Advances related to the use of solubility parameters and free energy theory for the phase behaviour study of polymer-modified bitumen (PMB) are reviewed in this paper. The origin and effects of PMB ...phase behaviour are criticised with a focus on PMB storage stability, morphology and swelling ratio. An overview of the solubility approach for studying PMB is given regarding the historical and future developments. Free energy expressions for PMB systems are analysed, including the free energy of mixing, elastic free energy and gradient energy. The kinetic aspects are discussed with respect to the diffusion and flow processes. It is indicated that the solubility bodies in the three-dimensional Hansen space and their degree of intersection can be useful for analysing the PMB thermodynamic equilibrium and thus storage stability. But they give no indication by themselves on the PMB morphology. With solubility parameters linked to the PMB free energy, however, an integrated thermodynamic approach can assist in understanding both PMB storage stability and morphology comprehensively. Due to the chemical complexity of bitumen and certain modifiers, the solubility body centres and radiuses should be both considered for a proper expression of the polymer-bitumen interaction in PMB. A hypothetical dilution process can simplify this process, but with limitations. The introduction of elastic free energy may lead to a new and more realistic expression of free energy for PMB system. With this overview, it is expected that a preliminary foundation is established towards a comprehensive and realistic thermodynamic framework for interpreting and predicting PMB phase behaviour.
•SEM imaging shows primary OM-hosted pores are common in thermally immature shales.•OM pores occur in immature and gas-mature samples, but not in oil-mature samples.•Lack of OM pores in oil mature ...samples is due to infilling of pores by bitumen.•Pore development with maturation is influenced by primary pores in immature OM.•Organic pore networks may play a significant role in primary oil migration.
Organic matter (OM)-hosted pores, rather than mineral-hosted pores, are considered to be the dominant contributors to total porosity and hydrocarbon storage in many organic-rich unconventional reservoirs. OM-hosted pores are thought to develop during thermal maturation as generated hydrocarbons are expelled from the kerogen, leaving behind pores. However, prediction of OM-hosted pore development is hampered by the lack of a simple relationship between thermal maturity and OM-hosted porosity, with the controls on pore distribution, size and morphology remaining poorly known. In particular, the extent to which thermally immature OM hosts primary pores and the influence that these have on subsequent organic pore development remains poorly understood. Here we employ Ar ion beam polishing and high resolution scanning electron microscopy to show that primary OM-hosted pores are common in thermally immature shales of varying ages and depositional settings, where they occur in both structured and amorphous OM. We further find, utilising a thermal maturity gradient in the Devonian-Mississippian Woodford Shale, that although OM-hosted pores are common in the least mature (<0.4%Ro) samples imaged they are not evident in examples that are mature (0.5–1.1%Ro). However, OM-hosted pores similar to those observed in the least mature samples are present in gas-mature samples (⩾1.5%Ro), where they are classified as secondary pores. Solvent extraction to remove bitumen from oil-mature samples results in an abundance of pores in samples where previously none were evident, which suggests that the absence of primary OM-hosted pores in untreated oil-mature samples is due to infilling of pores by generated and retained bitumen. The similar size and morphology of more complex secondary pores and primary pores is consistent with re-emergence of primary pores in gas-mature structured organic matter, following expulsion of infilling bitumen. Inheritance of pore structure is less evident in amorphous OM types, where secondary pores exhibit a distinctive spherical morphology that has previously been attributed to a gas bubble origin within bitumen. However, similar spherical pore morphologies are evident in immature amorphous OM, arguing against a maturation related origin, so that re-emergence of primary pores cannot be ruled out. Our findings are also relevant to models of hydrocarbon storage and migration. Given that bitumen filled organic pores are likely open in regards to hydrocarbon migration, the importance of organic pore networks for primary migration in the oil window may have been underestimated – well developed organic pore networks contributing to permeability and storage capacity are otherwise assumed to be a feature characteristic of gas-mature shale reservoirs.
