The demand for bituminous materials is continuously growing; crude oil-based asphalt binders are non-renewable, and are facing rapid depletion. With the increase of petroleum-based asphalt prices, seeking an alternative, renewable material such as bio-asphalt has become a hot research topic. However, shortcomings in this research area have been identified, notably concerning the high-temperature performance of bio-asphalt at present. This research aims to comprehensively apply conventional tests to, and study the rheological behavior of, the high-temperature performances of bio-asphalt binders, i.e., by temperature and frequency sweeps, using a dynamic shear rheometer (DSR). It will also assess the chemical functional groups of specimens prepared by different aging conditions. Fifty penetration grade base asphalt binder (50#), bio-oil modified asphalt binders with 0%, 5%, 10%, and 30% bio-oil contents by mass, and bio-oil modified asphalt binder with combinations of 5% bio-oil-1% SBS, and 10% bio-oil-1% SBS were used in this study. The conventional performance of bio-asphalt binders was tested using penetration, ductility, and softening point, before and after short-term aging conditioning. The temperature sweep and frequency sweep of bio-asphalt under different bio-oil contents were carried out via DSR. Two-logarithmic equations of rutting factor and temperature were established, and the temperature sensitivity of bio-asphalt was analyzed. The master curves of virgin asphalt and bio-asphalt were constructed at 64 °C. The results indicate that the incorporation of bio-oil reduced the anti-rutting performance of asphalt, and the bio-oil content had a significant effect on the mass loss of the bio-asphalt binder. The performance of bio-oil modified asphalt binders using 5% bio-oil, 5% bio-oil-1% SBS, and 10% bio-oil-1% SBS, could meet the requirements of 50# grade asphalt. The temperature sensitivity of bio-asphalt did not show obvious change before and after short-term aging, whereas the temperature sensitivity of bio-asphalt with 5% bio-oil was relatively small. With an increase in temperature, the phase angle increased gradually. In contrast, the storage modulus, loss modulus, and complex modulus decreased progressively. The complex modulus and rutting factor of bio-asphalt with 5% bio-oil steadily increased with the increase in testing frequency. Otherwise, chemical reactions were detected in the 50# base asphalt modified with the bio-oil.

To uniform the evaluation indicators of Styrene-Butadiene-Styrene (SBS) modified asphalt, the SK70# and SK90# matrix asphalt were modified by different SBS modifier dosage in this study. The test methods in China and Superpave were used to test the performance of each SBS-modified asphalt respectively, from which the appropriate evaluation index of SBS-modified asphalt was determined. The results showed that the addition of SBS modifier improved the high temperature performance and lowered the temperature sensitivity of asphalt binder, while it increased the viscosity of asphalt binder in high temperatures. Due to the variability that appeared in the results of the penetration test by the swelling of SBS-modified asphalt, the penetration test was not recommended to evaluate the performances of SBS-modified asphalt. The softening point of SBS-modified asphalt with the modifier dosages of 4.5%, 5%, 5.5% and 6% increased 5.7%, 12.8%, 22.5% and 26.4% respectively compared to the matrix asphalt for SK70# matrix asphalt, and increased 21.2%, 26.3%, 33.6% and 46.6% respectively compared to the matrix asphalt for SK90# matrix asphalt. The effect of SBS-modifier on the softening point of SK90# matrix asphalt is significantly better than that of SK70# matrix asphalt. The improvement effect of SBS modifier on low temperature performance of matrix asphalt decreased with a decrease in test temperature. When studying the influence of the SBS modifier on the low temperature performance of asphalt binder, it was recommended to use the bending beam rheometer (BBR) test to evaluate the low temperature performance of SBS-modified asphalt.

Macroperformance, i.e., skid resistance, high-temperature, and compaction performance, are related to the functional performance, safety, and durability of asphalt pavement. Currently, the research on such influencing factors focuses on the properties of asphalt, gradation composition, pavement structure, and so forth, whereas the geometrical characteristics of coarse aggregate, especially its angularity, has not gained due attention from researchers. This paper investigated the effects of coarse-aggregate angularity on the skid resistance, high-temperature performance, and compaction performance of asphalt mixtures. Three-dimensional angularity (3DA) computed by X-ray computed tomography (XCT) was employed to characterize coarse-aggregate angularity. Texture depth (TD) and British pendulum number (BPN) were evaluated through the sand patch test and the British pendulum test (BPT), respectively. The dynamic stability and rutting depth of mixtures with different coarse-aggregate angularities were examined with the wheel tracking test. The variation in height of the specimen with different angularity asphalt mixtures during the compaction process was tested through the Superpave gyratory compactor (SGC). The dynamic modulus ($|E^{*}|$ ) of the asphalt mixtures was analyzed with the asphalt mixture performance tester (AMPT) and the generation of master curves. The results showed that three-dimensional (3D) angularity is able to characterize the angularity of the coarse aggregate. A lower coarse-aggregate angularity leads to a smaller skid resistance of the asphalt mixture. The angularity greatly influences the high-temperature and compaction performance of asphalt mixtures. Higher angularity leads to better high-temperature stability but causes difficulty in compaction. The angularity has a significant influence on the $|E^{*}|$ values of SMA-16 asphalt mixture. The results revealed that the decrease in coarse-aggregate angularity translated into a decrease in $|E^{*}|$ values on average. This study provides support for further research into and application of macroscopic properties of asphalt mixtures.

This paper investigates the influence of fuel-resistant polymer on the consistency and performance properties of asphalt binder and hot mix asphalt (HMA) mixtures. The study uses wearing course gradation (nominal maximum size of 19 mm), penetration grade 60/70 bitumen, and Elvaloy reactive elastomeric terpolymers (RET) 4170 as a fuel-resistant polymer. Laboratory tests conducted on unmodified and modified (1–4% Elvaloy) mixtures include an indirect tensile (IDT) strength test and a resilient modulus ($M_R$ ) test for evaluating cracking potential and stiffness parameters, respectively; a Hamburg wheel tracker (HWT) test for quantifying the rut propensity; and a solubility test to determine the fuel-resistance capacity. The two-level factorial design of the experiment is conducted on the rheological properties of the binder including elastic recovery/complex modulus and creep stiffness values, which suggest that 1% polymer-modified binder (PMB) is least susceptible to high-temperature and low-temperature variations. Performance evaluation reveals that 1% PMB is an optimal proportion of Elvaloy in asphalt concrete mixtures, yielding maximum $M_R$ values (both before and after conditioning in fuel), the lowest rut susceptibility, and high fuel resistance. This research is useful for public aviation/highway agencies and private contractors to minimize the deterioration caused by fuel slippage and to control foreign object debris damage to aircraft.

Rutting or permanent deformation is one of the severe distresses manifested in flexible pavements caused by the various mechanisms such as densification, lateral plastic flow, and/or loss of materials under wheel path due to repeated heavy traffic loads. Various laboratory tests have been devised to determine the rutting propensity and to optimize the field performance of hot mix asphalt (HMA) mixtures as a part of the HMA mix and structural design processes. Although various approaches exist to predict the permanent deformation of HMA, this study develops a relationship of flow number (FN), dynamic modulus (DM), and uniaxial repeated-load permanent deformation (RLPD) to enable the trade-off analysis among them. Also, a novel parameter, FN index, is explored and used to determine the rutting potential of HMA mixtures. Twelve globally practiced HMA mixtures are investigated with three different performance grade binders and single limestone aggregate source. Superpave gyratory compacted specimens are subjected to performance testing (FN, DM, and RLPD) and results indicate a strong correlation of FN index with DM and exhibit better correspondence than the traditional FN (cycles) parameter.