Air blowing of supercritical asphalt fractions

Air blowing of asphalt at higher temperature does not greatly impact such p arameters as the softening point-penetration relationship. With new Superpa ve specification, very good grade asphalts can be produced by air blowing, and the blowing temperature does not seriously impact the grade span. It is shown, however, that the subsequent 88 degreesC hardening and oxidation ra tes are higher for materials blown at higher temperature, and this is not d etected by Superpave specifications. Blowing fluxes with high saturate cont ent may result in higher grade but can cause subsequent susceptibility to o xidative hardening. The mechanism by which air blowing can affect the 88 de greesC hardening rate is related to oxidation kinetics and the tendency of oxidation products to form asphaltenes, causing hardening. For some materia ls air blown at higher temperature, the subsequent accelerated hardening ra te results from an increase in the oxidation rate, while the hardening susc eptibility may actually decrease.