Development of a simplified fatigue test and analysis procedure using a viscoelastic, continuum damage model and its implementation to WesTrack mixtures

This dissertation presents a methodology by which the material response under any uniaxial tensile testing condition (type of loading and temperature) can be predicted from the material response obtained from a single testing condition. The methodology makes use of a uniaxial constitutive model for asphalt concrete that is based upon the elastic-viscoelastic correspondence principle and work potential theory, a continuum damage theory based on thermodynamics of irreversible process. Uniaxial tensile testing is performed under controlled crosshead mode for both cyclic and constant rate to failure tests. Various strain amplitudes, frequencies, and rates are applied at several test temperatures. A single characteristic curve can be found that describes the reduction in material integrity as damage grows in the specimen regardless of the applied loading conditions (cyclic versus monotonic, amplitude/rate, frequency). The characteristic curve at any temperature can be found by utilizing the time-temperature superposition principle and the concept of reduced time. Eight WesTrack mixtures are tested and the methodology is used to successfully predict the fatigue damage at different testing conditions from a single condition. A test and analysis procedure for the fatigue characterization of asphalt mixtures based on this methodology is proposed and potential applications are discussed. Additionally, the framework for the inclusion of the effect of aging on the fatigue performance prediction is developed and presented along with the effect of aging on the properties of an asphalt mixture and validation of the applicability of the elastic-viscoelastic correspondence principle to aged mixtures.