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  • 1. Abd-Alla, E. S. M .
    et al.
    Moriyoshi, A.
    Partl, Manfred
    EMPA, Swiss Federal Laboratories for Materials Testing and Research.
    Takahashi, K.
    Kondo, T.
    Tomoto, T.
    New wheel tracking test to analyze movements of aggregates in multi-layered asphalt specimens2006Ingår i: Journal of the Japan Petroleum Institute, ISSN 1346-8804, E-ISSN 1349-273X, Vol. 49, nr 5, s. 274-279Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper describes a new wheel tracking test for analyzing movements of aggregates in mixtures. The test device is conducted using as examples four-layered specimens taken from two Swiss national motorways, where severe rutting (G section) and longitudinal cracking (H section) were observed. This test method was developed by Moriyoshi. Tests can be carried out under temperature distributions similar to field situation. Two-dimensional movements and strains between aggregates for four-layered specimens due to the moving wheel loads were analyzed by right angle for direction of wheel pass. For this purpose, the cross section of the slabs with a width of 30 cm was divided optically into 5 vertical subsections. The transverse permanent surface deformations, the area changes in the transversal subsections as well as the maximum deformation of the surface and layer-interface through the centerline of the applied wheel load were determined. Strain distributions between aggregates in mixtures at high temperature (45 degrees C) under 600 passes were also measured by photo analysis. Test results show consolidation of the asphalt mixtures and material flow on the surface near the wheel load. The results also demonstrate that the aggregates (size of aggregate: 2 mm or larger) in each mixture move mainly in vertical direction. Large strains (40% or larger) between aggregates at summer condition were measured in the surface mixture near wheel track after 600 passes.

  • 2. Arraigada, M
    et al.
    Partl, Manfred
    Swiss Federal Laboratories for Materials Testing and Research (Empa).
    Angelone, S
    Determination of Road Deflections from Traffic Induced Accelerations2007Ingår i: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 8, nr 3, s. 399-421Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Vertical elastic pavement deflections from moving vehicles provide valuable information for assessing the structural behaviour of a road under real loads. Various types of sensors can be installed in a road for deflection monitoring. This paper explores the use of accelerometers. It discusses the problems involving the calculation of deflections from measured acceleration by double integration due to the amplification of measurement errors in the acceleration signal. It proposes a simple algorithm to correct integration errors and obtain deflections from acceleration measurements. It also presents a laboratory testing method to evaluate the performance of two accelerometers for their suitability in road applications. In addition, using a selected accelerometer, pavementdeflections at a wheel tracking test site are calculated and discussed. 

  • 3. Arraigada, M
    et al.
    Partl, Manfred
    Swiss Federal Laboratories for Materials Testing and Research (EMPA).
    Angelone, S
    Martìnez, Francisco
    Evaluation of Accelerometers to Determine Pavement Deflections under Traffic Loads2008Ingår i: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 42, nr 6, s. 779-790Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The purpose of this work was to study the use of accelerometers to measure pavement deflections due to traffic loads. To this end, accelerometers were embedded in two sites: the full scale load simulator Circular Test Track (CTT) and the A1 motorway in Switzerland. Deflections were derived from acceleration measurements using an algorithm that double integrates the measured signal and corrects any errors derived from the procedure. In the motorway, deflections were monitored using a set of three magnetostrictive deflectometers. Additionally, the pavement's material viscoelastic parameters determined in the laboratory were incorporated in Finite Element (FE) models to estimate the theoretical deflections. The calculated deflections were then compared to the measured and to the theoretical deflections. Deflections calculated from acceleration showed a reasonable qualitative correlation to those measured by magnetostrictive deflectometers. In addition, the FE models revealed the inability of the accelerometers to measure very slow or quasi-static motion.

  • 4. Bressi, S.
    et al.
    Dumont, A. G.
    Partl, Manfred N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. Carleton University, Ottawa, Canada; Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland.
    A new laboratory methodology for optimization of mixture design of asphalt concrete containing reclaimed asphalt pavement material2016Ingår i: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 49, nr 12, s. 4975-4990Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The reduction of virgin bitumen added to asphalt mixtures containing Reclaimed Asphalt Pavement (RAP) is based on the typical assumption that all the aged binder function in the same way as the virgin binder. However, recent studies conducted by the authors for a specific case show that a blend or mobilization of RAP binder are negligible. The aged bitumen becomes softer acting as glue facilitating cluster formation between small-size RAP particles. The reduction of small-size particles causes changes in the target grading curve and in the voids-fill, affecting the compactability of RAP mixtures. Therefore the target grading curve of RAP mixtures needs to be readjusted, using different proportions of virgin aggregates and taking into account the cluster phenomenon. The objective of this paper is to develop a new mix design approach for RAP mixtures, taking into account the cluster phenomenon and the contribution of the aged bitumen in the compactability. The virgin aggregates, filler and RAP are investigated and individually included in the calculation. 3D images of the virgin aggregates allowed the determination of new surface area factors; the concept of critical filler concentration led to the definition of the minimum bitumen quantity required to maintain the mastic in a diluted state and fill the voids. A RAP clustering model was introduced to predict the agglomeration of small-size RAP particles. The readjustment of the target grading curve was analytically calculated, allowing the correct estimation of the amount of virgin bitumen to be added to asphalt mixtures. Finally, a first verification of the entire process was carried out performing laboratory tests. These promising results enable the challenge of a new mix design optimization for HMA with high RAP content to be addressed.

  • 5. Bressi, Sara
    et al.
    Dumont, A. G.
    Partl, Manfred
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. Carleton Univ, Ottawa, Canada.
    An advanced methodology for the mix design optimization of hot mix asphalt2016Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 98, s. 174-185Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The bitumen quantity to add to asphalt mixtures depends on the surfaces of aggregates and filler to be coated. The formulas currently available in the literature have limitations such as considering all the fillers with the same specific surface or the aggregates with spherical or cubical shapes. This paper aims to define an analytical approach for the determination of the optimal dosage of bitumen in HMA proposing new methodologies to go a step further in the resolution of the above mentioned approximations. Indeed, new surface area factors were calculated to determine the aggregates surface considering their real shapes and volumes. Afterwards, the authors proposed a detailed characterization of two types of fillers and the critical filler concentration, introduced by Faheem and Bahia, was used to calculate the minimum amount of bitumen for maintaining the mastic in a diluted state and filling the voids in the mixtures. Finally, a verification of the formula developed was carried out with specific laboratory tests. These results allow the challenge of revising the method of calculating the specific surface of the aggregates and filler to be addressed with the final goal to include them in a new mix design optimization for HMA. 

  • 6. Bueno, M.
    et al.
    Hugener, M.
    Partl, Manfred
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Fracture toughness evaluation of bituminous binders at low temperatures2015Ingår i: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 48, nr 9, s. 3049-3058Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    When asphalt roads turn brittle at low temperatures, they are no longer able to relax completely from traffic induced stresses and may also suffer damage through crack initiation and propagation. In order to avoid early structural damages, the bituminous binders must be selected very carefully. However, conventional test methods for assessing performance of bituminous binders at low temperatures are often unsatisfactory reliable, in particular in case of polymer modified bituminous binders. In this study, an alternative experimental method based on fracture mechanical principles was performed on pre-notched specimens in the brittle state inside a cooling media. This fracture toughness test was evaluated in terms of its suitability for distinguishing different types of polymer modified and unmodified bituminous binders. In addition, the feasibility to evaluate different ageing states was also analysed by testing samples after artificial short-term and long-term ageing procedures. The repeatability obtained from the experimental results showed that the fracture toughness test is a suitable candidate for being introduced in a standardization framework.

