The proper design of asphaltic overlay thicknesses involves four major factors; the in-place modulus of the subgrade, an estimate of the structural capacity of the existing pavement, estimates of the future traffic expressed as equivalent axleloads and required or desired design levels, and a thickness design procedure. This paper deals with estimating the in-place subgrade modulus and the remaining load-carrying capacity of the existing pavement. The method presented herein is valid for any Road Rater or other dynamic tester such as the Dynaflect. This procedure was based upon a 600-pound (272.4-kg) peak-to-peak dynamic load applied at a rate of 25 Hz. The steady-state deflections have to be adjusted for load, dynamic frequency, and location of sensors. This method should be applied only to those testers that use a constant vibratory load.

Report Date


Report Number


Digital Object Identifier