Recent advances in characterizing the “bee” structures and asphaltene particles in asphalt binders

Abstract

The microscopic surface features of asphalt binders are extensively reported in existing literature, but relatively fewer studies are performed on the morphology of asphaltene microstructures and cross-examination between the surface features and asphaltenes. This paper reports the findings of investigating six types of asphalt binders at the nanoscale, assisted with atomic force microscopy (AFM) and scanning transmission electron microscopy (STEM). The surface features of the asphalt binders were examined by using AFM before and after being repetitively peeled by a tape. Variations in infrared (IR) absorbance at the wavenumber around 1700 cm−1, which corresponds to ketones, were examined by using an infrared s-SNOM instrument (scattering-type scanning near-field optical microscope). Thin films of asphalt binders were examined by using STEM, and separate asphaltene particles were cross-examined by using both STEM and AFM. In addition, connections between the microstructures and binder’s physicochemical properties were evaluated. The use of both microscopy techniques provide comprehensive and complementary information on the microscopic nature of asphalt binders. It was found that the dynamic viscosities of asphalt binders are predominantly determined by the zero shear viscosity of the corresponding maltenes and asphaltene content. Limited samples also suggest that the unique bee structures are likely related to the growth of asphaltene content during asphalt binder aging process, but more asphalt binders from different crude sources are needed to verify this finding.

Future Directions for Applications of Bio-Oils in the Asphalt Industry: A Step to Sequester Carbon in Roadway Infrastructure

“…The most important layer cells (subcells) in wax crystallization are the first two layers. 77 The wax crystal has an important role in the formation of bee-like structures. Bee size has a significant effect on the stiffness, deformation, and viscosity of asphalt.…”

“…Wax as an n -paraffin has a structure of layered packs. The most important layer cells (subcells) in wax crystallization are the first two layers . The wax crystal has an important role in the formation of bee-like structures.…”

“…The wax crystal has an important role in the formation of bee-like structures. Bee size has a significant effect on the stiffness, deformation, and viscosity of asphalt . Sometimes bee structures may be composed of wax crystals through nonpolar interactions between them, and a small amount of wax plays a role as a nucleation center.…”

“…Bee size has a significant effect on the stiffness, deformation, and viscosity of asphalt. 77 Sometimes bee structures may be composed of wax crystals through nonpolar interactions between them, and a small amount of wax plays a role as a nucleation center. Another viewpoint says that a bee structure is a solid-like deposit from the coprecipitation of wax and asphaltenes.…”

Changes in the Nanoscale Asphaltene Particles and Relaxation Spectra of Asphalt Binders During Aging and Rejuvenation

“…As asphalt binder ages, some NA changes into PA, and some PA changes into asphaltenes, resulting in a net increase of asphaltene content [8]. For a same type of asphalt binder, rheological property changes are well related to changes in asphaltene content [6,9,10]. For different types of asphalt binder, however, relationships between the rheological properties and asphaltene content vary greatly.…”