structures in place of their more conventional silica-fume overlays. While most problems that have been encountered were not attributed to material problems, there has been no concerted effort to track or document polymer overlay performance with time or to relate performance to material usage and/or workmanship.
The objectives of this work were to document the state-of-the-practice with respect to polymer concrete overlays, document the placement of two overlays in Iowa, monitor the field performance of the overlays over a two-year period, and relate their performance to material usage and/or workmanship.
The two bridges—a Johnson County, Iowa bridge over I-80 on 12th Avenue in Coralville, and the Keg Creek Bridge on Hwy 6 in western Iowa, 10 miles east of Council Bluffs—were overlaid during the summer/fall of 2013. The process by which each bridge was overlaid was similar in many ways, although a few slight differences existed.
Over time, each overlay has generally performed quite well with only a few areas of exception. It is believed that these localized areas likely underperformed due to poor deck preparation, improper polymer mixing, snowplow impact, or a combination thereof.