Asphalt Research Articles

A spatial autocorrelation analysis of road traffic accidents by severity using Moran’s I spatial statistics: a study from Nepal 2019–2022

BackgroundRoad traffic accidents (RTAs) are a significant global public health issue, leading to injuries, fatalities, and substantial economic losses. In Nepal, RTAs are a major concern, with notable regional variations in incidence and severity. This study analyzed the spatial distribution and types of road traffic injuries in Nepal from Fiscal Year (FY) 2019–2020 to 2021–2022, focusing on the impact of road types and geographic factors.MethodsThe study covers all 77 districts of Nepal, incorporating diverse geographic and climatic regions. Data on RTAs, including fatal and non-fatal injuries, were obtained from the Kathmandu Valley Traffic Police Office, Nepal. Spatial analysis was conducted using Quantum GIS (QGIS) and GeoDa software. Univariate and bivariate risk factor analyses were performed using Moran’s I statistics to detect spatial autocorrelation in RTA severity.ResultsThe overall fatality rate increased from 7.70 to 9.89 per 100,000 population from FY 2019–2020 to 2021–2022. However, spatial clustering of crashes showed a decline over the years. In FY 2019–2020 (Moran’s I; 0.276, p-value; 0.001), moderate clustering was observed, which weakened in the subsequent years (Moran’s I; 0.127, p-value; 0.002), with a near-random distribution by FY 2021–2022 (Moran’s I; -0.015, p-value; 0.457). The analysis of crash severity revealed significant variations across districts, with high fatality rates in remote areas like Mustang and Mugu, and low rates in districts such as Manang.Road Network AnalysisThe study examined the impact of different road types on RTA severity. Bitumen (BT) roads showed a negative correlation with RTA rates, while Earthen Roads (ER) were positively associated with higher RTA rates. Hot-spot and cold-spot clusters were identified for each road type, highlighting higher or lower RTA severity areas.ConclusionThis study provides valuable insights into the spatial patterns of RTAs in Nepal and the influence of road types on accident severity. The findings emphasize the need for targeted road safety interventions and infrastructure improvements, particularly in high-risk areas. By understanding spatial distributions and road network impacts, policymakers can better address road safety challenges and reduce the incidence of RTAs in Nepal.

Different mechanisms of two oil-soluble additives to reduce heavy crude oil viscosity

The depletion of light crude oil resources necessitates the efficient development of heavy crude oil, characterized by high density and viscosity. In this work, we used molecular dynamics (MD) simulations to investigate the mechanisms by which two oil-soluble viscosity reducers (VRs) reduce the viscosity of heavy crude oil. Our results reveal that direct interaction between VRs and asphaltene (ASP) aggregates is not the sole pathway for viscosity reduction. Instead, targeting resin (RES) emerges as a critical strategy. The first kind of VR (VR1), with its polar acrylamide head, binds effectively to ASP, reducing the exposure of ASP to other heavy oil components and thereby decreasing the friction between ASP and these components. In contrast, the second kind of VR (VR2), with a maleic anhydride head, tends to disperse away from ASP aggregates, reducing viscosity by weakening the intermolecular interactions between RES and lighter components. These findings elucidate distinct mechanisms by which VRs mitigate the viscosity of heavy crude oil and provide insights for the design of more effective oil-soluble VRs for future heavy oil exploitation.

Selection and performance evaluation of roof materials in arid oasis cities: The advantages of white polymer materials

