Complex modulus is one of the key parameters in the Mechanistic-Empirical Pavement Design Guide (MEPDG). The purpose of this study is to implement an accurate and high-efficiency mechanical method to measure and calculate the complex modulus gradient of asphalt concrete cores in different field locations. Because field cores are different from the asphalt mixtures made and compacted in the lab, field cores should not be substituted by lab made lab compacted (LMLC) asphalt mixtures perfectly. For field cores complex modulus measuring methods, except some expensive pavement field testers, empirical and semiempirical models are widely used, but an accurate mechanical test method is more desired. In this research, Arizona, Yellowstone National Park and Texas field cores and three types of asphalt mixtures including hot mix asphalt (HMA), foaming warm mix asphalt (FWMA), and Evotherm warm mix asphalt (EWMA) were used. There were nearly forty field cores with different aging times from these three locations have been collected and tested using this new viscoelastic method. The complex modulus at a random depth and the depth of highly aged pavement can be calculated and estimated from these stiffness gradient figures. After analyzing the results, a strong correlation between test results and solar radiation and some other models have also been established which can be used for estimating the complex modulus of an in-service pavement.
