Bitumen Mixtures Research Articles

Electrophoresis and its applications in oil sand tailings management

Oil sands mines generate tailings during the extraction process, which are a mixture of water, clay, sand and residual bitumen. When the tailings are released to tailings ponds, the coarse solids settle quickly, whereas fine solids containing clay minerals, namely mature fine tailings (MFT), remain suspended for years, even decades. A study is carried out to assess the suitability of electrokinetic (EK) sedimentation to accelerate sedimentation of MFT. A series of laboratory-scale column experiments are carried out to examine the effects of electrophoresis during settling processes. The investigation focuses on the effects of EK sedimentation as related to the initial solid content of the tailings suspension, applied electric field intensity, water pH, and the use of an optimized coagulant FeCl3. Based on the experimental data, an electric field intensity of 150V/m along with an initial tailings solid content of no >5% are the optimum condition for EK sedimentation of MFT, in terms of reducing the overall sedimentation time and increasing the final solid content. The results show that the current density of EK sedimentation for MFT should not be >20A/m2 to control the bubble effect and reduce power consumption.

Experimental and modeling studies of water, light n-alkanes and MacKay River bitumen ternary systems

Water plays an important role as energy carrier in the solvent-aided thermal recovery processes of heavy oil and bitumen. The effect of water on phase behaviour of bitumen and solvent (light n-alkanes) mixtures is often ignored in thermal reservoir simulation. In this work, the effect of the presence of water on the phase behaviour of solvent in bitumen is studied. The solubility of solvents in bitumen as well as the density and viscosity of the bitumen rich phase are measured in both the presence and the absence of water. Results show a remarkable effect of water on solvent solubility in bitumen especially at high temperature conditions (T>150°C). A three-phase equilibrium calculation of the water-solvent-bitumen ternary system is carried out using a Peng-Robinson equation of state (PR-EoS) coupled with Henry’s constant. The results show that the PR-EoS regenerates the ternary system with acceptable accuracy. The density and viscosity of the bitumen rich phase in the presence of water are correlated using the experimental binary data.

Structural design of pavements incorporating foamed bitumen mixtures

This paper presents a rational structural design methodology termed the ‘cumulative damage approach’ for road, port and airport pavements incorporating cold bituminous mixtures with foamed bitumen. This has been developed along with a laboratory test, the uniaxial indirect tensile test, to evaluate the fatigue characteristics of these mixtures. The test was developed with a view to addressing the limitations of conventional fatigue tests for foamed bitumen mixtures. The new design approach takes account of the actual stiffness evolution of the mixtures obtained from the fatigue test. It is compared with a traditional approach for conventional flexible pavements, which is based on pavement life as a function of computed tensile strain in the material and interpretation of fatigue data in a conventional way. The results show that the traditional design approach yields conservative outcomes for pavements with foamed bitumen mixtures if the same transfer function or shift factor used for hot mix asphalt is applied. The results also show that if all factors other than induced load influence are the same, the shift factor for foamed bitumen mixtures could be 25–35% higher than for hot mix asphalt.

The influence of nanoclay on the performance properties and moisture susceptibility of rubberized asphalt mixture

ABSTRACTThe authors investigated the effect of nanoclay (NC) on the performance properties and moisture susceptibility of rubberized asphalt mixtures. Two percent crumb rubber modifier (CRM) and NC in both combined and separate modes and the effects of each additive on bitumen performance were examined through administering tests of penetration grade, softening point and temperature susceptibility. Also, indirect tensile strength tests in both dry and saturated states were performed to allow for measuring the moisture susceptibility of asphalt mixtures. Moreover, the effect size of both additives on improving the bitumen performance and asphalt mixtures was assessed by running analysis of variance method and sensitivity analysis. The results of the laboratory test and statistical analyses revealed that CRM and NC improved the properties of bitumen and asphalt mixtures. This improvement was associated with the content and type of the additives applied, and also bitumen and asphalt mixtures had the best performance in presence of a combination of CRM and NC.

