# Effect of Gradation Segregation on Mechanical Properties of an Asphalt Mixture  
[PERSON]  
1 School of Civil Engineering and Transportation, South China University of Technology, Guangzhou 510000, China; [EMAIL_ADDRESS] (W.W.); [EMAIL_ADDRESS] (Z.T. ); [EMAIL_ADDRESS] (Z.Z.) [PERSON]  
1 School of Civil Engineering and Transportation, South China University of Technology, Guangzhou 510000, China; [EMAIL_ADDRESS] (W.W.); [EMAIL_ADDRESS] (Z.T. ); [EMAIL_ADDRESS] (Z.Z.) [PERSON]  
1 School of Civil Engineering and Transportation, South China University of Technology, Guangzhou 510000, China; [EMAIL_ADDRESS] (W.W.); [EMAIL_ADDRESS] (Z.T. ); [EMAIL_ADDRESS] (Z.Z.) [PERSON]  
2 Institute of Highway Engineering, RWTH Aachen University, 52066 Aachen, Germany  
analyzing the temperature segregation of asphalt mixture. [PERSON] et al. [12] presented an imaging method to assess the homogeneity of asphalt concrete using X-ray computed tomography, the improved OTSU image method, and fractal theory. The pavement-quality indicators were applied to test asphalt pavement and to choose four specimens with various degrees of segregation. Finally, a segregation evaluation standard based on fractal dimensions and the imaging method was proposed. In addition, the effect of segregation on the performance of asphalt pavement and the corresponding quality control methods were also documented in many publications [13; 14; 15]. Based on previous studies, it was recommended that the effects of segregation and air voids should be taken into consideration when building the correlation between tensile strength and pavement performance. Besides, it is also found that the fatigue life and moisture resistance of asphalt mixture strongly related to the aggregate segregation. [PERSON] et al. [16] used an infrared camera to identify cooler portions of the mat.the aggregate gradation and asphalt binder content of asphalt mixture was also determined. The results showed no significant aggregate segregation within the cooler areas; however, these cooler portions of the mat consistently showed higher air voids than the surrounding pavement. The influence of aggregate segregation on rutting resistance and raveling was also reported in previous studies [3]. Researchers also tried to determine factors affecting the gradation segregation, for instance, mixing plant, volumetric properties, aggregate shape properties, mixing temperature, paving conditions etc. [17; 18; 19]. However, the above studies have some limitations. Both laboratory and in field tests are conducted with phenomenological methods. Changes in the micro-parameters of asphalt mixture resulting from gradation segregation are unclear. Low repeatability of test results occurs because of various experimental variables. Despite this, the correlation between gradation segregation and mechanical property of asphalt mixture still deserves more effort. DEM has been applied to analysis road material performance because of its superiority in address non-uniformity, discontinuity, and large deformation problems [20; 21; 22; 23]. [PERSON] et al. [20] using DEM to describe the microstructure of asphalt mixtures and simulate creep behavior. [PERSON] et al. [21] developed a software for processing and analyzing 2D images of asphalt mixtures. By means of this software, radial distribution, orientation and segregation of aggregates were analyzed. [PERSON] et al. [22] described the development of a fracture test for determining the fracture energy of asphalt concrete. [PERSON] et al. [23] investigated the stiffness anisotropy of asphalt mixtures using micromechanics-based models. Therefore, this paper presents an attempt to evaluate the effects of gradation segregation on asphalt mixture in terms of structural characteristics and mechanical properties using the DEM method. To achieve this objective, a 2D asphalt mixture model was built using PFC2D5.0 software, which is a computing software developed by the Itasca company in the USA.