  • 7. Bueno, M.
    et al.
    Hugener, M.
    Partl, Manfred Norbert
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Low temperature characterization of bituminous binders with a new cyclic shear cooling (CSC) failure test2014Ingår i: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 58, s. 16-24Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Low temperature cracking of asphalt pavements is associated to the thermal stresses created when asphalt binder changes from a ductile into a brittle state during cooling. Under repetitive traffic loads, this change of properties can become a significant problem, resulting in the formations of large cracks on the driving surface, thus requiring early pavement repair. Nevertheless, the conventional test methods for assessing low temperature properties of bitumen are often insufficient and subject to low reproducibility. Therefore, a reliable method is necessary to characterize the performance of bituminous binders at low temperature. This work presents the cyclic shear cooling failure test (CSC-failure test) as an alternative method based on a failure test with the dynamic shear rheometer (DSR) at decreasing temperature until fracture occurs. Operational parameters, like shear strain amplitude or loading frequency, have been analysed in order to develop a reproducible procedure applicable for different types of bituminous binders. Moreover, a failure criterion has been defined by analysing the different characteristic temperatures from the failure curves obtained in the test.

  • 8. Canestrari, F.
    et al.
    Ferrotti, G.
    Lu, X.
    Millien, A.
    Partl, Manfred
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. Empa, Swiss Federal Laboratories for Materials Science and Technology.
    Petit, C.
    Phelipot-Mardelé, A.
    Piber, H.
    Raab, C.
    Mechanical testing of interlayer bonding in asphalt pavements2013Ingår i: Advances in Interlaboratory Testing and Evaluation of Bituminous Materials, Springer Netherlands, 2013, s. 303-360Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Steadily increasing requirements on pavement performance properties, in terms of bearing capacity and durability, as well as new innovative developments regarding pavement materials and construction, are observed worldwide. In this context interlayer bonding at the interfaces of multi-layered bituminous systems is recognized as a key issue for the evaluation of the effects, in terms of stress-strain distribution, produced by traffic loads in road pavements. For this reason a correct assessment of interlayer bonding is of primary importance, and research efforts should be addressed in order to improve the lack of correlation and/or harmonization among test methods. Following this principle RILEM TG 4 organized an interlaboratory test in order to compare the different test procedures to assess the interlayer bonding properties of asphalt pavement. The results of the experimental research are presented with a preliminary overview of basic elements, test methods and experimental investigations on interlayer bonding. Then the RILEM TG 4 experimental activities, based on the construction of three real- scale pavement sections, are presented in detail. Each pavement section was composed of two layers, and three different interface conditions were chosen. The first pavement was laid without interface treatment and the others with two different types of emulsion. Fourteen laboratories from 11 countries participated in this study and carried out shear or torque tests on 1,400 cores. The maximum shear or torque load and the corresponding displacement were measured, and the shear or torque strength was calculated as a function of the following parameters: diameter, test temperature, test speed, stress applied normal to the interface and age of the specimen. The results of this study are presented in terms of precision and correlations regarding the parameters which results in useful information on asphalt pavement interlayer bond tests.

  • 9.
    Celma Cervera, Carlos
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Jelagin, Denis
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Partl, Manfred N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. bEMPA Swiss Federal Laboratories for Materials Testing and Research, Switzerland.
    Larsson, Per-Lennart
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Contact-induced deformation and damage of rocks used in pavement materials2017Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 133, s. 255-265Artikel i tidskrift (Refereegranskat)
    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.

  • 10. Chailleux, E.
    et al.
    Partl, M. N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    General summary and outlook2013Ingår i: RILEM State-of-the-Art Reports, Springer, 2013, s. 429-438Konferensbidrag (Refereegranskat)
    Abstract [en]

    Final considerations based on the experience and feedback of this RILEM technical committee TC 206-ATB on “Advanced Testing and Characterization of Bituminous Materials” are given. Some open questions within the general methodology as introduced in Chap. 1 and used as guideline for RILEM activities are listed. Future prospects and direction of activities of joint voluntary research efforts within the frame of such asphalt-related committees are also discussed. It is suggested that these future efforts will most certainly have to focus even more on sustainability and environmental aspects but without neglecting general materials and systems quality aspects during production and construction as well as safety and performance during use. Future activities will also have to dealwith multifunctionality aspects of pavements and multi-scaling approaches as a basis for better understanding and tailoring of pavements and pavement materials.

  • 11.
    Chen, Feng
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Jelagin, Denis
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Partl, Manfred
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. EMPA–Swiss Federal Laboratories for Materials Science and Technology, Duebendorf, Switzerland.
    Experimental and numerical analysis of asphalt flow in a slump test2019Ingår i: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 20, s. S446-S461Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The mechanical behaviour of uncompacted asphalt mixtures is still not well understood,threatening directly to the pavement practices such as control of mixture’s workability andsegregation. This situation may become even worse due to the gradually increasing complexityand advances in paving materials and technologies. This study adopts a slump flow testbased on concrete technology and a Discrete Element (DE)-based numerical tool to investigatethe mechanical behaviour of uncompacted asphalt mixture from a microstructural point ofview, particularly focusing on the bituminous binder effects. The combined experimental andnumerical analysis indicates that bitumen distinctly influences the contact interactions withinthe mixture and thus its macroscopic flow, which can be physically interpreted as a combinedeffect of lubricated friction and bonding force. Additional case studies demonstrate that the DEmodel is capable of simulating the flow response of asphalt mixtures under changed particlecontact conditions and driven force.

  • 12.
    Fadil, Hassan
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Jelagin, Denis
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Larsson, Per-Lennart
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Hållfasthetslära (Avd.).
    Partl, Manfred
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Measurement of the viscoelastic properties of asphalt mortar and its components with indentation tests2019Ingår i: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402Artikel i tidskrift (Refereegranskat)
    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. Fang, X.
    et al.
    Garcia, A.
    Partl, Manfred N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik. Swiss Federal Laboratories for Materials Science and Technology, Switzerland .
    Lura, P.
    Investigation on hardening mechanism and cement hydration of Cement Asphalt Emulsion Composites2014Ingår i: Asphalt Pavements - Proceedings of the International Conference on Asphalt Pavements, ISAP 2014, 2014, s. 1441-1450Konferensbidrag (Refereegranskat)
    Abstract [en]

    Cement Asphalt Emulsion Composites (CAEC) are mixtures of bitumen emulsion, cement, water and aggregates that harden at ambient temperature. They are mixed at ambient temperature and harden due to breaking of the emulsion, water evaporation and cement hydration. Potential advantages of CAEC are lower temperature susceptibility than asphalt concrete and higher flexibility than cement concrete. To quantify the effects of cement hydration on the mechanical properties of CAEC, two different emulsions (cationic and anionic) mixed with either 0%, 3% and 6% Ordinary Portland Cement (OPC) by mass of dry aggregates were studied by isothermal calorimetry and Marshall tests. By monitoring the mass of the specimens and estimating the amount of water bound by the cement, the water content was calculated. This study shows that bitumen emulsion has no significant effect on the degree of cement hydration. Cement hydration, however, significantly contributes to the hardening of CAEC. Moreover, a higher amount of cement added to the mixture results in a higher amount of bound, adsorbed and capillary water in the CAEC.

