Bitumen Film Research Articles

Adherence Energy of Asphalt Thin Films Measured by Force-Displacement Atomic Force Microscopy

AbstractViscoelastic materials exhibit rate- and temperature-dependant behavior in terms of stress-strain response and fracture. As a representative of this class of materials, rate-dependant fracture should be expected for the bituminous asphalt binders used in the construction of pavement. Preliminary results are reported regarding studies using atomic force microscopy (AFM) to determine rate- and temperature-dependent adhesive fracture in bitumen thin films. This AFM technique involves creating then fracturing a microadhesive contact joint between a bitumen thin film and a glass microbead tip affixed to a cantilever by application of a direct tensile force to the contact. The mechanical work required to fracture this contact is measured as a function of temperature and separation rate. Results of this study suggest that adherence fracture energy of bitumen films is rate and temperature dependant based on measures of energy dissipation at and below the temperature of 25°C. These materials also exhibit a...

Influence of different polishing conditions on the skid resistance development of asphalt surface

The development of the skid resistance of asphalt road surfaces was simulated in a laboratory. Asphalt plates were taken from a test track. They were polished using the Aachen Polishing Machine (APM) with real tires under various conditions and their skid resistances were determined using the Wehner/Schulze machine (W/S). The process of binder removal and polishing of the aggregate can be accurately described using a five-parameter skid resistance model. It was observed that the asphalt plates showed different skid resistance behaviors and reached different final states under varying polishing conditions. It can be concluded that wetness conditions, polishing agents and the affinity between aggregate and bitumen were decisive for the skid resistance development. They could influence the removal speed of the bitumen film, the peak value as well as the final value of the skid resistance. The polishing using the W/S test could lead to an overestimation of the predicted skid resistance level when the grain size and composition of dust on the road surface deviates excessively from that of the standard polishing agent applied in the W/S test. For a realistic skid resistance prediction, it is therefore recommended that the asphalt specimen should be polished using a polishing agent with similar gradation to that of the dust on the road surface.

Evaluation of Hydraulic Permeability of Open-Graded Asphalt Mixes Using a Full Numerical Simulation

AbstractPermeability of open-graded asphalt mixes is defined as the ability to transmit fluids through the voids. The infiltration of water affects the durability and safety of pavement systems. Traditionally, an empirical approach, based on laboratory tests or on field measurements, is used to evaluate hydraulic permeability. In general, such an approach allows the ex post calculation of the drainage capability of the open-graded pavement. In order to evaluate the hydraulic permeability during the phase of mix design, in this paper a novel method is proposed, based on simulation of unsteady flow of water through open-graded mixture. In particular, a real sample of asphalt mix is simulated in the shape of a Marshall test sample. It is composed of a set of particles, selected according to the real grading, positioned in the space domain following the random sequence adsorption approach (RSA) and covered by a film of bitumen. The flow of water through the synthetical sample is simulated through the lattice ...

Interfacial energy of heavy naphthenic bitumen in aqueous medium

The impact of the interfacial properties of naphthenic bitumen is very relevant for road paving. In this work, we propose an approach for predicting the interfacial energy of bitumen in aqueous media based on contact angle hysteresis measurements. We measured the surface tension of naphthenic bitumen at high temperature with the pendant drop method. We estimated the surface energy of bitumen as the value of surface tension extrapolated to room temperature. The acid–base properties of naphthenic bitumen films were investigated by contact angle titration with buffered water. Due to the occurrence of contact angle hysteresis, we performed advancing–receding contact angle measurements on bitumen films at different values of pH with the low-rate dynamic contact angle technique. We observed that the receding angle was dependent on pH. Instead, advancing contact angle just reflected the nature of bitumen in dry conditions. We chose the average contact angle of advancing and receding contact angles as an estimate of the thermodynamically meaningful contact angle. Finally, the bitumen-water interfacial energy at room temperature was calculated using the Young equation. The low interfacial energy of bitumen at high pH confirmed the existence of native surfactants.

