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  • 1.
    de Frias Lopez, Ricardo
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Ekblad, Jonas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Highway Engineering Laboratory.
    Silfwerbrand, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    A Numerical Study on the Permanent Deformation of Gap-Graded Granular Mixtures2016In: Proceedings of the Third International Conference on Railway Technology: Research, Development and Maintenance / [ed] J. Pombo, Stirlingshire, UK: Civil-Comp Press , 2016Conference paper (Refereed)
    Abstract [en]

    Permanent deformation accumulation of unbound granular layers under traffic plays a critical role in the performance and need for maintenance of pavements and railway structures. In this paper, the discrete element method is used to study the permanent strain behaviour of binary mixtures of elastic spheres, as an idealization of gap-graded mixtures, under triaxial monotonic loading. The effects of stress level and soil fabric structure, based on a recently proposed classification system founded on micromechanical considerations, are assessed by subjecting mixtures with varying fines contents to different stress levels. Additionally, mixtures are loaded to static failure to study the dependency of the permanent strains on the closeness of the applied stress to failure stress, in accordance with existing empirical models. Numerical results are also compared with the experimentally determined behaviour of granular materials. The findings indicate that numerical mixtures are able to reproduce some of the most significant features observed in laboratory tests on granular materials, further encouraging the use of numerical simulations to enhance the understanding of granular media behaviour. Additionally, a good correlation between fabric structure and performance is obtained, giving additional support to the use of the studied fabric classification system for performance characterization.

  • 2.
    de Frias Lopez, Ricardo
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Ekblad, Jonas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Highway Engineering Laboratory.
    Silfwerbrand, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Resilient properties of binary granular mixtures: A numerical investigatio2016In: Computers and geotechnics, ISSN 0266-352X, E-ISSN 1873-7633, Vol. 76, p. 222-233Article in journal (Refereed)
    Abstract [en]

    The effect of stress level on the resilient modulus for binary mixtures of elastic spheres under triaxial loading is investigated using the discrete element method. The secant modulus during the first cycle of unloading is used as an estimate of the modulus after several load cycles due to computational time restrains. Later in the paper, its adequacy as an accurate and efficient estimator is shown. Numerical results are statistically compared with existing relations characterizing the stress dependency of the resilient modulus for real granular materials. It is concluded that the modulus prediction is significantly improved considering the effect of the deviator stress in addition to the confinement stress, obtaining a good correlation between the modulus and the confinement to deviator stress ratio for the numerical mixtures. The stress dependency of a recently proposed soil fabric classification system, based on force transmission considerations at particulate level, is also studied and its correlation with performance investigated. It is found that the relative load-bearing role of coarse and fine components is governed by the deviator to confinement stress ratio. However, the implemented fabric classification is fairly insensitive to changes in this ratio. Regarding resilient performance, interactive fabrics show the stiffest response whereas underfilled fabrics should be avoided due to a potential for instability.

  • 3.
    Edvardsson, Karin
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Highway and Railway Engineering (closed 20110301).
    Ekblad, Jonas
    NCC Roads AB.
    Magnusson, Rolf
    Dalarna Högskolan.
    Methods for Quantification of Lignosulphonate and Chloride in Gravel Wearing Courses2010In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 11, no 1, p. 171-185Article in journal (Refereed)
    Abstract [en]

    Due to oxidation, breakdown, and leaching, dust suppressants will be lost from the gravel road surface. Methods for residual dust suppressant concentration supervision are a valuable tool for estimating life-length and optimal application rates, and, hence, efficiency of different products. The objective of this study was to identify methods for quantitative analyses of lignosulphonate and chloride, develop and adapt the methods for application on a gravel matrix, and validate the methods using samples collected in-situ. Results strongly suggest that the reliability and repeatability of the developed methods (23% for lignosulphonate and 30% for chloride, respectively) are acceptable for determination of relative variations in residual concentrations of dust suppressed gravel wearing courses.

