Low-Temperature Performance Characterization of Biomodified Asphalt Mixtures That Contain Reclaimed Asphalt Pavement

The sustainability movement in paving materials has led to the increased use of reclaimed asphalt pavement (RAP). New developments in this area in the recent past include the use of biomodified asphalt binders (BMBs) such as those containing bio-oils derived from swine manure. The study reported in this paper examined the low-temperature properties of RAP and virgin BMB mixtures to determine if these mixtures exhibited better low-temperature performance than conventional hot-mix asphalt (HMA). Disk-shaped compact tension [DC(T)], Superpave (R) indirect tension (IDT), and acoustic emission (AE) tests were employed to characterize low-temperature properties of the asphalt mixtures. BMB mixtures exhibited higher DC(T) fracture energies than HMA at all RAP levels. In addition, BMB mixture fracture energy displayed a reduced dependence on RAP content. The difference in average fracture energy between BMB and HMA mixtures increased with higher RAP contents. Furthermore, BMB mixtures displayed consistently higher creep compliance, which indicated that these mixtures could alleviate thermal stresses more easily than HMA. A recently developed AE testing procedure evaluated the effects of BMB as well as RAP in the mixtures. The overall trends identified through AE testing were consistent with the findings from the DC(T) and IDT tests. In addition, AE results suggested a fundamental change in the behavior of the BMB RAP mixture relative to the HMA RAP mixture (i.e., rejuvenating effect). In general, it was observed that BMB RAP mixtures exhibited low-temperature cracking behavior superior to that of HMA mixtures.