Fatigue damage evolution in asphalt mixture based on X-ray CT images

The fatigue damage of asphalt pavement occurs and develops under repeated vehicle loads, and its macro manifestation is the deterioration of mechanical properties and serviceability. In order to explore the internal cause of fatigue damage of asphalt mixtures, this paper proposed a method to obtain the internal section images of asphalt mixtures in different fatigue damage stages based on the X-ray CT (Computed Tomography) scanning technique and indirect tensile fatigue test. The fatigue damage evolutions in two different gradation types of AC and OGFC asphalt mixture were studied. The results show that the difference in gradation type causes different initial air void shapes, size and distribution, which result in different formation modes of the main cracks and fatigue damage resistance of asphalt mixture. The evolution of air voids during fatigue loading can be divided into three stages: compression, steady growth and rapid expansion. The macro fatigue damage presents an excellent linear relation (R-values > 0.98) with the internal structural damage.