Asphalt mixture is a skeleton filling system consisting of aggregate, asphalt, and mineral powder. High performance asphalt mixture design is directly affected by internal stress transmission of skeleton filling system. In this paper, the discrete element method based on digital image was employed to study the stress transmission. By analyzing the effect of skeleton structure on the contact force between aggregate and mortar, it is concluded that the skeleton aggregate in the asphalt mixture is the main stress transmission medium. The lower the degree of disruption, the higher the contact force of skeleton aggregate. At the same time, the variation coefficient of contact force of asphalt mortar with low filling coefficient is larger and the localization phenomenon is more serious. By analyzing the effect of mortar properties on the contact force between aggregate and mortar, it is concluded that the lower the modulus of asphalt mortar, the higher the degree of localization of contact force and the more likely to have local damage.

Asphalt mixture is a kind of granular material, which consists of aggregates with different particle sizes. Extracting the particle distribution around the failure location of asphalt mixture is important for revealing the failure mechanism. In this paper, the digital image correlation (DIC) method is used to obtain the full-field strain of asphalt mixture, and then the high strain zone of asphalt mortar is extracted by digital image processing technology. For getting the aggregate distribution around the failure position, aggregate extraction method is proposed based on the image dilation algorithm. For AC-16, SMA-16 and OGFC-16 asphalt mixtures, under different temperature and loading speed conditions, according to the analysis of the aggregates distribution around the high strain area, it can be seen that the proportion of the main skeleton aggregates and the disruption aggregates around the high strain area is constantly changing with the loading process. It shows that the proportion of the main skeleton aggregates around the high strain area is decreasing, while the proportion of the disruption aggregates is increasing. This phenomenon shows that the damage evolution of asphalt mixture is expanding from the surrounding area of main skeleton aggregates to that of disruption aggregates.