| 1. |
- Xiao, Tian, et al.
(författare)
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Numerical study of heat transfer and load-bearing performances of corrugated sandwich structure with open-cell metal foam
- 2023
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Ingår i: International Journal of Heat and Mass Transfer. - 0017-9310. ; 215
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Tidskriftsartikel (refereegranskat)abstract
- Critical engineering applications require lightweight components that can effectively dissipate heat and provide sufficient load-bearing capacity. Examples of such applications include the jet blast deflector (JBD) on an aircraft carrier and engine combustion chambers in supersonic vehicles. While lightweight corrugated sandwich structures (CSSs) exhibit excellent load-bearing capacity, their heat transfer capacity falls short. To overcome this limitation, a strategy of filling the CSS with an open-cell metal foam (MF) is proposed to create a sandwich structure with ultralight load bearing and heat transfer capabilities. Numerical simulations were conducted to study the heat transfer and load-bearing performance of this new structure. The findings indicate that the use of a MF significantly improves the heat transfer capabilities of the CSS. Compared to the CSS, the Nusselt number of MF and CSS-foam composite at a Reynolds number of 240 were enhanced by 51.3% and 102.3%, respectively. The overall thermal performance of CSS-foam composites was optimized under the same pumping power constraints. In turbulent conditions, the overall thermal performance of CSS-foam composites was 5.9% to 55.4% higher than that of CSS in turbulent conditions. Furthermore, the simulations showed that when the CSS was subjected to static and quasi-static compression, the maximum von Mises stress occurred at the connection between the panel and the web.
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| 2. |
- Ahmed, Abubeker W, 1981-, et al.
(författare)
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Pavement performance follow-up and evaluation of polymer-modified test sections
- 2019
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Ingår i: The international journal of pavement engineering. - : Taylor and Francis Ltd.. - 1029-8436 .- 1477-268X. ; 20:12, s. 1474-1487
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Tidskriftsartikel (refereegranskat)abstract
- Between 2003 and 2006, a test road consisting of several conventional and polymer-modified structures was built on a motorway. Different combinations of styrene–butadiene–styrene (SBS) and ethyl vinyl acetate (EVA) polymer-modified binders were used. The test structures have been in service since then and have been monitored for over 9 years. The resistance of the different types of asphalt concrete mixes to rutting and cracking was measured and predicted. The impact of ageing on the mixes was also evaluated. Although all the sections are in good condition after 9 years of traffic, the predicted differences between the test sections based on the PEDRO (Permanent Deformation of asphalt concrete layers for Roads) approach and laboratory evaluations are noticeable. Lateral wander and transverse profile measurements indicated that studded winter tyre wear contributed to most of the rutting compared to permanent deformation due to heavy traffic. The unmodified mixes exhibited considerable ageing and the SBS-modified mixes were least affected by ageing. Furthermore, the SBS-modified base mix produced significantly better fatigue resistance than the conventional base mix. However, further investigations of the relationships between bitumen and mix properties and further follow-ups of the test sections are recommended to validate the findings.
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| 3. |
- Farcas, Florentina Angela
(författare)
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Evaluation of Asphalt Field Cores with Simple Performance Tester and X-ray Computed Tomography
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The importance of aggregate structure and air voids distribution for asphalt mixture rutting and cracking performance has been well established on the basis of experience and is well documented in the literature. Past and current investigations are limited to assessment of performance based on macroscopic behavior due to the difficulty associated with the quantitative measurement and analysis of the internal structure of asphalt mixtures. Lately, technical advances in X-ray Computed Tomography (CT) and image processing and analysis has made possible to bring the attention also to the internal structure of asphalt mixtures. SPT results from asphalt field cores, including dynamic modulus (before and after loading) and microstrain accumulation (flow number), exhibited significant variability; most likely, induced by irregularities in the core shape. The analysis of aggregate structure and air voids distribution performed trough X-ray CT, clearly identified segregation in the asphalt mixture as a key factor that induced variability in SPT results.
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| 4. |
- Hu, Rukun, et al.
