Interlayer and Design Considerations to Retard Reflective Cracking

Abstract

To protect the structure and provide a new, smoother riding surface, many highway agencies overlay deteriorating portland cement concrete pavements with hot-mix asphalt (HMA) overlays. Reflective cracking through the overlays has been a persistent problem. Most methods that are used to delay the cracks have been based on tension (the horizontal movement occurring at the crack or joint interface). A performance-related flexural fatigue test addresses the tension, shear, and bending forces that result in reflective cracks. A reflective crack relief system consisting of an impermeable, highly elastic interlayer that uses fine-graded aggregates and a quality HMA overlay has been specified with flexural fatigue for crack resistance and Hveem stability for rutting resistance. Preliminary cracking data from several projects that used the specification and their control sections show that reflective cracking is delayed. Cores taken from the test sections show that even when the overlay cracks, the interlayer remains intact and impermeable, protecting the pavement structure from moisture intrusion. These cores also show that, unlike those in the control sections, the reflective cracks over the new system are offset from the underlying joints and further disrupt paths for water and giving better rideability. Seven state departments of transportation have used the performance-related specification for constructing the interlayer and overlay.