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| 2. |
- Gudmarsson, A., et al.
(author)
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Apps for modal analysis to characterize the complex modulus of asphalt concrete
- 2018
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In: 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. - 9781138295957 ; , s. 209-215
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Conference paper (peer-reviewed)abstract
- The time and temperature dependent dynamic modulus of asphalt concrete is a key parameter to modern pavement design and to pavement quality. However, accurate measurements of the complex modulus through conventional cyclic testing are expensive regarding both time and costs. Novel test methods based on modal analysis facilitate economic, accurate and faster determination of linear viscoelastic material properties of asphalt concrete. The modal analysis is performed by using an impact hammer and an accelerometer to measure frequency response functions of asphalt concrete specimens with free boundary conditions. The complex modulus and complex Poisson’s ratio are determined by matching finite element computed frequency response functions to the measurements. This paper presents one software application to perform the modal testing and one application to compute and optimize frequency response functions to determine the complex modulus and complex Poisson’s ratio. The software applications greatly simplifies the methodology to determine material properties through modal analysis of asphalt concrete specimens.
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| 3. |
- Kringos, Nicole, et al.
(author)
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Determination of Moisture Susceptibility of Mastic-Stone Bond Strength and Comparison to Thermodynamical Properties
- 2008
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In: 2008 Journal of the Association of Asphalt Paving Technologists. ; , s. 435-478
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Conference paper (peer-reviewed)abstract
- The fundamental characterization and quantification of the moisture susceptibility of asphaltic mixes is a very important and timely topic for the asphaltic pavements industry, and has thus far posed a serious challenge for asphalt mix designers. In this research a fundamental computational-experimental test procedure is demonstrated to measure the moisture susceptibility of the mastic-aggregate bond strength and bond energy. The methodology combines displacement controlled direct tension tests with numerical moisture diffusion analyses and is demonstrated for six different mastic-stone combinations which are frequently used in the Dutch open friction courses. From the results it can be seen that the computed adhesive moisture susceptibilities are consistent with the expected field performance. The measured bond moisture susceptibilities are furthermore compared with the thermodynamical work of adhesion. It is shown that, qualitatively, the moisture resistance performance ranking is similar, but that the actual bond energies show three to four orders of magnitude difference. From this it can be concluded that, even though the surface energy approach can be very useful in enhancing material selection procedures, it is still important to actually measure the mechanical strength of the selected aggregate-mastic bond with a mechanical test.
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| 4. |
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| 5. |
- Kringos, Nicole, et al.
(author)
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Towards and Understanding of the Self Healing Capacity of Asphaltic Materials
- 2011
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In: Heron. - 0046-7316 .- 1574-4078. ; 56:1-2, s. 49-79
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Journal article (peer-reviewed)abstract
- Theself-restoring orhealingcapacityof asphalt has been known for quite some time. Yet, to this date, there is no consensus of the fundamental mechanism underlying this phenomenon. In this paper a multi-scale model is presented which focuses on thehealingphenomenon from a thermodynamic point of view. In the model,healingof bituminousmaterialis simulated at the micro scale via a phase field model, utilizing a modified version of the Cahn Hilliard and Flory-Huggins equations. This model is then connected to a more general elasto- visco-plastic constitutive framework for the simulation of asphalt mixtures. The paper presents the developed hypothesis, the experimental evidence and summarizes some of the theoretical background. The model has been implemented in the 3D finite element system CAPA-3D and preliminary results are shown.
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| 6. |
- Scarpas, A. T., et al.
(author)
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Preface
- 2012
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In: RILEM Bookseries. ; , s. III-IV
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Conference paper (peer-reviewed)
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| 7. |
- Schmets, A.J.M., et al.