(författare)
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Design and assessment on a bottom-cut shape for latent heat storage tank filled with metal foam
- 2024
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Ingår i: International Journal of Thermal Sciences. - 1290-0729. ; 197
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Tidskriftsartikel (refereegranskat)abstract
- The utilization of phase change materials (PCMs) holds tremendous potential of heat storage domain. The PCM's refractory at the latent heat thermal energy storage (LHTES) unit bottom hinders the heat storage efficiency, despite the significant improvement in thermal conductivity achieved through the addition of metal foam. This study employs numerical simulation to examine the impact of applying bottom cross-cut on PCM's spatial distribution in a horizontal LHTES unit. The manuscript analyzes parameters including melting fraction, complete melting time, Rayleigh number, natural convection heat transfer gain, melting phase interface, velocity and temperature distributions, and heat storage. The findings indicate that the proximity to the heating tube results in a reduction of solid volume at the LHTES unit bottom. A 0.6 bottom cross-cut ratio leads to an 18.84 % faster heat storage rate compared to a concentric-circle unit. Furthermore, a bottom cross-cut ratio of 0.5 enhances natural convection heat transfer gain by 3.28 times.
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| 5. |
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| 6. |
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| 7. |
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| 8. |
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| 9. |
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| 10. |
- Jelagin, Denis, Docent, 1979-, et al.
(författare)
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Asphalt layer rutting performance prediction tools
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Flexible pavement rutting due to permanent deformation accumulation in asphalt layers is one of the most common modes of road failures. In addition to creating high maintenance costs, rutting is a major concern for traffic safety, as the rut development increases the risk of hydroplaning and introduce difficulties in vehicle steering. In this context, accurate methodologies for pavement rutting performance prediction are crucial for decision support in pavement design and rehabilitation. In particular, better rutting performance models are needed to evaluate, new asphalt materials as well as to evaluate the impact of different vehicle types on roads’ service life.The main goal of this report is to present a summary of the existing asphalt rutting performance prediction tools. The present review is limited to available and/or frequently referred to tests and models with an established link to field rutting performance. Accordingly, models focusing solely on permanent deformation on the material level are beyond the framework of the present study.Road structure and its materials, heavy vehicle parameters and climate affecting rutting accumulation in the field are identified. Their significance has been evaluated based on the experimental and numerical findings reported in the literature. Several rutting performance prediction models recently proposed in the literature are summarized along with the material characterization tests used in the models. The reviewed models’ capability to quantify the influence of various structural, material and traffic parameters on the pavement’s rutting performance is examined.It is concluded that implementation of rutting performance models incorporating experimentally measured viscoelastic and permanent deformation properties of asphalt mixtures is a promising way to improve the accuracy of pavement performance predictions. In particular since they allow the effect of novel materials, e.g. polymer-modified, on the pavement’s rutting performance to be quantified.
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| 11. |
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| 12. |
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| 13. |
- Li, Fangfei, et al.
(författare)
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Application and analysis of flip mechanism in the melting process of a triplex-tube latent heat energy storage unit
- 2023
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Ingår i: Energy Reports. - : Elsevier BV. - 2352-4847. ; 9, s. 3989-4004
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Tidskriftsartikel (refereegranskat)abstract
- In order to improve the characteristics of uneven melting in the melting process of the horizontal latent heat energy storage system, the triplex-tube latent heat energy storage unit is taken as the research object, and the flip mechanism is applied to its melting process. Numerical simulation is used for the research, and the numerical model is verified by experimental data. The results show that under different dimensionless times, the melting performance of the unit can be significantly improved by a single flip. When the dimensionless time is 0.4576, it is found that the total melting time of the unit is reduced by 16.17 %, the average heat absorption rate is increased by 14.7 %, but the total heat energy absorption is reduced by 3.85 %. The results show that the addition of a flip can effectively shorten the melting time and increase the heat absorption rate, but it has a negative effect on the total heat absorption in one melting cycle. Moreover, through the comparison of dynamic flow rate, dynamic temperature response, and temperature interval, it is shown that the addition of flip effectively reduces the negative influence of the hard-to-melt zone on the melting performance of the unit during the melting process. The flip mechanism reduces the proportion of high-temperature phase change material in the melting process and makes the melting process more uniform.
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| 14. |
- Lu, Liu, et al.
(författare)
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High-performance formaldehyde prediction for indoor air quality assessment using time series deep learning
- 2024
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Ingår i: Building Simulation. - : TSINGHUA UNIV PRESS. - 1996-3599 .- 1996-8744.
