OXIDATION KINETICS OF ASPHALT CORBETT FRACTIONS AND COMPOSITIONAL DEPENDENCE OF ASPHALT OXIDATION

Abstract

ABSTRACT This paper investigates the oxidation kinetics of asphalt generic fractions and the contribution of each individual fraction to the oxidation of the whole asphalt. Polar aromatic (PA) and naphthene aromatic (NA) fractions of five Strategic Highway Research Program (SHRP) core asphalts (AAA-1, AAD-1, AAF-1, AAG-1 and AAM-1) were prepared and aged at multiple conditions to obtain their kinetic parameters. Aromatics/saturates/asphaltenes blends of four of the five asphalts were also aged to deduce the influence of saturates and asphaltenes. Carbonyl growth in the PA and NA fractions as a result of oxidation follows a similar profile as the whole asphalts. The kinetic parameters of the NA fractions occur in two groups, one with high reaction order and activation energy, and the other with low values of each. The kinetic parameters of the PA fractions all fall into the low-values group. Although the PA fraction is the most reactive portion in an asphalt, its kinetic parameters (reaction order and activation energy) may be much different from those of its parent asphalt. Saturates have only a dilution effect. The data indicate that the addition of asphaltene increases the oxidation rate. The data also indicate that the PA and NA fractions age faster in a separated state than in a mixed state. This study shows that the kinetic characteristics of an asphalt are determined not only by the kinetic characteristics of the fractions but also by the interactions and molecular associations between the fractions.