Selecting the appropriate roofing material is crucial for addressing the urban heat island effects. However, uncertainty remains regarding the best roofing material for improving subsurface cooling during hot summers in temperate continental arid climates. Comparative studies on different roof materials under various climatic conditions are essential to determine the most effective heat mitigation strategies for arid oasis cities. We present a conceptual model to examine the relationship between roofing materials and their thermal mitigation capabilities in arid regions during hot summers, while assessing the influence of climate factors on their cooling performance. An experiment in Urumqi evaluated the subsurface heat mitigation capabilities of four roofing materials: white polymer materials (WPM), sod (SOD), asphalt (ASP), and solar photovoltaic panels (SPP). The results showed that the WPM provided the most effective subsurface cooling. Compared with SOD, ASP, and SPP, WPM showed the lowest subsurface temperature. Notably, the subsurface temperature of the WPM was minimally affected by climatic factors and showed no correlation with solar radiation intensity, precipitation, and cloudiness (P > 0.05), highlighting its superior cooling performance. WPM roofs are recommended for heat mitigation during hot summers in arid oasis cities owing to their low maintenance costs, ecological benefits, and superior cooling performance. This study highlights the subsurface cooling capabilities of various roofing materials and their interaction with climatic factors and provides valuable insights for heat mitigation strategies in arid regions.

Partial upgrading of heavy oils by catalytic aquathermal visbreaking with dispersed iron oxide catalysts

The impact of water and red mud-like Fe oxide catalysts on aquavisbreaking (AVB) of heavy-oils was studied under various circumstances. Vacuum residue (VR) was employed as a good substitute for low-viscous bitumen grades. The reaction products were separated into SARA fractions using open-column liquid chromatography (OCLC), and boiling point groups were classified using thermogravimetric analysis (TGA). In addition, Fourier-transform infrared (FTIR) spectroscopy was used to study the structural features of VR and its derivatives. It was observed that the thermal visbreaking of VR led to a severe coke formation with asphaltene (ASP) to coke selectivity over 130 %, while the addition of water and Fe catalyst could increase the conversion of ASP to liquid oil products while inhibiting coke formation, resulting in improved conversion of ASP. Furthermore, the structural properties of spent catalysts recovered after reactions were analyzed using X-ray absorption near edge structure (XANES) and X-ray diffraction (XRD) to identify the active phase, confirming that the Fe precursor is converted to a 20–30 nm Fe2O3 and Fe3O4 during VR AVB. Moreover, the addition of carbon additives to AVB further improved the dispersion of ASP and catalyst particles, contributing to the decrease of the selectivity for ASP conversion to coke by 50 %.

Study of the effect of ultrasonic technology on the extraction of bitumen from bituminous rocks

Background: Nowadays, there are few studies focused on the extraction of targeted products from bituminous rocks. Published research on the on the use of ultrasound for bitumen extraction refers to unconventional technologies. A distinctive feature of the bituminous rocks under study is their exposure at the surface, where they are situated in open areas. Due to various technogenic factors and prolonged atmospheric, light fractions are lost, while the heavier components undergo oxidation. These processes lead to the formation of heavy oils and hard bitumens with complex composition. Aim: To study the effect of ultrasonic technology on the bitumen extraction of from bituminous rocks and to determine the physical and chemical properties of the product obtained. Materials and methods: Thу ultrasonic method has many benefits, in particular energy and water savings, high productivity within a short period of time, and possibility of organizing a mobile unit installation at the production site. The main process parameters includes the determination of the required frequency and power depending on the object of ultrasound technology research. The results of the work have demonstrated that ultrasonic cavitation of bituminous rocks in an alkaline medium increases the degree of bitumen extraction. Results: The physical and chemical properties of bitumen obtained as a result of studying the effect of ultrasonic technology on bitumen extraction from oil-bituminous rocks were determined. Conclusion: The study identified the optimal process parameters based on the specific research object. When selecting the ultrasonic power it was found that clay compounds of bituminous rocks have a direct effect on the extraction of natural bitumen. It was demonstrated that ultrasound technology is a promising and industrially applicable technology for extracting bitumen from the bituminous rocks of the Munaily Mola field.