Effects of Partial Substitution of Styrene-butadiene-styrene with Granulated Blast-furnace Slag on the Strength Properties of Porous Asphalt

The present experimental research investigates the feasibility of partial substitution of styrene-butadiene-styrene (SBS) with ground granulated blast-furnace slag (GGBS) for the modification of bitumen and porous asphalt mixtures. The control asphalt mixture and the seven modified porous asphalt mixtures have been analyzed separately and their performance was compared. Modified bitumen and asphalt mixtures were evaluated based on the penetration test, softening point, ductility, Marshall stability, indirect tensile strength (ITS), moisture susceptibility, uniaxial compression test, porosity, and permeability. According to the results, a blend of GGBS and SBS can be used to modify porous asphalt mixtures since it either improves or does not change their properties. The results show that using these additives have decreased penetration and ductility of bitumen and also there is an increase in softening point, so that the additives have strengthened asphalt mixture properties such as Marshall strength, ITS and Uniaxial compression strength. Furthermore, in the current research work, artificial neural networks (ANN) are used to estimate the permeability of modified porous asphalt mixtures. Sensitivity analysis was discussed for the measurement of the importance of different input parameters. The laboratory experiments and proposed ANN model indicated that a new method can be developed for permeability control.

Investigation of Sterol Chemistry to Retard the Aging of Asphalt Binders

The addition of petroleum-derived oils (aromatic or paraffinic) and bioderived oils (typically low-viscosity, unsaturated hydrocarbons modified to remove acid functionality) to bitumen has become a burgeoning business to facilitate the use of increasing amounts of reclaimed asphalt pavement, reclaimed asphalt shingles (RAS), and combinations. These additives have been marketed as softening agents, to reduce high- and low-temperature performance grades, and as rejuvenators. Given the aging mechanism of bitumen and chemical changes that occur during aging, it is unlikely that any true form of rejuvenation is possible. In this paper data are provided on investigations into the use of a chemical class known as sterols, which can be obtained from seed oils and tall oil to retard the aging of bitumen. Investigations were carried out with RAS, with re-refined engine oil bottoms, and with the accelerated aging of bitumen and bituminous mixtures that contained sterol chemistry. The results demonstrated that, relative to controls without sterol, increases in the bitumen rheological index were reduced, and decreases in the colloidal index were reduced, as were decreases in the difference between bitumen low-temperature stiffness critical temperature and bitumen m-value critical temperature (ΔTc). Investigations with atomic force microscopy of bitumen samples with sterol additive, compared with those without, were used to understand the sterol additive function as the bitumen was aged.

PENGARUH KONSENTRASI SURFAKTAN DAN KECEPATAN PUTAR PENGADUK TERHADAP PROSES PEMISAHAN BITUMEN DARI ASBUTON

Asbuton is a rock contain of the bitumen. Asbuton can be used as road construction alternatives after extracting bitumen from the mineral. A method for separating bitumen is separation process using hot water medium. The process was carried out in a stirred tank, 200 grams of asbuton was mixed with diesel oil and added by hot chemical solution (surfactant) in the digestion tank. The separation process in the extractor was made at 900C and time set was 30 minutes. Surfactan concentration and the speed of stirrer were set according to the variable. After the process completed, the mixture was moved into a beaker glass and 500 ml hot water was added. The mixture of diesel oil and bitumen will float in the surface then the density will be measured to determine the bitumen concentration. It can be concluded that concentration of surfactant solution and speed of stirrer have the significant results. The highest recovery percentage of bitumen is 81,99 %.
 Keywords: Asbuton, Hot water, Speed of stirrer, Surfactant.

Performance evaluation of Hot Mix Asphalt (HMA) containing bitumen modified with Gilsonite

Iran-produced bitumen under the circumstances of severe temperature fluctuation, heavy traffic load and raining/freezing conditions show low efficiency; therefore, it is necessary to improve its properties accordingly. Existence of weakness in produced bitumen result in failure occurrence in asphalt pavements during service life of asphalt roads. Given the existence of considerable reserves of Gilsonite in Iran, its low costs compared with other additives and its remarkable properties, we can study asphalts modified by Gilsonite. At the present time, little research has been conducted on this modifier in the world and Iran (which its properties are still not quite evident for researchers). The most important failure in flexible pavements is permanent deformations which are known as rutting. Rutting is longitudinal depression in the wheel path in bituminous pavements. The rate and depth of rutting depend on the internal factors such as bitumen properties, aggregate, mixture properties and thickness of pavement layers. In this lab study, with regard to the technical and executive issues, common functional performance-based tests of bitumen were performed on specimens through addingGilsonite with 0, 2, 4, 6, 8, 10wt.% of made bitumen specimens. Then, the optimum percentage was calculated using the AHP. The specimens containing pure bitumen 60–70 and modified bitumen 60–70 with Gilsonite in two different aggregations (4 and 5) were made and the effects of adding Gilsonite in Marshall Stability and flow, indirect tensile strength and moisture sensitivity, as well as dynamic creep, and resilient modulus were evaluated by the UTM device. The research showed that adding Gilsonite to bitumen in hot asphalt mixtures considerably increases Marshall Stability and resilient modulus parameter in asphalt specimens. However, resilient modulus test indicated a significant reduction in flexibility property of asphalt mixtures made of modified bitumens. Moreover, increasing the flow number obtained from the dynamic creep test indicate the increase of rutting resistance.

