Research on the Performance of Hot Recycled Asphalt Mixture Based on Recycled Asphalt Pavement Dispersion Uniformity

For hot recycled asphalt mixture with high content of recycled asphalt pavement (RAP) material, the road performance of the recycled asphalt pavement may be degraded if the aggregate particles of RAP are unevenly dispersed. In this study, recycled asphalt mixture with a RAP content of 50% was used to investigate the uniformity of RAP aggregate. On this basis, the road performance of recycled asphalt mixtures with different RAP dispersion uniformity was analyzed. Firstly, the Marshall test specimens of hot recycled asphalt mixture were prepared and saw-cut, and the microstructure of each cross-section was extracted using digital image processing. Then, based on the distribution characteristics of RAP aggregate inside the mixture, a uniformity index was proposed using the distribution eigenvalue method. Finally, the road performance test was conducted on the recycled asphalt mixture with different RAP dispersion uniformity. The results demonstrate that the homogeneity can be accurately and quantitatively evaluated by a uniformity index based on the area ratio of the RAP aggregate in each cross-section. Higher RAP heating temperature and mixing time result in improved uniformity of RAP aggregates. Meanwhile, the gray correlation analysis revealed a good correlation between the proposed uniformity index and the moisture susceptibility of the recycled asphalt mixture. In short, the quantitative uniformity evaluation index of RAP aggregate presented in this study reflects the homogeneity of hot recycled asphalt mixture, which is helpful for controlling the quality of recycled asphalt pavement.