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Tidskriftsartikel (refereegranskat)abstract
- Indoor air pollution resulting from volatile organic compounds (VOCs), especially formaldehyde, is a significant health concern needed to predict indoor formaldehyde concentration (Cf) in green intelligent building design. This study develops a thermal and wet coupling calculation model of porous fabric to account for the migration of formaldehyde molecules in indoor air and cotton, silk, and polyester fabric with heat flux in Harbin, Beijing, Xi'an, Shanghai, Guangzhou, and Kunming, China. The time-by-time indoor dry-bulb temperature (T), relative humidity (RH), and Cf, obtained from verified simulations, were collated and used as input data for the long short-term memory (LSTM) of the deep learning model that predicts indoor multivariate time series Cf from the secondary source effects of indoor fabrics (adsorption and release of formaldehyde). The trained LSTM model can be used to predict multivariate time series Cf at other emission times and locations. The LSTM-based model also predicted Cf with mean absolute percentage error (MAPE), symmetric mean absolute percentage error (SMAPE), mean absolute error (MAE), mean square error (MSE), and root mean square error (RMSE) that fell within 10%, 10%, 0.5, 0.5, and 0.8, respectively. In addition, the characteristics of the input dataset, model parameters, the prediction accuracy of different indoor fabrics, and the uncertainty of the data set are analyzed. The results show that the prediction accuracy of single data set input is higher than that of temperature and humidity input, and the prediction accuracy of LSTM is better than recurrent neural network (RNN). The method's feasibility was established, and the study provides theoretical support for guiding indoor air pollution control measures and ensuring human health and safety.
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| 15. |
- Lu, Xiaohu, et al.
(författare)
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Analysis of asphaltenes and maltenes before and after long-term aging of bitumen
- 2021
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Ingår i: Fuel. - : Elsevier Ltd. - 0016-2361 .- 1873-7153. ; 304
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Tidskriftsartikel (refereegranskat)abstract
- Asphaltenes and maltenes of bitumen before and after aging are investigated by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (1H NMR), time of flight - secondary ion mass spectrometry (TOF-SIMS), and gel permeation chromatography (GPC). It has been shown that bitumen differs in terms of wax. After fractionation, more wax is found in the maltenes compared to the bitumen, and this is even more evident when bitumen is aged. For one bitumen, asphaltenes from the virgin binder do not contain carbonyls, which all fall into the maltenes. After bitumen aging, a large part of the carbonyl and sulfoxide signals is shifted to the asphaltenes. Differences in aromaticity are also evidenced as asphaltenes > bitumen > maltenes. TOF-SIMS shows that maltenes are close to the bitumen, but asphaltenes are more different. Also, maltenes are relatively unaffected by aging while larger differences are found in the asphaltenes between the virgin and aged binders. By GPC, a large molecular weight fraction of bitumen is shown as main part of the asphaltenes. However, asphaltenes also contain low molecular weight molecules that overlap with maltenes. Upon bitumen aging, some low molecular weight compounds may become part of asphaltenes, making the average molecular weight of the asphaltenes lower.
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| 16. |
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| 17. |
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| 18. |
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| 19. |
- Lu, Xiaohu, et al.
(författare)
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Chemical and Rheological Characteristics of Styrene-Butadiene-Styrene Polymer Modified Bitumens
- 1999
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Ingår i: Transportation Research Record. - : SAGE Publications. ; :1661
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Tidskriftsartikel (refereegranskat)abstract
- Styrene-butadiene-styrene (SBS) polymer-modified bitumens were prepared in the laboratory and characterized using rheological and chemical methods. The results showed that morphology of the modified binders was influenced by bitumen composition and polymer content. Polymer modification was found to improve the rheological properties of bitumens. The degree of modification was dependent on the base bitumen and SBS content and structure. It was also observed that aging resulted in degradation of the SBS polymer. Changes in the rheological properties of aged modified binders were dependent on a combined effect of bitumen oxidation and polymer degradation, which varied with the source and grade of bitumen and type and content of polymer. Generally, the aged modified binders showed better rheological properties than aged base bitumens. The study also indicated that aging index is not suitable for evaluating the aging susceptibility of polymer-modified binders.
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| 20. |
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| 21. |
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| 22. |
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| 23. |
- Lu, Xiaohu, et al.