Modeling of viscosity for mixtures of Athabasca bitumen and heavy n-alkane with LSSVM algorithm

ABSTRACTThe resources of heavy oil and bitumen are more than those of conventional light crude oil in the world. Diluting the bitumen with liquid solvent can decrease viscosity and increase the empty space between molecules. Tetradecane is a candidate as liquid solvent to dilute the bitumen. Owning to the sensitivity of enhanced oil recovery process, the accurate approximation for the viscosity of aforementioned mixture is important to decrease uncertainty. The aim of this study was to develop an effective relation between the viscosity of Athabasca bitumen and heavy n-alkane mixtures based on temperature, pressure, and weight percentage of n-tetradecane using the least square support vector machine. This computational model was compared with the previous developed correlation and its accuracy was confirmed. The value of R2 and MSE obtained 1.00 and 1.02 for this model, respectively. This developed predictive tool can be applied as an accurate estimation for any mixture of heavy oil with liquid solvent.

Active fillers’ effect on in situ performances of foam bitumen recycled mixtures

Cold recycling is one of the most employed rehabilitation techniques for asphalt pavements and it is becoming more and more important as reducing emissions becomes a priority in the reduction of the greenhouse effect. The main advantages of asphalt cold recycling techniques are the use of reclaimed materials and the fact that there is no need of aggregate heating to make the mixtures. This paper describes the evolution with time of in-situ performances of different foam bitumen-stabilised mixtures made with different active fillers (cement and lime), monitored during the first year from construction. Results are part of a more extensive research programme aimed to investigate the effects of using lime as an active filler in cold-recycled mixtures. Mixtures have been laid down on a specifically designed trial section in Italy, close to Florence. Short-term bearing capacity, immediately after construction, has been evaluated using a light weight deflectometer while to evaluate the mid-term performances falling weight deflectometer (FWD) tests have been performed after 24 hours, 14 days, 28 days and 9 months from construction. During these 9 months the test road was not opened to traffic, so the mixtures experienced almost no traffic (only construction traffic loads). This fact allowed to have the curing process without any influences other than the temperature: it means same curing conditions for all mixtures. Subsequent FWD tests are still ongoing to evaluate the evolution over time of pavement bearing capacity due to traffic. Results obtained positively support the use of lime as an active filler in the foam bitumen-stabilised material and allow to underline the effect of different active fillers in the material behaviour, even if all the mixtures underline excellent performances under traffic loading. FWD tests are scheduled to be repeated every 6 months in order to monitor the stiffness evolution of the mixtures and evaluate the nature of traffic damage.

Grading highly modified binders by multiple stress creep recovery

The multiple stress creep recovery (MSCR) test was developed in the USA to evaluate the high-temperature permanent deformation resistance of bitumens. It is credited as representing world best practice for high-temperature shear response of binders for asphalt production. However, some researchers have questioned the suitability of the current test protocol for characterisation of highly modified binders. Five highly polymer-modified elastomeric and plastomeric Australian grades of binder and one conventional binder were tested by MSCR at various temperatures (64–76°C) and the results compared with laboratory asphalt mixture properties indicative of asphalt field performance. The results indicated the current MSCR protocols are not suited to highly modified binders and that an increased level of applied stress and longer recovery periods between stress cycles should be considered for improved characterisation. Furthermore, the MSCR creep compliance, intended to be indicative of asphalt permanent deformation, was found to be poorly correlated with asphalt mixture wheel track rutting and repeated shear flow test results. This lack of agreement between bitumen and asphalt mixture test results may reflect the limitations of the current MSCR protocol for highly modified binders. However, further investigation is required to understand the impact of base bitumens imported into Australia and other contributing factors.