Performance of natural asphalt as a paving material: A laboratory and field evaluation

The ever-growing need to build roads to meet the necessary transportation demands is challenging, especially for developing countries. Low-volume roads (LVRs) are usually the backbone of catalyzing economic growth in these countries. With impediments surrounding Petroleum bitumen (price fluctuations) and environmental concerns, scientists are putting their effort into finding an alternative. The presented research is an attempt to check if Natural asphalt can be used as a full or partial replacement of the Petroleum bitumen. To the best of the authors' knowledge, only limited studies have focused on characterizing and understanding the engineering properties of Natural asphalt. The available techniques do not provide reliable information to the road authorities and hence they are discouraged from using it in practice. Particularly for countries, where the Natural asphalt source is available, the overall dependence on importing the Bitumen could be substantially reduced. Empirical and experience-based design criteria may not be sufficient as the standards were never developed for such materials, hence, a scientific approach is required before bringing it into practice. In this research, Natural asphalt sourced from different locations in Nigeria was assessed. Before performing the mixture level tests using Marshall and Cantabro design methods, the rheological and fatigue properties of the extracted Natural bitumen were examined in the laboratory. In the design of the experiment, various percentages of Natural asphalt were added between 0 % and 20 % by total mix weight; implying that the remaining required fraction of binder was fulfilled by the addition of petroleum bitumen. By using a ranking system (supported by statistics), an optimal design of mixture was obtained which was used in the field (exposed to normal traffic) at 30 different sections. Overall, results showed a good correlation between laboratory and field performance as compared to the petroleum-based mixture which was used as a reference mixture

RESPONSE SURFACE METHODOLOGY OPTIMIZATION AND UPGRADING OF AGBABU BITUMEN IN THE PRESENCE OF RICE HUSKS

With the current global trend in energy demand due to the increase in human population and technological inclination in carrying out day to day activities, the conventional crude oil is fast depleting and thus an alternative source of energy is needed for sustainability for the fuel/energy supply. Natural bitumen upgrading could serve as an alternative source for the future fuel supply but the process of upgrading the bitumen needs to be optimized to obtain the best conditions at which the bitumen upgrading process would effectively take place which brought about this study. In this study research work, optimization of Agbabu bitumen in the presence of rice husks using response surface methodology (RSM) was carried out to determine the optimal conditions at which the bitumen could be upgraded. Box-Behnken Designed experiment (BBD) was used as the template to design the experiment where the chosen variable factors were temperature, residence time and rice husks at a range or level of (300 – 350 oC), (30 – 180 min) and (0.6 – 1.0 wt.%) for each of the variable factor respectively and the chosen responses were viscosity, API gravity, residue yield and light oil yield. The Agbabu bitumen was characterized by viscosity at 70 oC to be 86.78 Pa.s, density at 60 oC to be 1.0153 Kg/L, H/C ratio 1.19:1 and API gravity of 7.87 o etc. The optimum conditions at which the Agbabu bitumen could be upgraded for maximum yield of light oil was found to be (temperature 345.716 oC, residence time 30.0 min, and rice husks 1.0 wt.%) at response value of viscosity 8.340 Pa.s, API gravity 24.520 o, residue yield 22.39 w/w% and light oil yield 50.064 w/w%. The light oil yield for the upgraded Agbabu bitumen at the optimum conditions had a desirability of 0.688989, amounting to 68.4% yield. The overall desirability for the whole upgrading process was 0.909415 at the optimum conditions. Thus, indicating an acceptable optimization and upgrading process for Agbabu bitumen.

Long-term effects of an early-life exposure of fathead minnows to sediments containing bitumen. Part II: Behaviour, reproduction, and gonad histopathology

