| 1. |
- He, Liang, et al.
(författare)
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A Coarse-Grained Molecular Model for Simulating Self-Healing of Bitumen
- 2022
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Ingår i: Applied Sciences. - : MDPI AG. - 2076-3417. ; 12:20, s. 10360-
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Tidskriftsartikel (refereegranskat)abstract
- The longevity of asphalt pavements is a key focus of road engineering, which closely relates to the self-healing ability of bitumen. Our work aims to establish a CGMD model and matched force field for bitumen and break through the limitations of the research scale to further explore the microscopic mechanism of bitumen self-healing. In this study, a CGMD mapping scheme containing 16 kinds of beads is proposed, and the non-bond potential energy function and bond potential energy function are calculated based on all-atom simulation to construct and validate a coarse-grained model for bitumen. On this basis, a micro-crack model with a width of 36.6nm is simulated, and the variation laws of potential energy, density, diffusion coefficient, relative concentration and temperature in the process of bitumen self-healing are analyzed with the cracking rate parameter proposed to characterize the degree of bitumen crack healing. The results show that the computational size of the coarse-grained simulation is much larger than that of the all-atom, which can explain the self-healing mechanism at the molecular level. In the self-healing process, non-bonded interactions dominate the molecular movement, and differences in the decreased rate of diffusion among the components indicate that saturates and aromatics play a major role in self-healing. Meanwhile, the variations in crack rates reveal that healing time is inversely proportional to temperature. The impact of increasing temperature on reducing healing time is most obvious when the temperature approaches the glass transition temperature (300 K).
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| 2. |
- Lövqvist, Lisa, 1992-, et al.
(författare)
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A Critical Analysis of the Standard Used to Evaluate De-icing Damage in Asphalt Materials
- 2022
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Ingår i: Proceedings of the RILEM InternationalSymposium on Bituminous Materials. - Cham : Springer Nature. - 9783030464547 - 9783030464554 ; , s. 73-79
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Konferensbidrag (refereegranskat)abstract
- De-icing fluids are known to have a potential to negatively affect infrastructure materials such as asphalt. In order to evaluate the resistance of asphalt materials to de-icing fluids, the European standard method EN 12697-41 is commonly used. There are however a number of issues related to the method, such as a high variability of the results and poor correlation between test results and behavior in the field, which may be caused by some of the parameters of the test. This paper aims to identify and investigate some parameters that are of importance to the relevancy of the test. To do this, experimental tests of asphalt mastic and mixture are performed with two concentrations of a deicer and water. Additionally, to gain a better understanding of what occurs in the tested samples during the conditioning and loading, finite element simulations using a microscale model with a mesh based on an X-ray CT scan of a real sample, are performed. The results show that both the geometry and the set-up of the conditioning and mechanical testing can cause misleading results. Based on this, recommendations are made for areas for future studies to improve the test method.
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| 3. |
- Porot, Laurent, et al.
(författare)
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Complex Bituminous Binders, Are Current Test Methods Suitable for?
- 2022
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Ingår i: Proceedings of the RILEM International Symposium on Bituminous Materials. ISBM 2020.. - Cham : Springer Science and Business Media B.V.. ; , s. 37-43
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Konferensbidrag (refereegranskat)abstract
- The asphalt industry is constantly working to enhance the performances of asphalt materials, introducing innovative and more sustainable solutions. In this context, the incorporation of materials, such as additives, polymers, is more and more used to improve the properties of neat bitumen. This leads to even more complex bituminous binders, raising the question, are the current specifications and test methods appropriate for complex materials? To deal with this, the RILEM Technical Committee 272-PIM ‘Phase and Interphase behaviour of innovative bituminous Materials’ with its Task Group TG1 is looking at the efficiency of various test methods for complex binders with an extensive inter-laboratory program with 17 laboratories. It includes seven different binders, two neat bitumen, two polymer modified bitumen and three binders with liquid additives, emphasising on compositional and physical changes at different conditions. The focus is low temperature; while a complementary experimental program encompasses as well as testing at intermediate and high temperatures. The outcomes of the work will provide indications on how robust the current binder characterisation techniques are and establish technical recommendations for future test methods specially designed for complex binders. Some first results are presented hereby. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.
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| 4. |
- Porot, Laurent, et al.
(författare)
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Multiple Stress Creep Recovery Test to Differentiate Polymer Modified Bitumen at High Temperature
- 2022
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Ingår i: Journal of Testing and Evaluation. - : ASTM International. - 0090-3973 .- 1945-7553. ; 51:4, s. 2168-2178
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Tidskriftsartikel (refereegranskat)abstract
- The constant demand for high-performing and more reliable roads has led to an increasing use of complex bituminous binders such as polymer-modified bituminous binders, which has become a widespread practice for asphalt pavement. As a result, specification and testing have evolved to better distinguish between quality materials. In recent years, more focus has been devoted to better evaluating the rutting resistance of bituminous binders. The multiple stress creep recovery (MSCR) test has gained popularity over the last decade, especially for polymer-modified binders, bringing more advantages in discriminating amongst quality binders such as polymer-modified bitumen. Within the International Union of Laboratories and Experts in Construction Materials, Systems and Structures technical committee 272, Phase and Interphase of Behavior of Innovative bituminous Materials, and its TG1 task group, several binders were thoroughly evaluated, including two non-modified and two polymer-modified bituminous binders, under various testing conditions to address the high-temperature behavior. Five laboratories performed MSCR on short-term aged binders after performing the rolling thin film oven test, in the same temperature conditions for all binders. Despite the limited data set, the variability between laboratories was reasonable. The MSCR results were compared with softening point temperature, high-temperature performance grade criteria, |G*| / sin delta, and equi-modulus temperature. MSCR was able to distinguish between complex binders better as compared with conventional parameters. It generates multiple useful parameters, amongst which percent recovery and non-recoverable creep compliance are the most relevant. This paper presents the analysis of MSCR results and comparison with other test methods.
