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  • 1.
    Butt, Ali Azhar
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Kringos, Nicole
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Using Life Cycle Assessment to Optimize Pavement Crack-Mitigation2012In: Scarpas et al. (Eds.), 7th RILEM International Conference on Cracking in Pavements: Vol. 1, Delft, The Netherlands, 2012, p. 299-306Conference paper (Refereed)
    Abstract [en]

    Cracking is very common in areas having large variations in the daily temperatures and can cause large discomfort to the users. To improve the binder properties against cracking and rutting, researchers have studied for many years the behaviour of different binder additives such as polymers. It is quite complex, however, to decide on the benefits of a more expensive solution without looking at the long term performance. Life cycle assessment (LCA) studies can help to develop this long term perspective, linking performance to minimizing the overall energy consumption, use of resources and emissions. To demonstrate this, LCA of an unmodified and polymer modified asphalt pavement using a newly developed open LCA framework has been performed. It is shown how polymer modification for improved performance affects the energy consumption and emissions during the life cycle of a road. Furthermore, it is concluded that better understanding of the binder would lead to better optimized pavement design, hence reducing the energy consumption and emissions. A limit in terms of energy and emissions for the production of the polymer was also found which could help the polymer producers to improve their manufacturing processes, making them efficient enough to be beneficial from a pavement life cycle point of view.

  • 2.
    Butt, Ali Azhar
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Tasdemir, Yuksel
    Dept of Civil Engineering, Bozok University, 66100 Yozgat, Turkey.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    The Effect of Wax Modification on the Performance of Mastic Asphalt2010In: International Journal of Pavement Research and Technology (IJPRT), ISSN 1997-1400, Vol. 3, no 2, p. 86-95Article in journal (Refereed)
    Abstract [en]

    The scope of this study is to evaluate the mechanical performance of the polymer modified mastic asphalt with 4% montan wax (Asphaltan A) additive. The impact of wax modification on binder, binder/filler mixtures and mastic asphalt was investigated in the laboratory. Wax modified binder properties were determined using dynamic mechanical analysis (DMA), Fourier transform infrared (FTIR) spectroscopy and conventional tests (softening point, penetration, elastic recovery, breaking point, viscosity and storage stability). The bending beam rheometer (BBR) was used for determining low temperature creep compliance and the tensile stress restrained specimen test (TSRST) for determining low temperature fracture. The fatigue cracking behavior of mastic asphalt was investigated using Superpave Indirect Tensile Test (IDT). Based on HMA Fracture Mechanics the influence of wax on the asphalt mixture resistance to fatigue and brittle cracking has been evaluated. The addition of wax to the polymer modified binder resulted in a viscosity reduction at higher temperatures, indicating a possible lower production and laying temperature as compared to asphalt without wax additive. DMA and BBR results showed some increase in stiffness and a more elastic response of the wax modified binder at medium and low temperatures. The TSRST fracture temperature was higher for the mastic asphalt containing wax, indicating a certain negative impact of wax modification.

  • 3.
    Celma Cervera, Carlos
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Partl, Manfred N.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. bEMPA Swiss Federal Laboratories for Materials Testing and Research, Switzerland.
    Larsson, Per-Lennart
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Contact-induced deformation and damage of rocks used in pavement materials2017In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 133, p. 255-265Article in journal (Refereed)
    Abstract [en]

    Performance of stone-based construction materials, such as asphalt and unbound aggregate mixtures is defined to a great extent by the mechanics of the stone-to-stone interactions. Accordingly, the Discrete Element Method (DEM) is gaining popularity as a modelling tool to investigate the mechanical behavior of these materials. Contact and failure laws defining particles force-displacement relationships and the propensity of particles to break are crucial inputs for the DEM simulations. The present study aims at providing an experimental contact mechanics basis for the development of physically based stone-to-stone interaction laws. The attention is focused on investigating stone's force-displacement relationship and damage characteristics at pure normal loading for two stone materials used by the road industry. Experiments are performed at spherical contact profiles for cyclic and monotonically increasing loads. The emphasis lies on the evolution of contact compliance and accumulation of contact induced damage. The effect of surface roughness on the materials response is examined through comparative experiments performed on the specimens with different roughness values. Optical and environmental scanning electron microscopy (ESEM) observations of the contact induced damage at the material surface are presented and discussed in the context of contact mechanics. The implications of the reported experimental findings on the development of mechanics based contact and failure laws for the DEM modelling of stone-based construction materials are discussed.

  • 4. Das, Prabir
    et al.
    Birgisson, Bjorn
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Importance of Thermal Contraction Coefficient in Low Temperature Cracking of Asphalt Concrete2016In: Proceedings of the Fifty-Ninth Annual Conference of the Canadian Technical Asphalt Association (CTAA): Winnipeg, Manitoba / [ed] Canadian Technical Asphalt Association, 2016Conference paper (Refereed)
    Abstract [en]

    A major distress mode in asphalt pavements is low temperature cracking, which results from the contraction and expansion of the asphalt pavement under extreme temperature changes. The potential for thermal cracking involves interplay between the environment, the road structure, and importantly the properties of the asphalt mixture. In the present study, the low temperature cracking performance of asphalt mixture has been investigated numerically and experimentally. A low temperature cracking model has been utilized, which was developed by integrating fracture energy threshold into an asphalt concrete thermal fracture model considering non-linear thermal contraction coefficients. Based on the asphalt concrete mixture viscoelastic properties, this enhanced model can predict thermally-induced stresses and fracture temperatures. It was observed that the thermal contraction coefficient in asphalt concrete is non-linear in the temperature range of interest for low temperature cracking. The implications of having non-linear thermal contraction coefficient were investigated numerically. From the analysis, it was found that this enhanced model can be utilized to evaluate the low temperature cracking performance of asphalt mixtures and rank them accordingly. Interestingly, non-linear thermal contraction coefficient gave much better prediction than the linear approach.