  • 4.
    Ekblad, Jonas
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Fibers inverkan på egenskaper hos asfaltbetong - en laboratorieundersökning1994Report (Other academic)
  • 5.
    Ekblad, Jonas
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Fibers inverkan på egenskaper hos asfaltbetong - en laboratorieundersökning1994Report (Other academic)
  • 6.
    Ekblad, Jonas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Influence of Water on Coarse Granular Road Material Properties2007Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Even though the practical experience of using coarse unbound granular materials is extensive, detailed knowledge on the mechanical and hydraulic behavior is to a large extent lacking. Regarding influence of water on mechanical properties, this is even more pronounced. The main objective of this work was to investigate the influence of water on behavior and properties of coarse granular materials. The study comprises measurements of resilient properties, soil-water characteristic curve and influence of water content on dielectric properties measured by the use of time domain reflectometry (TDR).

    The work described herein comprised two test series in terms of materials: firstly, a series where the grading was changed and secondly, a series where the influence of increased contents of free mica was studied. To measure resilient response, triaxial testing, using sample size of 500 mm diameter and 1000 mm height, was performed mainly using constant confining pressures. Tests were performed at incrementally varying water contents up to almost full saturation. Dielectric response and matric suction of compacted specimens were measured in a steel box at varying water content.

    Results from the first series indicated that the influence of water content on resilient properties depends on the material grading. The coarsest grading, containing least fines, experienced only a small reduction when brought close to saturation. Specimens with an increased amount of fines and more even distribution responded with a substantial loss of resilient modulus upon increased water content. It also appeared as water content increased, the specimens became more dilative. From the second series, generally, resilient modulus decreased with increased mica content and furthermore, elevated water contents caused reduction in stiffness. However, in relative terms, the reduction in resilient modulus caused by water decreased with increased mica content. The soil-water characteristic curves are influenced by grading coefficient and mica content; retentive capacity increases with decreased grading coefficient and increases with increased amount of mica. Volumetric water content as a function of apparent relative permittivity was fitted using a third-degree polynomial. Although, determined relationships deviated from Topp's (1980) relationship.

    Detailed information on the work is given in five enclosed papers.

  • 7.
    Ekblad, Jonas
    KTH, Superseded Departments, Civil and Architectural Engineering.
    Influence of water on resilient properties of coarse granular materials2004Licentiate thesis, monograph (Other scientific)
  • 8.
    Ekblad, Jonas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Statistical evaluation of resilient models for characterizing coarse granular materials2008In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 41, no 3, p. 509-525Article in journal (Refereed)
    Abstract [en]

    Consistent material modeling is a prerequisite for a mechanistic approach to pavement design. The scope of this investigation was to statistically evaluate the efficiency of various resilient models commonly encountered in highway engineering. These models were categorized as describing either resilient modulus or shear and volumetric strains. Triaxial tests using constant and cyclic confining pressure were performed on coarse granular materials of various gradings (maximum particle size 90 mm). Two statistical methods, the extra sum of squares F-test and the Akaike information criterion, were used for model comparison. Concerning resilient modulus, the Uzan model provided, in general, a statistically significant improvement compared to the k-theta model. However, this improvement is lost if a constant Poisson ratio is used to predict shear and volumetric strains. In case of the shear-volumetric approach, no single model was most likely to be the best model for all gradings studied.

  • 9.
    Ekblad, Jonas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Edwards, Ylva
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Precision of LFV method 2-98: Effect of de-icing fluid on the surface tensile strength of asphalt concrete for airfields-Adhesion test2005Report (Other academic)
  • 10.
    Ekblad, Jonas
    et al.
    KTH, Superseded Departments, Infrastructure and Planning.
    Hellers, B.
    Creep of prestressed sulphur concrete1996In: Proceedings of the 7th International Conference on Durability of Building Materials and Components, 7DBMC, Stockholm, 1996Conference paper (Refereed)
  • 11.
    Ekblad, Jonas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Civil and Architectural Engineering Laboratory.
    Isacsson, U
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Water in coarse granular materials: Resilient and retentive properties2008In: ADVANCES IN TRANSPORTATION GEOTECHNICS / [ed] Ellis, E Yu, HS McDowell, G Dawson, A Thom, N, CRC PRESS-TAYLOR & FRANCIS GROUP , 2008, p. 117-+Conference paper (Refereed)
    Abstract [en]

