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  • 1.
    Ahmed, Abubeker
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Carlsson, Håkan
    Swedish National Road and Transport Research Institute, Infrastructure, Measurement technology and engineering workshop.
    Lundberg, Thomas
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Utvärdering av gummiasfalt: provväg E22 Mönsterås : etapp 12019Report (Other academic)
    Abstract [en]

    Laboratory and filed investigations have been carried out to evaluate the performance of rubber modified asphalt test road on E22 Mönsterås.

    The laboratory investigations indicated that there are no significant differences in stiffness and shear modulus between the reference and rubber modified mixtures. The rubber modified mixture however showed slightly lower phase angle compared to the reference mixture which indicate that the rubber modified mixture is more elastic. The rubber modified mixtures also showed lower modulus at lower temperatures and slightly higher modulus at higher temperature which are desired properties for resistance against low temperature cracking and permanent deformation respectively. The fatigue tests indicated that the rubber modified asphalt mixture has slightly better fatigue cracking performance. But the difference is not significant.

    The road surface profile measurements indicated no significant differences between the reference and asphalt rubber sections. It is however early to draw conclusions after one year of traffic therefore additional follow-up of the test sections is needed to draw a conclusion.

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  • 2.
    Ahmed, Abubeker
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Hellman, Fredrik
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Erlingsson, Sigurdur
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Full scale accelerated pavement tests to evaluate the performance of permeable and skeletal soil block pavement systems2016In: The Roles of Accelerated Pavement Testing in Pavement Sustainability: Engineering, Environment, and Economics, Springer International Publishing , 2016, p. 131-144Chapter in book (Other academic)
    Abstract [en]

    The increasing proportion of paved surface due to urbanization means that the conditions for urban trees and vegetation to survive have deteriorated. Factors such as air pollution, poor drainage, and the lack of usable soil for root growth contribute to the short life expectancy of urban trees. To meet this challenge, several permeable and "structural" or "skeletal soils" have been developed as alternatives to the typical compacted soil required to bear the weight of vehicular traffic in urban areas. The main objective of this study is to evaluate the resistance to permanent deformation of permeable and skeletal soil pavement structures based on full scale accelerated pavement tests (APT) using a heavy vehicle simulator (HVS). Interlocking paving stones of various types were used as permeable surface layer for the test structures. The results demonstrated that the permeable test structures exhibited higher permanent deformation than the corresponding impervious structures. The skeletal soil with bituminous base layer, however, produced performance comparable to the impervious reference test structures.

  • 3.
    Ahmed, Abubeker
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Rahman, Shafiqur
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Erlingsson, Sigurdur
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Iron sand as a frost protection layer: thickness design charts2022Report (Other academic)
    Abstract [en]

    Frost depths and frost heaving calculations were performed to prepare design charts and tables for the iron sand (järnsand) layer thickness design for roads typically used for residential area, parking lots and other low to medium traffic roads, and for ground insulation. 

    A segregation potential based frost design method was employed to generate the design charts and tables. The segregation potential method allows the prediction of both frost heaving and frost penetration depth of a pavement structure for a prescribed winter temperature profile or freezing index. Thus, the iron sand layer thickness design tables/charts for roads were prepared for different levels of maximum permitted heaving criteria of 50, 80, 100, and 120 mm. Whereas for ground insulation, a design chart/table was prepared to eliminate any frost action in the ground. In addition to the frost design calculations, two triaxial tests were conducted to evaluate the bearing capacity of the iron sand material. The limited test results indicated that, the bearing capacity of iron sand is similar to conventional sand both in terms of stiffness as well as permanent deformation behavior.

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  • 4.
    Ahmed, Abubeker W.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology. KTH.
    Mechanistic-Empirical Modelling of Flexible Pavement Performance: Verifications Using APT Measurements2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Mechanistic-Empirical  (M-E)  pavement  design  procedures  are  composed  of  a  reliable  response model to estimate the state of stress in the pavement and distress models in order to predict the different types of pavement distresses due to the prevailing traffic and environmental conditions. One of the main objectives of this study was to develop a response model based on multilayer elastic  theory   (MLET)  with  improved  computational  performance  by   optimizing  the   time consuming parts of the MLET processes. A comprehensive comparison of the developed program with  two  widely  used  programs  demonstrated  excellent  agreement  and  improved  computational performance.  Moreover,  the  program  was  extended  to  incorporate  the  viscoelastic  behaviour  of bituminous materials through elastic-viscoelastic correspondence principle. A procedure based on collocation of linear viscoelastic (LVE) solutions at selected key time durations was also proposed that improved the computational performance for LVE analysis of stationary and moving loads. A comparison  of  the  LVE  responses  with  measurements  from  accelerated  pavement  testing  (APT) revealed a good agreement. Furthermore the developed response model was employed to evaluate permanent deformation models  for  bound  and  unbound  granular  materials  (UGMs)  using  full  scale  APTs.  The  M-E Pavement  Design  Guide  (MEPDG)  model  for  UGMs  and  two  relatively  new  models  were evaluated  to  model  the  permanent  deformation  in  UGMs.  Moreover,  for  bound  materials,  the simplified  form  of  the  MEPDG  model  for  bituminous  bound  layers  was  also  evaluated.  The measured  and  predicted  permanent  deformations  were  in  general  in  good  agreement,  with  only small discrepancies between the models. Finally, as heavy traffic loading is one of the main factors affecting the performance of flexible pavement, three types of characterizations for heavy traffic axle load spectrum for M-E analysis and design of pavement structures were evaluated. The study recommended an improved approach that enhanced the accuracy and computational performance.

    List of papers
    1. Evaluation of permanent deformation models for unbound granular materials using accelerated pavement tests
    Open this publication in new window or tab >>Evaluation of permanent deformation models for unbound granular materials using accelerated pavement tests
    2013 (English)In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 14, no 1, p. 178-195Article in journal (Refereed) Published
    Abstract [en]

    Mechanistic-empirical (M-E) pavement design methods have become the focus of modern pavement design procedure. One of the main distresses that M-E design methods attempt to control is permanent deformation (rutting). The objective of this paper is to evaluate three M-E permanent deformation models for unbound granular materials, one from the US M-E pavement design guide and two other relatively new models. Two series of heavy vehicle simulator (HVS) tests with three different types of base material were used for this purpose. The permanent deformation, wheel loading, pavement temperature, and other material properties were continuously controlled during the HVS tests. Asphalt concrete layers were considered as linear elastic where stress-dependent behaviour of unbound materials was considered when computing responses for the M-E permanent deformation models with a nonlinear elastic response model. Traffic wandering was also accounted for in modelling the traffic by assuming it was normally distributed and a time-hardening approach was applied to add together the permanent deformation contributions from different stress levels. The measured and predicted permanent deformations are in general in good agreement with only small discrepancies between the models. Model parameters were also estimated for three different types of material.

    Place, publisher, year, edition, pages
    Taylor & Francis Group, 2013
    Keywords
    Rutting (wheel), Unbound base, Granular, Stress (in material)
    National Category
    Infrastructure Engineering
    Research subject
    Road: Highway design, Road: Pavement design; Road: Materials, Road: Aggregate and stone materials
    Identifiers
    urn:nbn:se:vti:diva-6941 (URN)10.1080/14680629.2012.755936 (DOI)
    Available from: 2014-07-17 Created: 2014-07-17 Last updated: 2022-10-21Bibliographically approved
    2. Modeling of flexible pavement structure behavior: Comparisons with Heavy Vehicle Simulator measurements
    Open this publication in new window or tab >>Modeling of flexible pavement structure behavior: Comparisons with Heavy Vehicle Simulator measurements
    2012 (English)In: Advances in Pavement Design Through Full-Scale Accelerated Pavement Testing / [ed] Jones, Harvey, Mateos & Al-Qadi, London: Taylor & Francis Group, 2012, p. 493-503Conference paper, Published paper (Refereed)
    Abstract [en]

     A response model to be employed in a mechanistic-empirical pavement performance predictionmodel based on multilayer elastic theory has been developed. An iterative approach using a method of successiveover-relaxation of a stress dependency model is used to account for the nonlinear behavior of unbound materials. Asphalt and subgrade materials are assumed to be linear elastic. The response model was verified against two series of Heavy Vehicle Simulator (HVS) response measurements made under a variety of wheel loadconfigurations and at different pavement temperatures. A comparison with Falling Weight Deflectometer (FWD)data was also carried out. The model was subsequently used to predict permanent deformation from the HVS testing using simple work hardening models. A time hardening approach has been adopted to combine permanentdeformation contributions from stress levels of different magnitude.The response model outputs and the predictedpermanent deformations were generally in good agreement with the measurements.

