Hassan Fadil - Academia.edu (original) (raw)
Papers by Hassan Fadil
Road Materials and Pavement Design, Dec 14, 2021
Construction and Building Materials, Aug 1, 2020
h i g h l i g h t s A new finite element micromechanical modelling approach for mastics is propos... more h i g h l i g h t s A new finite element micromechanical modelling approach for mastics is proposed. The approach allows predicting the viscoelastic properties of mastic from its composition. Model predictions are validated with DSR measurements on four mastic materials. The measurements are performed in temperature interval from 0°to 10°C for a wide range of filler concentrations. The proposed model captures the measured viscoelastic behaviour of mastic for the full range of material parameters examined.
Materials and Structures, Apr 1, 2022
The indentation test is a promising technique for the viscoelastic characterisation of asphalt co... more The indentation test is a promising technique for the viscoelastic characterisation of asphalt concrete (AC). Indentation measurements are primarily influenced by the material properties in the direct vicinity of the indenter-specimen contact point. Accordingly, it may become a useful alternative for the characterisation of thin asphalt layers as well as for a quasi-non-destructive AC characterisation in the field. In this study, the spherical indentation test is used to measure the linear viscoelastic properties of AC mixtures extracted from a road test section. The measured complex moduli are compared to those obtained by the shear box test and are found to exhibit a linear correlation. The measurements are further analysed using the Gaussian mixture model to assign each indentation test to either aggregate-dominated or mastic-dominated response. The measurements attributed to mastic-dominated response are found to be more sensitive to the temperature and AC's binder properties as compared to the average measurements. Accordingly, the proposed test method may provide a promising tool to measure AC viscoelastic properties and monitor the changes in AC binder phase in a nondestructive manner. A finite element micromechanical model is used to identify a representative scale for the response measured in mastic-dominated tests as well as to quantify the effect of measured properties on the AC damage propensity.
Experimental Mechanics, Oct 10, 2017
In the present paper, a methodology for complete characterization of linear isotropic viscoelasti... more 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.
Construction and Building Materials, Oct 1, 2023
Asphalt mastics act as a binding phase in asphalt mixtures and their rheological properties stron... more 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.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.…
Road Materials and Pavement Design, Apr 13, 2021
The viscoelastic characterisation of asphalt mixtures using the indentation test
Construction and Building Materials
Materials and Structures
The present study aims at experimentally and numerically investigating the effect an encapsulated... more The present study aims at experimentally and numerically investigating the effect an encapsulated healing agent on the mechanical characteristics of a stone mastic asphalt (SMA). As a healing agent a thiol-containing urethane AR-polymer is used in this study. In order to gain a numerical insight into mechanical behavior of the capsules in SMA, a micromechanical finite element modeling is employed. The developed model allows capturing the stresses induced in the capsules at different load cases applied to the SMA on macro-scale. Particular attention is paid presently to the numerical evaluation of the local stress state that arises around capsules during compaction, operation, and also during crack initiation. SMA mixtures with various volumetric contents of healing capsules were manufactured and the capsules survival during mixture production was evaluated based on X-Ray Computed Tomography measurements. The effect of capsules on the self-healing properties of asphalt mixtures has f...
Road Materials and Pavement Design
Materials and Structures
The indentation test is a promising technique for the viscoelastic characterisation of asphalt co... more The indentation test is a promising technique for the viscoelastic characterisation of asphalt concrete (AC). Indentation measurements are primarily influenced by the material properties in the direct vicinity of the indenter-specimen contact point. Accordingly, it may become a useful alternative for the characterisation of thin asphalt layers as well as for a quasi-non-destructive AC characterisation in the field. In this study, the spherical indentation test is used to measure the linear viscoelastic properties of AC mixtures extracted from a road test section. The measured complex moduli are compared to those obtained by the shear box test and are found to exhibit a linear correlation. The measurements are further analysed using the Gaussian mixture model to assign each indentation test to either aggregate-dominated or mastic-dominated response. The measurements attributed to mastic-dominated response are found to be more sensitive to the temperature and AC’s binder properties as...
