Effect of aging on morphology, rheology, and chemical properties of highly polymer modified asphalt binders

Abstract

The highly polymer modified asphalt binders (HPMBs) are proposed and used for improving raveling resistance of porous asphalt pavement. However, HPMBs undergo aging in service, which has not been well understood from the perspective of morphology, rheology, and chemistry. The main aim of this study is to investigate the aging mechanism of HPMBs with different formulations. In this article, seven HPMBs with different SBS and sulfur contents were subjected to RTFO (Rolling Thin Film Oven) and PAV (Pressurized Aging Vessel) aging. The effect of short-term and long-term oxidative aging on the morphological, chemical, and rheological properties of the HPMBs were analyzed using fluorescence microscopy (FM), dynamic shear rheometer (DSR), Fourier transform infrared spectroscopy (FTIR), and gel permeation chromatography (GPC), respectively. The results indicate that both polymer and sulfur are helpful in improving rheological properties and aging resistance of HPMBs. However, excessive polymer and sulfur are not necessarily better. Furthermore, there is a potential bias in using GPC curves and FTIR spectra to evaluate chemical properties changes of HPMBs during aging. For unaged and aged HPMBs, the plateau region and decreased phase angle at low frequencies region could not be simply attributed to the continuous polymer phase presented in fluorescent images. These findings from the present study offer insights into the aging mechanism of HPMBs.