  • 5.
    Das, Prabir Kumar
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Kringos, Niki
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Investigation of the asphalt mixture morphology influence on its ageing susceptibility2015In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 48, no 4, p. 987-1000Article in journal (Refereed)
    Abstract [en]

    The main objective of this study is to investigate the influence that asphalt mixture morphology aspects have on its overall ageing behavior. Since mixture morphology is controllable, having insight into how the various morphological parameters influence the mixture’s long-term behavior can be of great value to optimize its design, regardless of the individual material properties. To do so, this study is utilizing a new framework to characterize the combined effect of aggregate packing, average air void size, porosity and level of compaction on ageing for a large set of data from different sources of field compacted and laboratory produced asphalt mixtures. The paper also hypothesizes about the mechanisms that lay behind the found influences and how thus mixture design improvements can be made. From all the investigated cases, it was found that the framework can be used to optimize the durability performance of asphalt mixtures. It was also observed that prediction of ageing behavior without considering the influence of mixture morphology may lead to erroneous conclusions and non-optimal mix design.

  • 6.
    Das, Prabir Kumar
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Evaluation of the low temperature cracking performance of asphalt mixtures utilizing HMA fracture mechanics2013In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 47, p. 594-600Article in journal (Refereed)
    Abstract [en]

    In the present study, the low temperature cracking performance of asphalt mixture has been investigated numerically and experimentally. To do so, the HMA thermal fracture model has extended by including fracture energy threshold and non-linear thermal contraction coefficient. This extended model is capable to predict thermally induced stress and fracture temperature, which is validated with experimental results obtained from three different types of asphalt mixtures. From the parametric study, it was observed that understanding the influence of thermal contraction coefficient, the cooling rate and the creep compliance parameters can make a significant contribution to the material's sustainability. From the analysis, it was found that this extended model can be utilized to evaluate the low temperature cracking performance of asphalt mixtures and capable to provide correct ranking. Interestingly, non-linear thermal contraction coefficient gave much better prediction than linear approach.

  • 7.
    Das, Prabir Kumar
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Kringos, Nicole
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Atomic Force Microscopy to Characterize the Healing Potential of Asphaltic Materials2012In: Atomic Force Microscopy - Imaging, Measuring and Manipulating Surfaces at the Atomic Scale / [ed] Victor Bellitto, InTech, 2012, p. 209-230Chapter in book (Refereed)
  • 8.
    Das, Prabir Kumar
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Kringos, Niki
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Micro-Mechanical Investigation of Low Temperature Fatigue Cracking Behaviour of Bitumen2012In: 7th RILEM International Conference on Cracking in Pavements: Mechanisms, Modeling, Testing, Detection and Prevention Case Histories / [ed] Scarpas, A.; Kringos, N.; Al-Qadi, I.; Loizos, A., Springer Netherlands, 2012, p. 1281-1290Conference paper (Refereed)
    Abstract [en]

    In an effort to understand the effect of low temperature fatigue cracking, atomic force microscopy (AFM) was used to characterize the morphology of bitumen. In addition, thermal analysis and chemical characterization was done using differential scanning calorimetry (DSC) and thin-layer chromatography/flame ionization detection (TLC/FID), respectively. The AFM topographic and phase contrast image confirmed the existence of bee-shaped microstructure and different phases. The bitumen samples were subjected to both environmental and mechanical loading and after loading, micro-cracks appeared in the interfaces of the bitumen surface, confirming bitumen itself may also crack. It was also found that the presence of wax and wax crystallization plays a vital role in low temperature cracking performance of bitumen.

  • 9.
    de Frias Lopez, Ricardo
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Silfwerbrand, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Highway Engineering Laboratory. School of Engineering and Applied Science, Aston University, Birmingham, UK.
    Force transmission and soil fabric of binary granular mixtures2016In: Geotechnique, ISSN 0016-8505, E-ISSN 1751-7656, Vol. 66, no 7, p. 578-583Article in journal (Refereed)
    Abstract [en]

    The effect of fines content on force transmission and fabric development of gap-graded mixtures under triaxial compression has been studied using the discrete-element method. Results were used to define load-bearing soil fabrics where the relative contributions of coarse and fine components are explicitly quantified in terms of force transmission. Comparison with previous findings suggests that lower particle size ratios result in higher interaction between components. A potential for instability was detected for underfilled fabrics in agreement with recent findings. It was also found that the threshold fines content provides an accurate macroscopic estimation of the transition between underfilled and overfilled fabrics.

  • 10.
    Dinegdae, Yared H.
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Onifade, Ibrahim
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Mechanics-based Topdown Fatigue Cracking Initiation Prediction Framework for Asphaltic Pavements2015In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 16, no 4Article in journal (Refereed)
    Abstract [en]

    In this paper, a new mechanics-based top-down fatigue cracking analysis framework is presented for asphalt pavements. A new mixture morphology-based set of material sub-models is presented for characterising key mixture properties and their change over time. Predicting the load induced top-down fatigue crack initiation (CI) time by utilising comprehensive mixture properties creates the possibility of optimising the mixture morphology while taking into account its subsequent effect on long-term pavement performance. The new framework was calibrated and subsequently validated against a number of field pavement sections with varying traffic levels that are representative for current practices and which have a wide range in material properties. The framework accounts the change in key mixture properties due to ageing and mixture-healing effect on damage accumulation while determining the overall effect of design inputs on cracking performance. Model calibration and validation were achieved based on the healing potential of the asphalt mixture. It was found out that the CI predictions for all the sections are in general agreement with the observed performance in the field, thus giving credibility for the framework.

  • 11.
    Elaguine, Denis
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Brudieu, Marie-Anne
    Ecole Polytechnique, Palaiseau, France.
    Storåkers, Bertil
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Hertzian fracture at unloading2006In: Journal of the mechanics and physics of solids, ISSN 0022-5096, E-ISSN 1873-4782, Vol. 54, no 11, p. 2453-2473Article in journal (Refereed)
    Abstract [en]

    Hertzian fracture through indentation of flat float glass specimens by steel balls has been examined experimentally. Initiation of cone cracks has been observed and failure loads together with contact and fracture radii determined at monotonically increasing load but also during unloading phases. Contact of dissimilar elastic solids under decreasing load may cause crack inception triggered by finite interface friction and accordingly the coefficient of friction was determined by two different methods. In order to make relevant predictions of experimental findings, a robust computational procedure has been developed to determine global and local field values in particular at unloading at finite friction. It was found that at continued loading it is possible to specify in advance how the contact domain divides into invariant regions of stick and slip. The maximum tensile stress was found to occur at the free surface just outside the contact contour, the relative distance depending on the different elastic compliance properties and the coefficient of friction. In contrast, at unloading invariance properties are lost and stick/slip regions proved to be severely history dependant and in particular with an opposed frictional shear stress at the contact boundary region. This causes an increase of the maximum tensile stress at the contour under progressive unloading. Predictions of loads to cause crack initiation during full cycles were made based on a critical stress fracture criterion and proved to be favourable as compared to the experimental results.