Modification using elastomeric thermoplastic polymers is commonly adopted to improve the high-temperature performance of paving bitumen. The performance of modified bitumen classified under the same ...grade is highly variable depending on the type of base bitumen, the polymer architecture, and its dosage. The current specification parameters are insensitive to such variability. Identification of a suitable set of parameters that can quantify the changes in rheological properties due to various interaction mechanisms of bitumen with modifier thus becomes necessary. In this study, the base bitumen obtained using two different processes, namely air rectification and component blending, are considered. Though the same grade of bitumen produced using both processes is considered, the material compositions are different, and this necessitated the use of different polymer architectures (diblock and triblock SBS) for the two binders. Three different dosages are used for each modifier. A stress relaxation experiment is conducted, and the peak modulus and stress relaxation time are determined. In addition, the continuous relaxation spectrum and the associated parameters are computed. The base bitumen and the polymer architecture of the corresponding polymer influenced the stress relaxation response substantially. These factors also influenced the response of the material captured using the relaxation spectrum and exhibited interesting insights regarding the influence of temperature.
This study analyzed the effects of the filler⁻bitumen interaction of the content and the meso powder characteristics of the mineral filler on the low-temperature performance of bitumen mastics. ...Control strategies for the mineral filler content (filler⁻bitumen ratio (
)) were also determined. Panjin #90 bitumen and styrene⁻butadiene⁻styrene polymer-modified bitumen were used in the experiment. Four kinds of limestone powder were used, all of which satisfy the Chinese standard for powder particle size but exhibit different meso characteristics. Each kind of limestone powder was used to prepare bitumen mastic samples under five different
. The meso voids in the unit mass (
) of the four kinds of mineral filler were tested on the basis of the principle of the Rigden void ratio. The fixed bitumen⁻free bitumen ratio in the bitumen mastic samples was determined using
, bitumen density, and
. The low-temperature cohesive strength of the bitumen mastics was used as the control index for critical failure, whereas variation rates of bending creep stiffness at low temperature were used as the control index for fatigue failure. Results showed that the effects of the filler⁻bitumen interaction of the content and the meso characteristics of the mineral filler are significant and such effects are determined by the fixed bitumen⁻free bitumen ratio. The optimal fixed bitumen⁻free bitumen ratio in the bitumen mastics under two low-temperature conditions (−30 °C and −10 °C) can be determined on the basis of the influence of the fixed bitumen⁻free bitumen ratio on the critical and the failure control indices. Moreover,
can be obtained through reverse calculation. The mineral filler content can therefore be precisely controlled, which is crucial for the rational use of mineral filler and for the improvement of the pavement performance of bitumen mastics at low temperatures.
In the present work, a mix design parametric study was carried out with the aim of proposing a practical and consistent mix design procedure for foamed bitumen mixtures (FBMs). The mix design ...parameters that were adopted in the study are mixing and compaction water content (MWC), compaction effort using a gyratory compactor and aggregate temperature. This parametric study was initially carried out on FBMs with virgin limestone aggregate without reclaimed asphalt pavement (RAP) material and a mix design procedure was proposed. This proposed methodology was also found to apply to FBMs with RAP. A detailed consideration was also given to characterising the RAP material so as to understand its contribution to the mechanical properties of FBMs. Optimum MWC was achieved by optimising mechanical properties such as indirect tensile stiffness modulus and indirect tensile strength (ITS-dry and ITS-wet). A rational range of 75-85% of optimum water content obtained by the modified Proctor test was found to be the optimum range of MWC that gives optimum mechanical properties for FBMs. It was also found that the presence of RAP influenced the design foamed bitumen content, which means that treating RAP as black rock in FBM mix design is not appropriate. To study the influence of bitumen and water during compaction, modified Proctor compaction and gyratory compaction were employed on mixes with varying amounts of water and bitumen. By this, the work also evaluated the validity of the total fluid (water + bitumen) concept that is widely used in bitumen-emulsion-treated mixes, and found it not to be applicable.
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•The surface forces between air bubbles and two types of bitumen in aqueous solutions were quantified.•Hydrophobic interactions dominate the attachment of bubbles and bitumen ...surfaces.•High-salinity condition facilitates bubble-bitumen attachment.•Increasing pH weakens the attachment of bubbles and bitumen surfaces.•The presence of surfactants hinders the bubble-bitumen attachment.
