Novel Analysis of Ultrasonic Pulse Propagation Tests for Characterization of Asphalt Concrete

Abstract

The need for better pavement material characterization has become the focus of several studies lately. Better characterization is necessary to promote mechanistic-based pavement analysis methods. The current availability of nondestructive testing methods offers significant benefits to improve the accuracy of conventional testing methods as well as the development of fast quality control tools. To this end, a new analysis of the ultrasonic pulse propagation tests (UPPT) in asphalt concrete mixes can provide a more complete evaluation of viscoelastic properties of these materials by providing results at a wider range of temperatures and loading frequencies. UPPTs can also be used as a complementary tool to improve conventional asphalt concrete characterization techniques. This study evaluates the use of UPPT for the characterization of asphalt concrete mixes using 2 main excitation frequencies of 54 and 150 kHz. Measurements are performed at 5 temperatures ranging from −11°C up to 54°C. The nondestructive nature of the UPPT allowed for the use of the same specimens for uniaxial dynamic modulus tests. These tests were performed using six different loading frequencies at each of the five selected temperatures. The results indicate that the accuracy of the modulus master curves can indeed be improved by combining the results from the UPPTs and the conventional dynamic modulus tests. The results also underline the importance of accounting for the temperature-dependent Poisson’s ratio of asphalt mixes when calculating the norm of complex modulus from P-wave ultrasonic measurements. Furthermore, to the traditional time-of-light analysis, the results show a strong correlation between the phase angle from conventional mechanical testing and the attenuation parameter from ultrasonic waves at different temperatures.