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Morphology Characterization of Foam Bitumen and Modeling for Low Temperature Asphalt Concrete
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.ORCID iD: 0000-0002-2318-2797
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.
Series
TRITA-BYMA, ISSN 0349-5752 ; 2016:1
Keyword [en]
foam characteristics, evolution of foam bitumen bubbles, image analysis, modeling rising of bubble, foam asphalt mixture
National Category
Infrastructure Engineering
Research subject
Transport Science
Identifiers
URN: urn:nbn:se:kth:diva-183105ISBN: 978-91-7595-865-1 (print)OAI: oai:DiVA.org:kth-183105DiVA: diva2:907667
Public defence
2016-04-01, Kollegiesalen, Brinellvägen 8, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20160303

Available from: 2016-03-03 Created: 2016-02-29 Last updated: 2016-03-09Bibliographically approved
List of papers
1. Dynamic X-ray radiography for the determination of foamed bitumen bubble area distribution
Open this publication in new window or tab >>Dynamic X-ray radiography for the determination of foamed bitumen bubble area distribution
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2015 (English)In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 50, no 1, 79-92 p.Article in journal (Refereed) Published
Abstract [en]

Foam bitumen is highly efficient in wetting and coating the surface of mineral aggregate at lower temperature. In order to improve understanding and characterization of the bitumen foam, X-ray radiography was used to study the formation and decay of bitumen foam in 2D representation. Image segmentation analysis was used to determine the foam bubble size distribution. In addition, the main parameters influencing foam bitumen formation, water content, and temperature were also investigated. The results demonstrate the influence of the water content on morphology and expansion of foam bitumen bubbles. Adding more water in the foaming process leads to quick collapse of bubbles and intensifies coalescence of foam bitumen. Higher temperatures produces larger bubbles at early foaming stage compared to lower temperature. Moreover the morphology of bubble formation depends on the types of bitumen used. An exponential function has been implemented to represent the bubble area distribution.

National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-158798 (URN)10.1007/s10853-014-8568-6 (DOI)000345077000011 ()2-s2.0-84949880571 (Scopus ID)
Note

QC 20150204

Available from: 2015-02-04 Created: 2015-01-12 Last updated: 2017-12-05Bibliographically approved
2. New experimental methods for characterizing formation and decay of foam bitumen
Open this publication in new window or tab >>New experimental methods for characterizing formation and decay of foam bitumen
2015 (English)In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873Article in journal (Refereed) Published
Abstract [en]

Formation and decay of foam bitumen is a highly dynamic temperature dependent process which makes characterization difficult. In this research, new experimental tools were applied for characterizing the bitumen foam during the foaming process. Ultrasonic sensors were used for accurately monitoring the expansion and decay of foam bitumen as a function of time. Assessment of foam bitumen viscosity was performed using high frequency torsional rheometer and in situ observation by X-ray radiography. A high-speed camera was applied for examining the foam bitumen stream right at the nozzle revealing that foam bitumen at a very early stage contains fragmented pieces of irregular size rather resembling a liquid than foam. Moreover, infrared thermal images were taken for obtaining information on the in situ surface temperature of foam bitumen during the hot foaming process. The result showed that the average surface temperature of foam bitumen depends on the water content of the bitumen and bubble size distribution, 108 and 126 °C for 4 and 1 wt% (by weight) water content respectively. The residual water content in the decaying foam bitumen was determined by thermogravimetric analysis. The result demonstrated that residual water content depends on the initial water content, and was found to be between 38 and 48 wt% of the initial water content of 4–6 wt%. Finally, X-ray computed tomography was applied for examining the decay of foam bitumen revealing that the bubbles of foam bitumen remain trapped close to the surface of the foam bitumen.

