Methods of recycling a large amount of waste asphalt mixture generated in pavement maintenance and decreasing the waste of existing resources are one of the problems that will be solved in the future. In this study, the mechanical parameters of asphalt mixture containing different amounts of RAP were analyzed by discrete element method (DEM), and the reasonable RAP content was discussed in combination with uniaxial compression test results. And it is considered that the contact between different particles will produce the failure of stress transfer between particles with different modulus, and the contact definition between RAP particles and virgin aggregate particles is added to make the discrete element model more in line with the actual situation. The results indicated that the trend of discrete element analysis was consistent with that of the uniaxial penetration test, but there were differences in the specific values. Uniaxial compression test results showed that the optimum RAP content of the recycled asphalt mixture was 30%. The optimal RAP content analysis result from the DEM simulation was smaller than the laboratory test result, and the theoretical optimal RAP content was 28%. The results of this study provide a reference for the mixture design of recycled asphalt mixture.

The distribution of contact stress of particles in asphalt mixture could be used to reflect the relationship between the macroscopic mechanical properties and the mesostructure of the material. However, there is no mature method to obtain the internal stress characteristics of asphalt mixture. In this study, the accurate stress distribution and stress transfer state information of particles in asphalt mixture were obtained by using pressure film technology, which provided a good theoretical basis for material gradation design. The pressure film was sandwiched between two Marshall specimens, and the compression part will appear red. After digital processing by software, the total contact area and stress distribution of the two specimens can be obtained. Three kinds of asphalt, three kinds of asphalt pavement gradation, and five kinds of asphalt aggregate ratio were selected to prepare asphalt mixture specimens. The effects of different asphalt, skeleton structure, and asphalt film thickness on the contact characteristics of aggregates were studied. The test results showed that, when the pressure between the two specimens is 0.23 MPa, the contact area of the particles reaches the maximum. The relationship between the contact point distribution probability and the pressure was fitted into a nonlinear curve. The gradation of the mixture, the type of asphalt and the thickness of the asphalt film were used as parameters A, B, and C. The prediction model had a good correlation with the test results. The prediction model proposed in this study could be used to improve the experimental efficiency, save test material and financial resources, as well as get complete contact stress information of the internal particle interface of asphalt mixture.