Evaluation of low temperature viscoelastic properties and fracture behavior of bio-asphalt mixtures

The overall national emphasis on sustainability in pavement construction has led to the promotion of recycled materials such as reclaimed asphalt pavement (RAP) and reclaimed asphalt shingles. In general, the inclusion of these materials has led to reduced performance at low temperatures leading to thermal cracking. Previous research by the authors showed that the application of bio-binder from swine manure could alleviate the effect of RAP while improving the overall low temperature bulk viscoelastic and fracture properties of the asphalt mixture. The current paper expands on the previous research on bio-modified asphalt mixtures by investigating three additional bio-asphalts produced by introducing wood, miscanthus and corn stover based bio-oils to a neat asphalt. These bio-asphalt mixtures were introduced in both virgin and reclaimed asphalt pavement mixtures to evaluate interaction between the bio-oils and reclaimed asphalt pavement, with a focus on properties related to low temperature pavement performance. Low temperature characterization was conducted using disk-shaped compact tension fracture (DC(T)) and indirect tension (IDT) bulk viscoelastic characterization tests. The IDT test, completed in accordance with AASHTO T-322, evaluated the creep compliance of mixtures at 0, -12 and -24 degrees C to examine the ability of the mixture to relax thermal stress development. The DC(T) test was completed according to ASTM D-7313 to determine the fracture energy of the mixtures at -12 degrees C. Test results demonstrate that the bio-asphalt mixtures had superior physical properties in terms of fracture resistance and creep compliance. Furthermore, the effect of increased RAP contents was less detrimental to low temperature properties in the bio-asphalt mixtures as compared to the reference hot-mix asphalt mixture.