Key Concepts

Thin overlays, either bonded or unbonded, can be applied to existing asphalt, concrete, and composite pavements. The selection of a bonded or unbonded overlay is largely dependent on the condition of the existing pavement. In general, thin bonded concrete overlays can be used over existing pavements that do not exhibit significant structural distresses (except rutting of the existing asphalt pavement) or durability problems. As the existing pavement condition deteriorates, the use of unbonded concrete overlays becomes an attractive rehabilitation option, as unbonded overlays require very little pre- overlay repair. In either case—bonded or unbonded—the thickness of the thin overlay will vary based on the type of application, the design traffic loadings, and the condition of the existing pavement.