Aging mechanism and effective recycling ratio of SBS modified asphalt

With the increase of road service life, SBS (styrene–butadiene–styrene block copolymers) modified asphalt waste materials are being discarded. Taking advantage of these waste pavement surfacing materials will not only reduce the pollution of the environment, but also save resources. This paper analyzes the aging mechanism of SBS modified asphalt through macroscopic examination and microcosmic analysis using conventional performance indicators: SHRP performance index, component analysis, Gel Permeation Chromatography (GPC), Infrared Spectrum Analysis (IR), etc. The recycling effectiveness was evaluated through the indicator of effective recycling ratio which is put forward by laboratory test. The results illustrated that the aging of SBS modified asphalt was formed by both aging of matrix asphalt and aging of SBS modifier. SBS modifier degradation could slow down the aging reaction of matrix asphalt because SBS modifier would degrade to small molecules in the process of aging. In addition, the matrix asphalt could also play a role in the protection of the SBS modifier. Therefore, the mutual protection of both makes the anti-aging performance of the modified asphalt significantly better than that of matrix asphalt. We also evaluated the recycling effectiveness of aged SBS modified asphalt under the presence or absence of rejuvenating agent, different mixing time and temperature. The presence of rejuvenating agent as well as appropriately increasing mixing temperature and time are proved to be able to improve the recycling effectiveness.