Brewster Angle Microscopy of Langmuir Films of Athabasca Bitumens, n-C5 Asphaltenes, and SAGD Bitumen during Pressure–Area Hysteresis

Bitumen films formed on water surfaces have negative consequences, both environmental and economic. CanmetENERGY has placed considerable research emphasis on understanding the structures of the bitumen films on water as a necessary step before optimization of bitumen extraction. The detailed structures of the adsorbed molecules and, especially, the role of asphaltene molecules at the interfaces are still under scrutiny and debate. In the present study, we compared bitumen and asphaltene films as they were compressed and expanded under various surface pressures in order to achieve a clearer understanding of bitumen film structures. We used a customized NIMA Langmuir trough interfaced to a Brewster angle microscope (BAM) and CCD camera (Nanofilm_ep3BAM, Accurion, previously Nanofilm Gmbh) to study images of bitumen films at the air/water interface. The bitumen film appeared uniform with high reflectivity at a surface pressure of 18 mN·m(-1) and exhibited a coarse pebblelike interface with reduced reflectivity in the liquid condensed (LC) phase at higher pressures (18-35 mN·m(-1)). During the first cycle of compression asphaltene films showed well-defined phase transitions and a uniformly smooth interface in the LC phase between 9 and 35 mN·m(-1). However, folding or buckling occurred at surface pressures from 35 to 44 mN·m(-1). On expansion, asphaltene films appeared to break into islands. The hysteresis of the pressure-area isotherm was much larger for asphaltenes than for bitumen. In both compression and expansion cycles, BAM images for bitumen films appeared to be more reproducible than those of the asphaltene films at the same surface pressures. Films for low-°API SAGD bitumen were almost identical to those for surface-mined bitumen. Films formed from partially deasphalted surface-mined bitumens showed higher compressibility and lower rigidity than the original bitumen. The BAM images illustrated significant differences between the partially deasphalted and original bitumen films. Other components in bitumen also played important roles in determining the interfacial properties of bitumen films.

Analysis of failure mechanism of bitumen films

The failure phenomena of a viscoelastic thin film of bitumen and polymer modified bitumen under direct tension tests is investigated in detail, experimentally and theoretically. Using video recording and image processing techniques, the time evolution of failure and film disintegration and separation phenomena were studied. The following failure stages were identified and recorded: Initial (=stage 1), necking (=stage 2), filamentation with void nucleation (=stage 3) and separation (=stage 4). The technique allowed the identification of an additional failure stage for the pure bitumen than the four identified for binders, namely light transparent thinning before void nucleation. The determination of stages to final separation allowed behavioral distinction between the straight run bitumen and the polymer modified bitumen. As the direct tensile tests proceed, in addition to shear forces demonstrative of viscous effects, gravity and capillary forces act on the binder film. In order to understand the relative effect of these forces the order of magnitude of relevant dimensionless numbers, representing ratios of these forces is considered and discussed. The analysis of the above numbers confirms that the flow in bitumen is dominated by viscous effects although capillary forces do play a role at later stages of the experiment with negligible inertia and gravitational effects. The detailed analysis of micromechanical behavior of straight run bitumen and polymer modified bitumen provided further indication corroborating the superior field performance of polymer modified bitumen in porous asphalt.

Unsteady Flow Simulation of Water Drainage in Open-graded Asphalt Mixtures

Laboratory tests or measures on the field are widely carried out in order to evaluate the drainage capability of pavement. Such an approach is in general not efficient and it shows poor significance. In this paper we propose a novel method, very effective for mix design, based on simulation of unsteady-flow of water through open-graded mixture. In particular we have modelled internal microstructures of an open-graded asphalt sample, positioning any aggregate particle and creating the bitumen film around each of them. The unsteady-flow of water inside the sample is simulated to evaluate the expected permeability for different specimens and compaction.