    Place, publisher, year, edition, pages
    London: Taylor & Francis Group, 2012
    Keywords
    Pavement, Simulation, Deflectograph, Model
    National Category
    Civil Engineering
    Research subject
    Road: Highway design, Road: Pavement design
    Identifiers
    urn:nbn:se:vti:diva-6942 (URN)10.1201/b13000-61 (DOI)ISBN 978-0-415-62138-0 (ISBN)
    Conference
    The 4th International Conference on Accelerated Pavement Testing
    Available from: 2014-07-17 Created: 2014-07-17 Last updated: 2022-10-21Bibliographically approved
    3. Fast layered elastic response program for the analysis of flexible pavement structures
    Open this publication in new window or tab >>Fast layered elastic response program for the analysis of flexible pavement structures
    2013 (English)In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 14, no 1, p. 196-210Article in journal (Refereed) Published
    Abstract [en]

    One of the key components in analysing pavement structural behaviour is the response model which is used to estimate the stresses, strains and displacements of the pavement structure subjected to the existing traffic, taking into account the material properties and prevailing environmental conditions. Multilayer elastic theory (MLET) is often preferred over other methods such as the finite element method, due to its computational performance for repeated applications. A new elastic response analysis program has been developed based on the Burmister MLET theory to calculate the response of flexible pavement structures. In the development of the program, the time-consuming part of MLET processes was optimised. To improve the convergence and accuracy of responses in the vicinity of the surface of the top layer, an approach based on Richardson's extrapolation was employed. Moreover, an iterative approach to model stress dependency of unbound granular materials was incorporated. A comprehensive comparison of the program with two frequently used programs demonstrated an excellent agreement and improved performance.

    Place, publisher, year, edition, pages
    Taylor & Francis Group, 2013
    Keywords
    Elasticity, Flexible pavement, Model (not math)
    National Category
    Civil Engineering
    Research subject
    Road: Highway design, Road: Surfacing
    Identifiers
    urn:nbn:se:vti:diva-6944 (URN)10.1080/14680629.2012.757558 (DOI)
    Available from: 2014-07-17 Created: 2014-07-17 Last updated: 2022-10-21Bibliographically approved
    4. Characterization of heavy traffic axle load spectra for mechanistic-empirical pavement design applications
    Open this publication in new window or tab >>Characterization of heavy traffic axle load spectra for mechanistic-empirical pavement design applications
    2015 (English)In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 16, no 6, p. 488-501Article in journal (Refereed) Published
    Abstract [en]

     Heavy traffic axle load spectrum (ALS) is  one of the key inputs for mechanistic-empirical analysis and design of pavement structures. Frequently, the entire ALS is aggregated into Equivalent Number of Single Axle Loads (ESAL) or assumed to have Constant Contact  Area  (CCA)  or  Constant  Contact  Pressure  (CCP).  These characterizations affect the accuracy and computational performance of the pavement analysis. The objective of this study was to evaluate these  characterizations  based  on  predicted  performances  to  rutting and fatigue cracking of several pavement structures subjected to ALS data collected from 12 Bridge-Weigh-In-Motion stations. The results indicated  that  for  layers  below  the  top  25  cm,  all  characterizations produced similar values of predicted rutting. However, for the top 25 cm, the methods differed in the predicted performances to rutting and fatigue cracking. Furthermore an improvement to the CCA approach was proposed that enhanced the accuracy while maintaining the same level of computational performance.

    Place, publisher, year, edition, pages
    Taylor & Francis Group, 2015
    Keywords
    Axle load, Heavy vehicle, Pavement design, Rutting, Cracking, Prediction, Accuracy
    National Category
    Infrastructure Engineering
    Research subject
    30 Road: Highway design, 32 Road: Pavement design
    Identifiers
    urn:nbn:se:vti:diva-6945 (URN)10.1080/10298436.2014.943131 (DOI)000354458200003 ()2-s2.0-84929283717 (Scopus ID)
    Available from: 2014-07-17 Created: 2014-07-17 Last updated: 2022-10-21Bibliographically approved
    5. Evaluation of a permanent deformation model for asphalt concrete mixtures using extra-large wheel-tracking and heavy vehicle simulator tests
    Open this publication in new window or tab >>Evaluation of a permanent deformation model for asphalt concrete mixtures using extra-large wheel-tracking and heavy vehicle simulator tests
    2015 (English)In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 16, no 1, p. 154-171Article in journal (Refereed) Published
    Abstract [en]

    This paper evaluates a mechanistic–empirical permanent strain model for asphalt concrete mixtures. The evaluation was carried out based on two different types of tests: an extra-large wheel-tracking (ELWT) test and a full-scale accelerated pavement test using a heavy vehicle simulator (HVS). Asphalt slabs from three different types of asphalt mixtures were prepared for the ELWT test and tested at several pavement temperatures and tyre inflation pressures. Lateral wandering was also incorporated.

    The measured permanent deformations in the asphalt slabs were thereafter modelled using the permanent strain model from the US Mechanistic-Empirical Pavement Design Guide and model parameters were estimated for the three types of mixes. For validation, data from an HVS tested pavement structure consisting of the same asphalt mixtures as those tested using the ELWT were used. A set of calibration factors for the three mixtures were therefore obtained between the two tests. In all cases, the calibration factors were within ±20% from unity. Differences in geometry, scale, wheel loading configuration as well as the speed of loading between the two test devices could be the possible reasons for the differences in observed calibration factors.

    Keywords
    Flexible pavement, Bituminous mixture, Mathematical model, Strain, Simulation, Loading
    National Category
    Infrastructure Engineering
    Research subject
    30 Road: Highway design, 32 Road: Pavement design
    Identifiers
    urn:nbn:se:vti:diva-9307 (URN)10.1080/14680629.2014.987311 (DOI)000349451300010 ()2-s2.0-84922800575 (Scopus ID)
    Available from: 2016-03-03 Created: 2016-03-02 Last updated: 2022-12-09Bibliographically approved
    6. Numerical validation of viscoelastic responses of a pavement structure in a full-scale accelerated pavement test
    Open this publication in new window or tab >>Numerical validation of viscoelastic responses of a pavement structure in a full-scale accelerated pavement test
    2015 (English)In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268XArticle in journal (Refereed) Published
    Abstract [en]

    This paper demonstrates the application of a generalised layered linear viscoelastic (LVE) analysis for estimating the structural response of flexible pavements. A comparison of the direct layered viscoelastic responses with approximate solutions based on the linear elastic (LE) and LVE collocation methods was also carried out. The different approaches were implemented by extending a layered elastic program with an improved computational performance. The LE and LVE collocation methods were further extended for analysis of pavements under moving loads.

    The methods were illustrated by analysing a pavement structure subjected to moving wheel loads of 30, 50, 60 and 80 kN using a Heavy Vehicle Simulator (HVS). The various responses (stresses and strains) in the pavement, at pavement temperatures of 0, 10 and 20°C, were measured using various types of sensors installed in the structure. It was shown that the approximated LVE solution based on the LE collocation method agreed very well with the measurements and is computationally the least expensive.

    Keywords
    Flexible pavement, Viscoelasticity, Unbound base, Loading, Mathematical model, Calculation
    National Category
    Infrastructure Engineering
    Research subject
    30 Road: Highway design, 32 Road: Pavement design
    Identifiers
    urn:nbn:se:vti:diva-9278 (URN)10.1080/10298436.2015.1039003 (DOI)2-s2.0-84929238620 (Scopus ID)
    Available from: 2016-03-07 Created: 2016-03-02 Last updated: 2022-12-09Bibliographically approved
  • 5.
    Ahmed, Abubeker W.
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Biligiri, Krishna Prapoorna
    Department of Civil Engineering Indian Institute of Technology Kharagpur .
    Hakim, Hassan
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    An Algorithm to Estimate Rational Values of Phase Angles and Moduli of Asphalt Mixtures2013In: International Journal of Pavement Research and Technology (IJPRT), ISSN 1997-1400, Vol. 6, no 6, p. 745-754Article in journal (Refereed)
    Abstract [en]

    The objective of this study was to develop and evaluate an algorithm based on Fast Fourier Transform (FFT) that can calculate rational values of phase angle (f) and moduli of the variants of asphalt mixtures for the data obtained from the different frequency sweep tests. f and moduli for ten different asphalt mixtures resulting in over 690 data points collected from both USA and Sweden were computed using FFT. Theoretical observations revealed that there were significant differences for f between FFT and other methods to the order of 10-50%; however, there was no difference in moduli estimates for any mix and was independent of the test. Precisely, the FFT method produced rational f for mixtures that deviate from conventional mixture properties. Furthermore, statistical comparisons corroborated the predicted f estimates indicative of significant differences between the analysis techniques; but, the moduli were unaffected by the analysis methods. The study successfully illustrated the FFT technique, a user-friendly analytical procedure that can obviate the errors in the rational estimation of the acutely sensitive viscoelastic parameters.

    Download full text (pdf)
    fulltext
  • 6.
    Ahmed, Abubeker W.
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Erlingsson, Sigurdur
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Characterization of heavy traffic axle load spectra for mechanistic-empirical pavement design applications2015In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 16, no 6, p. 488-501Article in journal (Refereed)
    Abstract [en]

     Heavy traffic axle load spectrum (ALS) is  one of the key inputs for mechanistic-empirical analysis and design of pavement structures. Frequently, the entire ALS is aggregated into Equivalent Number of Single Axle Loads (ESAL) or assumed to have Constant Contact  Area  (CCA)  or  Constant  Contact  Pressure  (CCP).  These characterizations affect the accuracy and computational performance of the pavement analysis. The objective of this study was to evaluate these  characterizations  based  on  predicted  performances  to  rutting and fatigue cracking of several pavement structures subjected to ALS data collected from 12 Bridge-Weigh-In-Motion stations. The results indicated  that  for  layers  below  the  top  25  cm,  all  characterizations produced similar values of predicted rutting. However, for the top 25 cm, the methods differed in the predicted performances to rutting and fatigue cracking. Furthermore an improvement to the CCA approach was proposed that enhanced the accuracy while maintaining the same level of computational performance.

