Characterisation of fatigue damage in asphalt mixtures using X-ray computed tomography

The high-resolution X-ray CT was applied to investigate the fatigue damage evolution of asphalt mixtures. The detailed Xray CT images in the centre of the samples were used to characterise the fatigue cracking and air voids increase at different vertical deformations. Air void content and surface area distribution before and after loading were also analysed. The results show that the main failure mode of asphalt mixtures at low temperature is debonding at the interface between aggregates and mastic, which is an adhesive failure. The maximum change of air void content due to fatigue damage often occurs near the middle of the sample. Cracks were observed in and around flat and elongated aggregates and on aggregates with insufficient fracture faces, demonstrating the effects of aggregate angularity and shape on fatigue cracking. The microcracks develop continuously throughout the entire fatigue process