Effects of environmental aging and ultra violet radiation on asphalt mixture dynamic modulus, permanent deformation and fatigue life

The aging process causes changes in the properties of asphalt mixtures, such as weak adhesion of mineral aggregates to the asphalt and increase of asphalt's rigidity and viscosity, which in turn directly affect the durability of asphalt pavement. This study aims to evaluate the behavior of asphalt mixtures at different aging stages through the comparison of samples treated under ultraviolet radiation and samples extracted from the field. Laboratory mixtures were prepared from one aggregate source and one asphalt cement. Four types of asphalt mixtures were analyzed: un-aged, laboratory-aged - UV and Pressure Aging Vessel, and field-aged. For laboratory accelerated aging a UV radiation chamber was designed and samples were exposed to 100, 200 and 500-hour treatment periods. Samples aged in the field were obtained from in-service pavements of 1.5 to 11 years after construction. Mechanical behavior was evaluated through dynamic modulus, rutting and trapezoidal fatigue. Results showed that when aging time increases all samples undergone significant increases in dynamic moduli up to two times of unaged mixtures. Permanent deformation exhibited better resistance in aged mixtures than the unaged ones. On the other side, aging affected negatively fatigue life due to significant changes in the slope of fatigue law. Accelerated aging by UV chamber simulated up to 1.5 years in fatigue life and 11 years in permanent deformation performance.