Construction Report for a Thin Unbonded Concrete Overlay on Minnesota TH 53

Status:  Complete
Report Date:  07/14/2010


Unbonded concrete overlays are generally used to rehabilitate pavements by restoring lost ride and structural capacity. Historically, their design has been conservative (thick) due to the lack of a rational design method. In the summer of 2008, TH 53 near Duluth, MN, was rehabilitated with a thin (5-inch thick) unbonded concrete overlay. The Minnesota Department of Transportation (Mn/DOT) included the TH 53 overlay as part of a research project on thin unbonded concrete overlays. Falling weight deflectometer (FWD) measurements were taken both before and after construction. A short section of the project was instrumented with electronic sensors designed to collect environmental and load response data. The TH 53 test section is currently undergoing thorough evaluations and rigorous testing in accordance with the research project work plan. This report presents the initial baseline testing results, which include: distress survey and mapping, ride quality measurements, and structural testing. A visual distress survey, conducted in April 2009, revealed that approximately 40 transverse cracks have formed in the overlay over the nearly nine mile project length. FWD measurements indicate that the new pavement is providing good structural support.

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