The objective of this research was to study the effect of the mode of loading on viscoelastic properties and damage characteristics of asphalt concrete. Four 12.5-mm nominal maximum aggregate size mixtures were designed according to Superpave® specifications. The specimens prepared with these mixtures were tested under uniaxial, biaxial, and flexure modes to obtain viscoelastic and damage properties. Viscoelastic and damage properties depended on loading mode and testing frequency. Statistically significant differences were found between mean values of measured modulus under different modes of loading. Also, regions of overlap in phase angle measurements were observed. A systematic variation in viscoelastic properties was found between different loading modes. The specimen underwent damage at a faster rate under the uniaxial mode than under the flexure loading mode. At a given value of normalized pseudostiffness, the damage parameter ratio, computed with parameters obtained under different modes of loading, remained approximately the same and was a function of material properties.
