Development of an Improved Design Procedure for Unbonded Concrete Overlays

Project summary:

An unbonded concrete overlay is a portland cement concrete (PCC) pavement slab that is separated from the existing PCC slab by a separation layer (also called interlayer). Although unbonded concrete overlays have been used since 1916 as a successful method of rehabilitation, there is still a lack of reliable procedures and guidance on the design and construction features that could make it a more cost-effective rehabilitation solution. Consequently, even though highway agencies in Minnesota, Michigan, California, Texas, and other states routinely use this type of overlay, a number of agencies do not even consider rehabilitation with unbonded concrete overlay and are unfamiliar with its design and construction. The objective of this project is to develop improved guidelines for design and construction features that highway agencies can use to build long-lasting concrete overlays. To meet this goal, a mechanistically based, field-test data-validated design procedure for various types of separated overlays will be developed.