| 1. |
- He, Liang, et al.
(författare)
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Discrete element simulation of porous asphalt mixture clogging law
- 2023
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Ingår i: Jiaotong Yunshu Gongcheng Xuebao/Journal of Traffic and Transportation Engineering. - : Chang'an University. - 1671-1637. ; 23:2, s. 78-91
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Tidskriftsartikel (refereegranskat)abstract
- To reveal the pore clogging law of porous asphalt mixture, the combination study of model experiment and simulation of porous asphalt mixture clogging was conducted. The pore characteristics of the porous asphalt mixture were analyzed based on the CT-scanning and discrete element software PFC3D V5. 0, and the pore data of the porous asphalt mixture were obtained. The aggregates of different particle sizes were put into PFC3D V5. 0, and the compacted virtual specimens were generated according to the pore characteristics. The accuracy of the model was verified by comparing the pore images of actual specimens with the MATLAB slices. In the self-weight condition, the simulation was set with the porous asphalt mixture specimen being intruded by clogging particles with specific gradation composition. The data of indoor experiments were compared and verified. The particle sizes of clogging particles were changed, and the pore decay rates of the specimen were analyzed. The clogging-sensitive particles were identified. In the self-weight condition, the fluid simulation experiment was introduced, and the change law of specimen clogging was analyzed by changing the seepage rate of fluid. Analysis results show that the virtual specimen generated by PFC3D V5. 0 has high accuracy, and the simulation reveals the clogging law of the specimen. The small particles not only accumulate at the throat position causing clogging, but also congregate and interlock with the particles of larger sizes resulting in clogging too. In the self-weight condition, the clogging is mainly concentrated at the upper 30 mm of the mixture specimen, and the size distribution of corresponding clogging-sensitive particles is 0. 150-0. 600 mm. The size distribution of clogging particles has a great impact on the clogging results. In the conditions of gravity and fluid, with the seepage rate increasing from 0. 005 m • s-1 to 0. 030 m • s-1, the changing rate of pore decay rate increases. In addition, the clogging particles remaining in the mixture decrease, accompanied by the reduction of the pore decay rate. Therefore, the local rainfall conditions should also be considered in the design and maintenance of drainage asphalt pavement. 2 tabs, 20 figs, 30 refs. © 2023 Chang'an University. All rights reserved.
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| 2. |
- Ekblad, Katarina, et al.
(författare)
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Ersättning av metylenklorid vid asfaltsextraktioner : Förstudie
- 2023
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- I flera provningsmetoder av asfaltmaterial, behöver man lösa upp bindemedlet i asfalten, bituminet, med hjälp av ett lösningsmedel. Det lösningsmedel som de flesta asfaltslaboratorier använder i Sverige, är metylenklorid. Metylenklorid eller diklormetan, som är ett annat namn för samma lösningsmedel, är ett halogenerat lösningsmedel, som effektivt löser fett, vax och harts. Å andra sidan kan exponering av metylenklorid leda till hälsorisker som yrsel, trötthet, illamående, huvudvärk och domningar, blodstörningar och det finns även misstankar om cancer, mutation och fosterskador. Dessutom har metylenklorid skadliga långtidseffekter för vattenlevande organismer och bör därför inte släppas ut i miljön och vatten.Denna förstudie syftar till att undersöka möjligheten att ersätta metylenklorid med ett eller flera, ur miljö- och arbetsmiljöperspektiv bättre lösningsmedel, som kan användas till extraktion och återvinning av bindemedel från asfalt. Skulle det gå att ersätta metylenklorid med ett bättre lösningsmedel, kan samtliga laboratorier i branschen börja driva sina verksamheter på ett mer miljövänligt sätt och samtidigt få en säkrare arbetsmiljö.
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| 3. |
- 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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| 4. |
- He, L., et al.
(författare)
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Biomass valorization toward sustainable asphalt pavements : Progress and prospects
- 2023
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Ingår i: Waste Management. - : Elsevier. - 0956-053X .- 1879-2456. ; 165, s. 159-178
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Tidskriftsartikel (refereegranskat)abstract
- To cope with the global climate crisis and assist in achieving the carbon neutrality, the use of biomass materials to fully or partially replace petroleum-based products and unrenewable resources is expected to become a widespread solution. Based on the analysis of the existing literature, this paper firstly classified biomass materials with potential application prospects in pavement engineering according to their application and summarized their respective preparation methods and characteristics. The pavement performance of asphalt mixtures with biomass materials was analyzed and summarized, and the economic and environmental benefits of bio-asphalt binder were evaluated. The analysis shows that pavement biomass materials with potential for practical application can be divided into three categories: bio-oil, bio-fiber, and bio-filler. Adding bio-oil to modify or extend the virgin asphalt binder can mostly improve the low temperature performance of asphalt binder. Adding styrene-butadienestyrene (SBS) or other preferable bio-components for composite modification will have a further improved effect. Most of the asphalt mixtures prepared by using bio-oil modified asphalt binders have improved the low temperature crack resistance and fatigue resistance of asphalt mixtures, but the high temperature stability and moisture resistance may decrease. As a rejuvenator, most bio-oils can restore the high and low temperature performance of aged asphalt and recycled asphalt mixture, and improve fatigue resistance. Adding bio-fiber could significantly improve the high temperature stability, low temperature crack resistance and moisture resistance of asphalt mixtures. Biochar as a bio-filler can slow down the asphalt aging process and some other bio-fillers can improve the high temperature stability and fatigue resistance of asphalt binders. Through calculation, it is found that the cost performance of bio-asphalt has the ability to surpass conventional asphalt and has economic benefits. The use of biomass materials for pavements not only reduces pollutants, but also reduces the dependence on petroleum-based products. It has significant environmental benefits and development potential.
