Time- and Composition-Dependent Evolution of Distinctive Microstructures in Bitumen

Abstract

Bitumen’s chemistry often results in complicated intermolecular associations, which are manifested by the diverse microstructures as observed by atomic force microscopy (AFM). These microstructures largely contribute to bitumens’ bulk mechanical properties; therefore, it is essential to understand the chemical–microstructural–mechanical relationships for optimal design of bitumen-related applications. However, the complex nature of bitumen and the various influencing factors often lead to practical challenges in investigation of bitumens’ microstructures and their chemical origins. This study aims at addressing some of the main concerns related to AFM characterization of bitumens’ microstructures, namely the dependence of bitumens’ microstructures on such factors as sample preparation methods, annealing conditions and durations, and chemical composition. Our results suggest that microstructures of bitumen films of a few micrometers or thicker (i.e., the thickness of the asphalt-coating layer over the aggr...