Stiffness Characterization of Stone Matrix Asphalt Using Ultrasonic Pulse Velocity and Dynamic Modulus Models

Direct measurement of dynamic modulus still has several limitations, as it requires specialized equipment, complex testing procedures, and relatively long testing times. This study aimed to evaluate the stiffness of Stone Matrix Asphalt (SMA) mixtures incorporating Portland Composite Cement (PCC) filler using Ultrasonic Pulse Velocity (UPV), shear modulus, and the dynamic modulus prediction models proposed by Witczak and Al-Khateeb. SMA mixtures were prepared with asphalt contents of 5.0%, 5.5%, and 6.0%. The results showed that the mixture containing 5.5% asphalt exhibited the most stable wave propagation pattern and the highest UPV value of 3,542.08 m/s. At this asphalt content, the UPV-based dynamic modulus and shear modulus reached their maximum values of 17,760 MPa and 6,580 MPa, respectively. The Witczak model predicted dynamic modulus values ranging from 4,189.63 to 6,345.60 MPa, whereas the Al-Khateeb model produced lower estimates, approximately 2,700–2,900 MPa. Overall, UPV proved to be an effective and non-destructive technique for rapidly characterizing the internal condition and small-strain, high-frequency stiffness of SMA mixtures, with the 5.5% asphalt content yielding the highest UPV-based stiffness among the three contents tested.