Segregation and Crystallization of Waxes on the Surface of Asphalt Binders as Observed by Atomic Force Microscopy

Abstract

In an effort to detail the thermal variation of the bitumen microstructure, one sample of asphalt cement (CAP 30/45) was analyzed by atomic force microscopy before and after thermal treatment. Phase contrast and topography images showed that sample morphology is highly dependent on the thermal history of the sample. It can be observed that thermal treatment can lead either to asphaltene flocculation or to wax crystallization. In situ measurements indicated that, after thermal cycles, “bees” appear to be immersed in a lamellar structure that resembles a surface crystallization process. Conditions for the crystallization of the waxes as well as the stability of the “bee” are discussed.