The role of hydroaromatics in oxidative aging in asphalt

The pavement engineering community recognized fifty years ago that age hardening and embrittlement of asphalt during service is a primary cause of road failure and that oxidation of asphalt is the major cause of age hardening. Oxidative aging is characterized by oxygen uptake, the formation of sulfoxide and carbonyl groups (as shown by IR spectra), and marked increases in dynamic viscosity and other rheological properties. Different asphalts show markedly different theological changes for similar amounts of oxidation, although elemental analyses indicate a similarity in CHO ratios as well as in molecular weights, with variability only in the heteroatoms, functional groups, and trace metal compositions.