  • 7.
    Ahmed, Abubeker W.
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Erlingsson, Sigurdur
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Evaluation of a permanent deformation model for asphalt concrete mixtures using extra-large wheel-tracking and heavy vehicle simulator tests2015In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 16, no 1, p. 154-171Article in journal (Refereed)
    Abstract [en]

    This paper evaluates a mechanistic–empirical permanent strain model for asphalt concrete mixtures. The evaluation was carried out based on two different types of tests: an extra-large wheel-tracking (ELWT) test and a full-scale accelerated pavement test using a heavy vehicle simulator (HVS). Asphalt slabs from three different types of asphalt mixtures were prepared for the ELWT test and tested at several pavement temperatures and tyre inflation pressures. Lateral wandering was also incorporated.

    The measured permanent deformations in the asphalt slabs were thereafter modelled using the permanent strain model from the US Mechanistic-Empirical Pavement Design Guide and model parameters were estimated for the three types of mixes. For validation, data from an HVS tested pavement structure consisting of the same asphalt mixtures as those tested using the ELWT were used. A set of calibration factors for the three mixtures were therefore obtained between the two tests. In all cases, the calibration factors were within ±20% from unity. Differences in geometry, scale, wheel loading configuration as well as the speed of loading between the two test devices could be the possible reasons for the differences in observed calibration factors.

  • 8.
    Ahmed, Abubeker W.
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Erlingsson, Sigurdur
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Evaluation of permanent deformation models for unbound granular materials using accelerated pavement tests2013In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 14, no 1, p. 178-195Article in journal (Refereed)
    Abstract [en]

    Mechanistic-empirical (M-E) pavement design methods have become the focus of modern pavement design procedure. One of the main distresses that M-E design methods attempt to control is permanent deformation (rutting). The objective of this paper is to evaluate three M-E permanent deformation models for unbound granular materials, one from the US M-E pavement design guide and two other relatively new models. Two series of heavy vehicle simulator (HVS) tests with three different types of base material were used for this purpose. The permanent deformation, wheel loading, pavement temperature, and other material properties were continuously controlled during the HVS tests. Asphalt concrete layers were considered as linear elastic where stress-dependent behaviour of unbound materials was considered when computing responses for the M-E permanent deformation models with a nonlinear elastic response model. Traffic wandering was also accounted for in modelling the traffic by assuming it was normally distributed and a time-hardening approach was applied to add together the permanent deformation contributions from different stress levels. The measured and predicted permanent deformations are in general in good agreement with only small discrepancies between the models. Model parameters were also estimated for three different types of material.

  • 9.
    Ahmed, Abubeker W
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Erlingsson, Sigurdur
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Mechanistic modelling of HVS flexible pavement structure2012In: EPAM 2012: Malmö, Sweden, 5–7 September: 4th European pavement and asset management conference, Linköping: Statens väg- och transportforskningsinstitut, 2012, , p. 13Conference paper (Other (popular science, discussion, etc.))
    Abstract [en]

    A response model to be employed in a mechanistic-empirical pavement performance prediction model based on multilayer elastic theory has been developed. An iterative approach using a method of successive over-relaxation of stress dependency model is used to account for the nonlinear behaviour of unbound materials. Asphalt and subgrade materials are assumed as linear elastic. The response model is verified using heavy vehicle simulator (HVS) response measurements made under variety of wheel load configurations and at different pavement temperatures. The permanent deformation behaviours of the HVS structure is also modelled using mechanistic empirical approach and by employing permanent deformation prediction models. A time hardening approach has been applied to combine permanent deformation contributions from stress levels of different magnitude. The response model outputs and the predicted permanent deformations are in general in good agreement with the measurements.

  • 10.
    Ahmed, Abubeker W.
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Erlingsson, Sigurdur
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Modeling of flexible pavement structure behavior: Comparisons with Heavy Vehicle Simulator measurements2012In: Advances in Pavement Design Through Full-Scale Accelerated Pavement Testing / [ed] Jones, Harvey, Mateos & Al-Qadi, London: Taylor & Francis Group, 2012, p. 493-503Conference paper (Refereed)
    Abstract [en]

     A response model to be employed in a mechanistic-empirical pavement performance predictionmodel based on multilayer elastic theory has been developed. An iterative approach using a method of successiveover-relaxation of a stress dependency model is used to account for the nonlinear behavior of unbound materials. Asphalt and subgrade materials are assumed to be linear elastic. The response model was verified against two series of Heavy Vehicle Simulator (HVS) response measurements made under a variety of wheel loadconfigurations and at different pavement temperatures. A comparison with Falling Weight Deflectometer (FWD)data was also carried out. The model was subsequently used to predict permanent deformation from the HVS testing using simple work hardening models. A time hardening approach has been adopted to combine permanentdeformation contributions from stress levels of different magnitude.The response model outputs and the predictedpermanent deformations were generally in good agreement with the measurements.

  • 11.
    Ahmed, Abubeker W.
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Erlingsson, Sigurdur
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Numerical validation of viscoelastic responses of a pavement structure in a full-scale accelerated pavement test2015In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268XArticle in journal (Refereed)
    Abstract [en]

    This paper demonstrates the application of a generalised layered linear viscoelastic (LVE) analysis for estimating the structural response of flexible pavements. A comparison of the direct layered viscoelastic responses with approximate solutions based on the linear elastic (LE) and LVE collocation methods was also carried out. The different approaches were implemented by extending a layered elastic program with an improved computational performance. The LE and LVE collocation methods were further extended for analysis of pavements under moving loads.

    The methods were illustrated by analysing a pavement structure subjected to moving wheel loads of 30, 50, 60 and 80 kN using a Heavy Vehicle Simulator (HVS). The various responses (stresses and strains) in the pavement, at pavement temperatures of 0, 10 and 20°C, were measured using various types of sensors installed in the structure. It was shown that the approximated LVE solution based on the LE collocation method agreed very well with the measurements and is computationally the least expensive.

  • 12.
    Ahmed, Abubeker W
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Erlingsson, Sigurdur
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology. University of Iceland.
    Viscoelastic Response Modelling of a Pavement under Moving Load2016In: Transportation Research Procedia, 2016, Vol. 14, p. 748-757Conference paper (Refereed)
    Abstract [en]

    This paper demonstrates the application of a generalized layered linear viscoelastic (LVE) analysis for estimating flexible pavements' structural response. The procedure is based on the Multi-Layered Elastic Theory (MLET) and the elastic-viscoelastic correspondence principle using a numerical inverse Laplace transform. A comparison of the direct layered viscoelastic responses with approximate solutions based on the elastic collocation method was also carried out. Furthermore, it is proposed to use the collocation method using LVE solutions at selected time durations in order to improve the accuracy of the elastic collocation method. The LVE collocation method was further extended for analysis of moving loads. The method was illustrated by analysing a pavement structure subjected to moving wheel loads of 30, 50, 60 and 80 kN using a Heavy Vehicle Simulator (HVS). The various responses (stresses and strains) in the pavement, at different pavement temperatures, were measured using various types of sensors installed in the structure. The LVE calculations agreed very well with the measurements.

  • 13.
    Ahmed, Abubeker W
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Gudmarsson, Anders
    PEAB.
    Waldemarson, Andreas
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Utvärdering av styvhetsförändring i asfaltmassor med returasfalt, rejuvenatorer och polymerer2020Report (Other academic)
    Abstract [en]

    Using reclaimed asphalt (RA) in new pavements reduces the environmental impact of the new pavement. As the proportion of RA in newly paved asphalt increases, it is important to maintain or improve the quality of the mixture so as not to create an increased maintenance requirement. Rejuvenators and mixing with softer bitumen are used to compensate for the harder aged binder in RA. Rejuvenators reduce the stiffness and brittleness of the bitumen, which improves resistance to cracking. However, the risk of initial deformation associated with the use rejuvenators or mixing with softer binder in RA mixes has not been evaluated.

    The objective of this project was to evaluate the stiffness changes with time of laboratory manufactured asphalt concrete mixtures having rejuvenators or softer bitumen with high percentage of RA. In this project, indirect tensile tests, modal analysis, and shear tests were conducted on five different asphalt concrete mixtures with RA, rejuvenators, and polymers.

    The results showed that there are no significant differences in stiffness change with time between the different mixes was observed within 7 to 21 days after production. However, there is stiffness change with time in the long term. The stiffness modulus and shear testing showed that mixing with soft bitumen, or using rejuvenators result in small differences in stiffness and shear modulus values, respectively. Polymer modified mixes have shown lower shear modulus at low temperatures and higher shear modulus at high temperatures compared to mixes with conventional bituminous binders which increases the resistance to cracking at low temperatures and the resistance to deformation at higher temperature, respectively. Storage and conditioning of the specimens and all measurements were carried out in a laboratory environment; thus, the results represent only the stiffness change that occurs without external influence from climate and traffic.

