A thin, bonded concrete overlay can improve the load-carrying capacity and rideability of an existing concrete pavement without incurring high replacement costs and causing months of traffic interruption. Compared with asphalt overlays, bonded concrete overlays provide significantly more structural improvement per inch of thickness. Bonded concrete overlays also have lower life-cycle costs than asphalt overlays. A typical design life for a bonded overlay is 15 to 25 years. Bonded concrete overlays can be placed by fast-track methods to shorten downtime and minimize traffic interruption.
A strong bond is a key to the long-term service of a bonded overlay. But a loss of bond doesn't mean on overlay has failed; it means performance will be reduced. Debonding can result from many factors, but the two most important factors are the strength and integrity of the existing concrete and the cleanliness of the surface. Therefore, surface preparation, by milling and shotblasting, must be done thoroughly. If a grout is specified, apply it by mechanical sprayer just ahead of the spreader or slipform paver. For most conditions, an overlay thickness of 3 to 4 inches is sufficient, although overlays as thin as 1 inch have been placed. To prevent excessive moisture loss, it is essential to begin curing procedures immediately after texturing the overlay surface.