Development of a tool to assess in-situ curing of Foamed Bitumen Mixtures

This paper discusses the simplest yet crucial mix design consideration of Foamed Bitumen Mixtures (FBMs); curing. The objective of the present study is to attain better understanding of the curing mechanism of FBMs and lessen the gap between laboratory curing and field evolution of these mixtures. This was achieved by carrying out a laboratory curing study in two phases. The first phase aimed to understand the curing mechanism and to interpret the level of impact of factors such as temperature and time on the curing of FBMs. The effect of these factors on curing was evaluated with reference to stiffness gain and water loss of FBM specimens. The second phase was intended to develop a tool to assess in-situ curing of FBMs. With a view to assessing in-situ strength (or stiffness) the applicability of the maturity method, which is commonly used to estimate in-situ compressive strength of concrete before removal of formwork, to FBMs was evaluated. A strong correlation was found between maturity and the stiffness values obtained from the laboratory tests which resulted in development of maturity-stiffness relationships. The application of the method to assess the in-situ stiffness was presented using three hypothetical pavement sections. The results illustrate the influence of ambient temperature and the importance of cement addition to FBMs.

Total Internal Reflection Fluorescence Microscopy To Investigate the Distribution of Residual Bitumen in Oil Sands Tailings

A major waste byproduct of oil sands in situ extraction is oil sands tailings, which are a mixture of water, clay, and residual bitumen. These tailings represent a huge ecological footprint in the form of tailings ponds, which not only render large land areas unusable but also prevent reuse of water. The slow dewatering of the tailings ponds poses a major challenge to the industry. The presence of complex inorganic–organic bitumen–clay mixtures in these tailings contributes to this problem. Hence, understanding the nature of the bitumen–clay association and the effect of bitumen on clay particle–particle interactions is important for the development of more effective chemicals or processes to accelerate particle aggregation and sedimentation during dewatering. Previous studies that investigate these interactions used techniques that are sensitive only toward inorganic clay but not sensitive towards organic bitumen. Here, we use a high-resolution total internal reflection fluorescence (TIRF) microscopy to ...

Analysis of a Medium Temperature Solar Thermal Installation with Heat Storage for Industrial Applications

Willing to be an active participant to the Swiss strategy for sustainable development, Colas Switzerland SA, has decided to integrate a solar thermal installation in one of its bitumen storage industrial site. Situated in Yverdon-les-Bains (Switzerland), the solar installation aims to provide up to 60% of the thermal energy demand of the site. Coupled with a gas boiler, the solar collectors were designed to meet the energy needs of an onsite building, and to ensure constant temperature of a bitumen tank and two emulsions tanks (mixture of bitumen and water).In order to analyse and optimise the thermo-economic and environmental efficiency of this installation, a R&D project funded by the Swiss Federal Office of Energy was launched in 2014. This article gives an overview of the project objectives and describes the solar thermal installation and its operating modes. It also presents the numerical model and the first experimental results.First observations have revealed a thermal installation operating well behind its expected targets. Typically, the solar collector efficiency at temperatures above 200°C is 50% lower than expected since it is operating under non-optimal conditions. Some technical dysfunctions have also been detected in the control system of one of the storage tanks. Consequently, a thorough evaluation of the operation of the installation was conducted to identify any other anomalies.In parallel to this work, the numerical model of the installation was developed and is currently under validation against the ongoing experimental measurements. Preliminary simulations of the installation in its current state have showed a solar yield nearly 2 times lower than expected, confirming the existence of anomalies in the running of the installation.

Phase Behavior and Thermophysical Properties of Peace River Bitumen + Propane Mixtures from 303 K to 393 K

Propane and mixtures including propane as a principal component are among the leading potential candidates for co-injection along with steam for improving the process and environmental efficiency of oil sands bitumen production processes. Phase diagrams and thermophysical property data enable technologies for the development and optimization of such processes. In this work, phase behavior, phase composition, and phase densities of propane + Peace River bitumen mixtures are reported in the temperature range 303 to 393 K at pressures ranging from 1 to 6 MPa. The phase behavior of this pseudobinary mixture can be categorized as Type III according to the van Konynenburg–Scott nomenclature. Pressure–temperature at fixed composition, and pressure–composition at fixed temperature phase diagrams, and pressure–temperature phase projections are presented, along with saturated compositions and densities of the coexisting bitumen-saturated propane liquid (L1) and propane-saturated bitumen liquid (L2) phases. Saturated L1 and L2 phases are both significantly less dense than liquid water phases at the same temperatures and pressures, and the volumes of mixing, particularly for the L1 phase, are large and negative. This data set provides a benchmark for process development and process design calculations for ongoing bitumen production and deasphalting applications.