Keyword
Foam bitumen characterization, Process monitoring, Thermal properties, X-ray analysis, Atmospheric temperature, Bubble columns, Computerized tomography, Decay (organic), High speed cameras, Surface properties, Thermodynamic properties, Thermogravimetric analysis, X ray analysis, X ray radiography, Bubble size distributions, Foam bitumens, Infrared thermal image, Initial water contents, New experimental method, Residual water content, Temperature dependent, X-ray computed tomography, Bituminous materials
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-177222 (URN)10.1617/s11527-015-0659-6 (DOI)
Note

QC 20151125

Available from: 2015-11-25 Created: 2015-11-17 Last updated: 2017-12-01Bibliographically approved
3. Influence of foaming water content on foam asphalt mixtures
Open this publication in new window or tab >>Influence of foaming water content on foam asphalt mixtures
2015 (English)In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 85, 65-77 p.Article in journal (Refereed) Published
Abstract [en]

Warm mix asphalt technology using foamed bitumen is being used widely despite the fact that high air void content and poor coating of large aggregate remain major drawbacks require enhancement. This paper manly focuses on the investigation of water content influence on the foamed bitumen and the asphalt mixture. Influence of the water content in combination with compaction temperature has been investigated using gyratory compaction method. AC11N foam asphalt mixture is produced in the lab using lab foamer. Marshall stability and indirect tensile test was used to evaluate the foam asphalt mixture performance. The investigation revealed that the Marshall stability of foam asphalt mixture is highly influenced by compaction temperature compared to water content. Moreover, increasing the water content helps in coating large aggregates when the mixture is produced at low temperature, nevertheless using high water content reduces the Marshall stability to certain extent. In addition the amount of water trapped in the mixture after the mixing process was determined using thermogravimetric analysis. The amount of water remaining in the asphalt mixture is less than 1% relative to the bitumen mass.

Keyword
Foamed bitumen, Water content, Asphalt mixture, Laboratory tests, Thermogravimetric analysis
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-169242 (URN)10.1016/j.conbuildmat.2015.03.071 (DOI)000354139400008 ()2-s2.0-84926052266 (Scopus ID)
Note

QC 20150616

Available from: 2015-06-16 Created: 2015-06-12 Last updated: 2017-12-04Bibliographically approved
4. A Closer Scientific Look at Foam Bitumen
Open this publication in new window or tab >>A Closer Scientific Look at Foam Bitumen
(English)Manuscript (preprint) (Other academic)
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-183161 (URN)
Note

QS 2016

Available from: 2016-03-02 Created: 2016-03-02 Last updated: 2016-03-03Bibliographically approved
5. Modeling of bubble rising velocity and shape for foam bitumen
Open this publication in new window or tab >>Modeling of bubble rising velocity and shape for foam bitumen
(English)Manuscript (preprint) (Other academic)
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-183162 (URN)
Note

QS 2016

Available from: 2016-03-02 Created: 2016-03-02 Last updated: 2016-03-03Bibliographically approved
6. Evolution of bubble size distribution during foam bitumen formation and decay
Open this publication in new window or tab >>Evolution of bubble size distribution during foam bitumen formation and decay
Show others...
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, Published 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
BOCA RATON: CRC PRESS-TAYLOR & FRANCIS GROUP, 2014
Series
ASPHALT PAVEMENTS, VOLS 1 AND 2
Keyword
Foamed bitumen, expansion ratio, half-life, X-ray radiography, image segmentation analysis
National Category
Construction Management Civil Engineering
Identifiers
urn:nbn:se:kth:diva-160009 (URN)000347408100115 ()2-s2.0-84904130891 (Scopus ID)978-1-315-73675-4 (ISBN)978-1-138-02693-3 (ISBN)978-113802713-8 (ISBN)
Conference
12th International Conference on Asphalt Pavements, ISAP 2014; Raleigh, NC; United States; 1 June 2014 through 5 June 2014
Note

QC 20150216

Available from: 2015-02-16 Created: 2015-02-12 Last updated: 2016-03-03Bibliographically approved

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