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  • 14.
    Ahmed, Abubeker W
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Larsson, Magnus
    WSP, Sweden.
    Said, Safwat
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Utilizing GPR and FWD for Pavement Structural Assessment and Moisture Detection2024Report (Other academic)
    Abstract [en]

    Asphalt pavement performance is affected by the presence of water(moisture). Increased moisture within the road structure can result in substantial cost increase for the for society. Research have showed that significant portion of the road sections need early maintenance measures regardless of traffic volume due to moisture-related damages. Monitoring moisture conditions, preferably using a non-destructive continuous method, offers important information into the decision-making and selecting appropriate maintenance intervention. Furthermore, understanding moisture conditions is critical for accurately interpreting automatic road condition measurements, especially during the spring (thawing) when the roads exhibit the lowest load bearing capacity due to increased levels of moisture.

    This study employed a multi-receiver ground penetrating radar (GPR) and a falling weight deflectometer (FWD) devices to assess moisture levels and structural condition of field and indoor full-scale test roads. The groundwater level of the test road was varied by introducing water to the system. The results revealed an apparent correlation between the FWD and the average GPR velocity measurements. The GPR measurements provided a relative water content of the test roads. Further exploration of other GPR parameters, such as frequency, magnitude, and amplitude of the GPR signal is recommended.

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  • 15.
    Ahmed, Abubeker W
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Rahman, Mohammad Shafiqur
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Erlingsson, Sigurdur
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Impact of longer and heavier vehicles on the performance of asphalt pavements: A laboratory study2018In: Bearing Capacity of Roads, Railways and Airfields - Proceedings of the 10th International Conference on the Bearing Capacity of Roads, Railways and Airfields, BCRRA 2017, CRC Press/Balkema , 2018, p. 483-490Conference paper (Refereed)
    Abstract [en]

    Historically, Longer and Heavier Vehicles (LHVs) have been permitted to operate in Sweden. Since 1996 and as of the beginning of 2015, the maximum gross vehicle weight of 60 tons and a length of up to 25.25 m have been permitted. The Swedish Transport Administration has decided to further increase the maximum gross vehicle weight to 74 tons and studies are undergoing to evaluate the impact of the proposed LHVs on existing transport infrastructure. To this end, repeated load triaxial tests and indirect tensile fatigue tests were conducted on selected conventional asphalt mixtures to investigate and quantify the impact of single, tandem and tridem axle configurations on permanent deformation and fatigue performances of conventional asphalt pavements. In addition, fatigue tests for selected LHV scenarios were conducted. This paper presents the results of the laboratory tests and simulations conducted. The test results have clearly demonstrated the impact of the different axle configurations on the rutting and fatigue performances of the mixture. Furthermore, such results can explain the significance of axle configuration on modelling the rutting and fatigue performances of asphalt pavements.

  • 16.
    Ahmed, Abubeker W
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Rahman, Mohammad Shafiqur
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Erlingsson, Sigurdur
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Impact of tire types and configurations on responses of a thin pavement structure2018In: Advances in Materials and Pavement Performance Prediction: Proceedings of the International AM3P Conference, 2018, London: CRC Press , 2018, p. 271-274Conference paper (Refereed)
    Abstract [en]

    The objective of this study was to assess the impact of tire and tire configurations on the responses of a thin asphalt pavement structure by means of full-scale tests using a Heavy Vehicle Simulator (HVS). A total of six different types of tires, four single and two dual tire configurations, were investigated. The structure was instrumented to measure tensile strains at the bottom of the asphalt layer and vertical stresses and strains in the unbound base, subbase and subgrade layers. The results indicated that, in general, single tire configurations produced higher tensile strain at the bottom of the asphalt layer and higher vertical stresses and strains in unbound base, subbase and subgrade layers.

  • 17.
    Ahmed, Abubeker W
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Said, Safwat
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Lu, Xiaohu
    Nynäs AB.
    Carlsson, Håkan
    Swedish National Road and Transport Research Institute, Infrastructure, Measurement technology and engineering workshop.
    Pavement performance follow-up and evaluation of polymer-modified test sections2019In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 20, no 12, p. 1474-1487Article in journal (Refereed)
    Abstract [en]

    Between 2003 and 2006, a test road consisting of several conventional and polymer-modified structures was built on a motorway. Different combinations of styrene–butadiene–styrene (SBS) and ethyl vinyl acetate (EVA) polymer-modified binders were used. The test structures have been in service since then and have been monitored for over 9 years. The resistance of the different types of asphalt concrete mixes to rutting and cracking was measured and predicted. The impact of ageing on the mixes was also evaluated. Although all the sections are in good condition after 9 years of traffic, the predicted differences between the test sections based on the PEDRO (Permanent Deformation of asphalt concrete layers for Roads) approach and laboratory evaluations are noticeable. Lateral wander and transverse profile measurements indicated that studded winter tyre wear contributed to most of the rutting compared to permanent deformation due to heavy traffic. The unmodified mixes exhibited considerable ageing and the SBS-modified mixes were least affected by ageing. Furthermore, the SBS-modified base mix produced significantly better fatigue resistance than the conventional base mix. However, further investigations of the relationships between bitumen and mix properties and further follow-ups of the test sections are recommended to validate the findings.

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  • 18.
    Dinegdae, Yared
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Ahmed, Abubeker W
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Erlingsson, Sigurdur
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology. University of Iceland, Iceland.
    Toward a Comprehensive Pavement Reliability Analysis Approach2023In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, Vol. 2677, no 7, p. 680-692Article in journal (Refereed)
    Abstract [en]

    Reliability has been incorporated in pavement design tools to account for input variability influence on predicted performance. As they are not based on a probabilistic method of uncertainty propagation, the reliability analysis methodologies that are currently implemented in pavement performance tools lack rigor and robustness. This paper investigates the potential of three reliability analysis methodologies for pavement application: the Pavement ME reliability analysis methodology, Monte Carlo simulation (MCS), and the first-order reliability method (FORM). The MCS and FORM involve a response surface method for the generation of a second-order surrogate model. The investigation was performed using inputs and performance data from accelerated pavement testing structures. Inputs that were identified as significant were characterized as random variables and their associated variability was established using measured structural and material properties. Pavement performance with respect to rutting was predicted using the ERAPave performance prediction tool, while MCS was used to generate the actual variability of the distress. The reliability analysis results have shown that a comprehensive reliability analysis methodology is required that effectively captures input variabilities and the error associated with surrogate models.

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  • 19.
    Dinegdae, Yared
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Ahmed, Abubeker W
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Rahman, Mohammad Shafiqur
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Erlingsson, Sigurdur
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology. University of Iceland, Iceland.
    Evaluation of ERAPave PP permanent deformation models using APT2023In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402Article in journal (Refereed)
    Abstract [en]

    Permanent deformation is one of the failure modes considered in the analysis and design of flexible pavements. ERAPave performance prediction (PP) which is a mechanistic empirical (ME) pavement design tool utilises two distinct models for the prediction of permanent deformation in the bound and unbound granular layers including subgrade. This paper aims to calibrate these models using pavement response and performance data from accelerated pavement testing (APT) structures. Material properties such as layer modulus were established through an optimisation that involves both falling weight deflectometer (FWD) and pavement response measurements. Based on the predicted performance results, a separate set of calibration was performed for permanent deformation development in moist and wet moisture conditions. The calibrated models have resulted in predictions that are in good agreement with observed performances. Furthermore, the model parameters successfully captured the initial densification behaviour and the associated sensitivity with axle load level.

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  • 20.
    Erlingsson, Sigurdur
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Ahmed, Abubeker
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    The Svappavaara road test sections: field coring and laboratory tests2015Report (Other academic)
    Abstract [en]

    This report describes laboratory testing of specimens taken from four new instrumented test road sections that have been built on E45 close to the Svappavaara municipality in Norrbotten County in Northern Sweden. The structures are located about 100 km north of the Arctic Circle in a climate that is characterized by long cold winters and short mild summers. The four test sections were built in a conventional manner. Each structure is about 200–250-metre-long with a central 100-metre-long part defined as the actual test section. All structures are in total 60 centimetres in thickness resting on top of a 70-centimetre-thick old existing road. The bitumen bound part of all the four structures consists of four layers; a thin surface course layer, two binder layers and a road base layer. All structures have the same wearing course, TSK 16 with a standard 160/220 penetration grade bitumen. The main difference between the structures lies in the binder as well as the two road base layers. As a part of the monitoring programme drilled asphalt specimens were taken in 2013 from the road structure and tested at VTI's material testing laboratory in Linköping. Furthermore, samples were taken from the unbound base course and tested. This report presents the test results for asphalt bound layers as well as for the unbound base course. For the bound layers the testing procedure included volumetric properties, stiffness modulus and fatigue tests for the different types of conventional and polymer modified asphalt mixtures. The tests were conducted in accordance with the Swedish or the equivalent European standards. For the unbound base course fundamental properties were estimated as well as stiffness and permanent deformation properties for different moisture contents.

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  • 21.
    Erlingsson, Sigurdur
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Ahmed, Abubeker W.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Fast layered elastic response program for the analysis of flexible pavement structures2013In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 14, no 1, p. 196-210Article in journal (Refereed)
    Abstract [en]

    One of the key components in analysing pavement structural behaviour is the response model which is used to estimate the stresses, strains and displacements of the pavement structure subjected to the existing traffic, taking into account the material properties and prevailing environmental conditions. Multilayer elastic theory (MLET) is often preferred over other methods such as the finite element method, due to its computational performance for repeated applications. A new elastic response analysis program has been developed based on the Burmister MLET theory to calculate the response of flexible pavement structures. In the development of the program, the time-consuming part of MLET processes was optimised. To improve the convergence and accuracy of responses in the vicinity of the surface of the top layer, an approach based on Richardson's extrapolation was employed. Moreover, an iterative approach to model stress dependency of unbound granular materials was incorporated. A comprehensive comparison of the program with two frequently used programs demonstrated an excellent agreement and improved performance.

