| 1. |
- 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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| 2. |
- Gudmarsson, Anders, et al.
(författare)
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Monitoring Stiffness Evolution of Asphalt Concrete Through Modal Analysis
- 2022
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Ingår i: ISBM 2020. - Cham : Springer Science and Business Media B.V.. ; , s. 1375-1381
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Konferensbidrag (refereegranskat)abstract
- The stiffness of asphalt concrete, which is used for thickness design of pavements, is known to increase with time due to age hardening of the binder. Therefore, aging models to account for the stiffness evolution over time are in some applications considered with the aim to improve pavement life predictions. Modal analysis is an economic test method with a verified precision for characterizing the complex moduli of asphalt concrete. In this paper, the stiffness evolution of asphalt concrete has been monitored through modal analysis. The simplicity of the modal test set-up facilitates accurate repeated testing under identical conditions. Therefore, modal testing was performed repeatedly at the temperatures of 20 and −20 °C over a period up to around 300 days. The testing was performed on samples in a controlled laboratory environment and does not intend to provide a measure of the age hardening of real pavements. The aim of this paper is to characterize the stiffness evolution of asphalt mixes with modified and unmodified binders in a controlled environment. Cyclic indirect tensile tests were performed in addition to modal analysis to characterize the stiffness evolution under different loading configurations. Results from the modal analysis clearly showed that the rate of the stiffness evolution is initially slower for the modified binder in comparison to the unmodified binder.
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| 3. |
- 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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