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Rheological effects of waxes in bitumen
KTH, Superseded Departments, Civil and Architectural Engineering.
KTH, Superseded Departments, Civil and Architectural Engineering.
2003 (English)In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 17, no 3, 511-520 p.Article in journal (Refereed) Published
Abstract [en]

Rheological effects of adding two bitumen waxes (isolated from SEC-II fraction) to three bitumens were studied using dynamic mechanical analysis (DMA). Also, a commercially available slack wax was used in the study. The results show that the magnitude and type of effect on bitumen rheology depend on the bitumen and type of crystallizing fraction in the bitumen. Effects due to wax content shown in DMA temperature sweeps are well related to the corresponding effects shown in DSC thermograms. The slope of the logarithm of the complex modulus between 25 degreesC and 60 degreesC is introduced as a possible proper factor for predicting rutting sensitivity due to wax content.

Place, publisher, year, edition, pages
2003. Vol. 17, no 3, 511-520 p.
Keyword [en]
Addition reactions, Crystallization, Dynamic mechanical analysis, Elastic moduli, Rheology, Sensitivity analysis, Temperature, Bitumen, Crystallizing fraction, Rheological effects, Rutting sensitivity
National Category
Building Technologies
Identifiers
URN: urn:nbn:se:kth:diva-8927DOI: 10.1021/ef020202bISI: 000183089500001OAI: oai:DiVA.org:kth-8927DiVA: diva2:14414
Note
QC 20101006Available from: 2005-01-08 Created: 2005-01-08 Last updated: 2010-10-06Bibliographically 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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