| 1. |
- Filippov, Andrei, et al.
(författare)
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Dynamics and Structure of a Bitumen Emulsion as Studied by 1H NMR Diffusometry
- 2023
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Ingår i: ACS Omega. - : Amer Chemical Soc. - 2470-1343. ; 8:39, s. 36534-36542
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Tidskriftsartikel (refereegranskat)abstract
- Self-diffusion in a bitumen emulsion was studied by H-1 NMR. The emulsion forms two phases: continuous and dispersed. The continuous aqueous phase contains mainly water, with the energy of activation of the diffusion process equal to that of bulk water, while its diffusivity is smaller than that of bulk water by a factor of 2. The dispersed phase consists of bitumen droplets containing confined water, whose dynamics is characterized by a fully restricted diffusion regime in cavities with sizes of similar to 0.11 mu m. Therefore, the studied bitumen emulsion can be described by a model of a complex multiple emulsion of the water/oil/water (WOW) type. The suggested model does agree well with data from H-1 NMR spectroscopy and diffusometry of the bitumen emulsion doped with paramagnetic MnSO4(aq) as well as with an additional H-1 NMR study of the emulsion structure, in which emulsion stability was compromised by freezing at 253 K.
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| 2. |
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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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
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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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| 6. |
- 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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| 7. |
- Lu, Xiauhu, et al.
(författare)
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Structural and chemical analysis of bitumen using time-of-flight secondary ion mass spectrometry (TOF-SIMS)
- 2017
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 199, s. 206-218
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Tidskriftsartikel (refereegranskat)abstract
- The chemical composition and structures of bitumen surfaces are characterised using time-of-flight secondary ion mass spectrometry (TOF-SIMS). The effect of wax is considered by comparing a wax-free bitumen with a bitumen that contains natural wax and a wax-free bitumen to which a small amount of wax has been added. The results demonstrate that TOF-SIMS is a powerful method for the chemical characterisation of surface structures and phase segregation phenomena in bitumen. It is evident that the structures formed on the bitumen surface are closely related to the wax content and that these structures, as well as the surface in general, are enriched in wax-related compounds (aliphatic hydrocarbons with a high degree of saturation). For the wax-free bitumen, the surface is characterised by a homogeneous distribution without chemical variations or phase structures and by a stronger signal intensity from aromatic compounds. When adding wax to the wax-free bitumen, extensive wax segregation occurs, but differently from the natural waxy bitumen, no bee structures are observed. Furthermore, fracture surfaces of all the wax-containing samples reveal circular structures, which are distinctly different from those observed on the original surfaces. The obtained chemical knowledge on bitumen surfaces and phase structures is of fundamental importance to understand performance differences of this type of materials.
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| 8. |
- 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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| 9. |
- 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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| 10. |
- 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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| 11. |
- 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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| 12. |
- Porot, Laurent, et al.
(författare)
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Bituminous binder
- 2018
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Ingår i: Testing and Characterization of Sustainable Innovative Bituminous Materials and Systems. - Cham : Springer Netherlands. ; , s. 15-74
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Bokkapitel (refereegranskat)abstract
- One of the most important aspects of asphalt pavement deterioration is the ingress of water in pavement which leads to loss of the material characteristics, even material integrity with loss of aggregates. Thus the behaviour of asphalt mixture under moisture conditions is one of the key parameter for specifications. It’s a complex phenomenon which is influenced amongst other things by materials properties with wetting, cohesion and adhesion of bituminous binder and by environmental conditions with temperature, moisture, loading and layer type. It has been a research subject for a very long time and still not precisely described. A large number of test methods is available to estimate the affinity between aggregates and bituminous binders. These test methods can be subdivided in different ways; a first distinction can be based on the presence or absence of water during the test procedure. If water is present, the evaluation is in fact referred to as water sensitivity or moisture damage testing. Another distinction can be based on the type of sample that is evaluated. The test sample can be loose aggregates coated with a bituminous binder or a compacted asphalt mix sample. Lastly the individual components, bitumen and aggregate, can be tested separately through intrinsic properties. Furthermore, test results can also be based on the quantification of the test results, whether this is based on a qualitative or a quantitative evaluation. In RILEM TC 237 SIB, TG1 the main purpose was to evaluate common test methods, used to assess the affinity of bitumen to aggregate surfaces, to determine, if possible, the repeatability and reproducibility and to give recommendations for improvement. In this study both binders and aggregates have been considered. Three bituminous binders, two unmodified from different sources, one polymer modified binder, and four aggregate types, with different mineralogy, have been selected. The test methods considered in the study include the rolling bottle test, the boiling water stripping test and the bitumen bond strength test; also surface energy was investigated. This chapter presents the results of these tests and their accuracy.
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| 13. |
- Soenen, Hilde, et al.
(författare)
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Differential Scanning Calorimetry Applied to Bitumen : Results of the RILEM NBM TG1 Round Robin Test
- 2013
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Ingår i: Multi-Scale Modeling and Characterization of Infrastructure Materials. - Dordrecht : Springer Netherlands. - 9789400768772 - 9789400768789 ; , s. 311-323
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Konferensbidrag (refereegranskat)abstract
- The application of Differential Scanning Calorimetry (DSC) has been proven useful in characterizing bituminous binders, distillates and crude oils. In this paper, results of the round robin test, organized by the Rilem TC 231 Nanotechnology-based Bituminous Materials (NBM) TG1 group are reported. The purpose is to investigate the repeatability and reproducibility of standard DSC measurements when applied to bituminous binders. In the full test program of the Rilem NBM group, DSC measurements are further compared to observations made in atomic force microscopy (AFM), AFM measurements are reported in a separate paper. Seven laboratories have participated in this round robin test. Four bituminous binders were investigated, containing various amounts of natural or added wax. The test program consisted of a well-defined isothermal annealing procedure, followed by a first heating and cooling scan, and afterwards followed by a second heating scan. At this stage, the data, as they were reported by the different participants, were compared. For the glass transition (Tg), mid temperatures, can be defined with a reasonable reproducibility, which improves if natural wax is not present. Regarding melting and crystallization, the shape of the melting curve is highly dependent on the thermal history of the samples. Peak temperatures of melting and crystallization phenomena were reported with a good reproducibility, while the reproducibility of melting enthalpies (or surface area’s under the melting and crystallization signals) was not satisfactory. Different reasons for this and recommendations for improving the results are discussed in the paper.
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| 14. |
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| 15. |
- 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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