    Granular material is, perhaps the most common construction material used in civil engineering, being an important constituent in road constructions, railways, embankments, foundations, buildings etc. This paper presents results from triaxial testing, at various water contents using constant confining pressure, of two different continuously graded granular materials with maximum particle size 90 mm and 63 mm, respectively. Furthermore, water retention properties of the unbound materials are presented and examples of water distributions in a common construction are shown. From the results presented, it can be concluded that increased water contents cause a reduction in resilient modulus and an increase in strain ratio. The distribution of water content in the vertical direction is highly nonlinear and the degree of saturation in the unbound layers of a road construction depends to a large degree on the level of the water table.

  • 12.
    Ekblad, Jonas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Influence of mica content on time domain reflectometry and soil-water characteristic curve of coarse granular materials2008In: ASTM geotechnical testing journal, ISSN 0149-6115, E-ISSN 1945-7545, Vol. 31, no 4, p. 321-333Article in journal (Refereed)
    Abstract [en]

    Elevated fractions of free mica particles in unbound granular materials, used in road constructions, are believed to reduce bearing capacity and influence the hydraulic behavior of the road structure. The objective of this investigation was to study the influence of mica content on the soil water characteristic curve and the dielectric response measured by time domain reflectometry, for coarse granular (maximum particle size 63 mm) materials. Increased fraction of mica was achieved by partly replacing the base crushed rock material smaller than 4 mm, by pure muscovite mica of similar grading, thereby keeping the overall particle size distribution unchanged. Acquired results indicated that, given equal matric suction, the water retention capacity increased with increased amount of mica. Concerning the time domain reflectometry measurements, no influence of mica content could be detected. Determined water contents required adjustment because of the nonlinear distribution of water in the sample.

  • 13.
    Ekblad, Jonas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Influence of water and mica content on resilient properties of coarse granular materials2008In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 9, no 3, p. 215-227Article in journal (Refereed)
    Abstract [en]

    Elevated amounts of free mica particles in unbound granular materials used in road construction are believed to detrimentally influence bearing capacity. The objective of presented work was to investigate the influence of mica content on resilient properties of coarse granular material (maximum particle size 63mm) under varying water contents. The test scheme comprised triaxial tests, using constant confining pressures, at incrementally raised water contents up to practically full saturation. Increased mica content was achieved by replacing a part of the base material grading smaller than 4mm, with an equal amount of pure muscovite mica of similar grading, hence keeping the overall particle size distribution unchanged. Generally, resilient modulus decreased with increased mica content and elevated water contents caused reduction in stiffness. In relative terms, the reduction in resilient modulus caused by water decreased with increased mica content.

  • 14.
    Ekblad, Jonas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Influence of water on resilient properties of coarse granular materials2006In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 7, no 3, p. 369-404Article in journal (Refereed)
    Abstract [en]

    The objective of this work was to investigate influence of water on resilient properties of a coarse (maximum particle size 90 mm) granular material using various gradings. Triaxial testing, using large-size samples (diameter 500 mm and height 1000 mm) and constant confining pressures, was performed at varying water content up to practically full saturation. Time Domain Reflectometry (TDR) was used to monitor transient in-sample water contents. Evaluation comprised resilient modulus and Poisson ratio in terms of total stresses, although the results were also discussed in the context of effective stresses. The coarsest grading experienced only a small reduction in resilient modulus when brought close to saturation, while specimens with an increased amount of fines and more even distribution responded with a substantial loss of resilient modulus upon increased water content. It also appeared that, as water content increased, the specimens became more dilative (increase in Poisson ratio).

