Evolution in thermal storage stability of SBS-polymer modified asphalt induced by differences in microscopic characteristics of base asphalt

In thermal storage process, the aggregation, segregation, and floating of styrene–butadiene-styrene block copolymer (SBS) modifier will affect the performances of SBS-modified asphalt (SBSMA). To investigate the significant impact of macro and micro characteristics of base asphalt (BA) on the storage stability of SBSMA, we prepared SBSMA samples with three different base asphalts (BA-A, BA-B, and BA-C). Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC) and atomic force microscopy (AFM) were used to investigate the microscopic properties of BAs and SBSMAs and to establish topological network nodes for their microscopic morphology. The storage performance of SBSMAs was inspected by the segregation softening point difference, complex modulus difference, and phase angle difference. Finally, the correlation analysis of microscopic structure of BA samples and storage stability of SBSMA was conducted via grey correlation methodology. The experimental results indicate that BA-A with higher molecular weight has an uneven size with honeycomb like structure, while modified asphalt using BA-A exhibits serious phase separation. In contrast, modified asphalt using BA-B and BA-C has better storage stability due to their uniform honeycomb structure size, which is consistent with the pattern presented by the microstructure of asphalt. Grey correlation analysis shows that there is a good correlation between the roughness of BA samples and the storage stability of SBSMA. In addition, the segregation softening point and the difference in complex modulus can be effective indicators for evaluating the storage stability of SBSMA.