A Review of the Fundamentals of Asphalt Oxidation: Chemical, Physicochemical, Physical Property, and Durability Relationships

This Circular is a synopsis of current physicochemical understanding of the chemistry, kinetics, and mechanisms of asphalt oxidation and its influence on asphalt durability. The oxidative behavior of asphalt is thought to be one of the critical factors contributing to the performance of hot-mix asphalt (HMA) pavements. The content of this review reflects more than half a century of research work on the physicochemical consequences of oxidative aging and its effects on the fundamental rheological properties of the oxidized asphalt. Emphasis is made on how the component fractions of asphalt behave under oxidation, including a consideration of the effects of the mineral aggregate and metals contained in asphalts. A section of the Circular reviews recent data and offers further insight on pavement aging as a function of air-void content of the mixture, temperature, and pavement depth and how oxidative hardening contributes to decreasing pavement service life. Civil engineers, chemists, and asphalt technologists developing fundamental pavement performance models will find this Circular to be of interest. Professionals in owner agencies will have at their fingertips a useful handbook to understand the subtleties of asphalt oxidation and how it contributes to distresses in an HMA pavement. Beginning students of asphalt technology will find this a welcome review with many references to original work.