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  • 1.
    Ahmed, Abubeker W.
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science. Swedish National Road and Transport Research Institute, Sweden.
    Erlingsson, Sigurdur
    KTH, School of Architecture and the Built Environment (ABE), Transport Science. Swedish National Road and Transport Research Institute, Sweden; University of Iceland.
    Characterisation of heavy traffic axle load spectra for mechanistic-empirical pavement design applications2015In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 16, no 6, p. 488-501Article in journal (Refereed)
    Abstract [en]

    Heavy traffic axle load spectrum (ALS) is one of the key inputs for mechanistic-empirical analysis and design of pavement structures. Frequently, the entire ALS is aggregated into number of equivalent single axle loads or assumed to have constant contact area (CCA) or constant contact pressure. These characterisations affect the accuracy and computational performance of the pavement analysis. The objective of this study was to evaluate these characterisations based on predicted performances to rutting and fatigue cracking of several pavement structures subjected to ALS data collected from 12 bridge weigh in motion stations. The results indicated that for layers below the top 25cm, all characterisations produced similar values of predicted rutting. However, for the top 25cm, the methods differed in the predicted performances to rutting and fatigue cracking. Furthermore, an improvement to the CCA approach was proposed that enhanced the accuracy while maintaining the same level of computational performance.

  • 2.
    Ahmed, Abubeker W.
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering. VTI.
    Erlingsson, Sigurdur
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering. VTI.
    Characterization of heavy traffic axle load spectra for mechanistic-empirical pavement design applicationsIn: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268XArticle in journal (Refereed)
  • 3.
    Ahmed, Abubeker W.
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Highway Engineering Laboratory. Swedish National Road and Transport Research Institute, Sweden.
    Erlingsson, Sigurdur
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Highway Engineering Laboratory. Swedish National Road and Transport Research Institute, Sweden.
    Numerical validation of viscoelastic responses of a pavement structure in a full-scale accelerated pavement test2017In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 18, no 1, p. 47-59Article in journal (Refereed)
    Abstract [en]

    This paper demonstrates the application of a generalised layered linear viscoelastic (LVE) analysis for estimating the structural response of flexible pavements. A comparison of the direct layered viscoelastic responses with approximate solutions based on the linear elastic (LE) and LVE collocation methods was also carried out. The different approaches were implemented by extending a layered elastic program with an improved computational performance. The LE and LVE collocation methods were further extended for analysis of pavements under moving loads. The methods were illustrated by analysing a pavement structure subjected to moving wheel loads of 30, 50, 60 and 80kN using a Heavy Vehicle Simulator (HVS). The various responses (stresses and strains) in the pavement, at pavement temperatures of 0, 10 and 20 degrees C, were measured using various types of sensors installed in the structure. It was shown that the approximated LVE solution based on the LE collocation method agreed very well with the measurements and is computationally the least expensive.

  • 4.
    Bagampadde, Umaru
    et al.
    Makerere University, Kampala.
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Kiggundu, Bob
    Makerere University, Kampala.
    Influence of aggregate chemical and mineralogical composition on stripping in bituminous mixtures2005In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 6, no 4, p. 229-239Article in journal (Refereed)
    Abstract [en]

    The influence of aggregate chemical and mineralogical composition on moisture sensitivity was investigated using 11 aggregates from typical tropical and temperate climates and one bitumen. Mix design and compaction were based on Swedish Road 94 hot mix base specifications and moisture damage was determined using resilient modulus and tensile strength ratios. As much as practically possible, air voids, gradation, compaction level, bitumen content and curing were controlled. Mixtures from aggregates containing sodium and potassium exhibited relatively high moisture sensitivity. The converse was apparent for aggregates with calcium, magnesium and iron. No significant correlation was observed between the strength ratios and contents of Al2O3 and SiO2. Stripping was generally high for aggregates with quartz and alkali feldspars, although one aggregate with practically 100% quartz showed low moisture sensitivity. Statistical analysis showed good correlation between resilient modulus and tensile strength ratios.