Modeling Mode I Fracture of Bitumen Films

AbstractThe fracture behavior of thin films of bitumen in double cantilever beam (DCB) specimens was investigated over a wide range of temperature and loading rate conditions using finite-element analysis. The model includes a phenomenological model for the mechanical behavior of bitumen, implemented into a special-purpose finite-element user material subroutine, combined with a cohesive zone model (CZM) for simulating the fracture process. The finite-element model is validated against experimental results from laboratory tests of DCB specimens by comparing measured and predicted load–line deflection histories and fracture energy release rates. Computer simulation results agreed well with experimental data of DCB joints containing bitumen films in terms of peak stress, fracture toughness, and stress-strain history response. The predicted “normalized toughness,” G/2h, was found to increase in a power-law manner with effective temperature-compensated strain rate in the ductile region as previously observed ...

Understanding Interfacial Behavior of Ethylcellulose at the Water–Diluted Bitumen Interface

An environmentally friendly and commercially available polymer, ethylcellulose (EC), was found to be effective for water removal from water-in-diluted-bitumen emulsions. In a previous study, atomic force microscopy images of bitumen films transferred from the water–toluene interface onto a silicon wafer revealed progressive disruption of bitumen films by increasing the addition of EC. The in situ micropipet experiments, on the other hand, demonstrated the flocculation and enhanced coalescence of two approaching water droplets at low and high EC concentrations, respectively. In this study, we investigated the effect of EC addition on compressibility, composition, thickness, and surface properties of the interfacial films formed by surface-active components of bitumen, aiming to understand the interfacial behavior of EC at the water–diluted bitumen interface. The pressure–area isotherms of Langmuir interfacial films indicated a transformation of a rigid interfacial film formed by surface-active components o...

Modeling Failure of Bitumen Films in Tension

AbstractFinite-element analysis is used to model the failure of thin-film butt-joint specimens of pure bitumen in tension for a wide range of test conditions (temperature and strain rate). The approach uses a powerful numerical scheme based on two components: a nonlinear viscous, temperature- and rate-dependent constitutive material model that describes the mechanical deformation behavior of bitumen, implemented into a special-purpose finite-element user material subroutine, and a cohesive zone model for simulating the fracture process. The finite-element model is validated by comparing computed fracture characterization parameters with experimental results. The predicted force versus displacement characteristics and the normalized toughness, G/2h, are found to compare favorably with experimental results in the ductile and brittle regimes, with the failure mode being accurately simulated.

Diffusion and reaction of oxygen in bitumen films

A numerical model to predict the diffusion and reaction of oxygen in petroleum bitumen films was developed, and compared to experimental data obtained by oxidation of bitumen films at 50°C and atmospheric pressure in the absence of light. Experimental viscosity–depth profiles were obtained by microtoming 3–4mm thick, oxidized, bitumen films at approximately 100μm intervals. Model parameters for the diffusion–oxidation process were obtained by correlating oxygen uptake of bitumen solutions to changes in carbonyl infrared spectral absorption and viscosity. The model developed, predicted the average viscosity in bitumen films after oxidation at 50°C for up to 126days (approximately equivalent to 2years in the field) with an accuracy of ±20%.

Design method and performance for large stone porous asphalt mixtures

Design method for large stone porous asphalt mixtures (LSPM) was analyzed to avoid the early distresses of semi-rigid asphalt pavements. Based on stone-to-stone skeleton structure concept, processes of LSPM gradation design was given. The gradation composite design for LSPM shows that the LSPM nominal maximum size (NMS) should be larger than 26.5 mm, and the NMS sieve passing percentage should be greater than 50%. Through experiments and calculations on the volume properties of the aggregate, the range of aggregate gradation curve of LSPM was given. In terms of asphalt binder’s normalized test results, MAC-70 and SBS modified asphalt were selected as the asphalt binders. The applicability of large scale Marshall Method and gyratory compaction method to shape specimens was investigated. Based on the asphalt mixture performance evaluation, the optimum asphalt content range (3.1%–3.6%), the bitumen film’s thickness range (13–16 μm) and the air void range (135–18%) were recommended. Finally, LSPM was tested by the laboratory performance tests including rutting resistance test, fatigue test and water stability test. The theoretic and practical analysis shows that LSPM has a good performance on water permeability, rutting resistance and reflection crack resistance.