  • 22.
    Erlingsson, Sigurdur
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology. University of Iceland.
    Ahmed, Abubeker W
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Mechanistic rutting modelling of a LTPP road structure2019In: Pavement and Asset Management: Proceedings of the World Conference on Pavement and Asset Management, WCPAM 2017, CRC Press/Balkema , 2019, p. 241-249Conference paper (Refereed)
    Abstract [en]

    A new Mechanistic-Empirical (M-E) approach is under development to predict the structural degradation of road structures as a function of time. The aim is that the method will become one of the backbones in a new pavement asset management system. The calculation scheme is based two main steps; i) a response calculation step for the different traffic loads applied taking into account the ambient climate and ii) a performance prediction step where pavement degradation is predicted in time steps and thereafter accumulated over the entire design period of the pavement structure. The paper describes the approach briefly and is thereafter demonstrated by a calculation of the degradation of an arterial road in Southern Sweden and compared with measurements from the Swedish Long Term Pavement Performance (LTPP) database. The arterial road had reached the critical 15 mm rut after 18 years in operation. The analysis shows that the rutting development can be simulated adequately although the calculations show slower rate than the measurements towards the end of the simulated period.

  • 23.
    Gudmarsson, Anders
    et al.
    Peab Asfalt, Sweden.
    Ahmed, Abubeker W
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Monitoring Stiffness Evolution of Asphalt Concrete Through Modal Analysis2022In: ISBM 2020: Proceedings of the RILEM International Symposium on Bituminous Materials, Springer Science and Business Media B.V. , 2022, p. 1375-1381Conference paper (Refereed)
    Abstract [en]

    The stiffness of asphalt concrete, which is used for thickness design of pavements, is known to increase with time due to age hardening of the binder. Therefore, aging models to account for the stiffness evolution over time are in some applications considered with the aim to improve pavement life predictions. Modal analysis is an economic test method with a verified precision for characterizing the complex moduli of asphalt concrete. In this paper, the stiffness evolution of asphalt concrete has been monitored through modal analysis. The simplicity of the modal test set-up facilitates accurate repeated testing under identical conditions. Therefore, modal testing was performed repeatedly at the temperatures of 20 and −20 °C over a period up to around 300 days. The testing was performed on samples in a controlled laboratory environment and does not intend to provide a measure of the age hardening of real pavements. The aim of this paper is to characterize the stiffness evolution of asphalt mixes with modified and unmodified binders in a controlled environment. Cyclic indirect tensile tests were performed in addition to modal analysis to characterize the stiffness evolution under different loading configurations. Results from the modal analysis clearly showed that the rate of the stiffness evolution is initially slower for the modified binder in comparison to the unmodified binder.

  • 24.
    Gudmarsson, Anders
    et al.
    Peab Asfalt AB.
    Carret, Jean -Claude
    University of Lyon .
    Pouget, Simon
    EIFFAGE Infrastructures.
    Nilsson, Richard
    SKANSKA.
    Ahmed, Abubeker W
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Di Benedetto, Hervé
    University of Lyon.
    Sauzéat, Cédric
    University of Lyon.
    Precision of modal analysis to characterise the complex modulus of asphalt concrete2019In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402Article in journal (Refereed)
    Abstract [en]

    Modal analysis is an economic and efficient test method to characterise the complex modulus of asphalt concrete. In this paper, the precision of modal analysis was evaluated by performing testing at several laboratories on two cylindrical asphalt concrete specimens. In addition, the complex moduli characterised by modal analysis were compared to cyclic tension-compression testing. The results showed that the coefficient of variation was less than 3% at loading frequencies above 10 Hz for the complex modulus determined through modal analysis. The comparison of the complex modulus determined from modal analysis and tension-compression testing resulted in a coefficient of variation values not more than 9% for loading frequencies ranging from 0.1 to 10 9 Hz.

  • 25.
    Jelagin, Denis
    et al.
    KTH.
    Ahmed, Abubeker W
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Lu, Xiaohu
    Nynäs AB.
    Said, Safwat
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Asphalt layer rutting performance prediction tools2018Report (Other academic)
    Abstract [en]

    Flexible pavement rutting due to permanent deformation accumulation in asphalt layers is one of the most common modes of road failures. In addition to creating high maintenance costs, rutting is a major concern for traffic safety, as the rut development increases the risk of hydroplaning and introduce difficulties in vehicle steering. In this context, accurate methodologies for pavement rutting performance prediction are crucial for decision support in pavement design and rehabilitation. In particular, better rutting performance models are needed to evaluate, new asphalt materials as well as to evaluate the impact of different vehicle types on roads’ service life.

    The main goal of this report is to present a summary of the existing asphalt rutting performance prediction tools. The present review is limited to available and/or frequently referred to tests and models with an established link to field rutting performance. Accordingly, models focusing solely on permanent deformation on the material level are beyond the framework of the present study.

    Road structure and its materials, heavy vehicle parameters and climate affecting rutting accumulation in the field are identified. Their significance has been evaluated based on the experimental and numerical findings reported in the literature. Several rutting performance prediction models recently proposed in the literature are summarized along with the material characterization tests used in the models. The reviewed models’ capability to quantify the influence of various structural, material and traffic parameters on the pavement’s rutting performance is examined.

    It is concluded that implementation of rutting performance models incorporating experimentally measured viscoelastic and permanent deformation properties of asphalt mixtures is a promising way to improve the accuracy of pavement performance predictions. In particular since they allow the effect of novel materials, e.g. polymer-modified, on the pavement’s rutting performance to be quantified.

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  • 26. Lindelöf, Peter
    et al.
    Said, Safwat
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Ahmed, Abubeker W
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Influences of bus traffic loading on asphalt concrete rutting2022In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268XArticle in journal (Refereed)
    Abstract [en]

    Permanent deformation is the primary failure mode for the asphalt concrete (AC) pavement in urban environment. It is mainly caused by a combination of heavy traffic load, low vehicle speed and channelised traffic. A rut prediction model would therefore be a valuable tool for planning maintenance scheduling and selecting an appropriate asphalt material. This study uses the PEDRO (Permanent deformation in asphalt concrete layers for roads) model to evaluate the rutting performance of flexible pavements in dedicated bus lanes and intersections in urban areas. For this purpose, three road sections along a bus lane in Malmö, Sweden, were selected. To achieve this, AC cores from the road sections were tested using a Shear Box Tester to characterise the asphalt mixtures. Traffic data such as axle load, tyre configuration, speed, and lateral wander distribution of vehicles, and climate data were measured for the selected sections. Field measurements were carried out to assess the structural conditions of the pavements and to measure transverse profiles. This study introduced a procedure for the evaluation and local calibration of the PEDRO rutting model. The results revealed that the prediction of the transverse profiles are generally in good agreement with the rut measurements.

  • 27.
    Lindelöf, Peter
    et al.
    Lunds Universitet.
    Said, Safwat
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Ahmed, Abubeker W
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Poisson’s Ratio of Asphalt Concrete Mixes Using Indirect Tensile Test2019In: Journal of Testing and Evaluation, ISSN 0090-3973, E-ISSN 1945-7553, Vol. 47, no 1Article in journal (Refereed)
    Abstract [en]

    Increased interest in mechanistic evaluation of flexible pavement structures has brought a demand for accurate and practical methods, models, or both to estimate the mechanical properties of asphalt concrete mixtures. One of these properties is the Poisson’s ratio (ν) of asphalt concrete mixtures, which is often assumed to have a constant value of 0.35 in asphalt concrete evaluations. However, investigations have reported that mixture type, air void content, and temperature produce considerable variation in measured ν-values that could have a significant effect on evaluations of asphalt concrete mixes. The objective of this study was to evaluate the effect of air voids, binder type, and testing conditions on the measured ν-values. Indirect tensile (IDT) tests were conducted to measure ν-values. The study indicated that the Poisson’s ratio of the asphalt concrete mixes, on average, attained a maximum value at a particular level of air void content. Furthermore, when comparing the Poisson’s ratio values in relation to the dynamic modulus, calculated using the Mechanistic Empirical Pavement Design Guide (MEPDG) equation, higher ν-values were attained. This demonstrates the importance of measuring the Poisson’s ratio of a mix type.

  • 28.
    Rahman, Mohammad Shafiqur
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Erlingsson, Sigurdur
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology. University of Iceland, Iceland.
    Ahmed, Abubeker W
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Modelling the permanent deformation of unbound granular materials in pavements2022In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402Article in journal (Refereed)
    Abstract [en]

    An existing permanent deformation (PD) model for the unbound granular materials (UGMs) in pavements, developed based on multistage (MS) repeated load triaxial (RLT) tests, was modified to better suit to field conditions and software applications. The model was calibrated for a few UGMs with a series of moisture contents (w) using MS (to include the stress-history effect) RLT tests and was validated by predicting the PD under different sets of stress levels and w's. Generally, it exhibited improved predictions over the Mechanistic-Empirical Pavement Design Guide (MEPDG) model. The model was further applied for field conditions and was implemented in a pavement design software entitled ERAPave PP, using data from accelerated testing of three structures employing a heavy vehicle simulator (HVS). Based on additional MS RLT tests, a guideline for the ranges of the material parameters for different types of UGMs was presented.

