The use of recycled materials in asphalt concrete (AC) pavement has increased significantly for economic and sustainable benefits. However, the use of recycled materials can pose risks to the performance of asphalt pavements. The Illinois Department of Transportation (IDOT) has developed five distinct total recycled asphalt (TRA) mixes, containing up to 60% asphalt binder replacement (ABR) obtained from reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS); whereas 100% recycled aggregates are acquired from RAP, steel slag, and recycled concrete aggregate (RCA). According to the laboratory testing, all mixes offered excellent rutting resistance as it contains high ABR. TRA is relatively less compliant and not very sensitive to field aging, whereas indirect tensile strength tests showed indistinguishable results. The TRAs become stiffer at higher temperatures, and likewise, all mixes have comparable a complex modulus (E*) and phase angle ( ) at low temperatures. Plant-mixed lab-compacted (PMLC) mixes have a relatively lower flexibility index (FI), from the Illinois Flexibility Index test (I-FIT), with time compared to the first field cores. The FI values for field cores decreased with aging and increased recycled materials. Furthermore, the field results confirm an excellent rutting performance. An exponential increase in transverse cracking was observed and a good correlation between FI and transverse cracking was observed. This allows the use of FI as a parameter with rut depth in constructing 2-D and 3-D balanced mix design charts and performance evaluation tools that can be used by practitioners.
Contributors: Safi F, Al-Qadi I, Hossain K, Ozer H.