Determination of the frequency dependent dynamic modulus for asphalt concrete beams using resonant acoustic spectroscopy

Abstract

The objective of this paper is to study the application of resonant acoustic spectroscopy (RAS) to beam shaped asphalt concrete samples. Natural modes of vibration are generated by a small load impulse at different temperatures and an accelerom-eter measures the resulting acceleration through the specimen. By using the Fast Fourier Transform the obtained information is transformed to frequency domain from which the solid's damped natural frequencies can be determined. For each frequency and temperature the corresponding complex modulus is calculated using the approach of RAS. Results of the dynamic modulus from RAS are presented and compared with results of the dynamic modulus calculated according to ASTM E 1876-99 [1]. By using ASTM E 1876-99 only the fundamental frequency of each type of vibrational mode can be used. However, using RAS several resonance frequencies from the same temperature can be used in the evaluation. This opens the possibility of determining the high frequency (or the low temperature) part of the dynamic modulus mastercurve directly from RAS. © RILEM 2013.