Quantification of Damage in the Dynamic Complex Modulus and Flow Number Tests Using X-Ray Computed Tomography

The dynamic modulus test is conducted based on the assumption that no damage is induced during the testing process and that measurements are conducted within the linear viscoelastic region. In addition, the level of damage that occurs in the flow number test has not been quantified. The objectives of this study are to quantify the levels of damage in the dynamic complex modulus and flow number tests by using X-ray computed tomography (CT) and to characterize the microstructural properties of asphalt mixtures under loading. Four Superpave mixtures, including one conventional hot-mix asphalt (HMA) and three warm-mix asphalt (WMA) mixes, were evaluated. Two WMA processes (i.e., water foaming and Rediset additive) were used in the preparation of the WMA mixes. In addition, reclaimed asphalt pavement (RAP) was used in the preparation of the mixes at a content ranging from 15-30%. Results of the experimental program indicated that the damage incurred in the dynamic modulus test is minimal and homogeneous, but the damage incurred in the flow number test is significant and heterogeneous. In addition, specimen preparation may significantly influence the three-dimensional air voids distribution in HMA.