Evaluation of the effect of segregation on coarse aggregate structure and rutting potential of asphalt mixtures using Dominant Aggregate Size Range (DASR) approach

Segregation of asphalt mixtures indicates an artificially altered aggregate gradation, which consists of excessive coarse aggregates and insufficient fine aggregates that may result in premature failures and eventually reduce the pavement service life. Since segregation may cause a significant change in aggregate structure of asphalt mixtures, segregated mixtures may exhibit an increased potential for rutting among all other distresses. However, the effect of segregation on rutting potential has not been clearly identified. In this study, the effect of segregation on change in aggregate gradation (particularly for coarse aggregate structure) that may negatively affect the rutting potential of asphalt mixtures was evaluated. The Dominant Aggregate Size Range (DASR) gradation model and the DASR porosity parameter found to be well correlated with rutting performance of asphalt mixtures were employed for evaluation. A total of four field sections exhibiting different severities of segregation were selected and evaluated. Results of laboratory testing and DASR analysis indicated that segregated mixtures caused a significant shift in aggregate gradation, especially for coarse aggregate portion of the mixture gradation, which may result in significantly increased the potential for rutting. The results obtained from laboratory tests and the DASR approach were then compared and verified with those of actual filed rutting performance.