Effect of Segregation on Coarse Aggregate Structure and Rutting Potential of Asphalt Mixtures

Segregation of asphalt mixtures, which denotes the non-uniform distribution of coarse and fine aggregate components, either causes short term premature failures or affects the long term pavement performance. Since segregation may result in a significantly altered aggregate structure of an asphalt mixture, it may increase the potential for rutting, among all other distresses. In this study, the effect of segregation or change in aggregate gradation that may negatively influence the rutting potential of asphalt mixtures was evaluated. The Dominant Aggregate Size Range (DASR) gradation model and the DASR porosity parameter, which have previously been identified to be well correlated with rutting performance, were used to identify the potential degradation of rutting performance due to segregation. A total of four roadway sections with different severity levels of segregation were selected and evaluated. The analysis results of mixture gradation, volumetric properties, and DASR porosity indicated that segregated mixtures exhibited a significant shift in gradation, especially for the coarse aggregate portion of the mixture gradation. Consequently, it was found that segregation of asphalt mixtures may significantly increase the potential for rutting. However, a need still exists for future verification using the actual field or laboratory rutting performance data, which were not available in this study.