  • 14. Fang, Xing
    et al.
    Garcia, Alvaro
    Winnefeld, Frank
    Partl, Manfred N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE).
    Lura, Pietro
    Impact of rapid-hardening cements on mechanical properties of cement bitumen emulsion asphalt2016Ingår i: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 49, nr 1-2, s. 487-498Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cement bitumen emulsion asphalt (CBEA) is obtained by mixing bitumen emulsion, cement, aggregates and filler at ambient temperature. CBEA is thought to be a promising substitute for hot mix asphalt because of its low environmental impact and cost-effectiveness. Disadvantages of this material are the long time required to reach its full strength and the inadequate understanding of the hardening mechanisms. This study aims at accelerating the development of mechanical properties of CBEA by using rapid-hardening cements while at the same time gaining a deeper understanding of the role of cement in CBEA. With this purpose, cold mix asphalt mixtures with cationic and anionic emulsions and different types of cement (ordinary Portland, calcium sulfoaluminate and calcium aluminate cement) were studied by means of isothermal calorimetry, measurements of water evaporation and Marshall tests. The results indicate that both anionic and cationic bitumen emulsions may affect the initial hydration rates of the cements used but have no significant influence on their degree of hydration after a few days. The addition of calcium sulfoaluminate and calcium aluminate cement to CBEA leads to mechanical properties after 1-day curing similar to those obtained with Portland cement after 1-week curing. Cement hydration dominates the strength gain, especially for rapid-hardening cements, and the type of cement influences both the amount of bound water and the rate of water evaporation from the CBEA.

  • 15. Garcia, A.
    et al.
    Bueno, M.
    Norambuena-Contreras, J.
    Liu, Q.
    Partl, Manfred
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap. EMPA, Swiss Federal Laboratories for Materials Science and Technology, Duebendorf, Switzerland .
    The model for induction-healing asphalt concrete2014Ingår i: Asphalt Pavements: Proceedings of the International Conference on Asphalt Pavements, ISAP 2014, 2014, Vol. 2, s. 1431-1440Konferensbidrag (Refereegranskat)
    Abstract [en]

    Induction heating of asphalt concrete is accomplished by adding electrically conductive particles to the asphalt mixture, and heating them with an induction heating device. When the temperature of the asphalt concrete is higher than 30-70 °C, cracks may start closing. In this article, the healing properties of 25 different mixtures, with the same aggregates distribution and amount of bitumen, but with 2 different lengths, 4 different quantities, and 4 different diameters of steel wool fibers have been considered. It has been found that the asphalt concrete studied can be healed up to 60% and that healing happens when the temperature is higher than 50 °C. Additionally, asphalt healing versus the increase of temperature has been fitted through an equation based on the capillary theory, showing that capillary flow is the main parameter affecting asphalt healing at high temperature.

  • 16. Garcia, A.
    et al.
    Lura, P.
    Partl, Manfred N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Influence of cement content and environmental humidity on cement-asphalt composites performance2012Ingår i: Concrete Repair, Rehabilitation and Retrofitting III - Proceedings of the 3rd International Conference on Concrete Repair, Rehabilitation and Retrofitting, ICCRRR 2012, 2012, s. 247-253Konferensbidrag (Refereegranskat)
    Abstract [en]

    Ideally, a material with low-environmental impact and combining the advantages of both asphalt and concrete could be obtained by combining bitumen emulsions and a cementitious material. These bitumen emulsions harden by a process where the water in the mixture is removed both by evaporation and by cement hydration. In this research, cold asphalt mixtures with different percentages of cement replacement have been prepared and tested with Marshall Stability tests. Furthermore, mixtures with 0% and with 3% of cement replacement were cured under different environmental relative humidity (35, 70 and 90% RH). Additionally, the mass evolution of the specimens cured under different humidity conditions was measured. According to the results of the present study, cement contributes to the hardening of cold asphalt mixtures by creating mortar bridges between the aggregates and by removing water from the mixtures through cement hydration.

  • 17. Garcia, Alvaro
    et al.
    Lura, Pietro
    Partl, Manfred N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Jerjen, Iwan
    Influence of cement content and environmental humidity on asphalt emulsion and cement composites performance2013Ingår i: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 46, nr 8, s. 1275-1289Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Asphalt and cement concrete are the most popular materials used in the construction of roads, highways, bridge deck surface layers and pavements in airports and other areas with heavy wheel roads. Whereas asphalt possesses, compared to concrete, the advantages of a short curing period, high skid resistance and easy maintenance, it also shows lower fatigue durability, ravelling and rutting due to repeated concentrated loads and susceptibility to temperature changes and moisture. On the other hand, concrete pavements are initially more expensive, have lower driving comfort and are susceptible to cracking due to volume changes and to salt damage. A material with low-environmental impact and with advantages of both asphalt and concrete may be obtained by combining bitumen emulsions and a cementitious material. In this paper, cold asphalt mixtures with different amounts of cement were tested with Marshall stability tests. Selected mixtures were also cured at different environmental relative humidity (35, 70 and 90 % RH). By monitoring the mass of the specimens and estimating the water bound by the cement, the total water remaining in the mixtures was calculated. Details of the microstructure in the mixtures were examined with X-ray microtomography. According to the results of the present study, cement contributes to the hardening of cold asphalt mixtures both by creating cement paste bridges between the aggregates and by removing water from the mixtures through cement hydration. Asphalt and cement composites appear to be promising materials for implementation in real pavements, although their rate of hardening needs to be improved further.

  • 18. Garcia, Alvaro
    et al.
    Norambuena-Contreras, J.
    Partl, Manfred N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik. Empa Swiss Federal Laboratories for Materials Science and Technology, Switzerland.
    A parametric study on the influence of steel wool fibers in dense asphalt concrete2014Ingår i: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 47, nr 9, s. 1559-1571Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Environmental conditions combined with traffic loads contribute to premature deterioration of asphalt concrete pavements, reducing their strength and durability over time. To improve it, fibers can be incorporated in the mixture. Additionally, electrically conductive fibers can be used for self-healing purposes. In this context, this paper evaluates the influence of flexible steel fibers (steel wool) on the mechanical and physical properties of dense asphalt concrete. With these purposes, 25 different mixtures, with the same aggregate gradation and amount of bitumen, but with two different fibers lengths, four different percentages, and four different diameters of steel wool have been considered. Additionally, the influence of fibers on test specimens with three different types of damage: water damage, salt water damage and ageing have been evaluated through particle loss tests. Moreover, the influence of different temperatures on the flexural strength of dense asphalt concrete with steel wool fibers has been studied. It was found that steel wool fibers do not significantly improve the mechanical properties and damage resistance of dense asphalt concrete. On the other hand, steel wool fibers can change the air void distribution of a mixture, and therefore even reduce its particle loss resistance. As a recommendation, it is indicated that, for induction heating purposes, short fibers, with big diameters should be used, since they do not seem to alter the original properties of dense asphalt concrete.

  • 19. Garcia, Alvaro
    et al.
    Norambuena-Contreras, J.
    Partl, Manfred N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Experimental evaluation of dense asphalt concrete properties for induction heating purposes2013Ingår i: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 46, s. 48-54Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Induction heating of asphalt concrete is a technique that has been recently developed to increase the self-healing rates of asphalt concrete. It consists in adding electrically conductive fibers to the asphalt mixture and heating them with an induction heating device. In this way, the temperature of asphalt concrete can be indirectly increased. But still, the factors that affect the increase of temperature are not well-known. With the purpose of finding them, 25 different mixtures, with the same aggregates distribution and amount of bitumen, but with two different lengths, four different quantities, and four different diameters of steel wool fibers have been considered. The influence of fibers on the air void content, electrical and thermal conductivity of dense asphalt concrete has been studied. Furthermore, the effect of these properties on the maximum temperature reached after a fixed time induction heating is analysed. It was found that steel wool fibers increase slightly the electrical and thermal conductivities of dense asphalt concrete. Additionally, in the case of the thermal conductivity, an increase on the volume of steel wool fibers serves to compensate the loss in the thermal conductivity that happens when the air void content is increased. Finally, it has been observed that the temperature reached due to the induction heating increases with the number of fibers in the mixture and with their diameter. As a recommendation, it is indicated that, for induction heating purposes, short fibers, with big diameters should be used.