  • 12.
    Fadil, Hassan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Larsson, Per-Lennart
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Partl, Manfred
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Measurement of the viscoelastic properties of asphalt mortar and its components with indentation tests2019In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402Article in journal (Refereed)
    Abstract [en]

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

  • 13.
    Gullberg, David
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Evaluation of a novel calibrated-mechanistic model to design against fracture under Swedish conditions2012In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 13, no 1, p. 49-66Article in journal (Refereed)
    Abstract [en]

    Sweden has initiated the development of a new calibrated-mechanistic pavement design procedure to replace the current mechanical-empirical pavement procedure entitled “PMS Objekt.” The first phase was focused on the implementation and calibration of the vi scoelastic fracture mechanics framework entitled “HMA Fracture Mechanics”, developed at the University of Florida. This paper outlines the implementation and calibration of a new pavement design module for Sweden that is based on the HMA fracture mechanics framework. Both the developed design module, as well as the reference model used for calibration (PMS Objekt) are presented in this paper. The results in thickness design after calibration of the design module indicate that the framework is clearly applicable for common Swedish conditions and design standards.

  • 14.
    Gullberg, David
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Evaluation of the predictive models used in the new swedish mechanistic-empirical design module2012In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 13, no 2, p. 300-311Article in journal (Refereed)
    Abstract [en]

    In order to perform thickness design of flexible pavements based on the HMA fracture mechanics framework prior to construction, the tensile strength and creep power law parameters of the mixture has to be determined. As samples are normally not available in the design stage, these properties will have to be modelled rather than determined in a laboratory. This paper evaluates material models based on the relationship between dynamic (complex) modulus and creep compliance in order to predict tensile strength and creep power law parameters for a mixture. For this evaluation, fourteen field sections from the United States have been used for verification and the results indicate that the crack resistance of a mixture can indeed be estimated without a development of extensive empirical relations between mixture properties and crack-resistance.

  • 15.
    Hesami, Ebrahim
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Kringos, Nicole
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Towards a New Experimental and Numerical Protocol for Determining Mastic Viscosity2012In: 7th RILEM International Conference on Cracking in Pavements, 2012, p. 103-113Conference paper (Refereed)
    Abstract [en]

    The rheological characteristics of mastics, or filler-bitumen mixtures, as a component of asphalt mixtures have a significant effect on the overall in-time performance of asphalt pavements such as low temperature cracking, fatigue and rutting behaviour. Viscosity is one of the rheological characteristics which is influenced by the physico-chemical filler-bitumen interaction. In this study, after reviewing some of more often used theories for calculating the viscosity of suspensions, a framework for calculating the viscosity of mastics is presented. This framework aims at covering the entire range of filler concentrations that is found in mastics. Also, a procedure for measuring viscosity mastic from dilute to high concentration mastic using a vane rotor viscometer is introduced. The paper is presenting the first experimental results and discusses the effect of the shape of the investigated fillers on the measured viscosity of the mastics.

  • 16.
    Hesami, Ebrahim
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Kringos, Nicole
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    An empirical framework for determining asphalt mastic viscosity as a function of mineral filler concentration2012In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 35, p. 23-29Article in journal (Refereed)
    Abstract [en]

    Sufficient coating, easy paving and good compaction are desirable parameters, which are approachable with the optimum viscosity of the mastic. In many studies, models have been developed for calculating the viscosity for different types of suspensions at various particle-to-fluid ratios. Unfortunately, none of them are applicable to asphalt mastics, since this material has a much wider range of mineral filler concentration from dilute to very concentrate. To give an overview of the existing viscosity models and to evaluate their range of applicability to asphalt mastics, an extensive literature review was performed. A new empirical framework was developed that removes some of the stipulated limitations of the existing theories.

  • 17. Hu, Chichun
    et al.
    Ma, Jiexian
    Zhao, Jianying
    Leng, Zhen
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Experimental Study of Dowel Bar Alternatives Based on Similarity Model Test2017In: Advances in Materials Science and Engineering, ISSN 1687-8434, E-ISSN 1687-8442, article id 3981908Article in journal (Refereed)
    Abstract [en]

    In this study, a small-scaled accelerated loading test based on similarity theory and Accelerated Pavement Analyzer was developed to evaluate dowel bars with different materials and cross-sections. Jointed concrete specimen consisting of one dowel was designed as scaled model for the test, and each specimen was subjected to 864 thousand loading cycles. Deflections between jointed slabs were measured with dial indicators, and strains of the dowel bars were monitored with strain gauges. The load transfer efficiency, differential deflection, and dowel-concrete bearing stress for each case were calculated from these measurements. The test results indicated that the effect of the dowel modulus on load transfer efficiency can be characterized based on the similarity model test developed in the study. Moreover, round steel dowel was found to have similar performance to larger FRP dowel, and elliptical dowel can be preferentially considered in practice.

  • 18.
    Jelagin, Denis
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Frictional Effects on Hertzian Contact and Fracture2007Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis addresses normal axisymmetric contact of dissimilar elastic solids at finite interfacial friction. It is shown that in the case of smooth and convex but otherwise arbitrary contact profiles and monotonically increasing loading a single stick-slip contour evolves being independent of loading and profile geometry. This allows developing an incremental procedure based on a reduced problem corresponding to frictional rigid flat punch indentation of an elastic half-space. The reduced problem, being independent of loading and contact region, was solved by a finite element method based on a stationary contact contour and characterized by high accuracy. Subsequently, a tailored cumulative superposition procedure was developed to resolve the original problem to determine global and local field values for two practically important geometries: flat and conical profiles with rounded edges and apices. Results are given for relations between force, depth and contact contours together with surface stress distributions and maximum von Mises effective stress, in particular to predict initiation of fracture and plastic flow. It is also observed that the presence of friction radically reduces the magnitude of the maximum surface tensile stress, thus retarding brittle fracture initiation.

