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New Experimental and Modelling Tools for Multiscale Characterization of Asphalt Mastic
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.ORCID iD: 0000-0001-9875-3913
2020 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Asphalt mastics act as a binding phase in asphalt mixtures and their rheological properties strongly affect the performance of asphalt mixtures with respect to virtually all damage modes. In order to measure mastics properties, relevant for field performance, testing should be performed at size-scales representative for the morphology and material inhomogeneity of asphalt mixtures. This thesis aims to contribute to solving these important issues by developing new experimental and modelling tools for the multi-scale characterization of asphalt mastics.

An instrumented indentation test for viscoelastic characterization of asphalt mastics is proposed as a new alternative to existing techniques. A methodology for spherical indentation testing of bituminous materials is developed allowing measuring their viscoelastic properties at arbitrary non-decreasing loading. The potential of indentation tests for multi-scale measurements of viscoelastic properties of binder-aggregate composites is investigated for the special case of asphalt mortar, composed of mastic and aggregates smaller than 2.36 mm. The effect of the test parameters on the measured apparent shear relaxation modulus of asphalt mortar is evaluated. Experimental and modelling results indicate that the measurement scale in the indentation tests can be controlled efficiently by testing with different indenter-specimen contact areas. Accordingly, indentation tests may be used for reliable viscoelastic characterization of binder-aggregate composites on macro-scale as well as on the mastic phase level. It may thus potentially provide a relatively simple tool for measuring viscoelastic properties of mastics in situ in asphalt mixtures. 

In order to establish a quantitative link between material design parameters of mastics and its rheology, a new finite element (FE) micromechanical modelling approach has been developed. It allows predicting the viscoelastic properties of bitumen-filler mastic from its volumetric, mechanical and geometrical design parameters. The influence of modelling parameters on the model’s accuracy is evaluated and optimal parameter combinations are identified. The model is validated with the measurements performed on several mastics and for a range of volumetric concentration of filler. It is shown that the proposed model can capture the measured viscoelastic behaviour of mastics for the examined range of loading, temperature and material parameters. Accordingly, it may be a useful tool for optimizing mastics material design for the target viscoelastic properties.

Abstract [sv]

Asfaltmastix fungerar som bindemedel i asfaltsblandningar och blandningens uppträdande vad gäller i stort sett alla skadetyper är starkt beroende av asfaltmastixens reologiska egenskaper. Att förstå de mekanismer och parametrar som beskriver asfaltmastixens reologi är därför nödvändigt för att försäkra sig om ett tillräckligt bra beteende hos asfaltsblandningar. Dessutom, för att kunna mäta mastix egenskaper, relevanta för materialets uppträdande i fält, bör provning genomföras för längdskalor som är relevanta för blandningens morfologi. Inhomogeniteter hos materialet måste också beaktas. Denna avhandling strävar mot att lösa dessa viktiga problem genom att utveckla experimentella verktyg och modelleringsverktyg för flerskalekarakterisering av mastix.Instrumenterad intryckningsmetodik, för viskoelastisk karakterisering av mastix, beskrivs i avhandlingen som ett alternativ till andra provningsmetoder. En ny metod, som utgår ifrån sfärisk intryckningsprovning av asfaltmastix, har tagits fram med avsikten att mäta viskoelastiska storheter vid godtycklig men ökande last. I avhandlingen undersöks nyttan med att använda intryckningsprov för flerskalekarakterisering av bindemedel/partikel kompositer, speciellt för fallet asfaltsbruk. Provparametrarnas inverkan på den uppmätta relaxationsmodulen utvärderas. De framtagna resultaten visar att mätskalan vid intryckningsproven kan kontrolleras effektivt genom att styra kontaktytans storlek vid experimenten. Sammantaget visas i avhandlingen att intryckningsprov är ett trovärdigt alternativ för viskoelastisk karakterisering av de aktuella kompositmaterialen, på både makronivå och komponentnivå. Metoden har alltså potential att vara ett relativt enkelt alternativ för att på plats mäta materialegenskaper hos asfaltsmaterial/asfaltsblandningar.För att fastställa en kvantitativ länk mellan materialets modellparametrar och dess reologi så har ett nytt mikromekaniskt angreppssätt, baserat på finit elementmetodik, utvecklats. Avsikten är då att beräkna de viskoelastiska egenskaperna hos asfaltmastix utgående från de av problemet givna parametrarna. Modellparametrarnas inverkan på noggrannheten utvärderas och optimala parameterkombinationer identifieras. Modellen valideras med hjälp av experiment på olika asfaltsmaterial och den visar sig kunna fånga det uppmätta viskoelastiska beteendet för det aktuella intervallet av olika undersökta parametrar. Följaktligen kan det vara ett användbart verktyg för att optimera framtagningen av asfaltsmaterial utgående från de riktmärken för det viskoelastiska beteendet som sätts upp.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2020. , p. 31
Series
TRITA-ABE-DLT ; 2012
National Category
Civil Engineering Applied Mechanics
Research subject
Civil and Architectural Engineering, Building Materials
Identifiers
URN: urn:nbn:se:kth:diva-272739ISBN: 978-91-7873-513-6 (print)OAI: oai:DiVA.org:kth-272739DiVA, id: diva2:1426965
Presentation
2020-05-28, Via Zoom - https://kth-se.zoom.us/j/68519700863, Du som saknar dator/datorvana kan kontakta jelagin@kth.se för information / Use the e-mail address if you need technical assistance, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20200506