The surface interactions of air bubbles and other components (e.g., particles, oil droplets) significantly influence the operation efficiency of a variety of engineering processes such as oily water treatment, bitumen extraction and flotation. Herein, the surface interactions of air bubbles with two types of Athabasca bitumen samples in aqueous solutions of varying pH, salinity, type of cations and in the presence of surfactants have been systematically characterized using a bubble probe atomic force microscope (AFM) technique. AFM imaging has revealed that exposure to high concentrations of NaCl and CaCl2 solutions or alkaline environments causes roughening of the bitumen surfaces. The results of surface force measurements demonstrate that the interaction and attachment behaviors between bubbles and bitumen are significantly affected by ionic strength, solution pH, and the presence of surfactants. The experimental force measurement results could be accurately described by a theoretical model that incorporates Reynolds lubrication theory and augmented Young-Laplace equation, with the inclusion of disjoining pressure. In low-salinity conditions, the bubble-bitumen interaction is dominated by electric double layer (EDL) repulsion, which prevents surface attachment. This effect is more pronounced at elevated pH conditions. In high-salinity solutions, however, the EDL interactions are significantly reduced, and the hydrophobic interaction becomes the dominant factor, overcoming the van der Waals repulsion and leading to the attachment of bubbles to bitumen surfaces. Raising aqueous pH weakens the bubble-bitumen hydrophobic interaction, whereas the introduction of calcium ions strengthens this interaction, resulting in enhanced surface attachment. Interestingly, even in high-salinity conditions, the presence of a small number of surfactants can inhibit bubble-bitumen contact, mainly caused by reduced hydrophobic attraction and increased steric repulsion. This work provides valuable nanoscale insights into how bubbles and bitumen interact in intricate aqueous environments, and the results show practical implications for controlling similar interfacial phenomena in various engineering processes.
This research presents a laboratory study on a polymer-modified bitumens (PMBs) made with a vacuum residue (VR) as a bitumen extender. Two different PMBs were prepared, one with a plastomeric Elvaloy ...and the other one with an elastomeric styrene-butadiene-styrene SBS. The mechanical properties of the samples were determined by means Multi Stress Creep Recovery tests (MSCR) and temperature sweep test. The results show that polymers can improve the mechanical properties of bitumen, and the vacuum residue can be used as softening bitumen extender. However, their simultaneous presence highlights non-additive effects giving optimal mechanical properties with a lowered temperature dependence of the viscoelastic properties and a high extension of the usage temperature range. The peculiar effect of the combined action of polymers and vacuum residue was also confirmed by chemical-physical analyses. In fact, Atomic Force Microscopy (AFM) and Nuclear Magnetic Resonance (NMR) relaxometry have shown that vacuum residue and polymers are able to effectively interact with the inner structures of the bitumen to give enhanced performances, with an increased stability upon temperature changes.
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•Hydrophilic clays had a significant depression on bitumen recovery.•Hydrophobic clays exhibited a serious deterioration in froth quality.•Clay mineralogy was negligible after ...coverage of organic contaminants.•Slime-coating of clays on bitumen occurred above a threshold clay concentration.•Kaolinite was confirmed to slime-coat on bitumen surface the first time.
Clays (<2 μm) in oil sands ores have a significant impact on the processability of the ores. The present study aims at understanding the effects of the type and wettability of clays on the performance of bitumen extraction from mined oil sands. The results from batch extraction tests showed a detrimental effect of doping with hydrophilic clays (kaolinite, illite and montmorillonite), with montmorillonite being the worst. The crucial role of clays in bitumen slime-coating was studied through atomic force microscopy and clay deposition tests. For the hydrophilic clays, clay concentration was an essential parameter in determining the bitumen-clay hetero-coagulation process. Strong slime-coating of clay particles on bitumen droplets occurred only above a critical clay concentration. This critical concentration varied with clay type and water chemistry. Compared with earlier studies, kaolinite was found to deposit strongly on bitumen surfaces for the first time in this study. Hydrophilic clays were contaminated by soaking in toluene-diluted-bitumen solutions to investigate the effect of solid hydrophobicity on bitumen extraction. Hydrophobic clays had a less significant depression on bitumen recovery but a more significant deterioration on froth quality than hydrophilic clays. Similar slime-coating was observed for the different clays once contaminated by diluted bitumen. Furthermore, the presence of a large content of clays in bitumen extraction could result in excessive emulsification of bitumen into small droplets, leading to low bitumen recovery. This work provides useful insights into the fundamental interactions of clays and bitumen, with implications for developing a viable solution in dealing with clays in oil sands operations.
