Effect of bitumen composition on micro-structure and rheological properties of styrene–butadiene–styrene modified asphalt before and after aging

The performance of styrene–butadiene–styrene modified asphalt (SBSMA) is strongly affected by the composition of asphalt. In this study, five kinds of bitumens were selected from different oil sources. Four-component separation test was conducted to obtain the composition information. Then, the selected bitumens were modified by linear styrene–butadiene–styrene modifier to prepare SBSMA samples and the aging tests were applied to simulate the short-term and long-term aging processes. Atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR) were utilized to test micro-structure of the five SBSMA before and after aging, respectively. The dynamic shear rheometer tests were performed to analyze the rheological properties of SBSMA. The results revealed that the surface morphology of asphalt samples observed in AFM varied due to the discrepancy of asphalt compositions. A high content of light components in asphalt could retard the growth rate of carbonyl index and the reduction rate of C=C index after short-term aging. For the original SBSMA, the lower the colloidal index, the higher the rutting factor, complex modulus and recovery. The SBSMA with high content of light components possessed a better high-temperature stability after short-term aging. Asphaltenes had a skeleton function so that the SBSMA with high content of asphaltene presented a strong elastic response after long-term aging. Moreover, there existed good correlations between the infrared indexes, rheological parameters and composition content.