  • 20. Garcia, Alvaro
    et al.
    Norambuena-Contreras, Jose
    Bueno, Moises
    Partl, Manfred N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap. University of Cantabria, Spain .
    Single and multiple healing of porous and dense asphalt concrete2015Ingår i: Journal of Intelligent Materials Systems and Structures, ISSN 1045-389X, E-ISSN 1530-8138, Vol. 26, nr 4, s. 425-433Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    When the temperature of asphalt concrete is above a certain threshold, bitumen may start flowing through any possible crack and healing it. Induction heating is a technique for increasing the temperature of asphalt mixture. It consists of adding electrically conductive and magnetically susceptible particles to the mixture. These particles can be heated thanks to the action of an induction heating apparatus. The objective of this article is to investigate the effect of different asphalt mixture porosities and different types of bitumen on the induction-healing rates of asphalt concrete. With this purpose, semi-circular test samples made of porous asphalt mixture, with bitumen pen 70/100, and dense asphalt mixture, with bitumen pen 40/50, both of them containing steel wool fibres, have been analysed through successive three-point bending and induction heating tests. It has been found that the minimum temperature above which healing of asphalt mixture starts depends on the capacity for flow of bitumen at the threshold temperature. Moreover, the maximum healing level reached by asphalt mixture after damage is related to the type of bitumen used. Finally, it has also been found that successive heating of asphalt mixture may damage the structure of the material, reducing its healing capacity.

  • 21. García, A.
    et al.
    Bueno, M.
    Norambuena-Contreras, J.
    Partl, Manfred N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Induction healing of dense asphalt concrete2013Ingår i: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 49, s. 1-7Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Induction heating can be used for repairing cracks in asphalt concrete. With this purpose, electrically conductive particles have to be added to the asphalt mixture, which is then heated with an induction heating device. Since the factors affecting the induction healing of dense asphalt concrete are not well-known, in this article, different mixtures, with different lengths, quantities and diameters of steel wool fibres have been considered. It was found that there is a minimum temperature for healing asphalt concrete. Additionally a semi-empirical model, explaining asphalt healing through the capillary theory has been developed and fitted to the results.

  • 22. García, A.
    et al.
    Norambuena-Contreras, J.
    Bueno, M.
    Partl, Manfred
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. Empa, Swiss Federal Laboratories for Materials Science and Technology, Duebendorf, Switzerland .
    Influence of steel wool fibers on the mechanical, termal, and healing properties of dense asphalt concrete2014Ingår i: Journal of Testing and Evaluation, ISSN 0090-3973, E-ISSN 1945-7553, Vol. 42, nr 5Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper summarizes the main results of experimental research on the induction healing of dense asphalt concrete with steel wool fibers. Different physical properties of dense asphalt concrete, as the steel wool fibers distribution, mechanical properties, thermal conductivity, and healing via induction heating have been analysed. The main results show that short and thick fibers disperse very well in the mixture, while long and thin fibers produce clusters. It was also observed that fibers can be damaged during the mixing and compaction processes. In addition, it was found that steel wool fibers do not significantly improve the mechanical properties and damage resistance of dense asphalt concrete. Moreover, steel wool fibers slightly increase the thermal conductivity of dense asphalt concrete. Furthermore, the temperature reached due to induction heating increases with the number of fibers in the mixture and with their diameter. Finally, it was found that dense asphalt concrete heals through the increase of temperature and that the type and diameter of fibers do not influence the healing properties of dense asphalt concrete.

  • 23. García, A.
    et al.
    Norambuena-Contreras, J.
    Partl, Manfred N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Schuetz, P.
    Uniformity and mechanical properties of dense asphalt concrete with steel wool fibers2013Ingår i: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 43, s. 107-117Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fibers in asphalt concrete are known for enhancing its strength and fatigue characteristics while increasing ductility. Additionally, fibers may increase the dynamic modulus, moisture resistance, creep compliance, rutting and freeze-thaw resistance of asphalt concrete, preventing the formation and propagation of cracks. The addition of fibers may influence the properties of the material, but it is not clear how is this influence, and which are the optimum amount, length and diameter of fibers needed for not having a negative impact on the mixture. For this reason, fibers (steel wool) distribution and their effect on the porosity and electrical conductivity of dense asphalt concrete have been studied. With that purpose, 25 different mixtures, with the same aggregates gradation and amount of bitumen, but with two different lengths of fibers, four different percentages, and four different diameters of steel wool have been built. Results show that long and thin fibers produce many clusters and a poor distribution, while short and thick fibers disperse very well in the mixture. It was also observed that fibers can be seriously damaged during the mixing and compaction processes. Finally, it has been found that steel wool fibers do not have a relevant influence on the particle loss resistance and flexural strength of dense asphalt concrete.

  • 24. García, A.
    et al.
    Partl, Manfred Norbert
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    How to transform an asphalt concrete pavement into a solar turbine2014Ingår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 119, s. 431-137Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Asphalt concrete can absorb a considerable amount of the incident solar radiation. For this reason asphalt roads could be used as solar collectors. There have been different attempts to achieve this goal. All of them have been done by integrating pipes conducting liquid, through the structure of the asphalt concrete. The problem of this system is that all pipes need to be interconnected: if one is broken, the liquid will come out and damage the asphalt concrete. To overcome these limitations, in this article, an alternative concept is proposed:parallel air conduits, where air can circulate will be integrated in the pavement structure. The idea is to connect these artificial pore volumes in the pavement to an updraft or to a downdraft chimney. Differences of temperature between the pavement and the environment can be used to create an air flow, which would allow wind turbines to produce an amount of energy and that would cool the pavement down in summer or even warm it up in winter. To demonstrate that this is possible, an asphalt concrete prototype has been created and basics calculations on the parameters affecting the system have been done. It has been found that different temperatures, volumes of air inside the asphalt and the difference of temperature between the asphalt concrete and the environment are critical to maximize the air flow through the pavement. Moreover, it has been found that this system can be also used to reduce the heat island effect.

  • 25.
    Ghafoori Roozbahany, Ehsan
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Partl, Manfred
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    A new test to study the flow of mixtures at early stages of compaction2016Ingår i: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 49, nr 9, s. 3547-3558Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Workability is one of the most commonly used indicators for the capability of asphalt mixtures tobe placed and compacted on the roads with long lasting quality and minimum maintenancethroughout its service life. Despite of valuable previous efforts for measuring and characterizingworkability, none of them has proven successful in representing the field conditions of roadconstructions. This paper is an attempt towards developing a systematic workability test methodfocusing on compaction, the so-called Compaction Flow Test (CFT), by simulating fieldcompaction at early stages and at laboratory scale with the main focus on mixture flow. The CFTwas applied for different mixtures in order to identify the parameters with highest impact on theasphalt particle movements under compaction forces. A new setting inside X-ray ComputationalTomography (CT) allowed tracing asphalt particles during the CFT and acquiring CT imagesunderlining the reliability of the CFT results. In addition, simple Discrete Element Models (DEM)were successfully generated to justify some of the CFT results.

