Changing Regularity of SBS in the Aging Process of Polymer Modified Asphalt Binder Based on GPC Analysis

Abstract

The investigation on aging mechanism of Styrene-Butadiene-Styrene block copolymer (SBS) in polymer modified asphalt binder (PMA) is helpful to the application of PMA and the selection of anti-aging technology. However, it is very complex because of the various chemical molecular structures of SBS and asphalt binder, as well as the complicated physical and chemical reaction between the two components. In order to study the reaction mechanism of SBS in the preparation and service life of PMA, the molecular changes of SBS were studied through gel permeation chromatography (GPC) analysis before and after the rolling thin film oven (RTFO) test and pressure aging vessel (PAV) test of SBS modified asphalt binders. The results showed that the crosslink of SBS was the main reaction in the preparation of PMA with the increasing of molecular weight. The degradation of SBS was a minor reaction in the RTFO aging, and SBS still had enough effect to modify the performance of asphalt binder after RTFO aging. SBS had significant degradation and lost the capability of modifying the performance of asphalt binder because of the decline of molecular weight after PAV aging. The conclusions prove that the GPC method can explain the crosslink and degradation mechanism of SBS. The degradation of linear SBS and radial SBS in PMA is slightly different. The degradation of pure SBS is more serious when it was aged in the PAV test alone (no blending with asphalt binder), compared with the SBS in PMA. The reason is that the SBS in PMA is covered by asphalt binder and has less contact with oxygen.