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Handbook of Size Exclusion Chromatography and Related ...

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percentage LMS at the other locations. Even so, Jennings’ results are too<br />

impressive to be ignored.<br />

As noted, Jennings also found some connections between rutting <strong>and</strong> alow<br />

LMS region.Thisisconfirmed bythedata inFig.14.Heresix asphalts havebeen<br />

ratedbyusersaccordingto“tenderness”(slowsettingthatcanresultinrutting).A<br />

high score indicates tenderness. Clearly there is a correlation between the<br />

tenderness rating <strong>and</strong> the size <strong>of</strong> the LMS region.<br />

Jenningshasalsodonesomeworkwithasphaltrecycling.Inthisprocessold<br />

road material in bad condition is stripped from the roadway, mixed with a<br />

s<strong>of</strong>tening agent, <strong>and</strong> relaid. Sufficient new material is generally added to restore<br />

viscosity<strong>and</strong>ductilitytolevelsapproximatingthose<strong>of</strong>newasphalt.Thisdoesnot<br />

usually reduce the percentage <strong>of</strong> LMS to that <strong>of</strong> new asphalt. One roadway done<br />

with acommercial recycling agent having 0% LMS showed ahigh percentage <strong>of</strong><br />

LMSeventhoughtheresultingmixturewasquites<strong>of</strong>t.Asrecyclingagentscontain<br />

littleornoasphaltenes,ithasbeensuggestedthatthereductionintheLMSregion<br />

could be used as arapid method to check recycling agent content (45).<br />

3.3 Correlating Physical Properties with SEC Results<br />

Attemptstocorrelateasphaltphysicalpropertieswithchemicalpropertieshavenot<br />

been particularly successful. This no doubt is primarily the result <strong>of</strong> the lack <strong>of</strong><br />

uniqueness in the chemical properties that are used. For instance, aCorbett<br />

fractionfromoneasphaltmayhaveverydifferentphysicalpropertiesfromthose<strong>of</strong><br />

the same fractions from another asphalt. Also, two asphalts with similar physical<br />

properties can have radically different SEC chromatograms.<br />

Bishara et al. (58,59) report good correlation <strong>of</strong> viscosity temperature<br />

susceptibility <strong>and</strong> LMS to medium molecular size ratio.<br />

The viscosity temperature susceptibility from 60 to 1358C <strong>of</strong> the Texas test<br />

section tank asphalts were correlated with percentage LMS <strong>and</strong> percentage small<br />

molecular size using both THF <strong>and</strong> toluene as carriers. The penetration index<br />

would not correlate, <strong>and</strong> later attempts to extend this to aged asphalts were not<br />

successful. Inclusion <strong>of</strong> other parameters can improve results. For instance, the<br />

viscosities<strong>of</strong>alltheasphaltsrepresentedinFig.8,excepttheanomalousDiamond<br />

Shamrock (black circles), were correlated by log viscosity at 608C ¼ A þ B<br />

(%LMS) 20.6 þ C(IR) 0.9 , r 2 ¼ 0.968, in which IR is the area <strong>of</strong> the carbonyl peak<br />

(27). Infrared carbonyl area <strong>and</strong> Heithaus parameters (a measure <strong>of</strong> asphalt<br />

compatibility) were more successful in correlating other properties than<br />

percentage LMS. The carbonyl peak was one <strong>of</strong> the best parameters, <strong>and</strong> because<br />

it is strongly cross-correlated with percentage LMS, the efficiency <strong>of</strong> the latter is<br />

affected.<br />

Because <strong>of</strong> the crudeness <strong>of</strong> representing the shape <strong>of</strong> the SEC<br />

chromatograph by three sections, Garrick <strong>and</strong> co-workers (55–57,61) divided<br />

© 2004 by Marcel Dekker, Inc.

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