  • 26.
    Ghafoori Roozbahany, Ehsan
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Partl, Manfred
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Investigation of asphalt joint compaction using discrete element simulation2019Ingår i: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Constructing high quality asphalt joints plays a vital role in preventing premature failures of pavements. Previous studies suggested that many construction parameters directly and indirectly influence the quality of asphalt joints. Due to uncertainties about the influence of each parameter on the quality of the finalised joints, closer and more detailed studies are still needed for achieving further improvements in this field. This study investigates the possible impacts of thickness, bottom layer roughness, joint interface geometries and compaction techniques on the particle flow of a coarse structured mixture during compaction. Therefore, discrete element method (DEM) was utilised to evaluate the influence of each construction parameter on the interlock between the cold and the hot side of an asphalt pavement joint. The results helped to explain earlier experimental findings about the joints and revealed potential for further laboratory and field investigations.

  • 27.
    Ghafoori Roozbahany, Ehsan
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. VTI Swedish National road and transport research institute, Olaus Magnus väg 35, Linköping, 583 30, Sweden.
    Partl, Manfred
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Elaguine, Denis
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Modelling the flow of asphalt under simulated compaction using discrete element2019Ingår i: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 227, artikel-id 116432Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The flow differences between the particles of asphalt mixtures compacted in the laboratory and in the field have been identified as one of the reasons for the discrepancies between laboratory and field results. In previous studies, the authors developed a simplified test method, the so-called compaction flow test (CFT), for roughly simulating the flow of particles in asphalt mixtures under compacting loads in laboratory. The CFT was used in different studies to examine its capability of revealing the differences between the flow behavior of different asphalt mixtures under various loading modes. The promising results encouraged further development of the CFT by investigating the possible impacts of simplifications and boundary conditions on the results of this test. For this reason, discrete element method (DEM) was utilized to investigate possible impacts of the mold size, geometry of the loading strip as well as the loading rate on the results of the CFT. The results of the simulation indicate that in case of wearing course layers with nominal maximum aggregate size of 11 mm, the length of the CFT mold can be increased from 150 mm to 200–250 mm for reducing flow disturbances from the mold walls. However, since the majority of the flow of asphalt mixture particles is expected to take place within the first 100–150 mm length of the mold, reasonable results can still be obtained even without changing the size of the CFT mold. Moreover, comparing results with different loading strip geometries and loading rates indicates that the current CFT setup still appears to provide consistent results.

  • 28.
    Ghafoori Roozbahany, Ehsan
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Partl, Manfred
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Guarin, Alvaro
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Influence of layer thickness on the flow of asphalt under simulated compaction2018Ingår i: Bearing Capacity of Roads, Railways and Airfields - Proceedings of the 10th International Conference on the Bearing Capacity of Roads, Railways and Airfields, BCRRA 2017, CRC Press/Balkema , 2018, s. 1435-1441Konferensbidrag (Refereegranskat)
    Abstract [en]

    Compaction is one of the most important phases in the life cycle of asphalt pavements and has therefore been a hot subject of research for a long time. However, despite of valuable research efforts on this topic, a remarkable gap between laboratory and field measurements still remains. Moreover, whereas most of the experimental methods are carried out on compacted pavement material, methods for evaluating compactability of asphalt mixtures for increasing the fundamental knowledge about internal movements within the asphalt during compaction are only scarce. Hence, in this study, a recently developed tool for simulating the compaction process with respect to the particle flow, i.e. Compaction Flow Test (CFT), was used along with simultaneous X-ray imaging for investigating the impact of thickness changes on two different asphalt mixture structures in terms of the compaction effort as well as flow pattern differences. The results of the investigation provided reasonably useful input for building up a better understanding of the behavior of mixtures under compaction loads. This method was able to successfully reveal the differences of the structural rearrangements within the asphalt mixtures for three different lift thicknesses. It also helped to explain some of the previous research studies results in a more comprehensive way. The achievements of this study may serve for developing an in-site evaluating test method for assessing compactability of asphalt mixtures before placing them on the roads.

  • 29.
    Ghafoori Roozbahany, Ehsan
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik. KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Partl, Manfred
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Guarin, Alvaro
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Introducing a new method for studying the field compaction2017Ingår i: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 18, s. 26-38Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The flow of particles during compaction may have a prominent influence on the difference of field and laboratory results as recently demonstrated by the authors with their newly developed compaction flow test (CFT). This test with a simple compaction simulator was used for studying the flow behaviour and rearrangement of particles for mixtures with different structures and thicknesses. However, validating the CFT results for practical purposes requires field measurements that provide more insight into the compaction process and eventually allowing to adjust the CFT for further use as an evaluating in-site tool. This study presents a new method for conducting such measurements during field compaction. In this method, some representative particles are tracked inside asphalt specimens and the accuracy of the results is examined by X-ray computed tomography. The results of the feasibility tests show that this method has potential for further use in the field and for building up a comprehensive basis of knowledge on field compaction towards closing the gap between the field and laboratory results.

  • 30.
    Ghafoori Roozbahany, Ehsan
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Partl, Manfred N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Guarin, Alvaro
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Particle Flow during Compaction of Asphalt Model Materials2015Ingår i: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 100, nr 15, s. 273-284Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Compaction is one of the key phases of the pavement construction and has been subject of research for a long time. However, very little is known regarding what really happens during compaction and how the pavement structure and the aggregate skeleton of the asphaltic layer are formed. Studies on that matter are of special practical importance since they may contribute to reduce the possibility of over-compaction and aggregate crushing. In this study, a new test method (Flow Test) was developed to simulate the material flow during compaction. Initially, asphalt materials were substituted by model materials to lower the level of complexity for checking the feasibility of the new test method as well as modeling purposes. Geometrically simple materials with densest possible combinations were tested for both dry and coated mixtures. X-ray radiography images were used for evaluating the material flow during compaction for different model mixtures. Results showed the capability of the test method to clearly distinguish mixtures with different properties from one another and also the potential of such a method to be used as an evaluating tool in the field. In addition, a simple discrete element model was applied for better understanding the flow of the model material during compaction as a basis for further improvement when moving from the asphalt model material to real mixtures. Therefore, real mixtures were prepared and tested under the same test configuration as for the model materials. The overall results of the real mixtures were found to support the model material test results.

  • 31.
    Ghafoori Roozbahany, Ehsan
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Partl, Manfred
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Witkiewicz, Patryk Jakub
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Fracture testing for the evaluation of asphalt pavement joints2013Ingår i: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 14, nr 4, s. 764-791Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Asphalt joints are inevitable parts of every pavement. Although much attention is dedicated to the construction of such joints, reliable tools for assessing the mechanical properties of joints for design and performance assessment are still scarce. This is particularly true for cold joints when attaching a new hot pavement to a cold existing pavement as in the case of large patches for pavement repair. This paper intends to evaluate different new or modified static fracture testing methods for ranking existing joint construction techniques. Some of these testing methods, such as indirect tensile test, direct tensile test and 4-point bending test are familiar in the field of asphalt pavement characterisation, but have scarcely been used for assessing the quality of joints so far. These three test types were adopted and evaluated for joints and the test results were analysed with finite element (FE) software ABAQUS. Different joints for testing were prepared in the laboratory using a special specimen construction procedure. The results suggest that joints with inclined interfaces seem to show more promising behaviour than vertical joints. It was confirmed that starting compaction from the hot side of the joint generally produces better results than compaction starting from the cold side of the joint. Pre-heating of the joint surface and using a bond sealant appears to provide the best results.