  • 15.
    Ekblad, Jonas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Time domain reflectometry measurements and soil-water characteristic curves of coarse granular materials used in road pavements2007In: Canadian geotechnical journal (Print), ISSN 0008-3674, E-ISSN 1208-6010, Vol. 44, no 7, p. 858-872Article in journal (Refereed)
    Abstract [en]

    Coarse granular materials are used extensively in road construction. Bearing capacity can be affected by the water content in the layers of these materials. The ability to estimate water content and to infer water movements is therefore important. The purpose of the work described herein was to determine soil-water characteristic curves and the relationship between relative apparent permittivity and volumetric water content for coarse (maximum particle size 90 mm) granular materials having various gradations. The relative apparent permittivity was measured with the aid of time-domain reflectometry (TDR), and the concurrent matric suction was measured with a tensiometer. Samples were prepared in a steel box and were heavily compacted, and TDR probes and a tensiometer cup were buried within the matrix. The variation in volumetric water content with apparent relative permittivity was found to deviate from the Topp et al. relationship. Soil-water characteristic curves were described using the Brooks-Corey and van Genuchten models. A pronounced hysteresis between wetting and drying paths was observed. For the low water retention coarse materials, measurements of water content might, in general, require correction because of the nonlinear distribution of water in the sample.

  • 16.
    Ekblad, Jonas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Varm Återanvändning av Asfaltbeläggningar1995Report (Other academic)
  • 17.
    Ekblad, Jonas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Varm Återanvändning av Asfaltbeläggningar1995Report (Other academic)
  • 18.
    Ekblad, Jonas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Varm Återanvändning av Asfaltbeläggningar - E20 Eskilstuna, E18 Täby. Arbetsmiljöundersökning1996Report (Other academic)
  • 19.
    Ekblad, Jonas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Varm Återanvändning av Asfaltbeläggningar - E20 Eskilstuna, E18 Täby. Arbetsmiljöundersökning1996Report (Other academic)
  • 20.
    Ekblad, Jonas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Varm Återanvändning av Asfaltbeläggningar. Resultat från fyra objekt utförda under 19941995Report (Other academic)
  • 21.
    Ekblad, Jonas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Varm Återanvändning av Asfaltbeläggningar. Resultat från fyra objekt utförda under 19941995Report (Other academic)
  • 22.
    Ekblad, Jonas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Highway and Railway Engineering (closed 20110301).
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Highway and Railway Engineering (closed 20110301).
    Water in coarse granular materials: Resilient and retentive properties2008In: Adv. Transp. Geotech. - Proc. Int. Conf. Transp. Geotech., 2008, p. 117-123Conference paper (Refereed)
    Abstract [en]

    Granular material is, perhaps the most common construction material used in civil engineering, being an important constituent in road constructions, railways, embankments, foundations, buildings etc. This paper presents results from triaxial testing, at various water contents using constant confining pressure, of two different continuously graded granular materials with maximum particle size 90 mm and 63 mm, respectively. Furthermore, water retention properties of the unbound materials are presented and examples of water distributions in a common construction are shown. From the results presented, it can be concluded that increased water contents cause a reduction in resilient modulus and an increase in strain ratio. The distribution of water content in the vertical direction is highly nonlinear and the degree of saturation in the unbound layers of a road construction depends to a large degree on the level of the water table.

  • 23.
    Ekblad, Jonas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Civil and Architectural Engineering Laboratory. NCC Rd AB, Upplands Vasby, Sweden.
    Lundström, Robert
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Civil and Architectural Engineering Laboratory. NCC Rd AB, Upplands Vasby, Sweden.
    Causes of rutting in flexible and semi-rigid test sections after 14 years of service2018In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 19, no 4, p. 878-897Article in journal (Refereed)
    Abstract [en]

    Rutting is a major distress and is commonly targeted in design-build contracts as a key requirement, but at the same time, contemporary design methods usually provide scarce information on evolution in absolute terms. The objective of this paper is to investigate and analyse rutting results from a large full-scale road test. The analyses concerned magnitudes and the causes of rutting with a main focus on flexible and semi-rigid structures: one Reference, one high-performance asphalt (HPA) and one asphalt on a lean concrete (LC) base. Field measurements and sampling for the current study comprised acquiring transversal profiles and coring pavement samples. The results suggest that for the HPA and the LC base pavements, rutting is mainly caused by studded tyre wear and densification of the asphalt layers. For the conventional reference pavement additional rutting, most likely in the lower layers, was noted.