KTH Royal Institute of Technology, 2020
Asphalt mastics act as a binding phase in asphalt mixtures and their rheological properties stron... more 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.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.…
Road Materials and Pavement Design, 2021
The viscoelastic characterisation of asphalt mixtures using the indentation test
Construction and Building Materials, 2020
h i g h l i g h t s A new finite element micromechanical modelling approach for mastics is propos... more h i g h l i g h t s A new finite element micromechanical modelling approach for mastics is proposed. The approach allows predicting the viscoelastic properties of mastic from its composition. Model predictions are validated with DSR measurements on four mastic materials. The measurements are performed in temperature interval from 0°to 10°C for a wide range of filler concentrations. The proposed model captures the measured viscoelastic behaviour of mastic for the full range of material parameters examined.
Experimental Mechanics, 2017
In the present paper, a methodology for complete characterization of linear isotropic viscoelasti... more 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.
9 Reliable determination of material properties is a key component for modeling and 10 understand... more 9 Reliable determination of material properties is a key component for modeling and 10 understanding performance of asphalt pavements. This paper deals with the potential use of 11 instrumented indentation tests for viscoelastic characterization of asphalt mortar as a new 12 alternative to existing techniques. The main focus lies on the potential of indentation tests for 13 multi-scale measurement of shear relaxation modulus. A three-dimensional finite element model 14 of a rigid spherical indenter penetrating an asphalt mortar sample is developed and used to model 15 indentation tests performed at different material scales. The asphalt mortar is modeled as an 16 idealized fine aggregate composite with elastic spheres, suspended within a viscoelastic bitumen 17 mastic matrix. Based on the obtained numerical results the scale-dependency of the shear 18 relaxation modulus measured with the indentation test is investigated. The minimum indentation 19 radius required for obtaining repre...
Road Materials and Pavement Design
Reliable determination of material properties is a key component for modelling and performance pr... more 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.
Road Materials and Pavement Design, Dec 14, 2021
Construction and Building Materials, Aug 1, 2020
h i g h l i g h t s A new finite element micromechanical modelling approach for mastics is propos... more h i g h l i g h t s A new finite element micromechanical modelling approach for mastics is proposed. The approach allows predicting the viscoelastic properties of mastic from its composition. Model predictions are validated with DSR measurements on four mastic materials. The measurements are performed in temperature interval from 0°to 10°C for a wide range of filler concentrations. The proposed model captures the measured viscoelastic behaviour of mastic for the full range of material parameters examined.
Materials and Structures, Apr 1, 2022
The indentation test is a promising technique for the viscoelastic characterisation of asphalt co... more The indentation test is a promising technique for the viscoelastic characterisation of asphalt concrete (AC). Indentation measurements are primarily influenced by the material properties in the direct vicinity of the indenter-specimen contact point. Accordingly, it may become a useful alternative for the characterisation of thin asphalt layers as well as for a quasi-non-destructive AC characterisation in the field. In this study, the spherical indentation test is used to measure the linear viscoelastic properties of AC mixtures extracted from a road test section. The measured complex moduli are compared to those obtained by the shear box test and are found to exhibit a linear correlation. The measurements are further analysed using the Gaussian mixture model to assign each indentation test to either aggregate-dominated or mastic-dominated response. The measurements attributed to mastic-dominated response are found to be more sensitive to the temperature and AC's binder properties as compared to the average measurements. Accordingly, the proposed test method may provide a promising tool to measure AC viscoelastic properties and monitor the changes in AC binder phase in a nondestructive manner. A finite element micromechanical model is used to identify a representative scale for the response measured in mastic-dominated tests as well as to quantify the effect of measured properties on the AC damage propensity.
Experimental Mechanics, Oct 10, 2017
In the present paper, a methodology for complete characterization of linear isotropic viscoelasti... more 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.