  • 32.
    Hailesilassie, Biruk
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap.
    Jerjen, Iwan
    Griffa, Michele
    Partl, Manfred N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik. Swiss Federal Laboratories for Material Science and Technology, Duebendorf, Switzerland .
    A Closer Scientific Look at Foam BitumenManuskript (preprint) (Övrigt vetenskapligt)
  • 33.
    Hailesilassie, Biruk
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap.
    Partl, Manfred N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik. Swiss Federal Laboratories for Material Science and Technology, Duebendorf, Switzerland .
    Modeling of bubble rising velocity and shape for foam bitumenManuskript (preprint) (Övrigt vetenskapligt)
  • 34.
    Hailesilassie, Biruk W.
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Hean, Sivotha
    Partl, Manfred N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik. Swiss Federal Laboratories for Material Science and Technology (EMPA), Switzerland.
    Testing of blister propagation and peeling of orthotropic bituminous waterproofing membranes2015Ingår i: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 48, nr 4, s. 1095-1108Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Bridge decks are commonly subjected to harsh environmental conditions that often lead to serious corrosion problems, which are triggered by blisters under the hot mix asphalt bridge deck pavement with waterproofing membranes. These blisters are secretly evolving during weather exposure until often being detected too late. Formation of blisters under the waterproofing membrane is caused by a complex mechanism governed by bottom-up pressure and loss of adhesion. This paper primarily intends to adopt the analytical blister propagation energy approach for waterproofing membranes and compare it with adhesive fracture energy from standard peeling test methods, already described in the literature. Three different types of polymer modified bitumen membranes (PBM) were used for this purpose. The investigation includes a comparison between uniaxial and biaxial testing conditions for determining the modulus of elasticity of the membranes. Moreover, the influence of the displacement rate and temperature on the adhesive fracture energy in peeling tests is investigated. It was found that the biaxial modulus of PBM in the longitudinal and transversal direction is comparable with the uniaxial tension testing results in the main directions. In addition, it was observed that the ratio of longitudinal and transversal modulus of elasticity was similar. The energy calculated from tests with elliptical blister propagation showed a comparable value to the standard peeling fracture energy for similar types of PBM.

  • 35.
    Hailesilassie, Biruk W.
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap.
    Hugener, Martin
    Partl, Manfred N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Influence of foaming water content on foam asphalt mixtures2015Ingår i: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 85, s. 65-77Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Warm mix asphalt technology using foamed bitumen is being used widely despite the fact that high air void content and poor coating of large aggregate remain major drawbacks require enhancement. This paper manly focuses on the investigation of water content influence on the foamed bitumen and the asphalt mixture. Influence of the water content in combination with compaction temperature has been investigated using gyratory compaction method. AC11N foam asphalt mixture is produced in the lab using lab foamer. Marshall stability and indirect tensile test was used to evaluate the foam asphalt mixture performance. The investigation revealed that the Marshall stability of foam asphalt mixture is highly influenced by compaction temperature compared to water content. Moreover, increasing the water content helps in coating large aggregates when the mixture is produced at low temperature, nevertheless using high water content reduces the Marshall stability to certain extent. In addition the amount of water trapped in the mixture after the mixing process was determined using thermogravimetric analysis. The amount of water remaining in the asphalt mixture is less than 1% relative to the bitumen mass.

  • 36.
    Hailesilassie, Biruk W.
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Schuetz, Philipp
    Jerjen, Iwan
    Bieder, Andrea
    Hugener, Martin
    Partl, Manfred N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik. Swiss Federal Laboratories for Material Science and Technology, Duebendorf, Switzerland .
    Evolution of bubble size distribution during foam bitumen formation and decay2014Ingår i: Asphalt Pavements: Proceedings of the International Conference on Asphalt Pavements, ISAP 2014 / [ed] Kim, YR, BOCA RATON: CRC PRESS-TAYLOR & FRANCIS GROUP , 2014, s. 1233-1240Konferensbidrag (Refereegranskat)
    Abstract [en]

    The warm asphalt mixture process using foam asphalt technology allows mixing and compaction at lower temperature. Nevertheless the higher air void content and incomplete coating of large aggregates are issues that need improvement to reach the properties of hot mix asphalt. In order to improve the understanding and characterization of the bitumen foam, X-ray radiography was used to investigate the formation and decay of bitumen foam in 2D representation. Image segmentation analysis was used to determine the foam bubble size distribution as a function of time. The impact of water content on the process has been studied for two penetration grade bitumen. The water content showed considerable influence on the foam quality in terms of expansion ratio and bubble size distribution. Increasing the water content in the foaming process leads to a quicker collapse of the bubbles and favors coalescence of individual bubbles.

  • 37.
    Hailesilassie, Biruk Wobeshet
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Hean, Sivotha
    Swiss Federal Laboratories for Material Science and Technology.
    Partl, Manfred
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Comparison between Blister Propagation and Peeling Test for an Orthotropic Bituminous Waterproofing MembraneArtikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    Bridge decks are commonly subjected to harsh environmental conditions that often lead to serious corrosion problems, which are triggered by blisters under the hot mix asphalt bridge deck pavement with waterproofing membranes. These blisters are secretly evolving during weather exposure until often being detected too late. Formation of blisters under the waterproofing membrane is caused by a complex mechanism governed by bottom-up pressure and loss of adhesion. This paper intends to adopt the analytical blister propagation energy approach for waterproofing membranes and compare it with adhesive fracture energy from standard peeling test methods, already described in the literature. Three different types of polymer modified bitumen membranes (PBMs) were used for this purpose. The investigation includes a comparison between uniaxial and biaxial testing conditions for determining the modulus of elasticity of the membranes. Moreover, the influence of the displacement rate and temperature on the adhesive fracture energy in peeling tests is investigated. It was found that the biaxial modulus of PBM in the longitudinal and transversal direction is comparable with the uniaxial tension testing results in the main directions. In addition, it was observed that the ratio of longitudinal and transversal modulus of elasticity was similar. The energy calculated from tests with elliptical blister propagation showed a comparable value to the standard peeling fracture energy for similar types of PBMs. This indicates that the peeling test assists in ranking the adhesive properties of different types of membranes. It also allows ranking between the membranes with respect to resistance to blister formation without time consuming and complicated pressurized blister propagation tests and digital image correlation techniques.

  • 38.
    Hailesilassie, Biruk Wobeshet
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Hugener, M.
    Bieder, A.
    Partl, Manfred N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. EMPA, Swiss Federal Laboratories for Material Science and Technology, Switzerland.
    New experimental methods for characterizing formation and decay of foam bitumen2015Ingår i: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Formation and decay of foam bitumen is a highly dynamic temperature dependent process which makes characterization difficult. In this research, new experimental tools were applied for characterizing the bitumen foam during the foaming process. Ultrasonic sensors were used for accurately monitoring the expansion and decay of foam bitumen as a function of time. Assessment of foam bitumen viscosity was performed using high frequency torsional rheometer and in situ observation by X-ray radiography. A high-speed camera was applied for examining the foam bitumen stream right at the nozzle revealing that foam bitumen at a very early stage contains fragmented pieces of irregular size rather resembling a liquid than foam. Moreover, infrared thermal images were taken for obtaining information on the in situ surface temperature of foam bitumen during the hot foaming process. The result showed that the average surface temperature of foam bitumen depends on the water content of the bitumen and bubble size distribution, 108 and 126 °C for 4 and 1 wt% (by weight) water content respectively. The residual water content in the decaying foam bitumen was determined by thermogravimetric analysis. The result demonstrated that residual water content depends on the initial water content, and was found to be between 38 and 48 wt% of the initial water content of 4–6 wt%. Finally, X-ray computed tomography was applied for examining the decay of foam bitumen revealing that the bubbles of foam bitumen remain trapped close to the surface of the foam bitumen.

