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

2010PDFTech ReportFHWA/LA.10/462Polymer asphaltBindersRecycled materialsWaste products (Materials)LouisianaLouisiana Transportation Research CenterDaly, William H.Negulescu, IoanGlover, IonelaLouisiana Transportation Research CenterLouisiana. Dept. of Transportation and DevelopmentLouisiana State University (Baton Rouge, La.). Department of Civil and Environmental EngineeringNTL-HIGHWAY/ROAD TRANSPORTATION-MaterialsNTL-HIGHWAY/ROAD TRANSPORTATION-Pavement Management and PerformanceUS Transportation CollectionDuring oxidative aging, polar and aromatic molecules interact through attractive forces to form molecular associations resulting insignificant changes in the physical properties of asphalts. One consequence is that these associations have effective molecular weights and hydrodynamic volumes larger than the true molecular weights of their components. A separation of the components is possible using gel permeation chromatography (GPC), which is also a fast and reliable method to determine the polymer content in asphalt. Since polymer molecules typically exhibit molecular weights 100 times greater than those of asphalt molecules, they can be easily identified using this method. GPC methodology was applied to follow the processing and paving sequences and to determine the changes in the mix during its lifetime. The research involved quantitatively assessing (1) the amount of the polymeric species in a polymer modified asphalt cement (PMAC) as received from a supplier, including changes imparted by the addition of recycled asphalt pavement (RAP) to the mix; (2) the amount of the polymeric modifier in the liquid extracted from cores taken from a new road paved with the same PMAC as that received from a supplier; and (3) the extent of on-the-road degradation of the polymeric species by oxidative aging for periods up to 20 months. The research was extended to evaluate mixes containing a crumb rubber modifier (CRM), which is practically insoluble in GPC solvents.93