  • 24.
    Ekblad, Jonas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Lundström, Robert
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Soft bitumen asphalt produced using RAP2017In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 50, no 1, article id 13Article in journal (Refereed)
    Abstract [en]

    Soft bitumen asphalt concrete is a common paving material in Scandinavia. The purpose of this investigation was to indicate the possibility to compensate for the stiff binder of reclaimed asphalt pavement (RAP) by using softer binders compared to the mix design. Characterization of binder mixing and diffusion were carried out using viscosity measurements and tests on asphalt concrete comprised stiffness modulus and cyclic compression testing. Acquired results suggest that virgin and reclaimed binders mix and the viscosity can be predicted using simple mixing models. In the case of asphalt made from mixing virgin and recycled material, the mechanical properties indicates fully mixed binders and mixing occurs during sample manufacturing. In general, this study suggests that soft asphalt mixtures can be produced using RAP and that nominal binder viscosity of the final product can be obtained by compensating the stiff binder of the RAP by virgin bitumen of a softer grade.

  • 25.
    Isacsson, Ulf
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Ekblad, Jonas
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Johansson, S
    Krigs, B
    Varm Återanvändning av Asfaltbeläggningar på Vägen - Sammanfattning av erfarenheter från försök utförda 1993-19951997Report (Other academic)
  • 26.
    Isacsson, Ulf
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Ekblad, Jonas
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Johansson, S
    Krigs, B
    Varm Återanvändning av Asfaltbeläggningar på Vägen - Sammanfattning av erfarenheter från försök utförda 1993-19951997Report (Other academic)
  • 27.
    Karlsson, Robert
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Ekblad, Jonas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Rheological characterisation of bitumen diffusion2007In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 42, no 1, p. 101-108Article in journal (Refereed)
    Abstract [en]

    Diffusion is considered important in the process of mixing old and new binders during asphalt recycling. The degree of mixing is presumed to greatly influence the final properties of recycled asphalt concrete. Previously, studies have been undertaken to investigate diffusion using FTIR-ATR (Fourier Transform Infrared Spectroscopy using Attenuated Total Reflectance). A need was identified to verify, if the rates of diffusion detected using FTIR-ATR were accompanied by changes in rheological properties. In this paper, a dynamic shear rheometer (DSR) with parallel plates is used for monitoring diffusion. Diffusion coefficients obtained at 60, 80 and 100 degrees C from tests of a soft bitumen (rejuvenator) diffusing into a stiff one are presented. The diffusion coefficients determined are compared with the corresponding diffusion coefficients obtained using FTIR-ATR. The comparison shows that the rates of diffusion detected by the DSR are of the same magnitude, but somewhat higher than the ones detected by FTIR-ATR.

  • 28. Lu, Xiaohu
    et al.
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Ekblad, Jonas
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Influence of polymer modification on low temperature behaviour of bituminous binders and mixtures2003Conference paper (Refereed)
  • 29.
    Lu, Xiaohu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Ekblad, Jonas
    Influence of polymer modification on low temperature behaviour of bituminous binders and mixtures2003In: Materials and Structures, Vol. 36Article in journal (Refereed)
  • 30. Lu, Xiaohu
    et al.
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Ekblad, Jonas
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Low-Temperature Properties of Styrene-Butadiene-Styrene Polymer Modified Bitumens1998In: Construction & Building Materials, Vol. 12Article in journal (Refereed)
  • 31. Lu, Xiaohu
    et al.
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Ekblad, Jonas
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Phase Separation of SBS Polymer Modified Bitumens1999In: ASCE Journal of Materials in Civil Engineering,, Vol. 11, no 1Article in journal (Refereed)
  • 32. Lu, Xiaohu
    et al.
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Ekblad, Jonas
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Rheological Properties of SEBS, EVA and EBA Polymer Modified Bitumens1999In: Materials and Structures, Vol. 32Article in journal (Refereed)
  • 33.
    Lundström, R
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Ekblad, Jonas
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Investigations of Stiffness and Fatigue Properties of Asphalt Mixtures2003In: Journal of Material Science, Vol. 38Article in journal (Refereed)
  • 34.
    Lundström, Robert
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Highway and Railway Engineering (closed 20110301).
    Ekblad, Jonas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Highway and Railway Engineering (closed 20110301).
    Fatigue characterization of asphalt concrete using Schapery's work potential model2006In: Nordic Rheology Society, 2006, Vol. 14Conference paper (Refereed)
    Abstract [en]

    This paper presents an investigation ofSchapery´s work potential theory (WPT), aconstitutive viscoelastic continuum damagemodel, applied to characterize fatigue behaviorof asphalt concrete. Although someanomalies were noted, results indicate thatthe model is applicable to characterizefatigue-related damage growth at differentloading modes, excitation amplitudes andtemperatures.