The oil sands area of northern Alberta has river sediments that contain natural bitumen. Eggs and fish in these rivers may be exposed to bitumen-related chemicals early in life. This paper assesses a short embryo-larval fish exposure to oil sands sediment and follows the fish behaviour as they mature in clean water and examines their breeding success as adults (5 months afterwards). The three different oil sands river sediments tested were: a sediment collected outside of the bitumen deposit (tested at 3 g/L, Reference sediment from upstream Steepbank River site), and two sediments collected within the deposit (each tested at low (1 g/L) and high (3 g/L) concentrations). The sediments within the bitumen deposit were from the Ells and Steepbank (Stp) Rivers, and both contained significant total PAHs (>170 ng/g wet weight sediment) and alkylated PAHs (>4480 ng/g). Fish were exposed to these sediments for 21 days (as eggs and larval fish), and then transferred permanently to clean water to mature and breed. There was a significant decrease in the number of egg clutches produced by fish exposed early in life to Stp downstream high sediment (compared to Reference sediment). There was also a decrease in overall cumulative egg production, with fish from Stp downstream high sediment producing just over 1000 eggs in total while fish exposed to Ref sediment produced nearly 6900 eggs. The fish with reduced egg production were also less social than expected as they matured, and they had a lower % of early vitellogenic eggs in their ovaries. Overall, the exposure shows that a single, brief exposure during early life stages to natural bitumen can affect fish in adulthood. Naturally occurring bitumen-derived PAHs can reduce fish reproductive output by complex mechanisms, measurable as lower ovary maturity and changes in social behaviour.

Synergistic effect of modified ethylene-vinyl acetate and asphaltenes on improving the flow properties of model oil

The effect of alcoholic polyethylene-vinyl acetate (EVA) product ethylene-vinyl alcohol copolymer (EVAL) on the low-temperature flow properties of model oil containing asphaltene (ASP) was investigated. The change of wax crystal microscopic morphology of model oil before and after modification were examined, and the influence of asphaltene mass fraction on the rheological improvement effect of EVAL was analyzed. The composite system of EVAL and asphaltene significantly reduced the pour point, gel point, apparent viscosity, storage modulus and loss modulus of waxy oil at low temperatures. When the EVAL concentration is 400 ppm and the asphaltene mass fraction is 0.5 wt%, the synergistic effect of the two is optimal, which can reduce the pour point by 17 °C and the modulus value by more than 98%. The introduction of EVAL strengthens the interaction between asphaltenes and wax crystals, forming EVAL-ASP aggregates, which promote the adsorption of wax crystals on asphaltenes to form composite particles, and the polar groups prevent the aggregation of wax crystals and reduce the size of wax crystals, thus greatly improving the fluidity of waxy oils.

Enhancing Pavement Durability: Comparative Rheological Evaluation of Conventional and Rejuvenated Reclaimed Binders under Aging Conditions.

A drawback of recycled mixtures containing reclaimed asphalt is their increased stiffness, further worsened by the accelerated aging of binders in extreme weather conditions. Previous studies have shown that while rejuvenating agents can mitigate some of these issues by improving flexibility and reducing brittleness, they often present challenges, such as performance variability and the potential for rutting. This study aims to develop an optimal blend of reclaimed bitumen, a rejuvenating agent, and pure bitumen to achieve rheological properties similar to a control 35/50 pen-grade bitumen for road paving. Hence, the rejuvenated binders comprised 30:70 blends of reclaimed asphalt bitumen and 50/70 pen-grade bitumen, adding 0.2% to 0.6% of a rejuvenating agent by mass of the reclaimed asphalt. Sample testing included conventional penetration grade, softening point, and viscosity tests, followed by dynamic shear rheometer tests under unaged, short-term, and long-term aging conditions. The results show that the binder blend with 0.4% rejuvenator closely resembles the rheological properties of 35/50 pen-grade bitumen. This blend exhibits a 20% to 55% stiffness reduction for recycled mixtures with 30% reclaimed asphalt. Notably, the rejuvenated binders exhibited a similar level of aging resistance to the control bitumen, with a marginal difference of less than 5% in aging ratios. Meanwhile, large strain amplitude tests showed the importance of defining maximum rejuvenating incorporation rates in recycled mixtures to avoid rutting problems, where binders with 0.4% rejuvenator doubled the rutting potential (Jnr values). This innovative study highlights the potential for enhancing recycled mixtures' performance by evaluating rejuvenated reclaimed binders' rheology subjected to different aging conditions, thus contributing to sustainability in pavement construction.