(författare)
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Evaluation of test sections with Polymer Modified Bitumens
- 2014
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Ingår i: Asphalt Pavements. - 9781138027121 ; , s. 287-296
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Konferensbidrag (refereegranskat)abstract
- It has been recognized that Polymer Modified Bitumens (PMB) have more potential for use in asphalt paving and can clearly demonstrate the value of their initial higher cost. To further assess sustainable benefits on heavy trafficked roads, test sections using various PMBs were built on highway E6 in Sweden during 2003-2006. The main objective of this paper is to study the aging and rheological properties of the binders used. A large number of cores were drilled and characterized with respect to stiffness, fatigue and permanent deformation. The binders (original, lab aged and recovered) were investigated extensively with rheological and chemical methods. It was found that PMBs, particularly SBS modified, demonstrate better rheological properties as compared to unmodified bitumens, even after several years in the field. These include higher strain recovery and lower non-recoverable compliance at high temperatures, and lower stiffness at low temperatures. For the SBS modified binders, good aging resistance was observed. The high resistance to aging for the SBS modified binders was also evident in the stiffness measurement made on asphalt field cores. Although significant differences have not yet been seen between the test sections (all the sections are in good condition after six years of traffic), the observed improvements for the modified binders are expected to be confirmed by a longer follow-up of the test road.
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| 24. |
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| 25. |
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| 26. |
- Lu, Xiaohu
(författare)
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Investigation of bituminous binders containing lignin
- 2024
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Ingår i: Sammanställning av referat från Transportforum 2024. - Linköping : Statens väg- och transportforskningsinstitut. ; , s. 410-410
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Reduction of carbon footprint is one of the key focus areas in the asphalt industry. Over the last decade, a comprehensive research and development program has been executed by Nynas to explore renewable materials in bitumen and asphalt, including various plant-based oils and different types of lignin obtained for example from the wood and paper industry or derived from biomass conversion. In the program, the biogenic materials were systematically studied through extensive laboratory tests on bituminous binders and asphalts. This presentation particularly deals with lignin, in which various bitumen and polymer modified bitumen (PMB) binders were formulated by incorporating Kraft lignin and lignin from bio-refinery. Lignin materials were analyzed with respect to elemental compositions and solubility. The binders containing lignin were investigated mostly in accordance with the standards SS-EN 12591 (paving grade bitumen) and SS-EN 14023 (polymer modified bitumen). Asphalt properties were also evaluated basically according to the standardized CEN methods. As expected, lignin differs in chemistry, for example in terms of carbon, sulfur, and oxygen contents. Properties (e.g. rheology and compatibility) of the binders containing lignin also vary, depending on the base bitumen, and the content and the type of lignin. In general, the binders containing lignin show comparable or improved properties compared with normal bitumen. Besides increased consistency and decreased temperature susceptibility, anti-aging effect was observed for lignin. Lignin also provides a wider binder performance grade. What should be particularly mentioned is that, for one of the PMB binders containing lignin which was targeted to 40/100-75 grade, remarkably enhanced low temperature properties were observed. With regards to asphalt properties, no significant differences were found between the asphalts with lignin-extended and conventional binders in terms of stiffness, fatigue, and cracking resistance. But asphalts with the binders containing lignin displayed lower aging susceptibility, which agrees with the observation made on the binders. This study shows that lignin is a potential renewable component both for bitumen and polymer modified bitumen. For further work, studies of long-term field performance (especially in PMB) and recyclability of the materials are recommended.
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| 27. |
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| 28. |
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| 29. |
- Lu, Xiaohu, et al.
(författare)
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Microstructures of bitumen observed by environmental scanning electron microscopy (ESEM) and chemical analysis using time-of-flight secondary ion mass spectrometry (TOF-SIMS)
- 2018
-
Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 229, s. 198-208
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study is to characterize structures induced on bitumen surfaces under analysis by environmental scanning electron microscopy (ESEM), and to examine possible contributing factors to the formation of their formation. Various bitumen samples are investigated, including soft and hard, as well as polymer modified bitumen. Chemical characterization is carried out by time-of-flight secondary ion mass spectrometry (TOF-SIMS), combined with principle component analysis (PCA). The study shows that, for soft bitumen, a tube pattern or worm structure is rapidly formed during ESEM analysis, but for hard bitumen, a longer exposure time is needed to develop a structure. The structures on the hard bitumen are also denser as compared to those on the soft bitumen. When sample specimens are deformed or stretched, the orientation of the created deformation is clearly reflected in the structures formed under ESEM, and for soft bitumen, the structure disappears overnight in vacuum but reappears with the same pattern upon repeated ESEM analysis. TOF-SIMS shows small but consistent chemical differences, indicating higher aliphatic and lower aromatic contents on the surface of the structured area compared to the unstructured area. Based on an estimated temperature increase on the bitumen surface due to the electron-beam irradiation, it is speculated that the ESEM-induced worm structure may be attributed to evaporation of volatiles, surface hardening and local expansion. In addition, under the electron-beam exposure, certain chemical reactions (e.g. breaking of chemical bonds, chain scission and crosslinking) may take place, possibly resulting in the observed chemical differences between the structured and unstructured areas.
