Morphology of asphalts, asphalt fractions and model wax-doped asphalts studied by atomic force microscopy

Abstract

Asphalts used in the construction of pavements exhibit unique properties at the micron and nanometre scale. Atomic force microscopy (AFM) images of asphalts and asphalt chromatographic fractions prepared as thin films clearly show that a variety of ‘microstructures’ can develop on the surface of these types of materials. Structure develops to different degrees and in different forms depending on the residua crude source from which the asphalt or asphalt fraction is derived, the thermal history of the sample and the sample thickness. Based on our current best interpretation of a very large number of AFM images obtained over several years, we hypothesise that the interaction between crystallising paraffin waxes and the remaining asphalt fractions is responsible for much of the structuring, including the well-known bee structures (Loeber et al. 1996, Journal of Microscopy, 182 (1), 32–39), which has been observed with asphalt materials.

Keywords:

• asphalt
• wax
• microstructure
• AFM
• paraffin
• crystallization

Acknowledgements

The authors gratefully acknowledge the Federal Highway Administration, US Department of Transportation, for their financial support: contract Nos DTFH61-99C-00022, DTFH61-07-D-00005 and DTFH61-07-H-00009. The authors also wish to acknowledge J.J. Miller, J.D. Beiswenger and J.E. MacNaughton, for their contribution to this research as key personal which conducted the majority of testing reported in this paper.

Disclaimer: This document is disseminated under the sponsorship of the US Department of Transportation in the interest of information exchange. The US Government assumes no liability for its contents or use thereof. The contents of this report reflect the views of Western Research Institute, which is responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views of the policy of the US Department of Transportation. Mention of specific brand names of equipment does not imply endorsement by the US Department of Transportation or by Western Research Institute.

Notes

1. J.F. Branthaver is retired.

Additional information

Notes on contributors

J. F. Branthaver

1