A novel gel permeation chromatography-based assessment methodology for aging condition of SBS modified asphalt in recycled asphalt pavement

As fossil energy sources gradually become depleted, the reclamation of recycled asphalt pavement (RAP) has received increasing attention. During the production process of recycled mixtures, the aging conditions of binders in RAP need to be measured prior to the mixing design process. The conventional method adopts chemical solvents, including trichloroethylene and toluene to extract and recovery binders in the RAP. And then measure the corresponding properties of RAP binders. However, the whole process is complicated and timeconsuming, and the used chemical solvents are highly toxic and harmful to researcher's health. Some scholars have proposed some methods to test the aging condition of asphalt binders in the RAP directly without extraction and recovery using the novel observation instruments. However, these methods are not suitable for modified asphalt. At present, modified asphalt has been often used in the road construction,especially for SBS modified asphalt. As such, the present study aims to introduce a novel approach to test the aging conditions of SBS modified binders in the mixtures avoiding the extraction and recovery process based on gel permeation chromatography (GPC). For this purpose, the molecular weight distribution as well as the physical properties of modified asphalt and binders in the mixtures at various aging degrees were first analyzed using GPC test. The polymer and asphaltene content of asphalt binders derived from GPC test were found correlation well with the aging degrees and properties of asphalt binders. Following this, several estimation models correlating the polymer and asphaltene content with penetration, viscosity and rutting factor were established. The robustness of established models were verified using laboratory-aged asphalt mixtures with three different SBS modifier contents and two kinds of on-site RAPs. The verification results showed that the properties in the mixture were reasonably estimated.