AN EXPERIMENTAL STUDY ON THE USE OF SEDIMENTATION COMPOSITIONS DURING STEAM INJECTION

At present time, many oil fields, especially in historically developed areas of The experience of developing deposits of high-viscosity oils (HVO) and natural bitumen has shown that thermal methods are the most promising technologies. Of the entire arsenal of thermal methods, areal steam injection and cyclic-steam stimulation have become the most widespread.When choosing an effective thermal impact technology, it is necessary to take into account the peculiarities of the geological and physical parameters of deposits and the factors involved in oil recovery. An effective technology should be based on the use of the main most important factors that increase oil recovery.One example of areal steam injection is the underground-surface method of developing the Yarega area of the Yaregskoef ield. With this technology, steam is pumped from the surface through vertical wells. Oil production is carried out in the underground galleries of the oil sheds.Twenty years of practice and geophysical studies of steam injection wells have revealed a number of factors that prevent uniform heating of the reservoir over the entire thickness and efficient use of coolant energy. It turned out that the injected steam is mainly concentrated in the bed zone of the formation. In this case, the formation does not warm up evenly in thickness. The heterogeneity of the reservoir (tectonic disturbances, cracks every 20-25 m) does not allow the creation of steam pressure up to 1,6 MPa along the contour of the developed areas in order to involve the inclined block. At design pressures, steam breaks into mine workings and gently descending production wells are observed.The experimental studies described in this work are aimed at finding alignment of the intake profile of steam injection wells and redistribution of coolant in a remote reservoir zone. The results of the application of sedimentation compositions in bulk reservoir models under various thermobaric conditions of steam injection are presented. As a result of injection of solutions of iron sulfate, sodium carbonate and calcium chloride, insoluble sediments were formed in the rock, which led to a decrease in permeability during water vapor filtration. The experimental study was performed on a bulk reservoir model using natural core grinding, as well as drilled and extracted core samples from wells of the Yaregskoe field. The use of sedimentation compositions in steam injection wells in the future may contribute to the involvement of rock sections in the development by redistributing the steam flow, which in turn will increase the oil recovery coefficient and reduce the steam-oil ratio.

Photo-induced ageing processes in bitumen

Asphalt roads and waterproofing membranes on roofs are exposed to sunlight, which induces irreversible changes in those materials. The underlying chemical processes initially affect the surface but later on impact the bulk chemistry and the mechanical properties. Bitumen, the binding and sealing material, is particularly susceptible to such influences. However, the molecular processes that initiate material deterioration are still poorly explored. Here, we show that ultraviolet and visible light cause the formation of a unique set of oxidation products and alter aromatic structures on the bituminous surface. Qualitative and quantitative information is obtained using infrared, fluorescence and NMR spectroscopy. Bulk ageing studies have shown a shift of molecules from the aromatics to the resins and asphaltenes fractions, potentially influencing colloidal stability. The evaluation of surface processes was facilitated in ageing studies with thin sub-µm specimens. We find that gaseous oxygen is essential for molecular changes to occur. The formation of carboxylic acids, esters and aliphatic alcohols, coupled with the degradation and restructuring of aromatic systems, demonstrates the unique nature of light ageing. This is due to a nuanced interplay between oxidation, degradation, condensation and aromatisation reactions. The ageing rates depend on the origin of the binder and increase as the wavelength of the light source decreases. Ageing follows an asymptotic growth with time. All results considered, this study enabled us to decipher critical molecular processes during photochemical ageing. In this regard, we hope to develop more effective strategies for mitigating and preventing the adverse impact of solar radiation on bituminous infrastructure in the future.