    Hertzian fracture through indentation of flat float glass specimens by steel balls has been examined experimentally for a full load cycle. It has been observed that if the specimen survived during loading to a maximum level it frequently failed at decreasing load. It has been proposed by Johnson et al. (1973) that the underlying physical cause of Hertzian fracture initiation during load removal is that at unloading frictional tractions reverse their sign over part of the contact region. Guided by these considerations a robust computational procedure has been developed to determine global and local field values in particular at unloading at finite friction. In contrast to the situation at monotonically increasing loading, at unloading invariance properties are lost and stick-slip regions proved to be severely history dependent and in particular with an opposed frictional shear stress at the contact boundary region. This causes an increase of the maximum tensile stress at the contour under progressive unloading. It is shown that the experimental observations concerning Hertzian fracture initiation at unloading are at least in qualitative correlation with the effect friction has on the maximum surface tensile stress.

    A contact cycle between two dissimilar elastic bodies at finite Coulomb friction has been further investigated analytically and numerically for a wider range of material parameters and contact geometries. With the issue of Hertzian fracture initiation in mind, results concerning the influence of the friction coefficient and compliance parameters on the absolute maximum surface tensile stress during a frictional contact cycle are reported along with the magnitudes of the relative increase of maximum tensile stresses at unloading. Based on a critical stress fracture criterion it is discussed how the predicted increases will influence the critical loads required for crack initiation.

    Fracture loads are measured with steel and tungsten carbide spherical indenters in contact with float glass specimens at monotonically increasing loading and during a load cycle. Computational predictions concerning the fracture loads are given based on Hertz and frictional contact theories combined with a critical stress fracture criterion. The computational results obtained for frictional contact are shown to be in better agreement with experimental findings as compared to the predictions based on the Hertz theory. The remaining quantitative discrepancy was attributed to the well-known fact that a Hertzian macro-crack initiates from pre-existing defects on the specimen’s surface. In order to account for the influence of the random distribution of these defects on the fracture loads at monotonic loading, Weibull statistics was introduced. The predicted critical loads corresponding to 50% failure probability were found to be in close agreement with experimentally observed ones.

  • 19.
    Jelagin, Denis
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    On Hertzian contact and fracture at finite friction2006Licentiate thesis, comprehensive summary (Other scientific)
  • 20.
    Jelagin, Denis
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    AHMED, ABUBEKER
    Lu, Xiaohu
    Said, Safwat F.
    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.

  • 21.
    Jelagin, Denis
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Larsson, Per-Lennart
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Hertzian Fracture at Finite Friction: A Parametric Study2008In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 265, no 5-6, p. 840-848Article in journal (Refereed)
    Abstract [en]

    Friction has a profound influence on Hertzian fracture initiation when dissimilar materials are involved. Experimental studies show that the presence of friction results in higher fracture loads and fracture radii as compared to the frictionless case. It has also been shown recently that the experimental observations concerning Hertzian fracture initiation at unloading may be explained by the effect friction has on a surface tensile stress distribution. Presently a contact cycle between two dissimilar elastic bodies at finite Coulomb friction has been investigated numerically for a wide range of material parameters and contact geometries. Emphasis has been given to the surface tensile stress distribution which is assumed to be a governing parameter for Hertzian fracture initiation. In particular it was found that during loading the contact region divides into invariant stick and inward slip regions and the presence of outward frictional shear tractions reduces the maximum surface tensile stress and shifts it away from the contact contour as compared to the frictionless case. At unloading, the distributions of stick-slip zones were found to be severely history- and geometry-dependent and shear tractions reversed their direction over part of the contact area. Consequently, tensile stresses were found to grow at unloading. Results concerning the influence of the friction coefficient, Dundur's parameter and the specimen's Poisson's ratio on the absolute maximum surface tensile stress obtained at a frictional contact cycle are reported along with the magnitudes of the relative increase of maximum tensile stresses at unloading. Based on a critical stress fracture criterion it is discussed how the predicted increases will influence the critical loads required for crack initiation.

  • 22.
    Jelagin, Denis
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Larsson, Per-Lennart
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Measurement of the Viscoelastic Properties of Bitumen Using Instrumented Spherical Indentation2013In: Experimental mechanics, ISSN 0014-4851, E-ISSN 1741-2765, Vol. 53, no 7, p. 1233-1244Article in journal (Refereed)
    Abstract [en]

    Indentation testing as a tool for determination of the viscoelastic mechanical properties of bitumen is examined in some detail using theoretical, numerical as well as experimental methods. In particular Brinell indentation is analysed and simple but rigorous formulae for a complete characterization of linear viscoelastic materials are presented. Numerical methods (finite element methods) are used in order to verify and substantiate these relations for an experimental situation. Indentation experiments are then performed on bitumen and special efforts are made in order to avoid size effects, i. e. anomalous results due to the fact that the indented specimens are too small and as a result, far field boundary conditions will influence the interpretation of the experimental output. The mechanical properties determined experimentally by indentation are compared with corresponding results from standard mechanical tests, and the results are encouraging considering the fact that non-linear effects are also influencing the outcome of the experiments.

  • 23.
    Jelagin, Denis
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Larsson, Per-Lennart
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Nonlocal Frictional Effects at Indentation of Elastic Materials2013In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 51, no 3, p. 397-407Article in journal (Refereed)
    Abstract [en]

    Indentation of elastic materials is investigated numerically using the finite element method. Large deformation theory is relied upon for accuracy. The study focuses on nonlocal frictional effects on relevant indentation quantities in the microindentation regime. The indentation quantities investigated include both local and global ones. It is shown that nonlocal frictional effects are small when global quantities are at issue, as is the case when conventional (Coulomb) theory of friction is used, also when these features are introduced at the ridges of a Vickers indenter where stress gradients are substantial. These effects are, however, shown to be of importance for particular indenter geometries as far as local field variables are concerned.