  • 35.
    Lundström, Robert
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Highway and Railway Engineering (closed 20110301).
    Ekblad, Jonas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Highway and Railway Engineering (closed 20110301).
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Highway and Railway Engineering (closed 20110301).
    Influence of hysteretic heating on asphalt fatigue characterization2004In: Journal of Testing and Evaluation, ISSN 0090-3973, E-ISSN 1945-7553, Vol. 32, no 6, p. 484-493Article in journal (Refereed)
    Abstract [en]

    This paper presents a study focusing on the influence of hysteretic heating on asphalt samples during laboratory fatigue testing. The experimental test setup for material characterization and temperature measurements, including its effect on fatigue test results, as well as theoretical aspects on hysteretic heating, are described. The experimental part of the investigation concerns linear viscoelastic and cyclic fatigue characterization of six asphalt concrete mixtures using uniaxial testing. All the mixtures show nominally identical volumetric properties (aggregate size distribution, binder and air void content) but different binder properties. Three base bitumens and three polymer modified binders were used. The cyclic fatigue tests were carried out at 0, 10, and 20 C using controlled strain and stress modes and different excitation amplitudes. In order to acquire knowledge regarding temperature changes during fatigue testing, several experimental techniques were used. The main thermal study was performed using thermocouples attached to the midheight envelope surface of each sample. The sample surface temperature distribution and its evolution during fatigue testing were investigated using an infrared thermal camera. Furthermore, a limited study of the magnitude of difference between surface and maximum temperature inside the sample was carried out using thermocouples embedded during gyratory compaction. When compared, each method shows advantages and disadvantages regarding simplicity and reliability. In principle, the three methods provide similar results, but the type of information obtained differs among the methods. The use of thermocouples attached to the envelope surface during fatigue testing provides accurate and consistent results of global temperature that can be used to investigate the influence of heating on asphalt fatigue characteristics. By use of thermal measurements and a continuum damage model, it was possible to show a pronounced effect of heating on fatigue behavior. The influence of heating was especially obvious at high excitation amplitudes and elevated temperatures, i.e., conditions where the material produces high amounts of viscoelastic dissipated energy as well as temperature sensitive material behavior.

  • 36.
    Lundström, Robert
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Ekblad, Jonas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Karlsson, Robert
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Fatigue modeling as related to flexible pavement design - State of the art2007In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 8, no 2, p. 165-205Article, review/survey (Refereed)
    Abstract [en]

    A literature study of rheological and fatigue modeling of asphalt mixtures is presented. Theoretical aspects on structural modeling, rheological behavior and the fatigue integration in design procedures are reviewed In principle, pavement design methods can be categorized in three broad groups: empirical, semi-mechanistic and fully mechanistic methods. Pavement design is generally performed using semi-mechanistic methods comprising analytical or numerical structural response models and deterioration modeling based on transfer functions and shift factors. In the case of fatigue deterioration, several approaches have been elaborated e.g. classical models, fracture mechanics and damage mechanics. The approaches differ regarding theoretical foundation and evaluation methods used. Recognizing significant limitations concerning theoretical basis as well as lack of empirical support for current design methods, a shift in paradigm from semi-empirical methods towards more advanced fully mechanistic methods have been initiated. According to this approach, improved pavements are achieved by appropriate design methods which are capable of predicting fatigue resistance in the actual pavement environment, and thus taking into account complex stress conditions, influence of temperature and material characteristics, such as aging and healing.

  • 37. Soenen, Hilde
    et al.
    Ekblad, Jonas
    KTH, Superseded Departments (pre-2005), Infrastructure and Planning.
    Lu, Xiaohu
    Redelius, P.
    Isothermal hardening in bitumen and in asphalt mixtures2004Conference paper (Refereed)
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