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| 30. |
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| 31. |
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| 32. |
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| 33. |
- Lu, Xiaohu, et al.
(författare)
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Performance Evaluation of Polymer Modified Bitumens on a Heavily Trafficked Test Road
- 2014
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Ingår i: International Journal of Pavement Research and Technology. - : Chinese Society of Pavement Engineering. - 1997-1400. ; 7:6, s. 381-388
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Tidskriftsartikel (refereegranskat)abstract
- In asphalt paving, polymer modified bitumens (PMBs) have more potential for use and can clearly demonstrate the value of their initial higher cost. To further assess the sustainable benefits of using PMBs, a test road was constructed on a highway in Sweden. In this paper, the asphalt binders used were investigated extensively using rheological and chemical methods, and asphalt field cores characterized with respect to permanent deformation and fatigue. It was found that the modified binders, particularly with SBS polymers, retain better rheological properties in comparison with conventional ones, even after several years in the field; these include higher strain recovery and lower non-recoverable compliance at high temperatures, and lower stiffness at low temperatures. The SBS modified binders also demonstrate good aging resistance, shown by both laboratory aging tests and field aging. the high resistance to aging for the SBS modified binders was also evident in the stiffness measurement made on asphalt field cores. Moreover, the modified binders with SBS polymers significantly enhance fatigue behaviour.
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| 34. |
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| 35. |
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| 36. |
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| 37. |
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| 38. |
- Lu, Xiaohu, et al.
(författare)
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Structural and chemical imaging analysis of bitumen
- 2021
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Ingår i: International Journal on Road Materials and Pavement Design. - : Taylor and Francis Ltd.. - 1468-0629 .- 2164-7402. ; 22:4, s. 852-870
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Tidskriftsartikel (refereegranskat)abstract
- Microstructures of bitumen surfaces (both air-cooled and fractured) were imaged by atomic force microscopy (AFM) and chemically characterised by time-of-flight secondary ion mass spectrometry (TOF-SIMS). For certain air-cooled bitumen surfaces, bee structures were observed by AFM, and chemical explanation by wax crystallisation was confirmed by TOF-SIMS analysis. Unlike the air-cooled surfaces, the fracture surfaces generally did not show clear structure patterns. Furthermore, TOF-SIMS analysis was conducted on the tube-like or worm structures which were generated by environmental scanning electron microscopy (ESEM) on the bitumen surfaces. In general, very small chemical differences were observed between the structured and unstructured areas, as well as between different areas of the structure. To understand the formation of the ESEM structures, possible contributing factors were examined, from which a mechanism involving electron-induced heating was proposed.
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| 39. |
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| 40. |
- Lu, Xiaohu, et al.
(författare)
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Visualization and chemical analysis of bitumen microstructures
- 2019
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Ingår i: RILEM Bookseries. - Cham : Springer International Publishing. ; , s. 168-173
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Konferensbidrag (refereegranskat)abstract
- Microstructures of bitumen were investigated using atomic force microscopy (AFM) and environmental scanning electron microscopy (ESEM), and a chemical characterization was successfully carried out using time-of-flight secondary ion mass spectrometry (TOF-SIMS). The bee structures were observed by AFM, for which a chemical explanation by wax was confirmed by the TOF-SIMS analysis. A tube pattern or worm structures were generated and visualized by ESEM on bitumen surfaces. Chemical differences between the structured and unstructured areas, as well as between different areas of the structure, were observed. A mechanism for the structure formation on bitumen surface during ESEM analysis is suggested.
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| 41. |
- Pipintakos, Giorgios, et al.