(author)
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First-principles investigation of the multiple phases in bituminous materials : the case of asphaltene stacking
- 2009
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In: ADVANCED TESTING AND CHARACTERISATION OF BITUMINOUS MATERIALS. - Rhodes, Greece. ; , s. 143-150
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Conference paper (peer-reviewed)abstract
- The existence of a microstructure in bituminous materials can explain this materials tendency to self heal. By means of atomic force microscopy and small angle neutron scattering the existence of the microstructure is demonstrated once again. Then it is suggested that the observed microstructure may very well be a consequence of the aggregation of asphaltenic molecules (providing internal volumes with a low H/C-ratio). This is a rather unadventurous suggestion, because flocculation of asphaltenes costs the global oil industry millions of dollars per day. A model asphaltene (a coronene-like molecule) has been selected for calculating semi-empirically the tendency to form stacks. It was found that there is some tendency to cluster, but the effect is not strong enough to be responsible for the observed microstructure.
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| 8. |
- Baldo, N, et al.
(author)
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Calibration and Validation of a Visco-Elasto-Plastic Constitutive Model for Bituminous Conglomerates
- 2009
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In: ADVANCED TESTING AND CHARACTERISATION OF BITUMINOUS MATERIALS. - Rhodes, Greece : CRC Press. - 9780415558549 ; , s. 879-888
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Conference paper (peer-reviewed)abstract
- The paper presents and discusses the calibration and validation of a three-dimensional constitutive visco-elasto-plastic model developed for the analysis of the mechanical behaviour of bituminous mixes. The methodology, an inverse problem technique, uses a one-dimensional analytic formulation of the constitutive model and four different algorithms of non-linear constrained optimisation: the Conjugate Gradient, Montecarlo, Davidon-Fletcher-Powell and Simplex. On the basis of the creep recovery data obtained from an experiment in support of the model calibration, it was verified that the values of the constitutive parameters can be reliably identified, even starting from different initial guesses. A subsequent comparison between the experimental creep curves and numerical ones of the 3-D model demonstrated minimal shifts, confirming the robustness of the identification procedure for the parameters.
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| 9. |
- Kringos, Nicole, et al.
(author)
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Combined Experimental and Numerical Analysis of Moisture Infiltration in the Modified Lottman Test
- 2009
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In: ADVANCED TESTING AND CHARACTERISATION OF BITUMINOUS MATERIALS. - Rhodes, Greece. ; , s. 261-270
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Conference paper (peer-reviewed)abstract
- The modified Lottman test method is frequently used for the evaluation of moisture susceptibility of asphalt concrete mixtures. Unfortunately, the test is known to be very variable and sometimes provides erroneous results. In this paper the various variables which are introduced in the T 283 test procedure due to moisture conditioning procedure are investigated via micro-scale finite element analyses. For the finite element meshes, X-Ray tomography scans are made of two gyratory and Marshall compacted mixtures. These mixtures are computationally analyzed for their outside and inside pore-space distribution, the moisture infiltration is simulated via finite element analyses and the resulting moisture fronts are discussed. From the research presented in this paper it can be seen that the two different compactions and geometries can result in entirely different moisture concentrations inside the specimen. This can have a significant impact on the variability of the test results.
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| 10. |
- Kringos, Nicole, et al.
(author)
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On the Importance of Performing Accurate Material Characterization Tests for Bituminous Materials
- 2009
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In: ADVANCED TESTING AND CHARACTERISATION OF BITUMINOUS MATERIALS. - Rhodes, Greece. ; , s. 839-848
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Conference paper (peer-reviewed)abstract
- Selecting appropriate experiments to measure the important parameters that define the behavior of bituminous materials is far from a trivial task. In most cases, testing and modeling go hand-in-hand, and one should be confident that the selected experiment is capturing the important parameters. At different stages of the investigation, different tests may be required. This paper is addressing some of the important issues and defines the differences between structural and material tests. The introduction of moisture in asphalt characterization tests is becoming a topic of increased interest in recent years. Using the 'wrong' conditioning procedure could result in misleading conclusions about the moisture susceptibility of the tested mixtures, which could lead to unexpected failures in the field. This paper is discussing some of the issues of moisture conditioning. The challenges involved with rotational tests, which are often used by pavement engineers, and the need to measure the behavior of mastics rather than neat bitumen are also discussed.
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