Development of a Failure Criterion for Asphalt Mixtures under Different Modes of Fatigue Loading

In the study reported in this paper, the previously developed failure criterion for the viscoelastic continuum damage (VECD) model (referred to here as G_O^R, where O indicates old and G^R is the rate of release of the pseudostrain energy) was applied to different modes of fatigue loading. The research team found that this criterion was mode-of-loading dependent and therefore considered insufficient. To mitigate this limitation, the G_O^R criterion was refined to become a new failure criterion, the G^R method, which resolved the mode-of-load dependency issue. A characteristic relationship, which was found to exist in recycled asphalt pavement (RAP) and non-RAP mixtures between the rate of change of the averaged released pseudostrain energy during fatigue testing and the final fatigue life was derived in this study. This relationship is independent of mode of loading, strain amplitude, and temperature. The proposed failure criterion combines the advantages of the VECD model and this characteristic relationship, which originate from fundamental mixture properties. This proposed method can predict the fatigue life of asphalt concrete mixtures across different modes of loading, temperatures, and strain amplitudes within typical sample-to-sample variability that is observed in fatigue testing.