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  • 29.
    Rahman, Mohammad Shafiqur
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Erlingsson, Sigurdur
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Ahmed, Abubeker W
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Dinegdae, Yared H.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    A model for the permanent deformation behavior of the unbound layers of pavements2021In: Proceedings Eleventh International Conference on the Bearing Capacity of Roads, Railways and Airfields: Volume 1 / [ed] Inge Hoff, Helge Mork & Rabbira Saba, London: CRC Press, 2021, Vol. 1, p. 277-287Conference paper (Other academic)
    Abstract [en]

    This article presents a model for the permanent deformation (PD) behavior of unbound granular materials (UGMs) used in the base and subbase layers of pavement struc- tures. The model was developed based on multistage (MS) repeated load triaxial (RLT) test- ing. This is essentially a modified version of a previously developed model to better suit to field conditions in a simple and effective manner. The model was calibrated for eight com- monly used UGMs using MSRLT tests with a range of moisture contents. For validation, the calibrated models were used to predict the PD behavior of three of the UGMs in MSRLT tests with stress levels and moisture contents different from those used during the calibrations. This model showed better quality of fit when compared with another widely used PD model. The model was further tested successfully for field conditions by capturing the PD behavior of an instrumented pavement test section in a controlled environment using a heavy vehicle simu- lator (HVS) based accelerated pavement testing (APT). Inputs for calibrating the model were based on the readings from the instrumentations. The parameters of the model were adjusted to match the measured data with the predictions. Based on these results for various design conditions, some ranges of values of the material parameters of the model were suggested.

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  • 30.
    Rahman, Mohammad Shafiqur
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Simonsen, Erik
    Cementa AB.
    Hellman, F.
    Ahmed, Abubeker W
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Erlingsson, Sigurdur
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Structural performance evaluation of block pavements using heavy vehicle simulator2020In: Lecture Notes in Civil Engineering, Springer , 2020, Vol. 96, p. 280-288Conference paper (Refereed)
    Abstract [en]

    Block pavements (BPs) can be of different types depending on applications and provide certain advantages in many instances. Among BPs, permeable concrete block pavements (PCBPs) play a vital role in sustainable drainage system and help the growth of trees and vegetations in urban environment. With the expansion of the usage of BPs from parking lots to heavier trafficked areas and owing to changing climatic conditions, it is necessary to develop guidelines for their designs and constructions. With this objective, ten different types of BPs were investigated in an accelerated pavement testing facility using a heavy vehicle simulator (HVS). The surface rutting developed during the load applications were measured. The impact of moisture was also investigated by raising the ground water table during the tests. By comparing the rutting performances of the BPs to a reference BP structure, the layer thicknesses of these BPs were adjusted using a pavement design software to attain the same rutting performance as the reference structure. Based on these analyses, design tables for BPs for Swedish conditions were developed. In this paper, the results from the HVS tests and the methodology used for the development of the design tables are summarized.

  • 31.
    Rahman, Shafiqur
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Waldemarson, Andreas
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Ahmed, Abubeker
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Evaluation of conditioning methods for the determination of water sensitivity of asphalt concrete mixtures: comparison of MIST, SS-EN 12697-12:2018 (Method A) and TDOK 2017:06502022Report (Other academic)
    Abstract [en]

    Water or moisture in different physical states is a major factor that contributes to various forms of damages in asphalt concrete (AC) pavements. For pavement design and maintenance, it is essential to evaluate the AC mixtures with respect to water/ moisture damage susceptibility. In Sweden, this is currently done according to the Swedish standard (TDOK 2017:0650) or alternatively can be done according to the European standard (SS-EN 12697-12). However, these methods are time consuming, and they do not simulate the pumping action of water due to passing wheels. On the other hand, the Moisture Induced Sensitivity Test (MIST) is intended to be a quick method that applies cyclic pore pressure to simulate the repeated pumping action of water. However, it is a relatively new approach that has not yet been properly studied for Swedish conditions and yet to be standardized in Europe. 

    In this project, the MIST, TDOK and the EN methods were evaluated using five different AC mixes. Results showed that the MIST with 12,000 cycles and the TDOK method have comparable and the strongest effect on the stiffness properties. MIST with 3,500 and 7,000 cycles and the EN method showed identical and relatively weak impact of water. MIST also indicated the changes of the indirect tensile strengths of the specimens. However, compared to the TDOK or EN methods, the changes in the indirect tensile strengths due to MIST conditioning were smaller. Overall, MIST was concluded to be a quicker, more convenient and a more realistic alternative. Comparing the various mixes with respect to moisture sensitivity, binder content and air voids showed great influences. The specimens with cut surfaces were less affected by moisture conditioning. The addition of amine additives significantly improved the resistance to moisture damage of the mixes. Generally, the results of this study formed the basis for further development of the EN and TDOK method as well as standardizing the MIST conditioning method in Europe.

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  • 32.
    Said, Safwat
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Ahmed, Abubeker W
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Prediction of heavy vehicle impact on rut development using pedro model2018In: Bearing Capacity of Roads, Railways and Airfields - Proceedings of the 10th International Conference on the Bearing Capacity of Roads, Railways and Airfields, BCRRA 2017, CRC Press/Balkema , 2018, p. 1359-1366Conference paper (Refereed)
    Abstract [en]

    Permanent deformation or flow rutting in bituminous layers is a common distress mode in flexible pavements that is exhibited as an excessive deformation of bituminous material in the wheel paths. Rutting gradually increases with repeated loading of heavy vehicles. To predict surface rutting, it is therefore essential to include the influence of heavy vehicle parameters such as the number of passages of wheel loads, axle load configuration (single or dual wheel), tire type, inflation pressure, vehicle speed and lateral wandering of the traffic in addition to variation in mixture properties at ambient temperatures over elapsed time. The linear viscoelastic permanent deformation model for a bituminous layer of roads, PEDRO, has been adopted in this work to analyse the vertical strain distribution in a flexible pavement and prediction of rutting under various combination of heavy vehicle parameters. The effects of heavy vehicles with different axle load configurations are evaluated with support of field measurements over a 14-year period.

  • 33.
    Said, Safwat
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Ahmed, Abubeker W
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Jelagin, Denis
    KTH.
    Lu, Xiaohu
    Nynas AB.
    Gudmarsson, Anders
    PEAB Asfalt.
    Nilsson, Roger
    Skanska Sverige AB.
    Oscarsson, Erik
    Trafikverket.
    Jarlsson, Heléne
    Volvo Technology.
    Prediction of rutting in asphalt concrete pavements: the PEDRO model2020Report (Other academic)
    Abstract [en]

    Flexible pavement rutting due to permanent deformation accumulation in asphalt layers is one of the most common modes of road failures. In addition to high maintenance costs, rutting is a major concern for traffic safety, as the rut growth increases the risk for hydroplaning and difficulties in vehicle steering. In this context, accurate methodologies for pavement rutting performance prediction are crucial for decision support in pavement design and rehabilitation. More rational rutting performance models are needed to enable the implementation of new and more sustainable and environmentally friendly asphalt materials as well as to evaluate the impact of high capacity traffic (HCT) vehicle types on bituminous layers.

    The main goal of this work is to implement and disseminate an asphalt rutting performance prediction tool called PEDRO (PErmanent Deformation of asphalt concrete layers for ROads). It focuses solely on the permanent deformation of asphalt concrete materials in the pavement structure. The PEDRO tool is a viscoelastic model for the calculation of permanent vertical strain under moving wheel loads over a viscoelastic half-space. The analysis is performed for the entire rutting zone and the permanent deformation of each layer or sub-layer, depending on its location in the pavement structure, is then integrated over the whole asphalt concrete depth.

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  • 34.
    Said, Safwat
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Carlsson, Håkan
    Swedish National Road and Transport Research Institute, Infrastructure, Measurement technology and engineering workshop.
    Ahmed, Abubeker
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology. VTI.
    Uppföljning av provväg E6 med polymermodifierade bundna lager: Uddevalla2021Report (Other academic)
    Abstract [en]

    The test road Geddeknippel–Kalsås was built in 2003–2006 as a part of the E6 motorway north of Uddevalla in both south and north directions. Test sections were constructed with polymer-modified bitumen (PMB) consisting of several variants of SBS (styrene-butadiene-styrene) and EVA (Ethylene-vinyl acetate). The test sections have been planned by the Swedish Transport Administration in collaboration with industry. The purpose is to clarify the benefit of using the PMB in asphalt mixtures in asphalt concrete layers of flexible pavements. 

    Long-term-pavement-performance was carried out through laboratory tests of samples and follow-up measurements. Evaluation of the pavement’s sections and prognoses of deterioration development at the test sections has been carried out with various models and test methods. The results showed that the asphalt concretes with and without PMB aged over time, however, to varying degrees. Hardening of asphalt concrete due to aging affects the development of pavement conditions and this must be considered for correct assessment of degradation of the sections. It was found that the PMBs used in this work can significantly affect the function of asphalt concretes. The choice of a PMB must be planned considering the desired functional characteristics and the asphalt concrete layer position in a road structure. Different PMB variants may be needed for different purposes. For example, different PMBs may be needed against rutting alternative fatigue cracking and sometimes the conventional asphalt concrete may be most optimal considering pavement life and from a socioeconomic aspect. 

