Effect of Clustering of Reclaimed Asphalt Pavement Particles on Rutting Performance of Asphalt Mixtures Containing RAP

Reclaimed asphalt pavement (RAP) mixtures consist of clusters of aggregates bonded together by the aged asphalt. Declustering of RAP particles during new asphalt mixing changes the gradation of the mixture, which affects the performance of the new asphalt mixtures containing the RAP. In this study, RAP materials with different degrees of clustering were used to make new Superpave mixtures. The degree of clustering in each RAP material was associated to its gradation change before and after the asphalt extraction. The Hamburg wheel tracking device (HWTD) was used to evaluate the rutting and stripping performance of the asphalt mixtures at regular and elevated temperatures. Finally, statistical analyses were performed to evaluate the relationship between the HWTD test performance and the degree of clustering of the original RAP material. The research results showed that clusters of the original RAP material has a negative impact on rutting and stripping performance of asphalt mixtures with a nominal maximum size of 9.5 to 25 mm. The impact is most evident under the HWTD test at elevated test temperatures.