Trr No. 1323 Materials And Construction, pp. 53-60

The use of the Corbett-Swarbrick fractionation procedure for characterization of age-hardening potentials of asphalts was studied. The fractionation procedure was used to separate asphalts into four different fractions (asphaltenes, saturates, naphtene-aromatics, and polar-aromatics), to identify trends in the changes of proportions of these asphalt fractions during aging. The technique of infrared spectroscopy was used to examine the changesin the charateristics of these fractions during aging. Analyses were performed to determine the relationship between the properties of these asphalt fractions in aphalts were found to change during aging: the proportions of the asphaltenes and polar-aromatics increase and the proportions of saturates and naphthene-aromatics decrease. For the asphalts tested, the higher the asphaltene content of an original asphalt, the higher the aging potential as determined by the absolute viscosity ratios after the thin film oven test (TFOT) or the rolling thin film oven test (RTFOT). The propotions of asphalt fractions in the original asphalts were found to correlate fairly well with the absolute viscosity ratios after the TFOT and moderately well after the RTFOT. The results of infrared spectral analyses on the asphalt fractions indicated that the characteristics of the fractions change as an asphalt ages. Anhydrides, carboxylic acids, and ketones develop in asphaltenes; carboxylid acids and ketones develop in polar-aromatics and naphthene-aromatics as a result of aging. No evidence exists that any functional group developed in saturates as a result of a aging.