  • 5.
    Birgisson, Björn
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Montepara, A.
    Romeo, E.
    Tebaldi, G.
    Characterization of Asphalt Mixture Cracking Behavior using the Three-Point Bending Beam Test2011In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 12, no 6Article in journal (Refereed)
  • 6.
    Birgisson, Björn
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Montepara, Antonio
    Department of Civil and Environmental Engineering and Architecture, University of Parma.
    Romeo, Elena
    Department of Civil and Environmental Engineering and Architecture, University of Parma.
    Tebaldi, Gabriele
    Department of Civil and Environmental Engineering and Architecture, University of Parma.
    Characterisation of asphalt mixture cracking behaviour using the three-point bending beam test2011In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 12, no 6, p. 569-578Article in journal (Refereed)
    Abstract [en]

    The use of a three-point bending beam (3PB) test was investigated to characterise hot mix asphalt (HMA) cracking behaviour. Fundamental HMA fracture properties, identified as tensile strength and fracture energy density at first fracture, were determined for six different asphalt mixtures (two natural and four SBS polymer modified) applying the HMA Fracture Mechanics framework. Full-field strain maps obtained from an in-house developed digital image correlation-based method were observed to better understand the crack initiation and propagation mechanisms in the 3PB specimen. The resulting fracture behaviour was predicted using a displacement discontinuity boundary element method to model the microstructure of the six asphalt mixtures and to predict their fracture properties. Both numerical and experimental results indicate that the fracture mechanism of asphalt mixtures can be properly described from 3PB test results when appropriate interpretation models are used.

  • 7.
    Butt, Ali Azhar
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Mirzadeh, Iman
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Toller, Susanna
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Environmental Strategies Research (fms).
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Life Cycle Assessment Framework for Asphalt Pavements: Methods to Calculate and Allocate Energy of Binder and Additives2014In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 15, no 4, p. 290-302Article in journal (Refereed)
    Abstract [en]

    The construction, maintenance and disposal of asphalt pavements may lead to considerable environmental impacts, in terms of energy use and emissions during the life of the pavement. In order to enable quantification of the potential environmental impacts due to construction, maintenance and disposal of roads, an open life cycle assessment (LCA) framework for the asphalt pavements is presented in this paper. Emphasis was placed on the calculation and allocation of energy used for binder and additives at the project level. It was concluded from this study that when progressing from LCA to its corresponding life cycle cost, the feedstock energy of the binder becomes highly relevant as the cost of the binder will be reflected in its alternative value as fuel. Regarding additives like wax, a framework for energy allocation was suggested. The suggested project level LCA framework was demonstrated in a limited case study of a Swedish asphalt pavement. It was concluded that the asphalt production and transporting materials were the two most energy-consuming processes, emitting most greenhouse gases depending on the fuel type and electricity mix.

  • 8.
    Chen, Feng
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Balieu, Romain
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Cordoba, Enrique
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Kringos, Niki
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Towards an understanding of the structural performance of future electrified roads: a finite element simulation study2018In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 20, no 2, p. 204-215Article in journal (Refereed)
    Abstract [en]

    Nowadays, many novel technologies are under investigations for making our road infrastructure functionbeyond providing mobility and embrace other features that can promote the sustainability developmentof road transport sector. These new roads are often referred to as multifunctional or ‘smart’ roads. Focusin this paper is given to the structural aspects of a particular smart road solution called electrified road or‘eRoad’, which is based on enabling the inductive power transfer technology to charge electric vehiclesdynamically. Specifically, a new mechanistic-based methodology is firstly presented, using a finiteelement simulation and an advanced constitutive model for the asphalt concrete materials. Based onthis, the mechanical responses of a potential eRoad structure under typical traffic loading conditions arepredicted and analysed thoroughly. The main contributions of this paper include thus: (1) introducing anew methodology for analysing a pavement structure purely based on mechanistic principles; (2) utilisingthis methodology for the investigation of a future multifunctional road pavement structure, such as aneRoad; and (3) providing some practical guidance for an eRoad pavement design and the implementationinto practice.

