A unified method for the analysis of controlled-strain and controlled-stress fatigue testing

Fatigue cracking is one of the primary distresses in asphalt pavements. This study presents a method to characterize fatigue resistance of the fine portion of the asphalt mixture using the dynamic mechanical analyzer (DMA). Three mixtures were characterized in controlled-strain and controlled-stress modes of loading. The new method has several advantages as it requires reasonable testing time, uses a small amount of material, utilizes fundamental properties of the mixture, and is able to unify the results from controlled-strain and controlled-stress modes of loading. The unified method relies on identifying the different mechanisms of energy dissipation during fatigue cracking that are related to changes in the phase angle, changes in stiffness, and development of permanent deformation during the fatigue damage process. Two fatigue damage parameters are derived in this paper. The parameters are shown to have reasonable and lower coefficients of variation than conventional parameters such as number of loading cycles to failure and cumulative dissipated energy.