  • 39.
    Hailesilassie, Biruk Wobeshet
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap.
    Jerjen, I.
    Griffa, M.
    Partl, Manfred N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. Swiss Federal Laboratories for Material Science and Technology, Duebendorf, Switzerland .
    A closer scientific look at foam bitumen2017Ingår i: Road Materials and Pavement Design, ISSN 1468-0629, Vol. 18, nr 2, s. 362-375Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the asphalt industry, a substantial interest is observed to find possibilities to reduce the production temperature of asphalt mixtures. In the context of this research, new methods for the visualisation of unstable bitumen foam, such as dynamic X-ray radiography, computed tomography (CT) and high-speed camera investigations, have been developed. Moreover, characterisation with empirical methods such as expansion ratio and half-life was determined accurately using ultrasonic measurements. This opens new possibilities to characterise bitumen foam (foaming process) for practical applications. Examination of the foam bitumen stream using a high-speed camera revealed that the foam bitumen contains fragmented pieces of bitumen, which resemble more a liquid than foam. This indicates that the foam is formed afterwards and not, as assumed, within the expansion chamber of the foam generator. In situ thermal imagery of the surface, during the hot foaming process, showed that the temperature distribution depends on the foaming water content (W.C.) and bubble size distribution. Higher W.C. results in more inhomogeneous temperature distribution as compared to lower W.C. (<2 wt%). The dynamic X-radiography results indicated that as the foam decays, the bubble size distribution becomes progressively larger with time for 160°C bitumen temperature. Furthermore, at the beginning of the foam formation, majority of the bubbles is small in cross-section size (0.2–10 mm2). At a later stage, the bubbles become polydisperse. Moreover, theoretical investigations based on the 3D X-ray CT scan data set of bubble merging show that the disjoining pressure increases as the foam film gets thinner with time and finally undergoes rupture. The speed of the bubbles also increases with time when the bubbles are getting closer to each other.

  • 40.
    Hailesilassie, Biruk Wobeshet
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Partl, Manfred
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Adhesive Blister Propagation under an Orthotropic Bituminous Waterproofing Membrane2013Ingår i: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 48, s. 1171-1178Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In most countries, waterproofing systems used on concrete bridge decks or roofs of buildings are generally based on orthotropic bituminous membranes; amongst these, styrene-butadiene-styrene copolymer (SBS) and atactic polypropylene (APP) polymer modified bituminous membranes are being used in most applications. One of the main technical concerns is the formation of blisters under the membrane caused by a complex mechanism governed by bottom-up pressure and loss of adhesion. This paper intends to contribute in understanding this mechanism by mechanical elastic modeling and experimental investigation. In order to study the material properties of SBS membranes under the in-plane complex stress state, the orthotropic mechanical behavior of a polymer modified bitumen membrane (PBM) was determined from biaxial test data. Hence, the measured stress-strain data were analyzed using the orthotropic equation to find the material properties in the longitudinal and transversal direction. Finally, blister tests were performed on concrete plates for studying adhesive blister propagation by applying controlled pressure between the PBM and the concrete plates. It was found that the ratio of the longitudinal to transversal adhesive blister propagation is comparable to the ratio of the modulus of elasticity in the longitudinal to transversal direction. Due to the orthotropic material property of the PBM, elliptical adhesive blister propagation was observed and a new model proposed for determining the energy for elliptical adhesive blister propagation.

  • 41.
    Hailesilassie, Biruk Wobeshet
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Partl, Manfred
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Mechanisms of asphalt blistering on concrete bridges2012Ingår i: Journal of ASTM International, ISSN 1546-962X, E-ISSN 1546-962X, Vol. 9, nr 3Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Blistering is a major problem in asphalt-covered concrete structures, such as multi-storage parking buildings, built-up roofs, tunnels, pedestrian areas, or concrete bridge decks. In this particular research, a linear viscoelastic finite-element model is developed to simulate time-dependent blister growth in an asphalt layer under uniformly applied pressure with and without temperature and pressure fluctuation. Indirect tensile tests on mastic asphalt (MA) are performed at three different temperatures to characterize and determine the material properties for the model. A three-dimensional thick-plate axisymmetric finiteelement model is developed using ABAQUS with linear viscoelastic properties and validated with closedform solution from first-order shear-deformation theory for thick plates. Elastic-viscoelastic analogy is used to find an analytic solution for the time-dependent deflection of the blister. In addition, the blister test is conducted on different samples of MA in the laboratory and digital image correlation measurement technique is used to capture the three-dimensional vertical deflection of the MA with time. Finally, the results from image correlation are compared with the finite-element simulation and thick-plate theory analytic solution. The finite-element model simulation shows that the daily temperature variations may have a significant influence on blister growth in asphalt pavements. It is found that the blister can grow continuously under repeated loading conditions over subsequent days. The study concludes that temperature fluctuation in the blister has more influence on blister growth than fluctuation of the pressure inside the blister.

  • 42.
    Hailesilassie, Biruk Wobeshet
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Partl, Manfred
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Mechanisms of Short-term Blistering Affecting Deterioration of Concrete Structures with Asphalt Pavements2011Konferensbidrag (Övrigt vetenskapligt)
  • 43.
    Hailesilassie, Biruk Wobeshet
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Partl, Manfred N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Mechanisms of asphalt blistering on concrete bridges2012Ingår i: Durability of building and construction sealants and adhesives: 4th volume, ASTM International, 2012, s. 308-330Konferensbidrag (Refereegranskat)
    Abstract [en]

    Blistering is a major problem in asphalt-covered concrete structures, such as multi-storage parking buildings, built-up roofs, tunnels, pedestrian areas, or concrete bridge decks. In this particular research, a linear viscoelastic finite-element model is developed to simulate time-dependent blister growth in an asphalt layer under uniformly applied pressure with and without temperature and pressure fluctuation. Indirect tensile tests on mastic asphalt (MA) are performed at three different temperatures to characterize and determine the material properties for the model. A three-dimensional thick-plate axisymmetric finite-element model is developed using ABAQUS with linear viscoelastic properties and validated with closed-form solution from first-order shear-deformation theory for thick plates. Elastic-viscoelastic analogy is used to find an analytic solution for the time-dependent deflection of the blister. In addition, the blister test is conducted on different samples of MA in the laboratory and digital correlation measurement technique is used to capture the three-dimensional vertical deflection of the MA with time. Finally, the results from image correlation are compared with the finite-element simulation and thick-plate theory analytic solution. The finite-element model simulation shows that the daily temperature variations may have a significant influence on blister growth in asphalt pavements. It is found that the blister can grow continuously under repeated loading conditions over subsequent days. The study concludes that temperature fluctuation in the blister has more influence on blister growth than fluctuation of the pressure inside the blister.

