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Modelling and numerical simulation of phase separation in polymer modified bitumen by phase-field method
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. (Highway Engineering Research Group)ORCID iD: 0000-0003-1779-1710
Nynas AB.
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. (Highway Engineering Research Group)ORCID iD: 0000-0001-7333-1140
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. (Highway Engineering Research Group)ORCID iD: 0000-0003-3968-6778
2016 (English)In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 107, 322-332 p.Article in journal (Refereed) Published
Abstract [en]

In this paper, a phase-field model with viscoelastic effects is developed for polymer modified bitumen (PMB) with the aim to describe and predict the PMB storage stability and phase separation behaviour. The viscoelastic effects due to dynamic asymmetry between bitumen and polymer are represented in the model by introducing a composition-dependent mobility coefficient. A double-well potential for PMB system is proposed on the basis of the Flory-Huggins free energy of mixing, with some simplifying assumptions made to take into account the complex chemical composition of bitumen. The model has been implemented in a finite element software package for pseudo-binary PMBs and calibrated with experimental observations of three different PMBs. Parametric studies have been conducted. Simulation results indicate that all the investigated model parameters, including the mobility and gradient energy coefficients, interaction and dilution parameters, have specific effects on the phase separation process of an unstable PMB. In addition to the unstable cases, the model can also describe and predict stable PMBs. Moreover, the phase inversion phenomenon with increasing polymer content in PMBs is also well reproduced by the model. This model can be the foundation of an applicable numerical tool for prediction of PMB storage stability and phase separation behaviour.

Place, publisher, year, edition, pages
Elsevier, 2016. Vol. 107, 322-332 p.
Keyword [en]
Polymer modified bitumen; Storage stability; Phase separation; Phase-field method
National Category
Infrastructure Engineering
Research subject
Civil and Architectural Engineering
Identifiers
URN: urn:nbn:se:kth:diva-188830DOI: 10.1016/j.matdes.2016.06.041ISI: 000381532800040Scopus ID: 2-s2.0-84974808182OAI: oai:DiVA.org:kth-188830DiVA: diva2:939564
Note

QC 20160620

Available from: 2016-06-20 Created: 2016-06-20 Last updated: 2017-11-28Bibliographically approved
In thesis
1. Storage Stability and Phase Separation Behaviour of Polymer-Modified Bitumen: Characterization and Modelling
Open this publication in new window or tab >>Storage Stability and Phase Separation Behaviour of Polymer-Modified Bitumen: Characterization and Modelling
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Polymer-modified bitumen (PMB) is a high-performance material for road construction and maintenance. But its storage stability and phase separation behaviour are still not sufficiently understood and need to be studied toward a more successful and sustainable application of PMB. In this thesis, the equilibrium thermodynamics and phase separation dynamics of PMB are investigated with the aim at a fundamental understanding on PMB storage stability and phase separation behaviour. The development of polymer modifiers for paving bitumen is reviewed. The phase separation process in unstable PMBs is captured by fluorescence microscopy at the storage temperature (180 °C). A coupled phase-field model of diffusion and flow is developed to simulate and predict the PMB storage stability and phase separation behaviour. The temperature dependency of PMB phase separation behaviour is modelled by introducing temperature-dependent model parameters between 140 °C and 180 °C. This model is implemented in a finite element software package and calibrated with the experimental observations of real PMBs. The results indicate that storage stability and phase separation behaviour of PMB are strongly dependent on the specific combination of the base bitumen and polymer. An unstable PMB starts to separate into two phases by diffusion, because of the poor polymer-bitumen compatibility. Once the density difference between the two phases becomes sufficiently significant, gravity starts to drive the flow of the two phases and accelerates the separation in the vertical direction. The proposed model, based on the Cahn-Hilliard equation, Flory-Huggins theory and Navier-Stokes equations, is capable of capturing the stability differences among the investigated PMBs and their distinct microstructures at different temperatures. The various material parameters of the PMBs determine the differences in the phase separation behaviour in terms of stability and temperature dependency. The developed model is able to simulate and explain the resulting differences due to the material parameters. The outcome of this study may thus assist in future efforts of ensuring storage stability and sustainable application of PMB.

Abstract [sv]

Polymermodifierade bitumen (PMB) är ett högpresterande material för väganläggning och underhåll. Men PMB:s lagringsstabilitet och fassepareringsegenskaper är inte tillräckligt förstådda än och behöver studeras för en mer framgångsrik och hållbar användning av PMB. I denna avhandling studeras termodynamisk jämvikt och fasseparation av PMB med målsättning att uppnå en grundläggande förståelse av PMB:s lagringsstabilitet och fassepareringsegenskaper. Utvecklingen av polymermodifierade bitumen sammanfattas. Fasseparationsprocessen av instabil PMB:s studeras med hjälp av fluorescens mikroskopi vid lagringstemperatur (180 °C). En kopplad fas-fälts modell som beskriver diffusion och flöde har utvecklats för att simulera och förutsäga PMB:s lagringsstabilitet och fassepareringsegenskaper. Temperaturberoendet hos PMB:s fasseparation har beskrivits genom att införa temperaturberoende modellparametrar mellan 140 °C och 180 °C. Denna modell är införd i ett finit element program och kalibrerad med experimentella observationer på verkliga PMB. Resultaten indikerar att lagringsstabiliteten och fasseparationen hos PMB är starkt beroende av den specifika kombinationen av basbitumen och polymer. En instabil PMB börjar separera i två faser genom diffusion, beroende på dålig bitumen-polymer kompatibilitet. När skillnaden i densitet mellan de två faserna blir tillräckligt stor kommer gravitationen att driva flödet av de två faserna och accelerera separationen i vertikalled. Den föreslagna modellen, baserad på Cahn-Hilliards ekvation, Flory-Huggins teori och Navier-Stokes ekvation, kan beskriva stabilitetsskillnaderna mellan de undersökta PMB:erna och deras distinkta mikrostruktur vid olika temperaturer. De olika materialparametrarna hos PMB bestämmer skillnaden i fassepareringsegenskaper i termer av stabilitet och temperaturberoende. Den utvecklade modellen kan simulera och förklara de resulterande skillnaderna på grund av materialparametrarna. Resultatet av denna studie kan bidra till att säkerställa lagringsstabilitet och hållbara applikationer för PMB.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. 71 p.
Series
TRITA-BKN. Bulletin, ISSN 1103-4270 ; 143
Keyword
Polymer-modified bitumen; Storage stability; Phase separation; Fluorescence microscopy; Phase-field modelling, Polymermodifierad bitumen, Lagringsstabilitet, Fasseparation, Fluorescensmikroskopi, Fas-fälts modellering
National Category
Infrastructure Engineering
Research subject
Transport Science
Identifiers
urn:nbn:se:kth:diva-195089 (URN)978-91-7729-187-9 (ISBN)
Public defence
2016-11-22, Kollegiesalen, Brinellvägen 8, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20161102

Available from: 2016-11-02 Created: 2016-11-01 Last updated: 2016-11-02Bibliographically approved

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