Estimation of asphalt concrete modulus using the ultrasonic pulse velocity test

The mechanical dynamic modulus test was used to determine the dynamic moduli of hot-mix asphalt (HMA) with and without different types of fibers, and master curves were developed. The ultrasonic pulse velocity (UPV) test was then conducted on the same specimens to estimate the dynamic moduli across multiple temperatures, and master curves were developed. The Poisson's ratios required for UPV modulus prediction were estimated for different reduced frequencies, and a sensitivity analysis on their effect on the modulus values was performed. The master curves developed using the UPV moduli were superimposed on the mechanical test master curves and matched closely. Witczak's predictive equation and the Hirsch model were also used to predict the dynamic modulus master curves. The UPV moduli closely matched the mechanical dynamic moduli better than those predicted from the Witczak or Hirsch models at intermediate and high reduced frequencies. An attempt was made to combine the UPV modulus prediction with the Witczak and Hirsch models to improve moduli estimation at low reduced frequencies. Typical mechanical test methods are time consuming and require an expensive load frame and instrumentation setup. The UPV test requires less time, and the equipment needed is relatively inexpensive. Using the UPV test in combination with either the Witczak or Hirsch model is recommended as a lower-cost alternative to develop the master curves of the HMA dynamic moduli.