  • 9.
    Das, Prabir Kumar
    et al.
    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.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Numerical study on the effect of mixture morphology on long-term asphalt mixture ageing2015In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 16, no 8, p. 710-720Article in journal (Refereed)
    Abstract [en]

    Asphalt mixtures with similar percentages of air voids can have different morphologies and can age differently. Prediction of ageing behaviour without considering the influence of mixture morphology may thus lead to erroneous conclusions and non-optimal mix design. This article investigates the long-term field ageing of asphalt mixtures by incorporating mixture morphology. For this, a computational analysis on diffusion-reaction process has been conducted by implementing fundamental mechanism of ageing and conducting a parametric sweep of the morphology. To investigate the ageing gradient along the depth of asphalt mixture, diffusion controlled oxidative ageing on one dense and one open-graded field core was investigated. The proposed model based on the mixture morphology information was able to predict the aged viscosity better than the existing model. As mixture morphology is controllable, having insight into how the morphology parameter influences the mixture's ageing susceptibility can be of great value to its design.

  • 10.
    Edvardsson, Karin
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Gustafsson, Alf
    Svevia.
    Magnusson, Rolf
    Dalarna Högskolan.
    Dust suppressants efficiency study: in situ measurements of dust generation on gravel roads2012In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 13, no 1, p. 11-31Article in journal (Refereed)
    Abstract [en]

    Dust suppressants were applied on fifteen 1km long test sections at four sites in Sweden during three summer seasons with the objective to compare their relative efficiency and determine minimum application rates in Nordic climate. Dust generation from the test sections was measured both visually and by PM10 measurements. All products except lignosulphonate, sugar and bitumen emulsion showed acceptable efficiency. Chloride solutions were the most efficient. Results indicate the possibility to reduce application rates of chlorides by applying them as solutions instead of solids. The minimum application rate for a chloride solution was estimated at 0.8m 3/km, which is equivalent to a rate reduction of 50% by weight compared with traditionally applied rates of solid chloride. The results are expected to reduce life cycle costs for gravel roads and contribute to environmental gains by reducing the release of dust into the atmosphere and chemicals into the environment.

  • 11.
    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.

  • 12.
    Guarin, Alvaro
    et al.
    University of Florida.
    Roque, Reynald
    University of Florida.
    Kim, Sungho
    University of North Florida.
    Sirin, Oka
    Qatar University.
    Disruption Factor of Asphalt Mixtures2013In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 14, no 5, p. 472-485Article in journal (Refereed)
    Abstract [en]

    Typically, aggregate gradation is selected to meet Superpave mix design specification; however, many Superpave mixtures have exhibited deficient field performance. The porosity of the dominant aggregate size range (DASR), which is the primary structural network of aggregates, has been extensively validated as a tool to evaluate coarse aggregate structure of laboratory and field asphalt mixtures. Mixtures identified by the system as having poor or marginal gradations resulted in poor rutting resistance. This study focused on how asphalt mixture performance is affected by changes in interstitial component (IC), which is the material between DASR particles. Laboratory testing clearly showed that IC characteristics may have a significant effect on rutting and cracking performance of mixtures. The disruption factor (DF) was developed to evaluate the potential of IC aggregates to disrupt the DASR structure. DF satisfactorily distinguished poor performing mixtures; therefore, it may eventually be used in combination with DASR porosity as a design parameter for rutting and cracking resistant asphalt mixtures.

  • 13.
    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.

  • 14.
    Kringos, Nicole
    et al.
    Faculty of Civil Engineering and Geosciences, Delft University of Technology.
    Scarpas, A.
    Copeland, A.
    Youtcheff, J.
    Modeling of combined physical-mechanical moisture induced damage in asphaltic mixes: Part 2: moisture susceptibility parameters2008In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 9, no 2, p. 129-151Article in journal (Refereed)
  • 15.
    Kringos, Nicole
    et al.
    Faculty of Civil Engineering and Geosciences, Delft University of Technology.
    Scarpas, T.
    Kasbergen, C.
    Selvadurai, APS
    Modeling of combined physical-mechanical moisture induced damage in asphaltic mixes: Part 1: governing processes and formulations2008In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 9, no 2, p. 115-128Article in journal (Refereed)
    Abstract [en]

