Minnesota Department of Transportation

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Road Research

Research Topics

Orange barrels on a highway

Performance of Thin Unbonded Concrete on High Volume Roads

Due to increased traffic congestion and reduced highway construction budgets, emphasis is now being placed on seeking effective rehabilitation techniques for older pavements. Whitetopping and unbonded concrete overlays have great potential as pavement rehabilitation methods.  Some whitetopping cells have been built previously at MnROAD.  However, the underlying HMA pavements were in good condition and did not represent typical conditions. Researchers and pavement designers still question if the data from these test sections can adequately represent the performance of whitetopping on asphalt pavements that show distress (cracking, rutting).  A new thin whitetopping section built on a full depth bituminous cell in poor condition will be constructed to create a test section to help to answer these questions as well as add to the performance database from which a rational design method for whitetopping will be developed.  The research on this cell will be done as part of a Multi-state Pooled Fund project TPF-5(165) that will use the MnROAD and other test section data to develop a rational design method for thin concrete overlays.

Current pavement design methods treat unbonded overlays similar to concrete pavements lying on traditional aggregate base layers.  Design thicknesses for these overlays tend to be greater than 7 inches.  Due to the large initial cost of constructing these relatively thick layers (which includes costs associated with raising of the shoulders, bridges, and intersections), there is interest in understanding the performance of thinner unbonded concrete overlays.  A test cell for a thin unbonded overlay will be constructed, evaluated for a five year period, and the results will also be incorporated into MnDOT design methods.

Pavement Automated Profiling System (PALPS)


Reports & Publications
Pooled Fund Website

Eight states are participating in this pooled fund project to create a Unified National Design Guide for unbonded concrete overlays of existing concrete and composite pavements.