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Evolution of bubble size distribution during foam bitumen formation and decay
KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
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2014 (English)In: Asphalt Pavements: Proceedings of the International Conference on Asphalt Pavements, ISAP 2014 / [ed] Kim, YR, BOCA RATON: CRC PRESS-TAYLOR & FRANCIS GROUP , 2014, 1233-1240 p.Conference paper (Refereed)
Abstract [en]

The warm asphalt mixture process using foam asphalt technology allows mixing and compaction at lower temperature. Nevertheless the higher air void content and incomplete coating of large aggregates are issues that need improvement to reach the properties of hot mix asphalt. In order to improve the understanding and characterization of the bitumen foam, X-ray radiography was used to investigate the formation and decay of bitumen foam in 2D representation. Image segmentation analysis was used to determine the foam bubble size distribution as a function of time. The impact of water content on the process has been studied for two penetration grade bitumen. The water content showed considerable influence on the foam quality in terms of expansion ratio and bubble size distribution. Increasing the water content in the foaming process leads to a quicker collapse of the bubbles and favors coalescence of individual bubbles.

Place, publisher, year, edition, pages
Keyword [en]
Foamed bitumen, expansion ratio, half-life, X-ray radiography, image segmentation analysis
National Category
Construction Management Civil Engineering
URN: urn:nbn:se:kth:diva-160009ISI: 000347408100115ScopusID: 2-s2.0-84904130891ISBN: 978-1-315-73675-4ISBN: 978-1-138-02693-3ISBN: 978-113802713-8OAI: diva2:788671
12th International Conference on Asphalt Pavements, ISAP 2014; Raleigh, NC; United States; 1 June 2014 through 5 June 2014

QC 20150216

Available from: 2015-02-16 Created: 2015-02-12 Last updated: 2016-03-03Bibliographically approved
In thesis
1. Morphology Characterization of Foam Bitumen and Modeling for Low Temperature Asphalt Concrete
Open this publication in new window or tab >>Morphology Characterization of Foam Bitumen and Modeling for Low Temperature Asphalt Concrete
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Development of new asphalt technologies to reduce both energy consumption and CO2 production has attracted great interest in recent years. The use of foam bitumen, as one of them, is attractive due to the low investment and production cost. Formation and decay of foam bitumen is a highly dynamic temperature dependent process which makes characterization difficult. In this thesis, new experimental tools were developed and applied for characterizing the foam bitumen during the hot foaming process. 

One of the main goals of this study was to improve understanding and characterization of the foam bitumen formation and decay. X-ray radiography was used to study the formation and decay of foam bitumen in 2D representation. The results demonstrate that the morphology of bubble formation depends on the types of bitumen used. Moreover, theoretical investigation based on the 3D X-ray computed tomography scan dataset of bubble merging showed that the disjoining pressure increased as the gap between the bubbles in the surface layer (foam film) decreased with time and finally was ruptured. 

 Examining the foam bitumen stream right at the nozzle revealed that foam bitumen at a very early stage contains fragmented pieces of irregular size rather resembling a liquid than foam. The result from thermogravimetric analysis demonstrated that residual water content depends on the initial water content, and was found to be between 38 wt% and 48 wt% of the initial water content of 4 wt% to 6 wt%.

Moreover the influence of viscosity and surface tension on bubble shape and rise velocity of the bubbles using level-set method was implemented in finite element method. The modeling results were compared with bubble shape correlation map from literature. The results indicated that the bubble shapes are more dependent on the surface tension parameters than to the viscosity of the bitumen, whereas the bitumen viscosity is dominant for bubble rising velocity.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. xiv, 134 p.
TRITA-BYMA, ISSN 0349-5752 ; 2016:1
foam characteristics, evolution of foam bitumen bubbles, image analysis, modeling rising of bubble, foam asphalt mixture
National Category
Infrastructure Engineering
Research subject
Transport Science
urn:nbn:se:kth:diva-183105 (URN)978-91-7595-865-1 (ISBN)
Public defence
2016-04-01, Kollegiesalen, Brinellvägen 8, KTH, Stockholm, 13:00 (English)

QC 20160303

Available from: 2016-03-03 Created: 2016-02-29 Last updated: 2016-03-09Bibliographically approved

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Hailesilassie, Biruk W.Partl, Manfred N.
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