  • 44. Hugo, Fred
    et al.
    deVos, E
    Tayob, H
    Kannemeyer, L
    Partl, Manfred
    EMPA Swiss Federal Laboratories for Materials Testing and Research.
    Innovative Applications of the MLS10 for Developing Pavement Design Systems2008Ingår i: Third International Conference on Accelerated Pavement Testing: Impacts and Benefits from APT Programs, Madrid, 2008Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents innovative applications of accelerated pavement testing (APT) to advance pavement design in 3 case studies using MLS technology. Initially the MLS10 system was used to evaluate response and performance of cement stabilized coastal sand bases (CTB) in Mozambique. The aim was development of guidelines for a mechanistic-empirical design method. Trafficking speed was varied with dual wheel loads of either 60kN or 70kN and tire pressures at 800kPa under simulated environmental conditions. Integrated, cost-effective full-scale and MMLS3 scaled laboratory tests were used. Cost would have been 16 times more if full-scale testing were used for pre-selecting test sections. In both test modes, 2 unique failure mechanisms were identified; namely, horizontal shear within the CTB layer and debonding at the interface between surfacing and CTB. PSPA stiffness monitoring enabled progressive deterioration of pavements to be evaluated and performance modeled for subsequent use. The second MLS10 application evaluated performance of an innovative, ultra-thin reinforced concrete pavement (UTCRCP). The SA Road Agency (SANRAL) is investigating UTCRCP for reconstruction or rehabilitation of heavily trafficked freeways. Trafficking differed from HVS APT that had already yielded very positive results. Limited trafficking was applied to evaluate performance of a strengthened construction joint. Trafficking was primarily channelized and unidirectional. Loading frequency was 6.9 fold higher than the HVS'. Performance under MLS10 was positive with smaller deflection and joint movement as expected. No failure occurred. However, a sharp increase in deflection of the construction joint occurred with the switch to limited laterally distributed wet trafficking. This was ascribed to a change in pore pressure patterns. This could not be investigated further due to unavoidable early termination of trafficking. Should the trend continue performance life is likely to be negatively affected. Larger deflection was detected away from the construction joint throughout the test. This could be due to a deficiency in the sub base, or the smaller quantity of reinforcing steel compared to the reinforcing at the joint where additional steel had been added. The test provided guidance for planned validation of APT performance on a specially constructed highway trial section. A third application by EMPA in Switzerland tested a 20-yr-old untrafficked, heavy duty deep structured HMA pavement with cement treated sub-base on a spur of a trafficked freeway. Trafficking was terminated after 1 million 65kN channelized half axle load applications. The performance provided a basis for comparison with the adjacent freeway that had carried ca. 6.5 million equivalent E100’s with one intervention for replacement of 50mm surfacing. Ground penetrating radar (GPR) monitoring showed progressive distress with trafficking. This correlated with decline in PSPA seismic stiffness and increased surface deflection. Pumping was experienced with wet trafficking. Diagnostic trenching ratified indications from GPR and seismic stiffness trends that indicated delamination between the 2 HMA layers. The one million E130 load applications equate to ca. 4.9 million E100 axle load applications on the test section in terms of damage. A detailed diagnostic study of the trafficked freeway should provide invaluable information for a more thorough comparison of respective performances.

  • 45. Jeoffroy, E.
    et al.
    Bouville, F.
    Bueno, M.
    Studart, A. R.
    Partl, Manfred N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. Swiss Federal Laboratories for Materials Science and Technology, Switzerland.
    Iron-based particles for the magnetically-triggered crack healing of bituminous materials2018Ingår i: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 164, s. 775-782Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Bituminous road pavements may suffer from cracking over the years due to repeated stresses. In this study, we compare the effect of different sizes and chemical compositions of magnetically-responsive iron-based particles used as additives to heat up road pavements and thus to close cracks. By applying an alternating magnetic field (AMF), we found that there is an optimal size depending on the particle electrical conductivity at which the temperature on the surface of asphalt samples is the highest. Even when particles are well-distributed after mixing, we found that asphalt samples containing larger particles display inhomogeneous heating during the exposure to the AMF. The mechanical recovery of samples during a double torsion test before and after the exposure to the AMF confirmed the healing capability of asphalt materials containing iron-based particles. Based on these results we provide guidelines for the design of magnetically-responsive asphalts for road pavements of enhanced durability.

  • 46. Jeoffroy, E.
    et al.
    Koulialias, D.
    Yoon, S.
    Partl, Manfred N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. Swiss Federal Laboratories for Materials Science and Technology, Switzerland.
    Studart, A. R.
    Iron oxide nanoparticles for magnetically-triggered healing of bituminous materials2016Ingår i: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 112, s. 497-505Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Healing of micro-cracks is crucial for recovering the mechanical properties and extending the service time of bituminous materials. However, crack closure is often challenged by the efficiency and repeatability of the healing process or its technical and economic feasibility for large-scale applications. Here, we propose an innovative method to close micro-cracks in bituminous materials by using magnetically-triggered iron oxide nanoparticles as heating agents. Heating is generated through the so-called hyperthermia effect upon exposure of the nanoparticles to an external oscillating magnetic field. When mixed in a low volume fraction of 1% within bitumen, the nanoparticles generate enough heat to decrease the viscosity of the surrounding material and thus promote crack closure. Oleic acid is used to coat the iron oxide nanoparticles and enable their homogeneous distribution in the bitumen. Because of high hysteresis losses, γ-Fe2O3 nanoparticles with a mean crystallite size of 50 nm exhibited specific absorption rates (SAR) as high as 285 W/g when subjected to a magnetic field of 30 mT at 285 kHz. In contrast to the relatively slow heating of electrically-conductive additives, we find that iron oxide nanoparticles pre-embedded in bitumen allows for crack closure in a few seconds when subjected to similar magnetic field conditions. This represents a new efficient way to heal damage in thermoplastic road pavements in the presence of mineral aggregates.

  • 47.
    Kim, H
    et al.
    Empa, Swiss Federal Laboratories for Materials Testing and Research, Dübendorf, Switzerland.
    Partl, Manfred
    Empa, Swiss Federal Laboratories for Materials Testing and Research, Dübendorf, Switzerland.
    Stiffness Comparisons of Mastics Asphalt in Different Test Modes2009Konferensbidrag (Refereegranskat)
  • 48.
    Kim, H
    et al.
    Empa, Swiss Fed Labs Mat Testing & Res, CH-8600 Dubendorf, Switzerland .
    Partl, Manfred
    Empa, Swiss Fed Labs Mat Testing & Res, CH-8600 Dubendorf, Switzerland .
    Pimanta, R
    Empa, Swiss Fed Labs Mat Testing & Res, CH-8600 Dubendorf, Switzerland .
    Hean, S
    Empa, Swiss Fed Labs Mat Testing & Res, CH-8600 Dubendorf, Switzerland .
    Experimental Investigation of Grid-Reinforced Asphalt Composites Using Four-Point Bending Beam Test2010Ingår i: Journal of Composite Materials, ISSN 0021-9983, Vol. 44, nr 5, s. 575-592Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Four-point bending beam tests are applied to investigate the bending behavior of asphalt composites strengthened by grid reinforcements made of carbon, glass, and polyester fiber grids. Both experimental and analytical predictions are compared considering the deflection behavior of carbon grid-reinforced beams. This study especially shows significant structural improvement and better crack resistance of asphalt composite beams by carbon grids. Temperature and loading rate dependencies are also evaluated and compared for both reinforced and unreinforced asphalt composite beams. The maximum bending forces of carbon grid-reinforced beams significantly decrease with decreasing loading rate and increasing the temperature. The deflection behavior of asphalt composite beams reinforced by carbon grids is reasonably predicted using a bilinear damage-based model and a viscoelastic beam theory. The layer-parallel direct shear test is conducted for investigating the interlayer shear behavior of asphalt composite beams.

  • 49. Kim, H
    et al.
    Partl, Manfred
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Wagoner, M
    Buttlar, W
    Size Effect Investigation on Fracturing of Asphalt Concrete Using the Cohesive Softening Discrete Element Model2009Ingår i: ADVANCED TESTING AND CHARACTERISATION OF BITUMINOUS MATERIALS: VOLS 1 AND 2 , Rhodes, Greece, 2009, s. 827-836Konferensbidrag (Refereegranskat)
  • 50. Kim, H
    et al.
    Sokolov, K
    Poulikakos, L
    Partl, Manfred
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Fatigue Evaluation of Carbon FRP-Reinforced Porous Asphalt Composite System Using a Model Mobile Load Simulator2009Konferensbidrag (Refereegranskat)
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