  • 24.
    Jelagin, Denis
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Larsson, Per-Lennart
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    On indentation and initiation of fracture in glass2008In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 45, no 10, p. 2993-3008Article in journal (Refereed)
    Abstract [en]

    The influence of indenter elasticity on Hertzian fracture initiation at frictional dissimilar elastic contact has been examined experimentally and numerically. In flat float glass specimens initiation of cone cracks has been observed and fracture loads measured with steel and tungsten carbide indenters at monotonically increasing loading and during a load cycle. The observed effect of indenter elasticity on fracture loads was found to be qualitatively different from the one predicted by the Hertz contact theory. This discrepancy may be explained by the presence of interfacial friction. The friction coefficient between the indenters and the specimen was measured and a contact cycle at finite Coulomb friction has been analyzed numerically. The influence of the indenter elasticity and the friction coefficient on the surface maximum tensile stress has been investigated and the results concerning the influence of these parameters on the fracture loads as given based on a critical stress fracture criterion. The obtained computational results were found to be in better agreement with experimental findings as compared to the predictions based on the frictionless contact theory. A remaining quantitative discrepancy was attributed to the well-known fact that a Hertzian macro-crack initiates from pre-existing defects on the specimen's surface. In order to account for the influence of the random distribution of these defects a Weibull statistics was introduced. The predicted critical loads corresponding to the 50% failure probability were found to be in close agreement with experimentally observed ones.

  • 25.
    Jelagin, Denis
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Larsson, Per-Lennart
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    On Indenter Boundary Effects at Elastic Contact2012In: Journal of Mechanics of Materials and Structures, ISSN 1559-3959, E-ISSN 2157-5428, Vol. 7, no 2, p. 165-182Article in journal (Refereed)
    Abstract [en]

    Axisymmetric contact problems at finite Coulomb friction and rounded profiles are examined for linear elastic solids. In previous analytical/numerical approaches to this problem often incremental procedures have been developed resulting in a reduced incremental problem corresponding to a rigid flat indentation of an elastic half-space. The reduced problem, being independent of loading and contact region, can be solved by a finite element method based on a stationary contact contour and characterized by high accuracy. Subsequently, with cumulative superposition procedures it is then possible to resolve the original problem in order to determine global and local field values. Such a procedure, when applied to for example to flat and conical profiles with rounded edges and apices, is exact save for the influence from boundaries close to the contact region. This influence could be exemplified by the indenter boundaries of a flat deformable profile with rounded edges indenting a linear elastic half-space. In the present analysis such effects are investigated qualitatively and quantitatively. In doing so, the results derived using previously discussed analytical/numerical approaches are compared with corresponding ones from full-field finite element calculations. Both local as well as global quantities are included in the comparison in order to arrive at a complete understanding of the boundary effects at elastic contact.

  • 26.
    Khavassefat, Parisa
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Birgisson, Bjorn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science.
    The effect of road surface deterioration on pavement service life2014In: Expanding horizons: 13th International Symposium on Heavy Vehicle Transport Technology, San Luis, Argentina, 27-31 October 2014, 2014Conference paper (Refereed)
    Abstract [en]

    The effect of pavement surface deterioration on pavement service life has been studied for a set of case studies. The Swedish mechanistic empirical design method is used in order to analyse the pavement performance under dynamic moving loads while the longitudinal profile unevenness is updated on yearly basis. The surface evolution assumed in the case scenarios are chosen in relevance with the general trend of surface deterioration in Swedish road network. Results from the case studies indicate that the pavement service life is highly affected by pavement surface deterioration, especially for pavement segments with high traffic. Moreover predictive maintenance for high traffic road segments might be beneficial as it increases pavement service life and decreases the user related costs, e.g. vehicle fuel consumption.

  • 27.
    Khavassefat, Parisa
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    A computational framework for viscoelastic analysis of flexible pavements under moving loads2012In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 45, no 11, p. 1655-1671Article in journal (Refereed)
    Abstract [en]

    A general quasi-static computational procedure is established to evaluate stresses and strainsinduced in the viscoelastic flexible pavement bymoving traffic. The procedure is based on superposition principle and is computationally favourable, as itrequires only reduced incremental problem to besolved numerically. The impact of traffic speed anddensity on the mechanical response of flexible pavement is examined numerically. Results relevant fortwo major modes of pavement’s distress, i.e. crackingand rutting, are reported. It is shown that the state-ofpractice layered elastic analysis used in pavementdesign is unable to capture several important qualitative and quantitative aspects of pavements response.

  • 28.
    Khavassefat, Parisa
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Dynamic Response of Flexible Pavements at Vehicle-Road Interaction2015In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 16, no 2, p. 256-276Article in journal (Refereed)
    Abstract [en]

    In the present paper a robust and general computational framework that captures the dynamic response of flexible pavements to a moving vehicle is presented. A finite element method is relied upon in order to establish the response function for a linear viscoelastic pavement structure with dynamic effects taken into account. In order to characterise the dynamic loads induced on the pavement by moving traffic, a quarter car model combined with measured road profiles is used. Once both the traffic loads and pavement response functions are known, the stresses and strains induced in the pavement can be obtained in the frequency-wavenumber domain through the convolution procedure. The computational procedure developed is applied in the present study to evaluate the effect of the pavement surface roughness on the pavement structure response to truck traffic loading. Stress field parameters governing fracture initiation in asphalt layers are reported for two measured road roughness profiles. It is shown that the dynamic effects at vehicle-road interaction may have a profound influence on the stresses induced in flexible pavements; therefore, these effects need to be taken into account for the accurate estimation of the road resistance to cracking.