A thermogravimetric analysis of residual char formation by gilsonite-filled, polyfurfuryl alcohol composites: acid treatment of gilsonite

Gilsonite (GLS), a natural bitumen containing a considerable amount of asphaltenes, is expected to leave heavy char after pyrolysis; however, its high potential as an efficient filler to enhance the thermal properties of composite materials is surprisingly neglected throughout the literature. On the other hand, polyfurfuryl alcohol (PFA) has attracted much attention as a thermosetting resin due to its excellent char-leaving characteristics, the renewable nature of the monomer(s), and high accessibility at an affordable cost. This study aimed to investigate the thermal stability and char-forming performance of composites made of a PFA resin matrix filled with chemically modified GLS. To modify the ash and sulfur contents of GLS, the nitric acid leaching process was performed according to a D-optimal experimental design approach. The nitric acid concentration (10, 20, and 30 wt.%), treatment time (30, 75, and 120 min), and reaction temperature (30 °C, 50 °C, and 70 °C) were set as the input variables. The morphology (SEM), chemical structure (FTIR), thermal stability (TGA), sulfur content, and ash content of the GLS particles were characterized before and after acid treatment. Thermogravimetric analysis revealed the lowest ash content for GLS after treatment with 10 wt.% acid conc. at 75 °C for 75 min. The nitric acid concentration, reaction temperature, and time were the most influential parameters for improving the ash content of GLS according to their order of appearance. In addition, the inorganic form of sulfur, pyrite, was separated through the acid leaching process. Then, the PFA resin matrix was filled with modified GLS particles at different weight percentages (5, 10, 15, and 20 wt.%) and cured in the presence of an acid catalyst. The thermal stability of the PFA resin was negatively affected by the presence of GLS, probably due to oxidation reactions and disruption of the integrity of the resin structure.

Effect of Simultaneous Application of Glass Fiber Reinforcement and Polymer-Modified Asphalt Emulsion on DBST’s Resistance to Aggregate Loss Using Laboratory Investigation

Double bituminous surface treatment (DBST) has been a widely utilized pavement maintenance material due to its capability to restore the surface roughness of existing pavement and provide a layer of protection against weathering, aging, and moisture. However, DBST is highly prone to aggregate loss at an early stage, which is a very common problem experienced by surface treatment. Therefore, to lessen the aggregate loss and prolong the service life of DBST, fiber additive can be incorporated to strengthen the adhesion between the asphalt emulsion and aggregates. This study investigated the performance of glass fiber-reinforced polymer-modified DBST against aggregate loss by conducting laboratory tests using typical DBST as the benchmark of the test results. Four laboratory tests were chosen to represent different loading applications on the surface of the pavement: the bitumen bond strength (BBS) test, the sweep test, the Hamburg wheel-track test (HWT test), and a one-third-scale model mobile load simulator (MMLS3) model. Furthermore, the curing time of the asphalt emulsion was considered in the BBS test and sweep test. Based on all results from the conducted laboratory tests, polymer-modified DBST with glass fiber reinforcement presented an increased resistance to aggregate loss compared with typical DBST. Moreover, it was found that a longer curing time of the asphalt emulsion, whether it was typical or modified, strengthened the surface treatment’s resistance to aggregate loss.

Surface Temperature Experienced and Irrigation Effects on Artificial Turf

Artificial turf has gained widespread use in sporting fields as it is considered a water-saving and maintenance-free alternative to natural turfgrass. However, the high surface temperatures that occur during the day are a potentially important unfavorable feature of artificial turfgrass. The objective of this study was to establish the temperatures experienced on an artificial turf surface and to evaluate the effect of irrigation on artificial turf surface temperature. Data was collected over five surfaces across a sports facility on the campus of the University of Thessaly in Larissa, Greece. Results showed surface temperatures on artificial turf (AT) as significantly higher than running track (RT), asphalt (AS), bare soil (BS), and natural grass (NG), with maximum surface temperatures of 72oC. Solar radiation accounted for most of the variation in surface temperature of the artificial turf (r2=0.92) as opposed to air temperature (r2=0.38), and relative humidity (r2=0.50). To lower surface temperature, four irrigation regimes were used (1x60 min, 1x30 min, 2x15 min, and 3x5 min water application). Irrigation reduced the surface temperature by as much as 30°C compared to the unirrigated surface, but these low temperatures were maintained for 90 to 120 minutes long. The most effective cooling effect occurred when water was applied in a 3-cycle, 5-minute duration, where the irrigated surface temperature remained below the unirrigated surface throughout the time after the first watering.

