Laboratory evaluation of physical and mechanical properties of recycled asphalt pavement

In many states, the use of RAP in surface, base, and sub-base courses is limited and large quantities of RAP aggregate remain unused. To explore the possibility of more or complete use of milled RAPs, it is necessary to study physical and mechanical properties of RAPs. In this study, RAPs from two sources were selected. Binder contents and properties of coarse and fine aggregates after removing asphalt binders were determined. RAPs were also tested for their maximum densities and California Bearing Ratios (CBRs). The influence of binder contents and aggregate properties on the physical and mechanical properties of RAPs was discussed. The binder content of RAPs was found to be higher than that in the original mix designs. The coarse aggregate angularity (CAA) of the RAPs was increased compared to that of the original mixes. The combined bulk specific gravities of aggregates from RAPs decreased slightly as compared with those in the original mixes. The percentage of fine particles in the RAPs was increased from that in the original mixes. The RAP with a higher binder content and a lower fine aggregate angularity had a higher optimum moisture content, a higher maximum dry density, and lower CBR values. The aggregates from the RAPs were not of uniform hardness based on the LA abrasion tests.