(författare)
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Experimental investigation of the oxidative ageing mechanisms in bitumen
- 2020
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Ingår i: Construction and Building Materials. - : Elsevier Ltd. - 0950-0618 .- 1879-0526. ; 260
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Tidskriftsartikel (refereegranskat)abstract
- Oxidative ageing in bituminous materials is considered one of the most important factors for distress types in road applications. This paper aims to offer insights into the validity of commonly held beliefs regarding the oxidation phases of ageing in bitumen, the fast- and the slow-rate phase, and explore the main oxidation products formed upon ageing. In order to evaluate possible differences between bitumen types, the penetration grade as well as the bitumen production process was varied. Thus, the ageing of three different binders was first studied by Fourier-Transform Infrared (FTIR) and Electron Paramagnetic Resonance (EPR) spectroscopy. The formation of oxygen-containing molecular structures on the bitumen surface during ageing was studied with Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS). The results of FTIR reveal a gradual increase of sulfoxides upon ageing, while the EPR results show an increase of organic carbon-centred radicals. In parallel, TOF-SIMS results provide evidence for an increase of oxygenated compounds, such as SOx--, HOx-- and NOx--containing compounds. It appears also that paramagnetic metal species, such as vanadyl-porphyrins, are insusceptible during ageing. Overall, the findings of this study are in agreement with a mechanism comprising two rate-determining phases and support the formation of different oxygenated products. It is believed that the experimental approach used in this work may contribute further to an improved understanding of the ageing mechanisms in bitumen.
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| 42. |
- Pipintakos, Georgios, et al.
(författare)
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Experimental Validation of the Dual-Oxidation Routes in Bituminous Binders
- 2022
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Ingår i: RILEM Bookseries. - Cham : Springer Science and Business Media B.V.. ; , s. 903-909
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Bokkapitel (refereegranskat)abstract
- Oxidative ageing in bituminous materials is considered to be one of the most important factors for distress types in road applications. The increasing interest in oxidative ageing has highlighted the need for a thorough understanding of the oxidation mechanisms at molecular level. This paper offers some insight in the validity of the proposed hypotheses about the oxidation routes of bitumen, the fast- and the slow-rate route, reflecting on previous studies. Fourier-Transform Infrared (FTIR) and Electron Paramagnetic Resonance (EPR) spectroscopy were utilised for this verification. To elucidate the uncertain formation of sulfoxides, an additional surface investigation with Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) was performed. The findings of the aforementioned techniques reveal the existence of the oxidation products reported previously and contribute to the understanding of the oxidation mechanisms. Overall, this research strengthens experimentally the hypotheses of the dual-oxidation routes of bitumen. © 2022, The Author(s)
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| 43. |
- Poulikakos, Lily D., et al.
(författare)
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Impact of temperature on short-and long-term aging of asphalt binders
- 2016
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Ingår i: RILEM Technical Letters. - : RILEM Publications SARL. - 2518-0231. ; 1, s. 6-9
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Tidskriftsartikel (refereegranskat)abstract
- Properties of asphalt concrete after aging are important parameters in determining the long-term performance of these materials. With the popularity of reduced temperature mixtures the question remains how this reduced temperature in short-term aging affects the long-term properties. This paper focuses on developing a robust and fundamental understanding of the effect of temperature on aging by connecting the chemistry of bitumen to its mechanics. To this end, round robin experiments are being currently conducted within 8 laboratories using four binders of the same grade 70/100 pen from different crude sources. In developing chemo-mechanical characterization techniques at the nano-and micro-scale, the material’s variability from crude-source to crude-source and its sensitivity to temperature needs to be taken into consideration. Furthermore, the development of uniform speci-men preparation procedures for these bituminous materials at the nano-and micro-structural level is the focus. The chemical characterization is per-formed using Fourier transform infrared spectroscopy (FTIR). For the mechanical characterization rheological data is used using the dynamic shear rheometer (DSR) as well as conventional tests, e.g. needle penetration and softening point using the ring and ball method. It is shown that the short-term aging temperature affects the increase in softening point, while the consequent effect on long term aging is less pronounced.
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| 44. |
- Said, Safwat, 1951-, et al.