Investigation of the use of strip-prone aggregates in hydraulic asphalt concrete

A study is made of the suitability of strip-prone aggregates for use in asphalt concrete water barriers in embankment dams. Standard boiling tests were used for ranking various aggregate types with respect to water susceptibility and aggregate-bitumen adhesion. Indirect tension tests (splitting tests) were used to study the effects of aggregate-bitumen adhesion on asphalt concrete tensile strength. The test results show the significant detrimental effects of using strip-prone aggregates for open-grade porous asphalt (air void 4–10%), but that aggregate-bitumen adhesion and tensile strength could be increased by adding amine or hydrated lime to the asphalt mix. However, a similar test series on dense-grade hydraulic asphalt (air void 2–3%) shows no detrimental effects of using strip-prone aggregates. Furthermore, there were no significant differences in compressive strengths or beam bending strengths and strains at failure between specimens with or without strip-prone aggregates and with or without amine added. This was the case even for specimens having been cured by exposure to 100 freeze–thaw cycles at +25 °C to −25 °C. For hydraulic asphalt, which is virtually impervious with a significant bitumen film thickness covering the aggregate particles, it does not seem required to use additives to improve the aggregate-bitumen adhesion properties. However, further testing should be done to study any long-term effects of using strip-prone aggregates.

Laboratory Study on Ultraviolet Radiation Aging of Bitumen

The effects of ultraviolet (UV) radiation on degradation of bitumen have received much attention from both academic and industrial points of view. However, quantitative evaluations of bitumen photo-oxidation in pavements have apparently not been determined. In this study, the effects of photo-oxidation of bitumen were investigated by exposing pressed thin films of bitumen. The data for thermal aging only were compared with corresponding data for photo-oxidation from exposure to UV radiation. The levels of aging were evaluated by following increases in the carbonyl functional group, and increases in viscosity. The results indicated that both thermal and UV aging occurred during exposure in the UV radiation oven test for thin bitumen films of both unmodified and SBS-modified bitumen. UV aging had a significant effect on bitumen properties, particularly when the bitumen film thickness was less than 150 μm. Results also showed that the level of UV irradiation intensity had a significant influence on the level of photo-oxidation of the bitumen.

California–Denmark Study on Acoustic Aging of Road Pavements

Knowledge of acoustic aging of road pavements is needed by road administrators when developing policies and strategies for noise abatement. It is important to know how noise-reducing pavements, as well as pavements without such acoustic properties, perform over time. Methods such as the American traffic noise model method or the Nordic NORD2000 method use acoustic aging for accuracy in predicting noise. Noise performance models for road pavements are necessary if noise is to be integrated as an active parameter in pavement management systems. This paper contributes to ongoing international development in the field of acoustic aging by performing a comprehensive analysis of results from four Californian and Danish long-time noise measurement studies on asphalt pavements. There is not much information on which changes in the surface structure cause an increase in noise in the period between when the bitumen film is worn off and when the pavement begins to deteriorate with distresses such as raveling, cracking, and so forth. This study analyzes and compares trends in the development of noise over time. The development of the noise spectra is also analyzed. The increase of noise has normally been analyzed in relation to the age of pavements. The traffic load and an artificial indicator, defined as the change of noise predicted as a combination of actual physical age and traffic load, are investigated.

