Wax morphology in bitumen

Wax crystallisation and melting in bitumen is usually considered detrimental to bitumen quality and asphalt performance. The objectives of this paper are to study wax morphology in bitumen and to investigate effects of time, temperature, and thermal cycling on wax crystallisation. Various samples we...

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Bibliographic Details
Published in:Journal of materials science 2005-04, Vol.40 (8), p.1893-1900
Main Authors: XIAOHU LU, LANGTON, M, OLOFSSON, P, REDELIUS, P
Format: Article
Language:English
Subjects:
Applied sciences
Asphalt
Bitumen. Tars. Bituminous binders and bituminous concretes
Bitumens
Blends
Buildings. Public works
Crystal structure
Crystallization
Differential scanning calorimetry
Exact sciences and technology
Food Engineering
Livsmedelsteknik
Materials
Materials science
Melting
Microscopy
Morphology
Product life cycle
Production management
Scanning microscopy
Temperature dependence
Test procedures
Thermal cycling
Transmission electron microscopy
Waxes
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Summary:Wax crystallisation and melting in bitumen is usually considered detrimental to bitumen quality and asphalt performance. The objectives of this paper are to study wax morphology in bitumen and to investigate effects of time, temperature, and thermal cycling on wax crystallisation. Various samples were selected, including eight waxy bitumens of different sources and three laboratory blends prepared by adding a slack wax and two isolated bitumen waxes to the non-waxy bitumen. Test methods used were differential scanning calorimetry (DSC), polarised light microscopy (PLM), confocal laser scanning microscopy (CLSM), and freeze etching (fracture) in combination with transmission electron microscopy (FF-TEM). The DSC results indicated that the selected bitumen samples differ widely in wax content and wax crystallisation starting and melting out temperatures. It was found that non-waxy bitumen displayed no structure or crystals neither in PLM, CLSM or FF-TEM, while waxy bitumens from different crude origins showed a large variation of structures. The morphology of wax crystals was highly dependent on crystallisation temperature as well as temperature history. The wax which has been isolated from waxy bitumen and mixed into non-waxy bitumen displayed similar morphology as the wax in the original bitumen. It was also found that bitumen wax usually melted at temperatures lower than 60°C although in one case a temperature of 80°C was needed until complete melting of the wax.
ISSN:0022-2461
1573-4803
1573-4803
DOI:10.1007/s10853-005-1208-4