| 1. |
- He, Liang, et al.
(author)
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Discrete element simulation of porous asphalt mixture clogging law
- 2023
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In: Jiaotong Yunshu Gongcheng Xuebao/Journal of Traffic and Transportation Engineering. - : Chang'an University. - 1671-1637. ; 23:2, s. 78-91
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Journal article (peer-reviewed)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.
(author)
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Ersättning av metylenklorid vid asfaltsextraktioner : Förstudie
- 2023
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Reports (other academic/artistic)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, L., et al.
(author)
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Biomass valorization toward sustainable asphalt pavements : Progress and prospects
- 2023
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In: Waste Management. - : Elsevier. - 0956-053X .- 1879-2456. ; 165, s. 159-178
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Journal article (peer-reviewed)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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| 4. |
- Wang, Di, et al.
(author)
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Multiple stress creep and recovery test for bituminous binders : influence of several key experimental parameters
- 2023
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In: International Journal on Road Materials and Pavement Design. - : Taylor & Francis. - 1468-0629 .- 2164-7402. ; 24:Sup1, s. 290-308
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Journal article (peer-reviewed)abstract
- The Multiple Stress Creep and Recovery test is recognised to better characterise the high-temperature property of bituminous binders than the traditional methods, especially for polymer modified bitumen (PmB). However, some experimental parameters may affect the test results, such as the preloading, measurement location, stress level. In this study, the effects of these parameters were evaluated through an interlaboratory experiment. Four bituminous binders were short-term aged and analysed by five different laboratories. The variability in most results met the requirements of the European standard, while some failed to pass the American precision criteria. The preloading at 0.1 kPa with ten cycles was found to have a recordable impact on PmB samples, but a less significant effect was observed for the unmodified ones. With the measurement locations, the influence is limited compared to other parameters. As for stress sensitivity, higher stresses lead to remarkable differences.
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