Experimental and Numerical Analysis of Crack Initiation and Growth in Thin Film of Bitumen

Experimental and Numerical Analysis of Crack Initiation and Growth in Thin Film of Bitumen

Impact of mica content on water sensitivity of asphalt concrete

It is well known that mineral fillers have an important influence on the performance of bituminous mixtures. Properties of filler are depending on the type and the nature of mineral filler. Experience has shown that presence of mica in the filler material has reduced the asphalt concrete resistance against water influence and freeze and thaw cycles. The purpose of the present work is to clarify the effect of free mica in the filler material on the durability of bituminous mixtures. Presence of free mica results in a tremendous increase of the total surface area of aggregate, which is intended to be covered by a bitumen film. It is concluded that making mix design in respect to surface area of the filler will almost vanish the disadvantage of using mica in production of asphalt mixtures. It will also result in using less amount of mineral filler.

Experimental and Numerical Analysis of Crack Initiation and Growth in Thin Film of Bitumen

ABSTRACT In order to estimate the influence of bitumen on the resistance to cracking and fatigue behaviour of bituminous mixes, a specific test has been developed to estimate fracture properties. A thin film of binder between two steel protuberances, simulating the pseudo contact of two aggregates, is subjected to successive tension loads with a constant strain rate during the test. Formation and evolution of the crack size during the test was investigated using numerical methods. This paper deals with the combination of the experimental evolution of the sample stiffness and modelling of the considered test by finite element method. The modelling method, described here, integrates both viscoelasticity with Prony series and the sample geometry. A quantitative method using stress intensity factor and displacement intensity factor is also presented to study the effect of strain rate on propagation of crack.

GEOCHEMICAL AUREOLES AROUND OIL AND GAS ACCUMULATIONS IN THE ZECHSTEIN (UPPER PERMIAN) OF POLAND: ANALYSIS OF FLUID INCLUSIONS IN HALITE AND BITUMENS IN ROCK SALT

Fluid inclusions in halite and bitumens in rock salt in Upper Permian Zechstein evaporites in West Poland were studied in locations where the evaporites lie above oil and gas reservoir rocks. The samples were taken from halite intercalated within the Basal Anhydrite; this unit lies above the Main Dolomite which serves as both source rock and reservoir. Samples came from a depth of 2.3–3.2 km. A characteristic feature of the fluid (gas‐brine) inclusions was their high methane content together with the occasional presence of bitumen globules of near‐spherical form. Geochemical analyses of the bitumen in bulk samples of rock salt (including content and distribution of n‐alkanes and isoprenoids, and carbon isotope ratios) suggest an algal origin, similar to that of the oil in the underlying source rocks. For comparison, we studied fluid inclusions in halite from Zechstein evaporites in northern Poland, where hydrocarbon accumulations do not occur in underlying strata and where mostly single‐phase (brine) inclusions with a low methane content have been recorded. However, published data indicate that similar inclusions to those occurring in the Zechstein of West Poland (comprising brine with a high methane content, bitumen films and/or oil droplets) are present in other salt‐bearing sequences, where their origin is related to the thermal degradation of organic material dispersed within the salt itself. Accordingly, such fluid inclusions in an evaporite succession can only be considered to form a geochemical aureole where the bitumens in the rock salt (including those in the fluid inclusions in halite) can be compositionally linked to those in the associated oil accumulation.

Wetting phenomena in oil sand systems and their impact on the water-based bitumen extraction process

The highly efficient and economically feasible technology for bitumen recovery from U.S. oil sands using a water-extraction approach was developed at the end of the last century. This water-based bitumen extraction process has been optimized based on observations and analysis of microscopic mechanisms of bitumen release from oil sands and the bitumen transfer to a froth product as well as measurements of interfacial properties of bitumen. The wetting mechanisms that occur in the diluent-assisted water-based processing of U.S. oil sands include bitumen film rupture and recession on sand grains and bitumen transfer to nucleated and injected gas bubbles. These mechanisms are reviewed in this contribution.