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Wax in bitumen: Part 1: Classifications and General Aspects
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Highway and Railway Engineering.
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Highway and Railway Engineering.
2005 (English)In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 6, no 3, 281-309 p.Article in journal (Refereed) Published
Abstract [en]

Wax in bitumen has for a long time been of great interest, particularly regarding effects on bitumen quality and methods for determining wax content. Opinions about wax in bitumen have varied over the years and sometimes been contradictory. The findings of a literature study are presented in two companion papers. The main intention of the study was to give an extensive description ofthe field of knowledge concerning wax in bitumen. In this paper, classifications and general aspects on effects of wax in crude oil and bitumen are described. Theories behind possible mechanisms are also discussed, and commercial wax as additive to bitumen for different purposes described. Effects of wax are influenced by chemical composition and rheological properties of the bitumen, amount of wax in the bitumen as well as chemical composition and crystalline structure of the wax. The effect of wax on bitumen is linked to its crystallinity and melting properties. The temperature range of application as well as the definition of wax in bitumen is also of great importance. The presence of large wax crystals (macrocrystalline wax) in bitumen is considered to be most problematic. However, waxes in bitumen generally are microcrystalline and/or amorphous and can contain branched, alicyclic and aromatic components with heteroatoms, which renders crystallization considerably more difficult.

Place, publisher, year, edition, pages
2005. Vol. 6, no 3, 281-309 p.
Keyword [en]
bitumen wax, state-of-the-art, chemical composition
National Category
Building Technologies
Identifiers
URN: urn:nbn:se:kth:diva-8925DOI: 10.3166/rmpd.6.281-309ISI: 000233195200001Scopus ID: 2-s2.0-33845672724OAI: oai:DiVA.org:kth-8925DiVA: diva2:14412
Note
QC 20101006Available from: 2005-01-08 Created: 2005-01-08 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Influence of waxes on bitumen and asphalt concrete mixture performance
Open this publication in new window or tab >>Influence of waxes on bitumen and asphalt concrete mixture performance
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This doctoral thesis consists of a literature review, presented in two papers, and another six papers describing experimental studies of the influence of different kinds of wax and polyphosporic acid on bitumen and asphalt concrete mixture properties.

The literature review should give an extensive description of the field of knowledge concerning wax in bitumen. Effects of wax in crude oil, bitumen and asphalt concrete as well as test methods for studying these effects are described. Theories behind possible mechanisms are also discussed, and commercial wax as additive to bitumen for different purposes included.

The experimental parts comprise laboratory studies involving totally five 160/220 penetration base bitumens from different sources, two isolated bitumen waxes, five commercial waxes and one polyphosphoric acid. Asphalt concrete slabs, containing base or modified bitumen were prepared and tested. Binder properties were evaluated using different types of laboratory equipment, such as dynamic shear rheometer (DSR), bending beam rheometer (BBR), differential scanning calorimeter (DSC), force ductilometer, as well as equipment for determining conventional parameters like penetration, softening point, viscosity, and Fraass breaking point. Fourier Transform Infrared (FTIR) spectroscopy and Thin Layer Chromatography (TLC-FID) were used for chemical characterization. The binders were aged by means of the rolling thin film oven test (RTFOT) and pressure ageing vessel (PAV) in combination. Asphalt concrete properties were evaluated at low temperatures using the tensile strain restrained specimen test (TSRST) and creep test at -25°C. Dynamic creep testing was performed at 40°C, as well as complex modulus tests between 0 and 20°C.

Binder test results indicated that the magnitude and type of effect on bitumen rheology depend on the bitumen itself, type of crystallizing fraction in the bitumen and/or type and amount of additive used. Bitumen composition was found to be of decisive importance. Adding polyethylene wax or polyphosphoric acid, especially to a non-waxy 160/220 penetration grade bitumen, showed no or positive effects on the rheological behaviour at low temperatures (decrease in stiffness) as well as medium and high temperatures (increase in complex modulus and decrease in phase angle). However, the corresponding positive effects could not be shown in dynamic creep testing (at 40°C) of asphalt concrete mixtures containing these modified binders. Adding FT-paraffin decreased the physical hardening index for all bitumens. Also polyethylene wax and montan wax showed this effect for some bitumens. Slack wax showed a large increasing effect on physical hardening, and polyphosphoric acid none or a minor negative effect. No correlation between physical hardening index (PHI) and wax content by DSC was found in this study, involving both natural bitumen wax and commercial wax.

Addition of the commercial waxes used showed no or marginally positive influence on bitumen ageing properties for the bitumens and test conditions used. Comparing asphalt mixture test results to the corresponding binder test results, the effects on asphalt mixtures from adding commercial wax or polyphosphoric acid were less evident. Significant binder physical hardening by BBR could not be confirmed by TSRST.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. iii, 48 p.
Series
Trita-VT. FR, ISSN 1650-867X ; 2005:1
Keyword
bitumen, asphalt, additives, wax in bitumen, polyphosphoric acid in bitumen, rheology, IR-spectroscopy, dynamic mechanic analysis (DMA), bending beam rheometer (BBR), literature study, low temperature physical hardening, highway materials, morphology, modified bitumens, temperature susceptibility, low temperature performance, ageing, microscopy, chromatography, Fourier transform infrared spectroscopy, force ductility, conventional binder tests, asphalt performance, tensile strain restrained specimen test (TSRST)
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-553 (URN)
Public defence
2005-12-16, Sal E1, Lindstedtsvägen 3, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20101006Available from: 2005-01-08 Created: 2005-01-08 Last updated: 2010-10-06Bibliographically approved

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