Nondestructive evaluation of complex moduli in asphalt concrete with an energy approach

A modified version of the impulse-echo method is presented to non-destructively estimate the average Poisson's ratio and the average dynamic complex bulk, shear, extensional, and longitudinal moduli of asphalt concrete specimens made of different mixtures. The estimated moduli represent an average over the volume of the specimens and over the frequency band of 10 to 50 kHz. By using principles of statistical energy analyses, the proposed methodology is based on the energy-density decay function of a diffuse wave field. The methodology allows evaluation of the energy dissipation characteristics of different asphalt concrete mixtures and their dependence on material microstructure. As a consequence, energy-density decay functions may be used to search for an optimum asphalt concrete microstructure. In this study, it was observed that the typical Superpave mixture generally exhibits higher average dynamic energy storage capacity and higher energy decay rates (i.e., loss moduli).