Construction and Building Materials, Oct 1, 2023
Asphalt mastics act as a binding phase in asphalt mixtures and their rheological properties stron... more 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.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.…
Road Materials and Pavement Design, Apr 13, 2021
The viscoelastic characterisation of asphalt mixtures using the indentation test
Construction and Building Materials
Materials and Structures
The present study aims at experimentally and numerically investigating the effect an encapsulated... more The present study aims at experimentally and numerically investigating the effect an encapsulated healing agent on the mechanical characteristics of a stone mastic asphalt (SMA). As a healing agent a thiol-containing urethane AR-polymer is used in this study. In order to gain a numerical insight into mechanical behavior of the capsules in SMA, a micromechanical finite element modeling is employed. The developed model allows capturing the stresses induced in the capsules at different load cases applied to the SMA on macro-scale. Particular attention is paid presently to the numerical evaluation of the local stress state that arises around capsules during compaction, operation, and also during crack initiation. SMA mixtures with various volumetric contents of healing capsules were manufactured and the capsules survival during mixture production was evaluated based on X-Ray Computed Tomography measurements. The effect of capsules on the self-healing properties of asphalt mixtures has f...
Road Materials and Pavement Design
Materials and Structures
The indentation test is a promising technique for the viscoelastic characterisation of asphalt co... more The indentation test is a promising technique for the viscoelastic characterisation of asphalt concrete (AC). Indentation measurements are primarily influenced by the material properties in the direct vicinity of the indenter-specimen contact point. Accordingly, it may become a useful alternative for the characterisation of thin asphalt layers as well as for a quasi-non-destructive AC characterisation in the field. In this study, the spherical indentation test is used to measure the linear viscoelastic properties of AC mixtures extracted from a road test section. The measured complex moduli are compared to those obtained by the shear box test and are found to exhibit a linear correlation. The measurements are further analysed using the Gaussian mixture model to assign each indentation test to either aggregate-dominated or mastic-dominated response. The measurements attributed to mastic-dominated response are found to be more sensitive to the temperature and AC’s binder properties as...
KTH Royal Institute of Technology, 2020
Asphalt mastics act as a binding phase in asphalt mixtures and their rheological properties stron... more 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.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.…
Road Materials and Pavement Design, 2021
The viscoelastic characterisation of asphalt mixtures using the indentation test
Construction and Building Materials, 2020
h i g h l i g h t s A new finite element micromechanical modelling approach for mastics is propos... more h i g h l i g h t s A new finite element micromechanical modelling approach for mastics is proposed. The approach allows predicting the viscoelastic properties of mastic from its composition. Model predictions are validated with DSR measurements on four mastic materials. The measurements are performed in temperature interval from 0°to 10°C for a wide range of filler concentrations. The proposed model captures the measured viscoelastic behaviour of mastic for the full range of material parameters examined.
Experimental Mechanics, 2017
In the present paper, a methodology for complete characterization of linear isotropic viscoelasti... more 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.
9 Reliable determination of material properties is a key component for modeling and 10 understand... more 9 Reliable determination of material properties is a key component for modeling and 10 understanding performance of asphalt pavements. This paper deals with the potential use of 11 instrumented indentation tests for viscoelastic characterization of asphalt mortar as a new 12 alternative to existing techniques. The main focus lies on the potential of indentation tests for 13 multi-scale measurement of shear relaxation modulus. A three-dimensional finite element model 14 of a rigid spherical indenter penetrating an asphalt mortar sample is developed and used to model 15 indentation tests performed at different material scales. The asphalt mortar is modeled as an 16 idealized fine aggregate composite with elastic spheres, suspended within a viscoelastic bitumen 17 mastic matrix. Based on the obtained numerical results the scale-dependency of the shear 18 relaxation modulus measured with the indentation test is investigated. The minimum indentation 19 radius required for obtaining repre...
Road Materials and Pavement Design
Reliable determination of material properties is a key component for modelling and performance pr... more 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.