(författare)
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Prediction of rutting in asphalt concrete pavements : the PEDRO model
- 2020
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Flexible pavement rutting due to permanent deformation accumulation in asphalt layers is one of the most common modes of road failures. In addition to high maintenance costs, rutting is a major concern for traffic safety, as the rut growth increases the risk for hydroplaning and difficulties in vehicle steering. In this context, accurate methodologies for pavement rutting performance prediction are crucial for decision support in pavement design and rehabilitation. More rational rutting performance models are needed to enable the implementation of new and more sustainable and environmentally friendly asphalt materials as well as to evaluate the impact of high capacity traffic (HCT) vehicle types on bituminous layers.The main goal of this work is to implement and disseminate an asphalt rutting performance prediction tool called PEDRO (PErmanent Deformation of asphalt concrete layers for ROads). It focuses solely on the permanent deformation of asphalt concrete materials in the pavement structure. The PEDRO tool is a viscoelastic model for the calculation of permanent vertical strain under moving wheel loads over a viscoelastic half-space. The analysis is performed for the entire rutting zone and the permanent deformation of each layer or sub-layer, depending on its location in the pavement structure, is then integrated over the whole asphalt concrete depth.
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| 45. |
- Sjövall, Peter, et al.
(författare)
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Analysis of kerogens and model compounds by time-of-flight secondary ion mass spectrometry (TOF-SIMS)
- 2021
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Ingår i: Fuel. - : Elsevier Ltd. - 0016-2361 .- 1873-7153. ; 286
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Tidskriftsartikel (refereegranskat)abstract
- Here, kerogens of differing heat treatments are subjected to extremely high dissociation energies by sample bombardment by 25 keV Bi3+ primary ions during analysis by time-of-flight secondary ion mass spectrometry (TOF-SIMS). Positive and negative secondary ions are produced from this decomposition and fragment ion distributions of model compounds and kerogens are compared and starkly different results are obtained for cations versus anions. Cations exhibit a large range of C/H ratios and include highly unsaturated linear chain ions and aromatic ions. Cations of kerogens possess predominantly no heteroatoms. Positive fragment ion distributions depend on the source material being bombarded. Mature, more aromatic kerogens produce higher yields of fragment ions of highly unsaturated carbon chains while immature, more aliphatic kerogens produce more aromatic fragment ions, particularly at the higher carbon numbers. This is consistent with the observation that aromatic model compounds produce a greater fraction of hydrogen-deficient, carbon chain fragment ions, as compared to a purely aliphatic model compound. There is substantial suppression of free radical fragment cations, except for large fragments. In contrast, there is little free radical suppression of the anions. The anions tend to be very hydrogen deficient, spanning a small range of C/H ratios. Highly unsaturated to pure carbon chain fragment anions dominate while aromatic anions are not found. In both positive and negative ion spectra, the yields of fragment ions corresponding to derivatives of the carbon chain molecules, polyynes and allenes, are substantial. Some heteroatom-containing fragment anions are produced, all of which are very hydrogen deficient.
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| 46. |
- Sjövall, Peter, et al.
(författare)
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Time of flight-secondary ion mass spectrometry (TOF-SIMS) study of diverse asphaltenes
- 2018
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 220, s. 638-644
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Tidskriftsartikel (refereegranskat)abstract
- Mass spectrometry has been used to elucidate a large variety of properties of asphaltenes. Here, time-of-flight secondary ion mass spectrometry (TOF-SIMS) is used to probe three diverse asphaltene types with wide ranging fractions of alkyl carbon to the sum of alkyl plus aromatic carbon (Rc), immature source rock asphaltenes (ISA with Rc ∼ 0.75); petroleum asphaltenes (PA with Rc ∼ 0.5); and coal-derived asphaltenes (CDA with Rc ∼ 0.25). In addition, the asphaltenes from a commercial bitumen are examined. Primary ion surface bombardment using the Bi3 + ion yields high energy density of deposition and significant molecular fragmentation with secondary ion formation. Formation of free radical cation fragments is generally suppressed especially for smaller fragments except for specific cases. Possible structures, especially cations of common aromatic compounds, are suggested for fragments with relatively large cross section of formation. Principal component analysis of the fragmentograms allows identification of key properties of the complex fragmentation patterns for the different samples. Comparisons of TOF-SIMS fragmentograms show a fundamental difference for small fragments between CDAs and all petroleum derived asphaltenes with CDAs being dominated by aromatic carbon fragments whereas all petroleum derived asphaltenes show a large fraction of fragments from alkyl carbon. However, the type of alkyl carbon fragments did not exhibit systematic trends with Rc, nor with the extent of chemical reaction or chemical processing of the materials. Consequently, it appears that having an appreciable alkane fraction is a basic property of petroleum derived asphaltenes, but the exact type of alkane carbon for differing samples of these asphaltenes is more idiosyncratic than systematic.
