Thin Concrete Overlays US Case Studies and Performance

The need for optimizing preservation and rehabilitation strategies used to maintain highway concrete and asphalt pavements has never been greater, given the current difficult economical outlook faced by highway agencies. Conventional bonded and unbonded concrete overlays have a long history of successful use to preserve and rehabilitate concrete and asphalt pavements and many of the practices are well established. However, of recent origin are techniques that use thinner concrete overlays with shorter joint spacing. These techniques are used for bonded overlays as well as unbonded (directly placed) overlays. Field experience over more than 15 years with these thinner bonded and unbonded concrete overlays under a range of traffic and site conditions in the USA has demonstrated their viability as a cost-effective solution to extend the service life of deteriorated asphalt, concrete and composite pavements. Thin concrete overlays are typically 4 to 7 in. (100 to 175 mm) in thickness. The overlay panels are typically 6 by 6 ft (1.8 by 1.8 m) or less in dimension. Thin concrete overlays can be designed for a range of traffic loading to provide long performance lives of 15 to 20+ years and to meet specific needs. Well-designed and well-constructed thin concrete overlays require low maintenance and can have low life-cycle costs. This paper provides a review of the US practice and experience related to thin concrete overlays. In addition, several recent case studies are presented that illustrate the wide range of applications of thin concrete overlays.