Available from: 2020-05-06 Created: 2020-04-28 Last updated: 2020-05-06Bibliographically approved
List of papers
1. On the Measurement of two Independent Viscoelastic Functions with Instrumented Indentation Tests
Open this publication in new window or tab >>On the Measurement of two Independent Viscoelastic Functions with Instrumented Indentation Tests
2018 (English)In: Experimental mechanics, ISSN 0014-4851, E-ISSN 1741-2765, Vol. 58, no 2, p. 301-314Article in journal (Refereed) Published
Abstract [en]

In the present paper, a methodology for complete characterization of linear isotropic viscoelastic material with spherical instrumented indentation test is proposed. The developed method allows for measuring two independent viscoelastic functions, shear relaxation modulus and time-dependent Poisson's ratio, from the indentation test data obtained at non-decreasing loading, but otherwise arbitrary. Finite element modelling (FEM) is relied upon for validating the proposed methodology and for quantifying the influence of experimental variables on the measurements accuracy. Spherical indentation experiments are performed on several viscoelastic materials: polyoxymethylene, bitumen and bitumen-filler mastics. The viscoelastic material functions obtained with the indentation tests are compared with the corresponding results from the standard mechanical tests. Numerical and experimental results presented indicate that the methodology proposed allows mitigating the machine compliance and loading rate effects on the accuracy of the viscoelastic indentation tests.

Place, publisher, year, edition, pages
Springer, 2018
Keywords
Indentation, Viscoelasticity, Mechanics of materials, FEM, Bitumen, Bitumen-filler mastics
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-222406 (URN)10.1007/s11340-017-0342-7 (DOI)000423584800008 ()2-s2.0-85030833837 (Scopus ID)
Note

QC 20180228

Available from: 2018-02-28 Created: 2018-02-28 Last updated: 2020-04-28Bibliographically approved
2. Measurement of the viscoelastic properties of asphalt mortar and its components with indentation tests
Open this publication in new window or tab >>Measurement of the viscoelastic properties of asphalt mortar and its components with indentation tests
2019 (English)In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402Article in journal (Refereed) Published
Abstract [en]

Reliable determination of material properties is a key component for modelling and performance prediction of asphalt pavements. This paper deals with the potential use of instrumented indentation tests for viscoelastic characterisation of asphalt mortar as a new alternative to existing techniques. The main focus lies on the potential of indentation tests for multi-scale measurement of the shear relaxation modulus. A three-dimensional finite element model of a rigid spherical indenter penetrating an asphalt mortar sample is developed and used to model indentation tests performed at different material scales. The asphalt mortar is modelled as an idealised fine aggregate composite with elastic spheres, suspended within a viscoelastic bitumen mastic matrix. Based on the obtained numerical results the scale-dependency of the shear relaxation modulus measured with the indentation test is investigated. It is shown that the measurement scale is effectively controlled by the size of the indenter-specimen contact area, while the effect of indentation depth is minimal. The minimum contact area size required for obtaining representative properties, measured at the mortar scale, is determined. The viscoelastic parameters obtained from the indentation model are compared to those obtained using a representative volume element (RVE) for the asphalt mortar. In this way, the paper provides a new impulse for linking the mortar and asphalt scales in the multiscale modelling of asphalt mixtures. Feasibility of the proposed testing technique is further evaluated experimentally. Viscoelastic indentation tests are performed on asphalt mastics and mortar at two different sizes of contact areas. Experimental results indicate that indentation tests allow reliable characterisation of mortars relaxation modulus on both macro-scale as well as on individual component level.

Place, publisher, year, edition, pages
TAYLOR & FRANCIS LTD, 2019
Keywords
indentation testing, asphalt mortar, bitumen-filler mastics, multiscale, viscoelasticity, FEM
National Category
Civil Engineering
Identifiers
urn:nbn:se:kth:diva-255414 (URN)10.1080/14680629.2019.1628434 (DOI)000486993600019 ()2-s2.0-85068229189 (Scopus ID)
Note

QC 20190815

Available from: 2019-08-15 Created: 2019-08-15 Last updated: 2020-04-28Bibliographically approved
3. A New Viscoelastic Micromechanical Model for Bitumen-Filler Mastic
Open this publication in new window or tab >>A New Viscoelastic Micromechanical Model for Bitumen-Filler Mastic
2020 (English)In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 253Article in journal (Refereed) Published
Abstract [en]

A new micromechanical model for predicting viscoelastic properties of mastic is proposed and validated with experiments. The developed model is based on the finite element method and allows predicting the viscoelastic properties of mastic by means of the fundamental mechanical and geometrical properties of its constituents. The influence of modelling parameters on the model’s accuracy is evaluated and optimal parameter combinations are identified. It is shown that the proposed model can capture the measured viscoelastic behaviour of mastics for the range of loading, temperature and material parameters examined. Accordingly, it may be a useful tool for optimizing mastics material design meeting the target viscoelastic properties.

Keywords
Mastic, FEM Modelling, Micromechanics, Mineral Filler, Rheology
National Category
Civil Engineering Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-272738 (URN)2-s2.0-85083517186 (Scopus ID)
Note

QC 20200430

Available from: 2020-04-28 Created: 2020-04-28 Last updated: 2020-05-25Bibliographically approved

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