Comparative Analysis of Modified Binders: Original Asphalts and Materials Extracted from Existing Pavements

摘要

This research demonstrated the application of gel permeation chromatography (GPC) as an analytical tool to ascertain the amounts of polymer modifiers in polymer modified asphalt cements, which are solublein eluting GPC solvents. The technique was applied to 29 samples from five refineries supplying asphalt mixes to Louisiana. Addition of recycled asphalt pavement (RAP) during the mixing process increases the asphaltene content with a corresponding decrease in the maltenes content. An assessment of the extent of oxidative aging of modified asphalt binders during the paving process confirmed minimal changes during the paving process. Field aging of mixes containing RAP is slowerthan that predicted by rolling thin film oven (RTFO) laboratory aging, suggesting that addition of 20 wt% RAP is beneficial. Although suppliersare using different types of poly(styrene- b-butadiene-b-styrene) (SBS) at different percentages to meet the requirements for a PG 70-22, the authors observed that 1 wt% up to 1.98 wt% polymer is added. To achieve PG 76-22, the authors observed that a minimum of 2 wt% polymer is added.The GPC test method can identify the type of polymer used as well as thepercentages of polymer and asphaltenes present. The content of crystallizable species of selected asphalt binders determined by differential scanning calorimetry (DSC) is presented together with the binder glass transition temperature more accurately determined by dynamic mechanical analysis (DMA). A method for quantification of GPC solvent insoluble crumb rubber modifier present in crumb rubber modifiedbinders was developed. The application of the GPC technique to forensic studies of pavement problem issues is demonstrated.