  • 29.
    Khavassefat, Parisa
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Impact of Long and Heavy Vehicles on Pavement Damage2013Conference paper (Refereed)
    Abstract [en]

    In the present paper the effect of vehicle configuration and traffic characteristics on the damage induced in pavements by traffic is investigated numerically. A three dimensional time-dependent pavement-vehicle interaction analysis is performed in order to study the impact of the parameters mentioned above on the mechanical response of flexible pavements. The analysis is based on a fast and robust computational procedure, developed by the authors. The numerical algorithm utilizes the three-dimensional finite element solution of the reduced problem of one tyre pavement interface loaded with tyre pressure. Afterwards, a superposition procedure based on fast Fourier transform techniques is applied to find the pavement response to moving loads. The method is general and capable of capturing the stress-strain response to any arbitrary loading history.One particular area of study with employing the current procedure is the analysis of long and heavy vehicle impact on pavement damage. Two major modes of distress, i.e. cracking and rutting have been discussed for 6 different truck types with 2 speeds. It is shown that an accurate numerical model provides a more accurate explanation of different distress modes. Moreover the conventional analysis and design methods with layered linear elastic behaviour assumption for asphalt layer are unable to capture several important aspects of pavement response.

  • 30.
    Khavassefat, Parisa
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Non-stationary Response of Flexible pavements to Moving Vehicles2016In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 17, no 5, p. 458-470Article in journal (Refereed)
    Abstract [en]

    In this paper the pavement surface deterioration is investigated based on field measurements of surface roughness profiles obtained in Sweden. A predictive function for surface deterioration, based on average gradient of yearly measurements of the road surface profile in Swedish road network, is proposed. In order to characterise the dynamic loads induced on the pavement by moving traffic a quarter car model is used. Afterwards a non-stationary stochastic approach is used to obtain the yearly response of the pavement to moving loads. The solution is in frequency-wavenumber domain and is given for a non-stationary random case as the pavement surface deteriorates in pavement service life influencing thus the magnitude of the dynamic loads induced by the vehicles. The effect of pavement surface evolution on the stress state induced in the pavement by moving traffic is examined for a specific case of quarter car model and pavement structure. The results showed approximately a 100% increase in the dynamic component of stresses induced in the pavement.

  • 31.
    Lindskog, Per
    et al.
    Sandvik Tooling AB.
    Barbier, Christophe
    Karlstad University.
    Jelagin, Denis
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Larsson, Per-Lennart
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Optimization as a Tool for Characterization of Advanced Constitutive Models describing Powder Compaction2007In: Proceedings of the Euro PM 2007 Congress and Exhibition, 2007, p. 381-386Conference paper (Refereed)
    Abstract [en]

    The applicability of optimization procedures used in combination with advanced constitutive models, describing dry pressing powder compaction, is investigated by aid of standard finite ele- ment and optimization commercial packages. It is found that, at fairly general conditions, this can be expected to be a very advantageous approach at material characterization.

  • 32.
    Lira, Bernardita
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Binder distribution model for asphalt mixtures based on packing of the primary structure2015In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 16, no 2, p. 144-156Article in journal (Refereed)
    Abstract [en]

    Film thickness describes the coating around aggregate particles on asphalt mixtures. The standard method of calculating film thickness has proven to present several limitations, such as assuming an average thickness independent of particle size, being completely independent to the porosity of the mixture and considering only one mineral type. In this paper, a binder distribution model is developed for aggregates according to size and role in the structure. The aggregates are separated into two different structures: primary structure, the load bearing one, and secondary structure, smaller material that provides stability to the skeleton. A coating thickness for these two structures is calculated from a geometrical consideration that includes the packing arrangement of particles and the effect of overlapping as the film grows. The results were compared with known rutting performance of field mixtures and moisture conditioned laboratory mixtures, showing a good correlation between film thickness and resistance to failure.

  • 33.
    Lira, Bernardita
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Gradation-based framework for asphalt mixture2013In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 46, no 8, p. 1401-1414Article in journal (Refereed)
    Abstract [en]

    Aggregates are the major component of asphalt mixtures, greatly influencing the mixtures resistance to failure. The structure that is formed by the aggregates will depend mostly on the size distribution, shape and mineral composition. Coarse aggregate have a strong influence on the resistance to rutting, while fines provide stability to the mixture. In the present study a generalized framework is developed to identify the range of aggregate sizes which form the load carrying structure in hot mix asphalt and determine its quality. The method has been developed as a numerical procedure based on packing theory. Parameters like porosity and coordination number have been used to evaluate the quality of the load carrying structure and relate it to resistance to rutting. The framework has been evaluated on several field and laboratory mixtures and related to their rutting performance. The gradation analysis of the mixtures has compared favorably with the performances reported from the field and laboratory testing. The developed gradation analysis framework has proven to be a tool to identify those mixtures with a poor rutting performance based on the gradation of the aggregates.

  • 34.
    Namutebi, May
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering. Makerere University, Uganda.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Guarin, Alvaro
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Exploratory study on bitumen content determination for foamed bitumen mixes based on porosity and indirect tensile strength2017In: International journal of traffic and transportation engineering, ISSN 2325-0062, E-ISSN 2325-0070, Vol. 4, no 2, p. 131-144Article in journal (Refereed)
    Abstract [en]

    Optimum bitumen content determination is one of the major aims for foamed bitumen mix design. However, mix design procedures for foamed bitumen mixes are still under development. In this paper a method to determine the optimum bitumen content for given foamed bitumen mix based on primary aggregate structure porosity and indirect tensile strength criterion is proposed. Using packing theory concepts, the aggregate gradation is divided into three aggregate structures which are oversize, primary and secondary structures. Porosity for the primary aggregate structure is determined for given bitumen contents. A maximum value for porosity of 50% for the primary aggregate structure is used to choose initial bitumen content. Furthermore, a minimum indirect tensile strength criteria is suggested to refine this bitumen content. This method enables a bitumen content value to be chosen prior to the start of experimental work, as porosity is expressed in terms of physical parameters such as aggregate and binder specific gravity, and aggregate gradation which are known before the mix design process. The bitumen content is then later refined when the indirect tensile strength is determined in the laboratory. This method would reduce resources such as time and materials that may be required during the mix design procedure.