    Rutting model PEDRO has been found to be a practical tool for clarifying the impact of the most important parameters on rut growth in bitumen-bound layers. It describes the proportion of rut depth from each asphalt layer and in respect of the layer’s functional properties and position in the road structure for an optimal choice of asphalt materials. The Swedish Transport Administration's investment in counting traffic volume through WIM (Weight-in-motion) measurements is superior to the current method based on estimation of the traffic volume from AADT (Average Annual daily traffic) in prediction of in-situ life. However, so far there are very limited WIM measurements.

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  • 35.
    Said, Safwat F
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Ahmed, Abubeker W
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Rheological characterization of asphalt concrete using shear box2023Report (Other academic)
    Abstract [en]

    Performance-orientated characterization of asphalt concrete materials is indispensable for analytic mix and pavement design. This report presents a test method for determining the shear modulus, phase angle and viscosity of bituminous mixes by the shear box test. The test is performed on laboratory compacted or cored bituminous mixes using a sinusoidal shear loading at different temperatures and frequencies. The procedure is used to characterize bituminous mixtures with respect to shear modulus, phase angle and viscosity. The obtained data can be used to estimate the bituminous layer’s structural behaviour in the pavement such as the development of ruts in the asphalt concrete layers.

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  • 36.
    Said, Safwat
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Lundberg, Thomas
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Rahman, Shafiqur
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Carlsson, Håkan
    Swedish National Road and Transport Research Institute, Infrastructure, Measurement technology and engineering workshop.
    McGarvey, Terence
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Ahmed, Abubeker
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Enocksson, Carl-Gösta
    Trafikverket.
    Utförandets inverkan på hållbarhet för beläggningslager2019Report (Other academic)
    Abstract [en]

    Non-destructive testing in quantifying the asphalt pavement layers homogeneity can be used for the quality assurance in paving contracts. This paper summarizes the findings from a field study on segregation in bituminous pavement mixes that relates pavement layer surface texture to the homogeneity of the paved bituminous layer by distinguishing mix segregated area. The mean profile depth (MPD) values of paved layer were measured. Based on these values three locations on the road were identified having low, intermediate and high MPD values. Thereafter, cored samples were tested for stiffness modulus before and after moisture conditioning by performing the moisture induced sensitivity test (MIST). Results clearly showed that the samples from the locations with high MPD values were mostly affected by the moisture conditioning for which the stiffness moduli were significantly reduced. The samples with high MPD values had the highest air voids as well. Thus, this study demonstrated that construction quality described by segregation in the paved asphalt mix has a significant impact on the moisture sensitive performance of pavements. A limited number of falling weight deflectometer (FWD) measurements were performed at positions with different degree of separation in the road base layer. There was a tendency for the effect of separation in the road base layer on FWD even though there was a variation in data. The strong correlation between the MPD values and change in stiffness modulus also suggests that the measurements of the MPD values can be a reliable and non-destructive method for evaluating the construction quality of a pavement and in developing the quality assurance criteria based on pavement performance that can be used in paving contracts.

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  • 37.
    Saliko, Denis
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology. KTH, Sweden.
    Ahmed, Abubeker W
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Erlingsson, Sigurdur
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology. University of Iceland, Iceland.
    Development and validation of a pavement temperature profile prediction model in a mechanistic-empirical design framework2023In: Transportation Geotechnics, ISSN 2214-3912, Vol. 40, article id 100976Article in journal (Refereed)
    Abstract [en]

    An accurate temperature prediction tool is an important part of any mechanistic-empirical (M-E) pavement design and performance prediction method. In this paper, a one-dimensional finite control volume (FCV) model is introduced that predicts the temperature within a pavement structure as a function of time and depth. The main input data required for the model are continuous time series of air temperature for conductive heat transfer, solar radiation for radiative heat transfer, and wind speed for convective heat transfer. The heat balance equation for each control volume of the FCV model is solved using an implicit scheme. To validate the numerical model, comparisons were made to measured temperature data from four test sections in Sweden located in regions with different climatic conditions. A good agreement was obtained between the calculated and measured temperature values within the asphalt layer, and temperature in the granular layers with the values of the coefficient of determination R2 ranging from 0.866 to 0.979. The model is therefore suitable to be implemented as a pavement temperature prediction tool in M-E design.

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  • 38.
    Sulejmani, Pajtim
    et al.
    Lund University.
    Said, Safwat
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Agardh, Sven
    Lund University.
    Ahmed, Abubeker W
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Impact of temperature and moisture on the tensile strain of asphalt concrete layers2021In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 22, no 13, p. 1711-1719Article in journal (Refereed)
    Abstract [en]

    Moisture in unbound layers and temperature in asphalt layers affect the structural response of pavements, such as the tensile strain at the bottom of asphalt concrete layers. Previous studies have proposed relationships for estimating tensile strain at the bottom of an asphalt layer from Falling Weight Deflectometer (FWD) surface deflection measurements. These relationships have been developed based on theoretical calculations of strains and surface deflections. The main objective of this study was to evaluate these relationships using measured FWD deflections and tensile strains at the bottom of asphalt concrete layers. Three instrumented test structures were considered in the study. FWD and strain measurements were conducted at varying groundwater levels in the subgrade and temperatures in the asphalt concrete layers. The results revealed that the relationships have poor agreement with measured strains. A new relationship is proposed that incorporates the volumetric water content in the subgrade and the temperature in the asphalt layers in addition to the surface FWD deflections. © 2020, © 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.

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  • 39. Sulejmani, Pajtim
    et al.
    Said, Safwat F.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Agardh, Sven
    Ahmed, Abubeker W
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Moisture Sensitivity of Asphalt Mixtures using Cycling Pore Pressure Conditioning2019In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052Article in journal (Refereed)
    Abstract [en]

    One of the major causes of premature failure in asphalt pavements is moisture damage. Asphalt mixtures designed without considering climate impacts may suffer from durability problems caused by movement of water inside the asphalt mixture. Rolling traffic over wet pavement builds up pore pressure in the mixture, which will consequently accelerate deterioration. The objective of the study was to assess the moisture damage to asphalt concrete mixtures by means of complex modulus testing of dry and moisture-conditioned asphalt specimens with various mixture compositions. The asphalt mixtures were conditioned with the Moisture Induced Sensitivity Tester (MIST), which aims to replicate pore pressure in field conditions. The results showed a decline in stiffness modulus and a reduction in elastic properties after MIST conditioning. In addition, the results indicated that binder content and air void content had a significant influence on the reduction in stiffness. To capture the relationship between air void content, binder content, and the reduction in stiffness, a relationship was developed and validated with measurements on cores extracted in the field.

  • 40.
    Viman, Leif
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Ahmed, Abubeker W
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Said, Safwat
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Lind, Lotta
    Evaluation of Slag as aggregates in Asphalt Mixtures2016In: Proceedings of 6th Eurasphalt & Eurobitume Congress, Czech Technical University in Prague , 2016Conference paper (Refereed)
    Abstract [en]

    During the last decade, the Swedish Transport Administration together with contractors, Steel industry in Sweden and the Swedish National Road and Transport Research Institute have built test road sections with Steel slag in various locations in Sweden.  Steel slag has well-known good adhesion, durability, wear resistance and noise reducing properties.  This project pointed out the importance for steel slag producers to produce a slag quality that fulfils the requirements as road material, where also particle emission is an important issue. There are over 10 producers of steel slag in Sweden. There are several goals for using steel slag in asphalt mixes; mainly longer technical lifetime caused by good wear resistance against studded tyres, good stability performance in binder and base course, and good durability performance, the latter being especially important in porous asphalt, where it also potentially gives some noise-reducing effects. In addition, the environmental aspects in terms of particle emission, were an important issue for this project.  So far, test sections show good performance according to road surface measurements.  Laboratory test according to European standards for aggregate and several road simulator test for wear resistance and particle emission have been performed during the last five years by means of the unique road simulator at VTI. An important part of the project is to increase the knowledge for the steel slag producers to develop a material that fulfils the requirements for road material in as many aspects as possible, both technical and environmental issues. The results are so far promising, and expectations are met.

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  • 41.
    Waldemarson, Andreas
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Ahmed, Abubeker W
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Validering av ålderssamband för asfaltbeläggningar2018Report (Other academic)
    Abstract [en]

    Asphalt pavements age due to climatic impact and oxidation. Aging affects the physical and chemical properties of the adhesive and results in an increase of stiffness and reduced sensitivity to deformation. As a result, asphalt pavement usually become harder, stiffer and brittle thus more sensitive to cracking over time.

    The Swedish Transport Administration specification document contains calculation formulas (aging models) which take the changes in mechanical properties over time into account. These formulas were derived based on asphalt mixtures with conventional binders. To investigate whether these formulas are valid for asphalt mixtures with modified bitumen, a study was conducted using laboratory manufactured samples of mix type ABb 16 with three different binders from Nynas, namely, 70/100, Nypol 67 and Nypol 73.