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| 47. |
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| 48. |
- Soenen, Hilde, et al.
(författare)
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Laboratory investigation of bitumen based on round robin DSC and AFM tests
- 2014
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Ingår i: Materials and Structures. - : Springer Science and Business Media LLC. - 1359-5997 .- 1871-6873. ; 47:7, s. 1205-1220
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Tidskriftsartikel (refereegranskat)abstract
- In the past years a wide discussion has been held among asphalt researchers regarding the existence and interpretation of observed microstructures on bitumen surfaces. To investigate this, the RILEM technical committee on nano bituminous materials 231-NBM has conducted a round robin study combining differential scanning calorimetry (DSC) and Atomic Force Microscopy (AFM). From this, methods for performing DSC and AFM tests on bitumen samples and determination of the influence of wax on the observed phases, taking into account thermal history, sample preparation and annealing procedure, are presented and critically discussed. DSC is used to measure various properties and phenomena that indicate physical changes such as glass transition temperature (T (g)) and phase transition such as melting and crystallization. In the case of existence of wax, either natural or synthetic, it can further indicate the melting point of wax, that could be used to determine wax content. The results from seven laboratories show that T (g) temperatures obtained from the heating scans are more repeatable and easier to obtain in comparison to the cooling scans. No significant difference was noted for T (g)'s obtained from the first and second heating scans. AFM is an imaging tool used to characterize the microstructures on a bituminous surface. Using AFM three phases in the materials with wax could be distinguished. The changes in the phases observed with AFM for increases in temperature were correlated with the DSC curve, and it could be established that the so called "Bee" structure disappeared around the melting peak in the DSC curve. Thus, this research has confirmed the relation between the microstructures on a bitumen surface and the wax content.
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| 49. |
- Tang, Bing, 1971-
(författare)
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Applications of Solid-Phase Microextraction to Chemical Characterization of Materials Used in Road Construction
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Environmental and health aspects of road materials have been discussed for a long time, mostly regarding bitumen and bitumen fumes. However, just a few studies on other types of road materials have been reported. In this doctoral study, two types of materials, asphalt release agents and bituminous sealants, were investigated with regard to chemical characterization and emission profiles. Besides conventional test methods, solid-phase microextraction (SPME) technique was applied for emissions profiles screening and quantitative analysis. General description of main characteristics of asphalt release agents and bituminous sealants is given, and a comprehensive state-of-the-art on SPME technique is presented, especially on methodologies for analyzing mono- and polycyclic aromatic hydrocarbons (MAHs and PAHs) in different sample matrices. In the experimental study, chemical characterization of the two material types was performed using conventional methods, including fourier transform infrared spectroscopy - attenuated total reflectance (FTIR-ATR), gel permeation chromatography (GPC), mass spectrometry (MS) and gas chromatography – mass spectrometry (GC-MS). General patterns regarding functional groups and molecular weight distribution were studied. In the case of asphalt release agents, more detailed information on chemical compositions, especially the contents of MAHs and PAHs, was obtained. General information on emission proneness of asphalt release agents was obtained using thermogravimetric analysis (TGA) and MS. Using headspace(HS)-SPME and GC-MS, emission profiles of asphalt release agents were characterized at different temperatures, whereas the profiles of bituminous sealants were obtained solely at room temperature. The results presented were used for ranking the materials with regard to degree of total emission as well as emission of hazardous substances. The applicability of HS-SPME for quantitative analysis of MAHs in asphalt release agents and emulsion-based bituminous sealants was investigated. The use of a surrogate sample matrix was concerned, and experimental parameters influencing the HS-SPME procedure, such as equilibration and extraction time, as well as effects of sample amount and matrices, were studied. The methods were evaluated with regard to detection limit, accuracy as well as precision. Different calibration approaches including external calibration, internal calibration and standard addition were investigated. The determination of MAHs in asphalt release agents and emulsion-based bituminous sealants using HS-SPME-GC-MS was conducted.
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| 50. |
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