Rheological and structural evolution of SBS modified asphalts under natural weathering

Styrene-butadiene-styrene copolymers (SBS) modified asphalt has been widely used for extending the service life of pavement. Understanding the natural weathering mechanism of SBS modified asphalt (SBSMA) is useful for both the extension of service life and recycling SBSMA pavement. The natural weathering process of base asphalt (BA) and SBSMA is traced by characterizing the rheological and structural evolution of different aged asphalts. Artificial aging such as rolling thin film oven test (RTFOT) and UV aging is compared with the weathering process. Infrared spectroscopic, gel permeation chromatography and dynamic shear rheometer are used to analyze this evolution. The results illustrate that significant changes occur in the chemical structures and rheological properties of SBSMA during natural weathering process. SBSMA shows the same aging trend as BA in terms of rheological and chemical evolution. The SBSMA aging is more serious than BA when comparing the aged ratio of rheological properties, whereas BA is more serious when comparing the ratio of carbonyl index. Furthermore, the molecular condensation is dominant in aging of BA than that of SBSMA. Comparing artificial aging and natural weathering of SBSMA, it is noted that RTFOT and UV aging could not completely simulate the natural weathering behavior of SBSMA.