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| 5. |
- 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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| 6. |
- Lövqvist, Lisa, 1992-, et al.
(författare)
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Evaluation of the standard test method for resistance of bituminous materials to de-icing fluids
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Ingår i: Construction and Building Materials. - 0950-0618 .- 1879-0526.
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Tidskriftsartikel (refereegranskat)abstract
- As an important maintenance measure, de-icing agents are commonly used to ensure safe surface conditions of highways and airport runways during winter. There are however issues related to their use, such as deteriorating effects on road materials, causing particle loss and a decreased low-temperature stiffness of asphalt pavements. To avoid this, it is therefore important to be able to evaluate the effect of the deicer on the asphalt mixture with reliable results. The European standard method for this, EN12697-41, is however associated with several issues such as a high variability of the results and a lack of consistency with the field. Using both experimental testing and numerical simulations, this paper aims to explain the cause of these and to identify the main dominant parameters which can potentially be modified for an improvement. The experimental testing evaluated both the diffusive properties of de-icing fluid and water in mastic and the standard method itself, and the numerical simulations evaluated the effect of different parameters related to the set-up of the test. From the evaluations, it was concluded that both the set-up of the test and the geometryof the test sample contribute to the high variability of the test method and its lack of consistency with the field. Recommendations are therefore made regarding the potential for improvement and further evaluation of the method.
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| 7. |
- Lövqvist, Lisa, 1992-, et al.
(författare)
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Evaluation of the standard test method for resistance of bituminous materials to de-icing fluids
- 2021
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Ingår i: Construction and Building Materials. - : Elsevier BV. - 0950-0618 .- 1879-0526. ; 308
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Tidskriftsartikel (refereegranskat)abstract
- As an important maintenance measure, de-icing agents are commonly used to ensure safe surface conditions of highways and airport runways during winter. There are however issues related to their use, such as deteriorating effects on road materials, causing particle loss and a decreased low-temperature stiffness of asphalt pavements. To avoid this, it is therefore important to be able to evaluate the effect of the deicer on the asphalt mixture with reliable results. The European standard method for this, EN12697-41, is however associated with several issues such as a high variability of the results and a lack of consistency with the field. Using both experimental testing and numerical simulations, this paper aims to explain the cause of these and to identify the main dominant parameters which can potentially be modified for an improvement. The experimental testing evaluated both the diffusive properties of de-icing fluid and water in mastic and the standard method itself, and the numerical simulations evaluated the effect of different parameters related to the set-up test. From the evaluations, it was concluded that both the set-up of the test and the geometry of the test sample contribute to the high variability of the test method and its lack of consistency with the field. Recommendations are therefore made regarding the potential for improvement and further evaluation of the method.
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| 8. |
- Porot, Laurent, et al.
(författare)
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Characterisation of complex polymer modified bitumen with rheological parameters
- 2021
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Ingår i: International Journal on Road Materials and Pavement Design. - : Taylor and Francis Ltd.. - 1468-0629 .- 2164-7402. ; 22:S1, s. S297-S309
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Tidskriftsartikel (refereegranskat)abstract
- The use of modifiers for bituminous binders has become common practice to enhance the performances of asphalt materials. As a result, the binder becomes more complex, with various phase morphologies. Conventional testing methods may not always be suitable. As example, the European standardisation committee is looking at different ways to characterise Polymer modified Bitumen. The RILEM Technical Committee 272-PIM ‘Phase and Interphase behaviour of innovative bituminous Materials’, with its Task Group TG1, is evaluating different test methods for complex binders. The aim is to evaluate how these tests could address complex bituminous binders. An inter-laboratory programme was conducted with 17 laboratories. Seven binders were evaluated; two were neat bitumen and two PmB. In addition to the conventional property measurements, an extensive effort was made on investigating various rheological parameters obtained from Dynamic Shear Rheometer measurements. Some initial results are presented and discussed in view of the future revision of the European product standard EN 14023 for PmB.
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| 9. |
- 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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| 10. |
- 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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