Laboratory Investigation of the Composite Influence of Rock Asphalt and Montmorillonite on the Performance of Bio-Asphalt

To improve the rutting resistance and anti-aging performance of bio-asphalt, the composite modifier of rock asphalt and montmorillonite is used to modify the bio-asphalt. The optimum content of each component was determined by orthogonal tests based on the results from penetration, softening point, ductility and viscosity tests. The rheological properties and anti-aging performance of rock asphalt and montmorillonite composite-modified bio-asphalt (RAMB) with the optimum content were evaluated as compared to those of matrix asphalt (MA), untreated/treated bio-asphalt (UBA/TBA) and rock asphalt-/montmorillonite-modified bio-asphalt (RMB/MMB). The test results illustrated that the optimum content of each component in the rock asphalt/montmorillonite composite-modified bio-asphalt—as determined by orthogonal experimental design and penetration, softening point, ductility and viscosity tests—was 7% bio-oil treated by thermostatic water bath, 5% rock asphalt and 30% montmorillonite. The high-temperature performance, low-temperature performance and anti-aging performance of RAMB were studied by comparison to those of matrix asphalt, UBA, TBA, RMB and MMB. Additionally, the composite modification mechanism was studied by Fourier transform infrared spectroscopy (FTIR). The results suggested that the high-temperature of TBA was obviously improved compared with UBA. The reason, as seen from infrared spectrum tests, was that the amount of ester compounds decreased after water bath treatment. The light components and soluble substances in bio-oil decreased. Compared to UBA, the unrecoverable creep compliance (Jnr) of RAMB decreased by 66.6% and the recovery rate (R) increased by 75.9% at 0.1 KPa. The stiffness modulus (S) of RAMB was 0.87 times that of matrix asphalt and the creep rate (m) was 1.03 times that of base asphalt. Compared to single-modified asphalt, the high- and low-temperature performance of RAMB was good. Meanwhile, the complex modulus aging index (CMAI) and stiffness modulus aging index (SAI) of RAMB were lower than all other asphalt studied, while the phase angle aging index (PAAI) and creep rate aging index (mAI) of RAMB were the largest. The results of infrared spectroscopy also suggest that the mixing of rock asphalt, montmorillonite, bio-oil and matrix asphalt is a physical blending process. During the process, no functional groups are formed. Pretreatment and addition of rock asphalt and montmorillonite can improve high-temperature performance, low-temperature performance and anti-aging performance of the bio-asphalt.