  • 35.
    Olsson, Erik
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.). KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    A contact model for the normal force between viscoelastic particles in discrete element simulations2019In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 342, p. 985-991Article in journal (Refereed)
    Abstract [en]

    DEM modeling of granular materials composed of viscoelastic particles can provide valuable insights into the mechanical behavior of a wide range of engineering materials. In this paper, a new model for calculating the normal contact force between visoelastic spheres is presented based on contact mechanics that takes the mechanical behavior of the DEM particles into account. The model relies on an application of the viscoelastic correspondence principle to elastic Hertz contact. A viscoelastic relaxation function for the contact is defined and a generalized Maxwell material is used for describing this function. An analytical expression for the increment in contact force given an increment in overlap is derived leading to a computationally efficient model. The proposed model provides the analytical small deformation solution upon loading but provides an approximate solution at unloading. Comparisons are made with FEM simulations of contact between spheres of different sizes of equal and dissimilar materials. An excellent agreement is found between the model and the FEM simulations for almost all cases except at cyclic loading where the characteristic times of the viscoelastic behavior and the loading are similar.

  • 36.
    Onifade, Ibrahim
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Birgisson, Björn
    Kringos, Nicole
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Towards Asphalt Mixture Morphology Evaluation with the Virtual Specimen Approach2015In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402Article in journal (Refereed)
    Abstract [en]

    The morphology of asphalt mixture can be defined as a set of parameters describing the geo-metrical characteristics of its constituent materials, their relative proportions as well as spatialarrangement in the mixture. The present study is carried out to investigate the effect of themorphology on its meso- and macro-mechanical response. An analysis approach is used forthe meso-structural characterisation based on the X-ray computed tomography (CT) data.Image processing techniques are used to systematically vary the internal structure to obtaindifferent morphology structures. A morphology framework is used to characterise the aver-age mastic coating thickness around the main load carrying structure in the structures. Theuniaxial tension simulation shows that the mixtures with the lowest coating thickness exhibitbetter inter-particle interaction with more continuous load distribution chains between adja-cent aggregate particles, less stress concentrations and less strain localisation in the masticphase.

  • 37.
    Onifade, Ibrahim
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Guarin, Alvaro
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Kringos, Nicole
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Asphalt Internal Structure Characterization with X-Ray Computed Tomography and Digital Image Processing2013In: Multi-Scale Modeling and Characterization of Infrastructure Materials: Proceedings of the International RILEM Symposium Stockholm, June 2013, Springer Netherlands, 2013, p. 139-158Conference paper (Refereed)
    Abstract [en]

    In this paper, detailed study is carried out to develop a new workflow from image acquisition to numerical simulation for the asphalt concrete microstructures. High resolution computed tomography scanned images are acquired and the image quality is improved using digital image processing techniques. Nonuniform illumination is corrected by applying an illumination profile to correct the background and flat-fields in the image. Distance map based watershed segmentation are used to segment the phases and separate the aggregates. Quantitative analysis of the micro-structure is used to determine the phase volumetric relationship and aggregates characteristics. The result of the quantitative analysis showed a very high level of reliability. Finite Element simulations were carried out with the developed micro-mechanical meshes to capture the strength and deformation mechanisms of the asphalt concrete micro-structure. From the micro-mechanical investigation the load transfer chains, higher strength characteristics and high stress localization at the mastic interface between adjacent aggregates was shown.

  • 38.
    Onifade, Ibrahim
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Guarin, Alvaro
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Kringos, Nicole
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Effect of micro-scale morphological parameters on meso-scale response of Asphalt Concrete2014In: Asphalt Pavements - Proceedings of the International Conference on Asphalt Pavements, ISAP 2014, CRC Press, 2014, p. 1775-1784Conference paper (Refereed)
    Abstract [en]

    With recent advancement in the use of X-Ray Computed Tomography to capture the internal structure of Asphalt Concrete (AC), results have shown several possibilities to account for the distribution of the different phases in the mix and quantify them in a reliable way. The morphology of asphalt mixtures which includes the aggregate size gradation and the distribution of the air-voids and bitumen phase are captured in a single morphological parameter called the Primary Structure (PS) coating thickness-(Tps). In this study, the effect of variations in the morphological micro-structural property on the mesoscale response of three (3) AC samples is examined using the 3D Finite Element Method (FEM). The AC internal geometry is acquired using X-Ray Computed Tomography (CT); the distribution of the aggregates, mastic and air-voids phase is considered and obtained using Digital Imaging Processing (DIP) techniques. Using a surface-based cohesive behavior and assuming a predominant adhesive failure at the interface between the mastic and aggregate, a maximum traction criterion is used to obtain the damage propensity of the different mixtures. The result of the analysis shows that the microstructural morphological parameter Tps adequately captures the meso-scale response of the mixtures; there exist an inverse relationship between mixture strength characterization and the morphological parameter Tps.

  • 39.
    Storåkers, Bertil
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Elaguine, Denis
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Hertz contact at finite friction and arbitrary profiles2005Article in journal (Refereed)
    Abstract [en]

    Axisymmetric contact at finite Coulomb friction and arbitrary profiles is examined analytically and numerically for dissimilar linear elastic solids. Invariance and generality are aimed at and an incremental procedure is developed resulting in a reduced benchmark problem corresponding to a rigid flat indentation of an elastic half-space. The reduced problem, being independent of loading and contact region, was solved by a finite element method based on a stationary contact contour and characterized by high accuracy. Subsequently, a tailored cumulative superposition procedure was developed to resolve the original problem to determine global and local field values. Save for the influence of the coefficients of friction and contraction ratio, it is shown that at partial slip the evolving relative stick-slip contour is independent of any convex and smooth contact profile at monotonic loading. For flat and conical profiles with rounded edges and apices, results are illustrated for relations between force, depth and contact contours together with surface stress distributions. The solution for dissimilar solids in a full space is transformed to a half-space problem and solved for a combination of material parameters in order to first determine interface traction distributions. Subsequently, full field values for the two solids were computed individually. In order to predict initiation of fracture and plastic flow, results are reported for the location and magnitude of maximum tensile stress and effective stress, respectively, for a range of geometrical and material parameters. In two illustrations, predicted results are compared with experimental findings related to initiation of brittle fracture and load-depth relations at nanoindentation.