Modified Bitumen Materials from Kazakhstani Oilfield

The oil bitumen BND 90/130, produced at the “LLP SP Caspi Bitum” with the modifier, which consists of copolymer of ethylene with butyl acrylate and glycidyl methacrylate taken in an amount of 0.5–1.6 wt%, and the tire reclaim (4–20 wt%), which is the destructate of mesh elastomers of different chemical nature, was modified; possibility of using the developed bitumen-elastomer binders in road asphalt concrete was justified. Modification of bitumen with a copolymer of ethylene with butyl acrylate and glycidyl methacrylate leads to an improvement in the properties of road bitumen: the softening point, hardness, deformability at low temperatures, elasticity, and adhesion to metal and mineral filler increase. It was shown that ethylene with butyl acrylate and glycidyl methacrylate chemically interacts with the functional groups of bitumen asphaltenes through the epoxy group of glycidyl methacrylate. Analysis of the spectra and group composition indicates an increased content of high molecular weight asphaltenes in the modified bitumen with a slight increase in structuring resins. It has been established that bitumen modified with rubber crumbs of 0.6–1.0 mm in size has high elasticity. The most effective composition of a bitumen-regenerated composite material based on tire reclaim has been determined. In terms of the totality of physicochemical and operational characteristics and comparative cost, the most acceptable is the bitumen-regenerated composition (with a regenerate content of 20%) and is superior in the complex of properties to bitumen modified with an optimal content of ethylene with butyl acrylate and glycidyl methacrylate (1.6%). The technology for modifying bitumen with tire reclaim is less time-consuming, more economically profitable, and environmentally effective, since it utilizes large-tonnage waste of worn-out tires. The resulting bitumen-polymer compositions have a high positive set of properties: softening point, hardness, elasticity, frost resistance, and low-temperature characteristics.

Influence mechanism of original components on mechanical properties and transformation behaviors of natural bitumen

Natural bitumen is an important component with high-purity organic matter in fossil energy and energy engineering scenarios. However, the production and application of natural bitumen could be severely hindered by the lacking of understanding the effects and influencing mechanisms of original components on physical properties of natural bitumen. Therefore, the main purpose of this work is to illustrate the influence mechanisms of original components (saturated hydrocarbon, aromatic hydrocarbon, resin and asphaltene) on mechanical properties of natural bitumen by the combination of nanoindentation technology and molecular structure analysis. The effects of each original component on the mechanical properties were carried out for Wuerhe natural bitumen which collected from Junggar Basin of China, and the influencing mechanisms were further revealed based on nanoindentation and X-ray diffraction (XRD) results. The occurrence units of each component in the chemical structural stacking of bitumen were established for the first time. It was found that hydrocarbons and resins can disintegrate the chemical structural stacking, thereby reducing the mechanical strength of natural bitumen. According to our micro-scale analysis results, the plastic and elastic deformation of natural bitumen were controlled by the structural units of amorphous carbon and aromatic carbon microcrystalline, as determined by saturated and aromatic hydrocarbons, respectively. And the schematic diagram of occurrence of each component in solid bitumen for the first time. Hence, the mechanical strength of natural bitumen can be effectively reduced by retaining or increasing the content of alkanes during exploitation, transportation and processing of natural bitumen. This research provided a new understanding for the stacking structure and physical property change mechanism of natural bitumen.