Effect of Diluents on the Rheological Properties of Maya Crude Oil

Understanding the rheological properties of mixtures of heavy oil or bitumen and diluents, specifically at low temperatures, is key in designing different processes employed in the production or transportation of these resources reliably and efficiently. The effect of diluents (n-heptane, toluene, and toluene + butanone (50:50 vol %)) on the non-Newtonian behavior of Maya crude oil including shear thinning and thixotropy at temperatures from 258 to 333 K are discussed. Toluene + butanone (50:50 vol %) addition to Maya crude oil induces the greatest reduction in shear thinning behavior irrespective of temperature. Thixotropic properties of mixtures of Maya crude oil and diluent were studied through startup experiments. It was shown that toluene + butanone (50:50 vol %) is the best diluent in moderating the thixotropic effect, whereas n-heptane showed the most pronounced thixotropic effect. It was shown that toluene + butanone (50:50 vol %) is more promising in decreasing oil viscosity in comparison to two other diluents tested. Less of this diluent is required to decrease the viscosity to a certain value, which confirms its potential to be used in the industry as a diluent. The results presented also provide a reliable database for model development and evaluation.

Effect of using Fibre on the Durability of Asphalt Pavement

Using the fibre additives with a uniform distribution in asphaltic concrete mixture is a well-known technique for improving the mechanical properties and durability of asphalt pavement. The purpose of this study is to investigate the effect of preparing fibre and production of the properties of bitumen and asphalt concrete mixture. In this study, a dense-graded aggregation, mineral fibres (asbestos) and synthetic fibres (polyester and nylon) were used. Laboratory studies were done by comparing different rheological properties, mechanical and moisture susceptibility of mixtures of fibres. Results of the penetration and softening point on mixtures of bitumen – fibre show that fibres improve the mixed rheological properties and stiffening effect of fibre properties. The results of Marshall Tests indicate that adding fibres reduces the strength in Marshall and results in the slight increase in the percentage of optimum bitumen content and asphalt percentage of air voids in comparison with typical fibre. The results of the indirect tensile tests showed that the addition of fibres, depending on the percentage of fibres significantly improves the durability of the mixture.

Mix design considerations of foamed bitumen mixtures with reclaimed asphalt pavement material

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.

Laboratory evaluation of the effect of bentonite on performance of bitumen and hot mix asphalt mixtures

ABSTRACTIn this research study, bentonite additive was used to modify original binder (60–70 penetration grade). The experimental program included use of five percentages of bentonite (10%, 15%, 20%, 25%, and 30%) by weight of bitumen. Physical properties of modified and unmodified bitumen were evaluated through penetration grade, softening point, ductility, and temperature susceptibility tests. The performance characteristics of mixtures were determined through indirect tensile strength, resilient modulus, and moisture susceptibility tests. The results demonstrate that addition of bentonite improves Marshall stability, tensile strength, and resilient modulus of mixtures, but led to decrease the resistance to moisture damage.

Investigation on the Combined Effect of Fibers and Cement on the Mechanical Performance of Foamed Bitumen Mixtures Containing 100% RAP

Concerns about virgin aggregate sources and increasing demands for construction materials of transport infrastructures as the key parameters in development are the most important reasons, which convinced pavement engineers to develop new methods in order to use higher amount of recycled asphalt pavement (RAP). One of the common methodologies to produce mixtures containing RAP is foamed bitumen mix (FBM). In addition, according to previous research studies, incorporating various types of fibers and hydraulic binders such as cement could significantly improve the mechanical performance of mixtures. The present research study evaluated FBM containing 100% RAP and two types of fiber and Portland cement. Dynamic modulus, unconfined dynamic creep compression, and indirect tensile strength were evaluated in the laboratory at optimum moisture content, which was investigated in this research. Both types of fiber and cement proved to enhance specific properties of mixtures.