  • 40.
    Tebaldi, G.
    et al.
    Italy.
    Apeagyei, A.
    United Kingdom.
    Elaguine, Denis
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Falchetto, A. C.
    Germany.
    Advanced measurement systems for crack characterization2018In: Mechanisms of Cracking and Debonding in Asphalt and Composite Pavements, Springer, 2018, p. 155-227Chapter in book (Refereed)
    Abstract [en]

    The previous chapters describe numerical models and testing methods designed to simulate, to repeat and to understand the cracking phenomena in asphalt materials and asphalt pavement (or pavements with at least one asphalt layer). This chapter shows some of the most advanced systems to measure the parameters related to cracking. They are classified using a classification grid that considers the most relevant characteristics of the measurement system. The proposed classification method was designed to provide a quick understanding of what data the systems are able to provide and what they can analyze.

  • 41.
    Yideti, Tatek Fekadu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    A new moisture distribution model for unbound granular materialsIn: Geotechnique, ISSN 0016-8505, E-ISSN 1751-7656Article in journal (Other academic)
    Abstract [en]

    The presence of waterin the unbound granular materials significantly influences the mechanicalperformance of the material. The ability to estimate the soil watercharacteristic curve (SWCC) is crucial thus to determine the effect themoisture has on the mechanical behaviour of granular materials. In this paper,an analytical moisture distribution model is proposed. A packing theory-based framework to evaluateperformance of unbound granular materials reported previously by the authorsallows identifying the two basic components of the unbound granular materialsskeleton: primary structure (PS) - a range of interactive coarse grain sizes thatforms the main load carrying network in granular materials and secondarystructure (SS) - a range of grain sizes smaller than the PS providing stabilityto the aggregate skeleton. In the new moisture distribution model presented inthis paper, moisture wasconsidered to be stored as meniscus water between SS particles and water thatfilled in small voids.The volume of meniscus water between SS particles and the measured matricsuction values are the two key parameters in the model. In order to validatethe model predicted results are then compared with measuredmatric suction of granite granular materials with different gradations. Theresults showed that the model developed is capable of predicting theexperimentally measured matric suction values for a range of gradations. 

  • 42.
    Yideti, Tatek Fekadu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Influence of aggregate packing structure on California bearing ratio values of unbound granular materials2014In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 15, no 1, p. 102-113Article in journal (Refereed)
    Abstract [en]

    Over the past several decades, California bearing ratio (CBR) value has been used in many countries for empirical pavement designs and still many countries are using it for unbound granular materials strength measurement and as input to their pavement design chart. Furthermore, CBR value of unbound granular material is frequently correlated with its fundamental mechanical properties such as resilient modulus, which in turn is often used as an input to a mechanistic pavement design procedure. In the present study, the effect the aggregate packing has on the CBR values of unbound materials is investigated. A packing theory-based framework that allows to identify the load-carrying part of the aggregate skeleton is presented. Aggregate packing parameters controlling the CBR performance of the unbound materials are introduced and evaluated with the experimentally measured CBR values of 20 unbound granular materials found in the literature. It is shown that the CBR values of granular materials are to a great extent controlled by the packing characteristics of their load-carrying skeleton.

  • 43.
    Yideti, Tatek Fekadu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Guarin, Alvaro
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Packing theory-based framework for evaluating resilient modulus of unbound granular materials2014In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 15, no 8, p. 689-697Article in journal (Refereed)
    Abstract [en]

    Enhancing the quality of granular layers is fundamental to optimise the structural performance of the pavements. The objective of this study is to investigate whether previously developed packing theory-based aggregate parameters can evaluate the resilient modulus of unbound granular materials. In this study, 19 differently graded unbound granular materials from two countries (USA and Sweden) were evaluated. This study validated both porosity of primary structure (PS) and contact points per particle (coordination number) as key parameters for evaluating the resilient modulus of unbound granular materials. This study showed that decreasing the PS porosity - higher coordination number - calculated based on the proposed gradation model, yields higher resilient modulus. Good correlation was observed between the proposed packing parameters and resilient modulus of several types of aggregates. The packing theory-based framework successfully recognised granular materials that exhibited poor performance in terms of resilient modulus.

  • 44.
    Yideti, Tatek Fekadu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Guarin, Alvaro
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Packing theory-based framework to evaluate permanent deformation of unbound granular materials2013In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 14, no 3, p. 309-320Article in journal (Refereed)
    Abstract [en]

    Permanent deformation of unbound granular materials plays an essential role in the long-term performance of a pavement structure. Stability of unbound granular materials is defined by the particle-to-particle contact of the system, the particle size distribution and the packing arrangement. This paper presents a gradation model based on packing theory to evaluate permanent deformation of unbound granular materials. The framework was evaluated by using 10 unbound granular materials from different countries. The disruption potential, which determines the ability of secondary structure (SS) to disrupt the primary structure (PS), is introduced. This study also identified the amount of PS and SS that may eventually be used as a design parameter for permanent deformation of unbound road layers. The evaluation of the model regarding permanent deformation behaviour of granular materials is found to compare favourably with experimental results.

  • 45.
    Yideti, Tatek
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science.
    Jelagin, Denis
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.). KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science.
    Moisture Distribution Model to Predict Matric Suction in Unbound Granular Materials as a Function of Fines Content2016In: TRB 95th Annual Meeting Compendium of Papers, 2016Conference paper (Refereed)
    Abstract [en]

    The existence of water in the layers of unbound road aggregates significantly influences the performance of pavement structure. Thus, the ability to estimate volumetric water content and its capillary effect is very important. Several models have been suggested to link the matric suction of unbound materials to their water retention properties. In this paper, an analytical moisture distribution model is proposed by using packing theory-based framework for unbound granular materials. The framework was previously developed by the authors of this paper and identifies two basic components of unbound granular materials skeleton: primary structure (PS) - a range of interactive coarse grain sizes that forms the main load-carrying network in granular materials and secondary structure (SS) - a range of grain sizes smaller than the PS providing stability to the aggregate skeleton. In the new moisture model, water was considered to be stored as both menisci water between SS particles and water that fully filled in very small voids. In order to validate the model, predicted results are compared with measured matric suction of a granite material with different gradations. The results showed that the model is capable of predicting the experimentally measured matric suction values for a range of gradations.

1 - 45 of 45
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