    Moisturehas for a long time been recognised as a serious contributor to premature degradation ofasphalticpavements. Many studies have been performed to collect, describe and measure themoisturesusceptibility ofasphalticmixes. Most of these are aimed at a comparative measure ofmoisturedamage, either via visual observations from field data or laboratory tests or viamechanicaltests, which give a so calledmoisturedamageindex parameter. The research presented in this paper ispartof an ongoing effort at Delft University of Technology, to move away from such comparative or empirical measures ofmoisture-induceddamageand start treatingmoisture-induceddamagein a comprehensive energy based framework. Such a framework would enable realistic predictions and time-assessment of the failure pattern occurring in anasphalticpavement under the given environmental and traffic loading which could be rutting, cracking, ravelling or any combination or manifestation thereof. Themodellingofmoisture-induceddamageis a complex problem, which involves a coupling betweenphysicalandmechanicaldamageprocesses. This paper discusses several modes ofmoistureinfiltration intoasphalticmixesand derives thegoverningequations for their simulations.Moisturediffusion into the mastic film, towards the aggregate-mastic interface and mastic erosion, due to high water pressures caused by the pumping action of traffic loading, are identified as the mainmoisture-induceddamageprocessesand are implemented in a new finite element program, named RoAM. The paper discusses the necessary model parameters and gives detailed verification of themoisturediffusion and advective transport simulations. In the accompanying paper the developed finite element model is demonstrated via an elaborate parametric study and the fundamentalmoisture-induceddamageparameters are discussed.

  • 16.
    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.

  • 17.
    Lövqvist, Lisa
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Balieu, Romain
    KTH, School of Architecture and the Built Environment (ABE), Architecture, Architectural Technologies. KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Kringos, Nicole
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    A micromechanical model of freeze-thaw damage in asphalt mixturesIn: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268XArticle in journal (Refereed)
    Abstract [en]

    Freeze-thaw damage in asphalt pavements is a complex phenomenon depending on many parameters such as moisture infiltration, temperature and mechanical properties of the asphalt constituents as well as the interface between them. As a first step in creating a comprehensive multiscale model including all of these parameters, a micromechanical model has been developed. This model couples the infiltration of moisture and the associated damage, the expansion caused by the water inside the air voids freezing, and the mechanical damage. The expansion of the air voids is implemented by applying a volumetric expansion in the air voids dependent on the temperature. The cohesive damage in the mastic and adhesive damage in the mastic-aggregate interface are included by implementing an energy based damage model and the cohesive zone model, respectively. To show the capabilities of the model, two different graded microstructures were exposed to 10 freeze-thaw cycles each and their stiffness was evaluated before and after the simulated freeze-thaw cycles. In addition, the sensitivity of the resulting damage to the time the microstructure was exposed to temperatures below zero was evaluated by simulating freeze-thaw cycles with a total time ranging between 10 hours and 14 days. From the analyses it was concluded that the model was capable of capturing the deteriorating effect of an increasing number of freeze-thaw cycles, and was sensitive to the freezing time in the freeze-thaw cycles.    

  • 18.
    Lövqvist, Lisa
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Balieu, Romain
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Kringos, Nicole
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    A micromechanical model of freeze-thaw damage in asphalt mixtures2019In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268XArticle in journal (Refereed)
    Abstract [en]

    Freeze-thaw damage in asphalt pavements is a complex phenomenon dependent on many parameters such as moisture infiltration, temperature and mechanical properties of the asphalt constituents as well as the interface between them. As a first step in creating a comprehensive multiscale model including all of these parameters, a micromechanical model has been developed. This model couples the infiltration of moisture and the associated damage, the expansion caused by the water inside the air voids freezing, and the mechanical damage. The expansion of the air voids is implemented by applying a volumetric expansion in the air voids dependent on the temperature. The cohesive damage in the mastic and adhesive damage in the mastic-aggregate interface are included by implementing an energy-based damage model and the cohesive zone model, respectively. To show the capabilities of the model, the effect of different parameters (the number of freeze-thaw cycles, the gradation of the microstructure, and the freezing time) was investigated through simulations. From the analyses it was concluded that the model was capable of capturing the deteriorating effect of an increasing number of freeze-thaw cycles, and was sensitive to the freezing time in the freeze-thaw cycles.

