United States Department of Transportation
i
Implementation of GPC characterization of asphalt binders at Louisiana materials laboratory.
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2013-10-01
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Abstract:This research implemented a procedure for using gel permeation chromatography (GPC) as an analytical tool to
define the percentage amounts of polymer modifiers, which are soluble in eluting GPC solvents, in polymermodified asphalt cements. It also addressed quantification of both GPC solvent soluble and insoluble crumb
rubber present in crumb rubber modified binders. Attention was also paid to using GPC for assessment of the
extent of oxidative rolling thin-film oven ( RTFO) and pressure aging vessel (PAV) aging of a series of asphalt
binders as well as forensic analysis of pavement failures.
The project was sub-divided into two phases including (I) purchasing, installing and calibrating a GPC instrument
at the DOTD Materials Laboratory and writing detailed procedures for conducting binder analysis to determine
the percent polymer content in polymer modified binders and (II) developing an efficient extraction process
capable of recovering binder from asphalt cement cores. Phase I included the GPC analysis of different polymers
and binders, and a quantitative estimation of polymers, asphaltenes, and maltenes present in the analyzed binders.
At DOTD, a large number of binders from various asphalt sources and polymer additives have been analyzed.
Over 180 samples of PG 64-, PG 67-, PG 70-22m and PG 76-22m grades were subjected to GPC analysis and the
polymer percentage was calculated and compiled. Phase II extended the development of a procedure to define the
percent amounts GPC solvent insoluble crumb rubber present in CRM binders. It included a comparison between
the extraction of soluble CRM species with a blend of toluene-ethanol (85:15 volumetric ratio) and bromopropane
at room or moderate temperatures. Since similar results have been obtained, due to the fact that bromopropane is
more expensive than toluene and ethanol, the toluene/ethanol mixture appears to be a better option, especially for
large scale extractions. An AASHTO standard test method for the quantification of polymer content in polymer
modified asphalt cements by GPC has been proposed.
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