Standardized Elastic Moduli of Pavement Layers for Overlay Design

Abstract

The application of elastic theory to the design of overlays on existing pavement requires that a modulus of elasticity be assigned to the existing structural system. Estimates of elastic modulus are obtained from dynamic deflection readings in the field; but asphalt is a highly temperature-sensitive viscoelastic material, and deflections not corrected to a standard temperature can produce misleading results. It is therefore the objective of the present study to develop a procedure for estimating an effective modulus of elasticity for a layer of asphaltic concrete in which a temperature gradient exists because of the combined influences of solar radiation, wind, air temperature, cloud cover, and other variables specific to time and location that cause temperature variations within the pavement layer. Two models are presented for the achievement of that objective. The first of the two models has been designed to utilize site-specific conditions for calculating a temperature profile at a given time within an asphaltic layer. The second model relates an equivalent elastic modulus to the calculated temperature profile.