  • 19.
    Namutebi, May
    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.
    Bagampadde, Umaru
    Development of a gyratory compaction procedure for laterite gravels treated with foamed bitumen2013In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 14, no 3, p. 256-264Article in journal (Refereed)
    Abstract [en]

    Determining of the optimum density of the compacted foamed bitumen-treated materials is an important part of determining the field placement conditions. Laterite gravels tend to be highly susceptible to breakdown during laboratory compaction with the standard Proctor hammer, which may not be representative of field conditions. In this paper, a new method is presented for determining the optimal compaction characteristics of laterite gravels-foamed bitumen mixes. A gyratory compactor was used for compaction. The modified locking point concept was used to determine the number of gyrations to compact mixes of laterite gravels and foamed bitumen. The optimal compaction moisture content was subsequently established at this point. The average number of gyrations that gave the locking point was 44; optimum moisture content (OMC) for compaction varied from 86% to 92% for gravels only. The modified locking point seems to be suitable for determining the optimal compaction characteristics of these mixes.

  • 20.
    Rahman, Mohammad Shafiqur
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering. Swedish National Road and Transport Research Institute (VTI).
    Erlingsson, Sigurdur
    Swedish National Road and Transport Research Institute (VTI).
    Moisture Influence on the Resilient Deformation Behaviour of Unbound Granular Materials2016In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 17, no 9, p. 763-775Article in journal (Refereed)
    Abstract [en]

    The influence of moisture on the resilient deformation (RD) properties of unbound granular materials (UGMs) was investigated based on repeated load triaxial (RLT) tests. Results showed that the resilient modulus (MR) decreased with increasing moisture for a relatively low number of load cycles (N) where the deformation behaviour was mostly resilient with a negligible amount of associated accumulated permanent deformation (PD). Modelling attempts on this behaviour were quite satisfactory. Furthermore, the MR showed an increasing trend with increasing moisture, up to the optimum, when the N was relatively large with a significant amount of accumulated PD. Above the optimum, the MR generally decreased. Further investigation suggested that moisture aided the post-compaction (PC) and possible particle rearrangement that resulted in the increased PD and increased MR. The existing model did not work in this case indicating that the effect of PC on MR should be considered in modelling.

  • 21.
    Rahman, Mohammad Shafiqur
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science. Swedish National Road and Transport Research Institute (VTI).
    Erlingsson, Sigurdur
    KTH, School of Architecture and the Built Environment (ABE), Transport Science. Swedish National Road and Transport Research Institute (VTI).
    Predicting permanent deformation behaviour of unbound granular materials2015In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 16, no 7, p. 587-601Article in journal (Refereed)
    Abstract [en]

    To reliably predict the permanent deformation behaviour of unbound granular materials (UGM) in a pavement structure, the material parameters of the constitutive models used in design should be evaluated using a multi-stage (MS) loading approach. This paper investigated the prediction of the accumulation of permanent strain in UGM using some current models, extended applying the time-hardening approach, based on MS repeated load triaxial tests (RLTTs). The material parameters of these models were optimised for five different UGM used in pavement construction using the MS RLTT data with a specific set of stress levels. With these models, the accumulations of permanent strain in the same materials for MS RLTTs with a different set of stress levels were predicted. Using this approach, three out of the four models performed very well, which may be further developed for field conditions for better prediction of rutting.

  • 22. Romeo, Elena
    et al.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Highway and Railway Engineering.
    Montepara, Antonio
    Tebaldi, Gabriele
    The effect of polymer modification on hot mix asphalt fracture at tensile loading conditions2010In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 11, no 5, p. 403-413Article in journal (Refereed)
    Abstract [en]

    A laboratory investigation was conducted to evaluate the effect of both cross-linked and linear styrene-butadiene-styrene (SBS) modifiers on the cracking resistance of hot mix asphalt (HMA) mixtures. Five types of asphalt mixtures composed by the same aggregate gradation but different asphalt binders were produced in the laboratory. The cracking performances of the mixtures were evaluated using a viscoelastic fracture mechanics-based model entitled 'HMA Fracture Mechanics'. Crack localisation and crack growth were investigated performing the indirect tensile test and the semi-circular bending test. A digital image correlation system capable of providing full-field strain maps was applied. The results show the benefit of SBS modifiers to the mixture's cracking resistance in terms of reduced rate of damage accumulation and increased tensile limits to failure. Finally, significant damage and first fracture have shown to be strongly more localised in modified specimens than in the unmodified one.

