Anisotropic Properties of Asphalt Concrete: Characterization and Implications for Pavement Design and Analysis

Asphalt concrete has been recognized as an anisotropic material, but the degree of anisotropy and its implications for pavement design and analysis have not been well understood. This paper illustrates the difference between the stress fields of an isotropic and an anisotropic pavement under wheel load through analytical solution and finite-element simulation for several cases. A servocontrolled true triaxial (cubical) testing device was used to test 4-in. cubical asphalt concrete specimens under general stress states to characterize the anisotropic properties of asphalt concrete. It was discovered that (1) the stiffness of a cored field specimen has significant differences in the vertical and horizontal direction; and (2) the significant difference may result in larger shear stress and tensile stress in a pavement. These findings indicate that characterization and modeling of the anisotropic properties of asphalt concrete are an important area that deserves further investigation.