A Study on the Hydro-Liquefaction Kinetics of Shengli Lignite during the Heating-Up and Isothermal Stages under Mild Conditions

Studying the hydro-liquefaction kinetics of lignite contributes to optimizing the mild liquefaction process for lignite. In this paper, the direct liquefaction performance of Shengli lignite (SL) was investigated using a H2/THN system with 4 MPa of initial pressure, and reaction kinetic models were established for the heating-up stage and the isothermal stage. The result showed that the liquefaction performance of the SL was excellent, with a conversion of 62.18% and an oil and gas (O + G) yield of 29.88% at 698.15 K. After one hour of reaction, the conversion and O + G yield were 94.61% and 76.78%, respectively. During the heating-up stage, the easily reactive part of the SL was 50.07%, and it was converted directly into oil, gas, asphaltene (AS), and preasphaltene (PA) simultaneously. There was no significant secondary hydrogenation conversion of the AS and PA products. During the isothermal stage, the hard-to-react part was predominantly converted into AS and PA, while the remaining easily reactive part continue to react completely. The conversion of AS and PA into oil and gas was a rate-controlling step during this stage. The amount of unreacted coal estimated using the model calculated in the isothermal stage was 2.98%, which was significantly consistent with the experimental value of 2.81%.

An experimental study on the tensile properties of reinforced asphalt pavement

Abstract Utilizing one of the most effective new technologies is the primary goal of this research, which uses a combination of bituminous surfacing materials with geotextile reinforcement sheets, to improve the behavior of asphalt mixes and fatigue reduction. The aim of this research is to analyze the impact of woven geotextile upon fatigue characteristics of hot mix asphalt mixtures. In order to improve the tensile qualities of the asphalt pavement, the experimental program for this study includes the application of geotextile within the wearing layer. Marshall fatigue and stability tests were carried out. Four-point bending test in a strain-controlled mode was adopted in this study. Three micro strain levels (250, 400, 750) at a frequency of 5 Hz were used. The findings demonstrated that unreinforced mixtures have a shorter fatigue life than wearing layers reinforced with geotextile. Additionally, exposure to different temperatures (5, 20, 30°C) showed that the performance of the geotextile interlayer system in cold environments is inferior to that of those in warm and moderate climates. The analyzed geotextile has a positive impact on the performance of the pavement and a large potential to extend the life of the pavement as a whole, according to the obtained results of fatigue life.

COMPOSITION OF BROMIDES FORMED UPON SELECTIVE CLEAVAGE OF ETHER/ESTER BRIDGES IN PETROLEUM AND NATURAL BITUMEN OILS

Gas chromatography with mass spectrometric detection (GC-MS) was used to study the composition of bromides obtained upon selective cleavage (chemolysis) of the C-O bond of ether/ester bridges under the action of BBr3 in oil components from ten oil and natural bitumen samples. It is shown that most of the samples under study demonstrate the absence of mono- and dibromides of alkanes, alkylcyclohexanes, pregnanes and steranes, cheilanthanes and hopanes in the products of chemolysis. Monobromides of n-alkanes have been identified only in the products of chemolysis of oil components isolated from maltha of the Ashalchinskoye oilfield and the products of its biodegradation under laboratory conditions. In total, the identified products of selective cleavage of ether/ester bridges include mono- and dibromides of alkylbenzenes: mainly (С13-С22)-alkyltrimethylbenzenes, (С1-С7)-naphthalenes, phenanthrene, dibenzothiophene and their homologues. Monobromides of C6-biphenyl, C4-tetralin, dibromides of (C2-C6)-benzothiophenes, (C2-C5)-biphenyls, C1-tetralin, fluorene, and C2-fluorene have been also identified. Tribromides of (С2-С4)-naphthalenes, С2-phenanthrene, and (С1-С2)-fluorenes have been identified in a limited number of samples. In chemolysis products, dibromides occur more rarely than monobromides, while tribromides are much less common than dibromides. The results obtained indicate that the above-mentioned compounds are partially present in oils as structural fragments connected with other fragments of the oil components through one or much less often through two or three ether/ester bridges. The list of structural fragments linked via ether/ester bridges, their composition and relative content differ in oil components of different oil and natural bitumen samples. Ethyl esters of aliphatic acids from C12 to C32, with a clear predominance of even acids and a maximum corresponding to C16 and C18, have been identified in the products of chemolysis of almost all samples.