Effect of treatment temperature on the microstructure of asphalt binders: Insights on the development of dispersed domains

Ilaria Menapace, E. Masad, A. Bhasin

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14 Citations (Scopus)


This paper offers important insights on the development of the microstructure in asphalt binders as a function of the treatment temperature. Different treatment temperatures are useful to understand how dispersed domains form when different driving energies for the mobility of molecular species are provided. Small and flat dispersed domains, with average diameter between 0.02 and 0.70 μm, were detected on the surface of two binders at room temperature, and these domains were observed to grow with an increase in treatment temperature (up to over 2 μm). Bee-like structures started to appear after treatment at or above 100°C. Moreover, the effect of the binder thickness on its microstructure at room temperature and at higher treatment temperatures was investigated and is discussed in this paper. At room temperature, the average size of the dispersed domains increased as the binder thickness decreased. A hypothesis that conciliates current theories on the origin and development of dispersed domains is proposed. Small dispersed domains (average diameter around 0.02 μm) are present in the bulk of the binder, whereas larger domains and bee-like structures develop on the surface, following heat treatment or mechanical disturbance that reduces the film thickness. Molecular mobility and association are the key factors in the development of binder microstructure. Lay description: The present paper offers insights about the development of the superficial microstructure of asphalt binders. The microstructure of asphalt binder is composed of two main phases, the matrix and the dispersed phase. In this paper, it was observed that the treatment temperature influences the resulting microstructure: if the treatment temperature increases, the dispersed domains increase in size. It was also observed that if no heat treatment is performed, the dispersed domains are very small, and they increase in size with deceasing binder thickness. Molecular mobility was found to be the key factor in the development of the binder microstructure.

Original languageEnglish
Pages (from-to)12-27
Number of pages16
JournalJournal of Microscopy
Issue number1
Publication statusPublished - 1 Apr 2016



  • Asphalt binder
  • Atomic force microscopy
  • Bee-like structures
  • Bitumen
  • Dispersed domains
  • Microstructure

ASJC Scopus subject areas

  • Pathology and Forensic Medicine
  • Histology

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