  • 23.
    Salour, Farhad
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering. Swedish National Road and Transport Research Institute, VTI, Sweden .
    Erlingsson, Sigurdur
    University of Iceland.
    Permanent Deformation Characteristics of Silty Sand Subgrades from Multistage RLT Tests2015In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 18, no 3, p. 236-246Article in journal (Refereed)
    Abstract [en]

    Rutting is one of the main forms of distresses in thin flexible pavement structures, often associated with accumulation of permanent deformation in unbound granular layers and subgrade soils under traffic loading. Realistic prediction of surface rutting requires models that can reliably capture the cumulative plastic deformation of pavement unbound layers under repeated loads. This study presents an evaluation of three models that incorporate the time-hardening concept for prediction of permanent deformation of silty sand subgrade materials. A series of multistage repeated load triaxial (RLT) tests, in which the material underwent a wide range of continuous stress conditions, were carried out on two silty sand subgrades. The RLT tests were conducted at four different moisture contents in which pore suctions were measured throughout the test. In the modelling of the permanent deformations, the effective stress approach was used taking into account the effects of soil suctions. The material parameters of the predictive models were optimised using the RLT test data and the effect of moisture content (matric suction) on the permanent deformation characteristics of the materials and the predictive model parameters were investigated. Generally, it was observed that the modified models that are based on the shakedown approach performed reasonably well in capturing the permanent deformation behaviour of the selected subgrade materials with minor discrepancies between the models. This indicates that using multistage RLT tests can be an efficient approach for characterising the permanent deformation behaviour of subgrade soils.

  • 24. Schmets, A.
    et al.
    Kringos, Nicole
    TU Delft, The Netherlands.
    Redelius, P.
    Wax Induced Phase Separation in Bitumen2010In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 11, no 6Article in journal (Refereed)
  • 25.
    Wennström, Jonas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Karlsson, Robert
    Possibilities to reduce pavement rehabilitation cost of a collision-free road investment using an LCCA design procedure2016In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 17, no 4, p. 331-342Article in journal (Refereed)
    Abstract [en]

    In the past decades, many single carriageway roads in Sweden have been converted to collision-free roads as a cost-effective alternative to conventional motorways. Investigations have concluded that the road type has been successful in reducing the number of fatal accidents, despite increased operation and maintenance costs. In recent years, the focus has shifted to converting narrower roads, which are anticipated to further increase pavement rehabilitation cost but also complicate traffic management during road works. This paper first examines the consequences in terms of road agency and road user costs; second, the possibilities to influence future costs by design alternatives. A life cycle cost analysis was employed to study future costs. The analysis indicated significant increase in life cycle cost compared to a single carriageway road. The analysis of design alternatives also indicated that future agency and road user cost can be substantially improved by finding an optimal alternative.

  • 26.
    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.

  • 27.
    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.

  • 28.
    Zhu, Jiqing
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Lu, Xiaohu
    Nynas AB.
    Kringos, Niki
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Experimental investigation on storage stability and phase separation behaviour of polymer-modified bitumen2018In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 19, no 9, p. 832-841Article in journal (Refereed)
    Abstract [en]

    Storage stability and phase separation behaviour of four styrene-butadiene-styrene (SBS) polymer-modified bitumen (PMB) binders are investigated by conventional binder tests and fluorescence microscopy in this paper. Since no separation happened in the stable PMBs, research focus was placed on capturing and analysing the phase separation process in the unstable PMBs. A phase inversion phenomenon was observed in one unstable PMB during the phase separation, showing the possible viscoelastic effects. Furthermore, it is indicated that criteria only based on compositional parameters can give misleading predictions of PMB storage stability. New criteria still need to be defined. The potential approaches to PMB phase behaviour prediction are reviewed and exploratively discussed in the context of the four investigated PMBs. This leads to a further discussion on the possibility of having a thermodynamic approach to PMB phase behaviour prediction by looking into the free energy of PMB. The Flory–Huggins theory provides a way to do this, upon the consideration of PMB as a pseudo-binary blend and some made assumptions. Free energy curves have the strength of giving more information like the equilibrium phase composition. In addition, some more aspects should be also considered for PMB phase behaviour prediction towards an applicable criterion.

1 - 28 of 28
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