| The behavior of asphalt concrete under external loads is complicated because of its multiple components. A series of triaxial compression creep tests with three loading programs (constant, repeated, and haversine creep) were conducted to capture the permanent deformation-related properties of asphalt concrete. Results showed the tested material was not incompressible and it deformed non-uniformly. Volumetric and shear strains were affected by both isotropic and shear stress; the influence of shear stress on volumetric strains was significant, but that of isotropic stress on volumetric strains was minimal. The analysis of constant creep tests revealed time-independent (elastic and plastic) and time-dependent (viscoelastic and viscoplastic) strains in shear were incorporated and present simultaneously in the total strains during the loading process. Both time-independent and time-dependent strains were proportional to the level of stress and stress history. A visco-elasto-plastic constitutive model was developed to describe the material behavior. The comparison showed good agreement between the prediction from the model and the results of repeated creep tests. Dynamic properties (complex modulus, complex compliance and phase angle) can be obtained from the results of haversine creep tests with the Hysteretic Loop Method. An analytical method to predict the viscoelastic creep compliance from dynamic properties was developed. The comparison between the prediction and the viscoelastic compliance from constant creep tests showed good agreement. |
