Fundamental Properties of Asphalts and Modified Asphalts, III

The majority of the results were presented in a journal article that will be published in the
proceedings of the 52 nd annual conference of Canadian Technical Asphalt Association in
November 2008 in Saskatoon, Saskatchewan.
Conclusion
The FTIR spectroscopic survey presented here provides a framework for further FTIR analysis
of complex pavement mastics including surface samples consisting of photo-oxidized asphalt
and aggregate with varying mineralogy. The results of this analysis suggest asphalt spectral
components can be removed from combined spectra of asphalt and aggregate. Asphalt PA
spectra compared favorably to liquid-cell spectra. Signal to noise ratios were lower for the PA
technique, however the PA signal to noise ratio can be significantly improved with additional coadded
scans. It remains an open question as to whether FTIR pavement surface spectra will be
predictive of the bulk mechanical properties of the pavement.
The complex shear modulus of AAD-1 (at 60˚C and 10 radians/sec) after standard PAV aging
(20 hours, 300 psi) was significantly less than the complex shear modulus of the asphalt
recovered from the edge and center of the LTA3 core (8 days oven aging at 85˚C).
At the Arizona field validation site, after five years in-service test sections constructed with
asphalts of similar performance grade but from different sources show significant differences in
the levels of pavement distress. Asphalt AZ1-1 has developed the most cracking based on nonwheel
path longitudinal cracking.
Work to be Conducted Next Quarter
• Investigations next quarter and probably several quarters after will include:
o Continue FTIR and rheological analysis of the validation site asphalts and
validation site pavement material to investigate photo-oxidation at the surface and
the extent of oxidation below the surface.
o Evaluate the variation in carbonyl moieties between field and PAV aged asphalts
due to, for example, aggregate catalytic effects.
o Expand the chemometric calibration data set to improve and verify the strength of
the observed statistical correlations reported last quarter.
o Explore the kinetic differences observed with regard to asphalt source.
o Evaluate solvent defined fractions to assess the contribution of these components
to physicochemical changes in asphalt due to aging.
o Apply the recently developed Hirsch model to evaluate the potential for
prediction of E* from carbonyl and other infrared derived indices.
o Perform a preliminary investigation to evaluate the efficacy of infrared
spectroscopy in evaluating steric and physical hardening. Infrared analysis may
show differences in amorphous (rapidly quenched) asphalt compared to more
crystalline asphalt (cooled slowly). Infrared spectra may also show subtle
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