The project developed guidelines for the design and construction of unbonded portland cement concrete overlays.

Portland cement concrete pavements constitute a large portion of those pavements that are designed to carry a high volume of heavy traffic. An unbonded portland cement concrete overlay is an effective resurfacing method for rehabilitating these pavements because it improves the structural capacity of the old pavement and enhances rideability by providing a new surface. There was a need to evaluate existing methods for rehabilitating portland cement concrete pavements with unbonded concrete overlays and develop guidelines for their use.

Research included a review of relevant domestic and foreign literature, survey of U.S. departments of transportation, analysis of field performance data, evaluation of design criteria and performance aspects of existing rehabilitation methods, and recommending guidelines for the design and construction of unbonded concrete overlays. NCHRP Report 415, "Evaluation of Unbonded Portland Cement Concrete Overlays," documents the work performed in this research.