    The samples were drilled from compacted asphalt slabs and cyclic compression creep and indirect tensile stiffness modules tests were carried out at a predefined time schedule. The drilled samples werestored at room temperature whereas the slabs were stored in a cold storehouse. Before testing, the densities of the constituent material were determined and theoretical air void content in each sample were calculated.

    The main purpose of the study was to validate the existing aging models for cyclic compression creep test and stiffness modulus tests using the collected test data. The collected data from the tests were analyzed using non-linear regression. The results indicated that time coefficient (exponent) for both test methods have lower absolute value in this study than stated in the specifications. The coefficients are different for penetration and polymer modified bitumen.

    There may be several reasons why the models in this study differ from the results of the previous investigations. The earlier relationships were derived based on analysis of samples aged in the field while the models in this study are based on analysis of samples aging in a more controlled laboratory environment. Another possible reason for the higher time coefficients (exponents) from the previousinvestigations could be that manufacturing temperatures for asphalt mixtures were generally significantly higher at that time.

    To establish a broader basis to assesses the impact of aging on asphalt mixture mechanical properties, it is recommended to investigate several types of polymer bitumen. A more frequent field follow-up ofnewly paved pavement sections should be carried out.

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  • 42.
    Zhu, Jiqing
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Ahmed, Abubeker
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Dinegdae, Yared
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology. VTI.
    Bitumen properties and the shear resistance of asphalt mixtures: towards a tool for bitumen selection2021Report (Other academic)
    Abstract [en]

    The shear resistance of asphalt mixtures is a crucial material property to ensure the pavement quality and minimize shear-related distresses. For a high shear resistance, proper protocols to select suitable raw materials for asphalt mixtures, mainly bitumen and mineral aggregates, are of great importance. The study presented in this report focuses on the selection of bitumen for asphalt mixtures. 

    Towards a tool for bitumen selection, this study aims to understand the relationship between asphalt mixture shear properties and bitumen. The research objective is to identify the correlation between them. Following this direction, this report presents an experimental investigation on the dynamic shear properties of asphalt mixtures and their relationships with the bitumen properties. The influence of binder content is also considered. Six bituminous binders, two of which were polymer-modified, were used to prepare asphalt mixtures in laboratory. The binders were tested with various methods, while their asphalt mixtures were characterized by the dynamic shear test. With the test results, the correlation between them was analysed. It is indicated that the iso-modulus temperatures of bitumen after short-term ageing by dynamic shear rheometer testing at 10 rad/s have very strong correlations with the asphalt mixture viscosity at the maximum phase angle. This was valid for both the studied neat (unmodified) bitumen and polymer-modified bitumen (PMB), although the number of studied PMB samples was limited in this study.

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  • 43.
    Zhu, Jiqing
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Ahmed, Abubeker W
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Dinegdae, Yared
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Waldemarson, Andreas
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Investigation on Ageing Behaviour of Bio-Extended Bituminous Binders and Asphalt Mixtures for Sustainable Road Infrastructure2024In: Transport Research Arena (TRA), Dublin, Ireland, 15 - 18 April, 2024, 2024Conference paper (Other academic)
    Abstract [en]

    This paper investigates the use of a plant-based bio-oil in bituminous binders as a partial replacement of petroleum-based bitumen for asphalt mixtures. Its effects on the ageing behaviour of bituminous binders and asphalt mixtures are studied. A total of six bituminous binders and their asphalt mixtures were prepared and analysed in laboratory, including three different binder formulations with varying percentages of bio-oil and their respective reference binders. Both the bituminous binders and asphalt mixtures were subjected to ageing protocols in laboratory. Softening point test, rheological and dynamic mechanical analyses were conducted to evaluate the changes in properties of the materials before and after ageing. The results indicate that the mechanical properties of aged binders and mixtures show very similar relationships as between the fresh materials, but the relationships after ageing are at changed levels due to the laboratory conditioning. This supports further studies to verify their functional performance in asphalt pavements.

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  • 44.
    Zhu, Jiqing
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Ahmed, Abubeker W
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Dinegdae, Yared
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Xiaohu, Lu
    Nynas AB, Sweden.
    Witkiewicz, Patryk
    Skanska Sverige AB, Sweden.
    Gardner, Eric
    Skanska Sverige AB, Sweden.
    Olsson, Kenneth
    Skanska Industrial Solutions AB, Sweden.
    Nilsson, Roger
    Skanska Sverige AB, Sweden.
    Durability assessment of bio-extended bituminous binders by rheological characterisation after long-term ageing2024In: 8th E&E (Eurasphalt & Eurobitume) Congress, Budapest, Hungary, 19-12 June, 2024, 2024Conference paper (Other academic)
    Abstract [en]

    The pursuit of sustainable road infrastructure is prompting extensive research into the utilization of bio-extended bituminous binders. This paper investigates the durability of bio-extended bituminous binders (both unmodified and polymer-modified) containing a plant-based bio-oil, aiming to assess their long-term performance. The research employed laboratory-scale tests and advanced rheological techniques to evaluate viscoelastic properties of the binders after long-term ageing. Accelerated ageing protocols were used to simulate prolonged exposure to environmental factors, including the Rolling Thin Film Oven Test (RTFOT) and Pressure Ageing Vessel (PAV) test. Dynamic Shear Rheometer (DSR) tests measured the shear modulus and phase angle of the binders under various conditions while Bending Beam Rheometer (BBR) tests measured the flexural creep stiffness at different low temperatures. Various performance indicators and specification parameters were analysed for the investigated binders regarding their resistance to both fatigue cracking at intermediate temperatures and thermal cracking at low temperatures.

    The results indicate that the bio-extended binders passed all the analysed criteria after RTFOT+PAV ageing. Using the investigated bio-oil in bituminous binders had largely a positive effect on the ΔTc and did not affect the standard performance low-temperature grade significantly. The bio-extended binders followed the same relationships between several durability-related performance indicators as the reference binders did. Certain slight negative effects could be noticed at low temperatures when the bio-oil content was high, but a further verification on the asphalt mixture scale will be necessary to assess if these effects are significant enough to impact the asphalt mixture performance in practical applications.

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  • 45.
    Zhu, Jiqing
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Ahmed, Abubeker W
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Lu, Xiaohu
    Nynas AB, Sweden.
    Said, Safwat
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Influence of Binder Properties on Dynamic Shear Response of Asphalt Mixture2022In: Proceedings of the RILEM International Symposium on Bituminous Materials. ISBM 2020, Springer Science and Business Media B.V. , 2022, Vol. 27, p. 1071-1078Conference paper (Refereed)
    Abstract [en]

    For predicting the shear-related rutting potential of asphalt pavement, it is important to understand the shear response of asphalt mixture and find the link between the mixture response and component material properties. Using controlled aggregate gradation, this paper investigates the influence of bituminous binder on the response of asphalt mixture under dynamic shear loading. Four asphalt mixtures, with two different grades of bitumen, were analysed by a simple shear test apparatus with dynamic loading. The binders, both original and after short-term aging, were characterised using a dynamic shear rheometer. The modulus and phase angle of both the asphalt mixture and bitumen samples were measured. Master curves were constructed. The results revealed that the asphalt mixture phase angle maximum, where a rutting performance indicator can be obtained, appears in a relatively narrow range of shear modulus. This range corresponds to a certain level of bitumen complex shear modulus (G*) and phase angle. By temperature sweep, a temperature value can be interpolated at the specified bitumen G* level. This temperature provides a possibility to predict the frequency of phase angle maximum for a given asphalt mixture type. It is noted that the asphalt mixture phase angle maximum corresponds to a relatively high bitumen modulus level compared to other high-temperature criteria. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.

  • 46.
    Zhu, Jiqing
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Ahmed, Abubeker W
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Said, Safwat
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Dinegdae, Yared H.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Lu, Xiaohu
    Nynas AB, Sweden.
    Experimental analysis and predictive modelling of linear viscoelastic response of asphalt mixture under dynamic shear loading2022In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 328, article id 127095Article in journal (Refereed)
    Abstract [en]

    The use of predictive models can facilitate the inclusion of shear parameters in asphalt mixture evaluation and design processes. Unlike more extensively studied tension–compression models, the currently existing shear model, the Hirsch model, has unrealistic constants, particularly for the prediction of phase angle. Aiming at an improved predictive model in shear, this study employs a simple shear apparatus to experimentally analyse the linear viscoelastic properties of asphalt mixtures for road paving. Master curves were constructed and compared between different asphalt mixtures. Additionally, the test results were also analysed in the Black space and the Cole-Cole space. The dynamic shear response of asphalt mixtures was thereafter modelled on the basis of the Hirsch model. As the original model for phase angle prediction was found to be unrealistic, a particular focus in this study was put on identifying realistic empirical relationships for predicting the phase angle of asphalt mixtures in shear. More reliable shear test results of asphalt mixtures were used to calibrate the model, and extra test data were utilized to validate the calibrated model. It is indicated that the predictive model after calibration could deliver results of greatly improved accuracy, especially at the high-frequency and low-frequency ends. The analysis and modelling also leads to realistic empirical relationships for predicting the phase angle of asphalt mixtures in shear. The experimental verification confirms the good prediction accuracy of the calibrated model and proposed empirical relationships. © 2022 The Authors

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