Gel permeation chromatography-based method for assessing the properties of binders in reclaimed asphalt pavement mixtures

Evaluating the properties of asphalt in reclaimed asphalt mixture (RAP) is a crucial step in the design of hot recycled mixtures. The conventional assessment approach involves the extraction and recovery of the aged asphalt with further assessing the aging condition of recovered binders via their penetration, viscosity, and performance-related properties. Since this approach is time-consuming, environmentally unfriendly and involve residue mineral powders that may alter the recovered binder properties, an alternative gel permeation chromatography-based method, requiring no extraction or recovery, was proposed in this study. The gel permeation chromatography (GPC) test were carried out to directly analyze the Large molecular size (LMS) content of unrecovered binders in asphalt mixture samples under different aging conditions, which were prepared via laboratory simulated aging procedure. LMS content was found sensitive in reflecting the aging condition for the binders in the mixture. In addition, the correlation between the aging levels of asphalt mixtures aged under laboratory conditions with those of single asphalt samples was established. Following this, the best-fit regression model linking the LMS content in a mixture sample with the rutting factor, penetration and viscosity were developed. According to the above regression model, the conventional properties of RAP binders were predicted by their LMS content, which can be further applied to assess the aging condition of RAP binders, eliminating the complicated extraction and recovery process. Three sources of on-site RAPs verified the proposed method feasibility: it reasonably estimates the properties of binders in RAP, especially for base asphalt.