Summary
This paper investigates the mechanism of bitumen surface ageing, which was validated utilizing the atomic force microscopy and the differential scanning calorimetry. To validate the surface ...ageing, three different types of bitumen with different natural wax content were conditioned in four different modes: both ultraviolet and air, only ultraviolet, only air and without any exposure, for 15 and 30 days. From the atomic force microscopy investigation after 15 and 30 days of conditioning period, it was found that regardless the bitumen type, the percentage of microstructure on the surface reduced with the degree of exposure and time. Comparing all the four different exposures, it was observed that ultraviolet radiation caused more surface ageing than the oxidation. It was also found that the combined effect was not simply a summation or multiplication of the individual effects. The differential scanning calorimetry investigation showed that the amount of crystalline fractions in bitumen remain constant even after the systematic conditioning. Interestingly, during the cooling cycle, crystallization of wax molecules started earlier for the exposed specimens than the without exposed one. The analysis of the obtained results indicated that the ageing created a thin film upon the exposed surface, which acts as a barrier and creates difficulty for the wax induced microstructures to float up at the surface. From the differential scanning calorimetry analysis, it can be concluded that the ageing product induced impurities in the bitumen matrix, which acts as a promoter in the crystallization process.
Lay Description
This paper investigates the mechanism of bitumen surface ageing which has been investigated utilizing the atomic force microscopy (AFM) and the differential scanning calorimetry (DSC). To do so, three different types of bitumen with different natural wax content were conditioned in four different modes: both UV and air, only UV, only air and without any exposure, for 15 and 30 days. From the AFM investigation after 15 and 30 days of conditioning period, it was found that regardless the bitumen type, the percentage of microstructure on the surface reduced with the degree of exposure and time. Comparing all the four different exposures, it was observed that UV radiation caused more surface ageing than the oxidation. It was also found that the combined effect was not simply a summation or multiplication of the individual effects. The DSC investigation showed that the amount of crystalline fractions in bitumen remain constant even after the systematic conditioning. From the experimental evidence, it could be concluded that the ageing created a thin film upon the exposed surface, which acts as a barrier and creates difficulty for the wax induced microstructures to float up at the surface.
•A new modifier, ZnO particles supported by EVMT, was developed and characterized.•ZnO particles were homogeneously distributed on the surface of EVMT.•Ultraviolet light absorption capacity of ...ZnO/EVMT had a notable enhancement.•ZnO/EVMT composite improved road performance and aging resistance of bitumen.
The multi-dimensional nanomaterial modifier composed of nano-zinc oxide (nano-ZnO) and expanded vermiculite (EVMT) can significantly improve resistance to thermo-oxidative and ultraviolet radiation aging and road performances of bitumen. However, the nano-ZnO particles are susceptible to agglomeration and the homogeneity between nano-ZnO particles and EVMT is hard to be achieved in bitumen. In the study, a new bitumen modifier, a combination of ZnO particles and EVMT, was developed by composite technology to reduce or avoid the agglomeration of the ZnO particles and generate a synergistic effect on bitumen properties, especially for the aging resistance of bitumen. The newly developed modifier was synthesized with a modified hydrolytic precipitation method and characterized by X-ray diffractometer (XRD), field emission scanning microscope (FESEM), Fourier transform infrared spectrometer (FTIR), and UV–Visible spectrometer. Further, the modified bitumen was prepared and then aged with thin-film oven aging test (TFOT), pressure aging vessel (PAV), and ultraviolet (UV) radiation aging methods, respectively. Finally, the effects of modifiers on physical, rheological, and aging resistance of bitumen were evaluated. Results showed that with the synthesis operation, ZnO particles homogeneously loaded on the surface of EVMT, greatly restraining ZnO particles agglomeration and achieving the homogeneity between ZnO and EVMT. Furthermore, due to higher softening point, ductility, and complex modulus values for the modified bitumen compared with that of unmodified bitumen, the introduction of the newly developed modifier can potentially enhance the low-temperature tensile properties and deformation resistance of bitumen. Meanwhile, when the bitumen is exposed to various environmental factors, such as heat, oxygen, and UV radiation, the composites modifier in bitumen can synergistically play a role in reducing the effects on bitumen aging. For that, regardless of aging methods, the introduction of ZnO/EVMT into bitumen can efficiently retard its softening point increase and mobility deterioration, namely, hinder bitumen aging. Therefore, the newly developed modifier, ZnO/EVMT, is promising in both resisting bitumen aging and improving bitumen properties at low and high temperatures, and thus a longer service life for bitumen pavement can be expected with its application.
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