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| 5. |
- Zhu, Jiqing, 1987-, et al.
(författare)
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Experimental analysis and predictive modelling of linear viscoelastic response of asphalt mixture under dynamic shear loading
- 2022
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Ingår i: Construction and Building Materials. - : Elsevier. - 0950-0618 .- 1879-0526. ; 328
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Tidskriftsartikel (refereegranskat)abstract
- The use of predictive models can facilitate the inclusion of shear parameters in asphalt mixture evaluation and design processes. Unlike more extensively studied tension–compression models, the currently existing shear model, the Hirsch model, has unrealistic constants, particularly for the prediction of phase angle. Aiming at an improved predictive model in shear, this study employs a simple shear apparatus to experimentally analyse the linear viscoelastic properties of asphalt mixtures for road paving. Master curves were constructed and compared between different asphalt mixtures. Additionally, the test results were also analysed in the Black space and the Cole-Cole space. The dynamic shear response of asphalt mixtures was thereafter modelled on the basis of the Hirsch model. As the original model for phase angle prediction was found to be unrealistic, a particular focus in this study was put on identifying realistic empirical relationships for predicting the phase angle of asphalt mixtures in shear. More reliable shear test results of asphalt mixtures were used to calibrate the model, and extra test data were utilized to validate the calibrated model. It is indicated that the predictive model after calibration could deliver results of greatly improved accuracy, especially at the high-frequency and low-frequency ends. The analysis and modelling also leads to realistic empirical relationships for predicting the phase angle of asphalt mixtures in shear. The experimental verification confirms the good prediction accuracy of the calibrated model and proposed empirical relationships.
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| 6. |
- Zhu, Jiqing, 1987-, et al.
(författare)
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Extending the Black diagram of bitumen to three dimensions
- 2022
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Ingår i: Construction and Building Materials. - : Elsevier BV. - 0950-0618 .- 1879-0526. ; 349
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Tidskriftsartikel (refereegranskat)abstract
- The ordinary Black diagram of bitumen has only two dimensions. Thus, it does not differentiate the complex shear modulus and phase angle measured under different temperature and frequency conditions. This study proposes to extend the Black diagram to three dimensions by adding a temperature axis. It leads to the combination of multiple necessary ordinary plots in the same three-dimensional (3D) space. In this 3D space, the location, shape, and eventually colour of the plot (either curve or surface) can together indicate the unique temperature-dependency and time-dependency of the bituminous binder's rheological properties, even the interplay between them. Hence, polymer-modified bitumen is distinguished from neat bitumen and harder bitumen is distinguished from softer bitumen. Furthermore, the additional temperature axis in the 3D Black diagram also enables direct visualisation and precise quantitative evaluations of bitumen properties by various current technical criteria in the same space, avoiding the inconvenient use of multiple ordinary plots. This may lead to the development of a practical tool towards more effective and efficient evaluation of rheological properties of bitumen.
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| 7. |
- Zhu, Jiqing, 1987-, et al.
(författare)
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Influence of Binder Properties on Dynamic Shear Response of Asphalt Mixture
- 2022
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Ingår i: Proceedings of the RILEM International Symposium on Bituminous Materials. ISBM 2020. - Cham : Springer Science and Business Media B.V.. ; , s. 1071-1078
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Konferensbidrag (refereegranskat)abstract
- For predicting the shear-related rutting potential of asphalt pavement, it is important to understand the shear response of asphalt mixture and find the link between the mixture response and component material properties. Using controlled aggregate gradation, this paper investigates the influence of bituminous binder on the response of asphalt mixture under dynamic shear loading. Four asphalt mixtures, with two different grades of bitumen, were analysed by a simple shear test apparatus with dynamic loading. The binders, both original and after short-term aging, were characterised using a dynamic shear rheometer. The modulus and phase angle of both the asphalt mixture and bitumen samples were measured. Master curves were constructed. The results revealed that the asphalt mixture phase angle maximum, where a rutting performance indicator can be obtained, appears in a relatively narrow range of shear modulus. This range corresponds to a certain level of bitumen complex shear modulus (G*) and phase angle. By temperature sweep, a temperature value can be interpolated at the specified bitumen G* level. This temperature provides a possibility to predict the frequency of phase angle maximum for a given asphalt mixture type. It is noted that the asphalt mixture phase angle maximum corresponds to a relatively high bitumen modulus level compared to other high-temperature criteria. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.
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