Composite Asphalt Research Articles

Assessment of various fatigue life indicators and fatigue properties of rock asphalt composite

Rock asphalt which is a natural asphalt, along with other modifiers, can be used to improve the performance of asphalt binder from crude oil. In this research, a systematic study was conducted to investigate the fatigue failure evolution behaviors of rock asphalt composite modified asphalt (RACMA). The fatigue performance of the modified asphalt subjected to rolling thin film oven (RTFO) and pressurized aging vessel (PAV) was explored to determine and assess various fatigue life indices. The applicability of various fatigue life indexes (Nf50, Nfm, Nδ, NR, and Np20) which are determined according to five different fatigue failure criteria were evaluated through statistical analysis and geometric position method. The results indicated that the Nf50 and Nfm in the stress-controlled mode and the Nf50 and NR in the strain-controlled mode of time sweep test exhibited comparable fatigue lives, respectively. The index Nf50 was recommended to estimate the fatigue performance in both stress and strain-controlled modes of time sweep test. Further, it was found that the optimal dosage of rock asphalt (RA) and styrene-butadiene-styrene (SBS) was 5% and 2% respectively in the composite modified asphalt (RA/SBS) in stress-controlled mode, while the content of RA and crumb rubber (CR) in the composite modified asphalt (RA/CR) was 5% and 18% respectively in strain-controlled mode to achieve maximum fatigue lives. The reduction of RA content and the increment of CR content can significantly improve the fatigue resistance of the RA/CR and extend its fatigue life by >5 times. The RACMA generally exhibits good fatigue resistance after RTFO aging.

Research on Vegetable Oil Based Rejuvenating Agent and Properties of Recycled Asphalt

Based on theory of dissolution and dispersion and special chemical structure of vegetable oil, the article chooses four kinds of vegetable oil (Tung oil, Castor oil, Rapeseed oil and Linseed oil) and blended them with asphalt. And then Rejuvenating Agents of asphalt based on the four kinds of vegetable oil are prepared. The test results show that good exponent relationship is presented between Tung oil content and Brookfield viscosity of Tung-oil-based Rejuvenating Agent. Furthermore, this paper studies the performance of recycled asphalt by conventional indexes, adhesion, SHRP indexes. The data show it by improving the composition of aging asphalt, thereby enabling recycled asphalt indexes recovered to close to or above the level of original asphalt.

Geochemistry of Asphaltenes in Organic Matter of Low Thermal Maturity

Changes in the elemental composition of asphaltenes in organic matter (OM) of different origin, with particular focus on their evolution from proto- to mesocatagenesis, were analyzed in samples of Devonian bituminous shales and brown coals from the Kuznetsk Basin and samples of Cenozoic brown coals and clays from the Middle Amur Basin. The composition of asphaltenes (protoasphaltenes) of different origin is shown to be differentiated as early as the stage of sedimentation: terrestrial asphaltenes are enriched in carbon and hydrogen, while sapropelic asphaltenes contain more oxygen (heteroelements). It is discovered that the formation of the two evolutionary catagenetic branches of asphaltene compositions corresponds to the onset of protocatagenesis. Both sapropelic and terrestrial OM undergo different transformations during diagenesis (at the sediment–protocatagenesis interface), with sapropelic OM subjected mainly to drastic carbonation with parallel hydrogenation, while redistribution of oxygen and hydrogen concentrations associated with a dramatic loss of the latter observed in the terrestrial OM (if the of carbon concentration level is constant). Further changes in the composition of asphaltenes within these branches take place during the mesocatagenesis through apocatagenesis, during which the evolutionary branches converge again.

Cohesive and adhesive healing evaluation of asphalt binders by means of the LASH and BBSH tests

Abstract Generally, the cohesive healing within the asphalt composites and the adhesive healing from the asphalt-aggregate interface always occur simultaneously in the asphalt concrete with growing damage. This study aims to investigate the cohesive and adhesive healing behaviors of asphalt binder respectively by utilizing the newly developed linear amplitude sweep based healing (LASH) and binder bond strength based healing (BBSH) tests. Seven unmodified asphalt binders and one styrene–butadienestyrene (SBS) polymer modified binder are selected in this study. A fracture mechanics based crack growth approach is proposed to define the cohesive healing recovery in the LASH test with two percent healing parameters, in terms of the %Ha of the crack length recovery and the %HA of the sample intact area recovery. In pre-failure conditions, the measured %Ha can at least reach beyond 30% while the %HA is normally within 30% for tested binders. Meanwhile, the %Ha results show more consistent trends to the traditional simplified-viscoelastic continuum damage (S-VECD) based LASH data interpretation. Furthermore, the cohesive failure occurrence is verified to significantly impact the healing performance comparison. The cohesive healing behaviors of neat and SBS binders respectively in pre-failure and post-failure conditions are distinguished to each other, which are validated either from S-VECD or crack growth approaches. Regarding to the binder adhesive healing behavior, it is observed that the presence of water and the using of granite substrate generally have positive effects on adhesive healing recovery in the BBSH tests. The SBS modification generally displays lower adhesive healing percentages than the neat binders especially in the wet conditions. Though no clear relationships can be found between the cohesive and adhesive healing behaviors in this study, it is recommended to quantify the binder contribution to the adhesive healing process in the future work.

The Effect of the use of Gypsum Waste as a Filler Substitution on Stone Matrix Asphalt Coarse

This research is intended to test the use of gypsum waste as a cement filler substitution in a mixture of coarse stone matrix asphalt (SMA). The methodology in this research is to conduct a series of tests for the characteristics of coarse, fine, and filler aggregates, then design the composition of the coarse Stone Matrix Asphalt (SMA) mixture as well as Marshall immersion testing to obtain the remaining Marshall Stability. The results of research conducted at the Road and Asphalt Laboratory of the Faculty of Engineering, Department of Civil, Indonesian Christian University, Paulus Makassar, through the Marshall immersion test obtained a mixture of rough Stone Matrix Asphalt (SMA) with the proportion of gypsum waste as cement filler substitution, namely 100%: 0%, 75%: 25%, 50%: 50%, 25%: 75%, 0%: 100% meets the requirements issued by the Directorate General of Highways of the Ministry of Public Works of the Republic of Indonesia, General Specifications 2018. Test results for Marshall Immersion mixture of Stone Matrix Asphalt (SMA) coarse in all proportions of gypsum waste to obtain Marshall Stability Time meet the limit requirements, namely ≥ 90% so that the mixture is resistant to immersion in water.

Evaluation of asphaltene adsorption on minerals of dolomite and sandstone formations in two and three-phase systems

Asphaltene adsorption on reservoir rock minerals causes wettability alteration and pore plugging which subsequently reduces crude oil production. Also, it has a negative effect on the efficiency of production and enhanced oil recovery operations. In this study, the adsorption of extracted asphaltenes of two samples of Iranian oil fields on dolomite, quartz, and magnetite was investigated in two-and three-phase systems in both static and dynamic flow modes. Mineral adsorbents were analyzed by Brunauer–Emmett–Teller and X-ray fluorescence methods. Also, several laboratory tests including elemental analysis, field emission scanning electron microscopy, and Fourier transform infrared spectroscopy were carried out to characterize asphaltenes. The results showed that in addition to the effect of known parameters such as asphaltenes concentration and specific surface area of the solid phase, the water phase also affects the amount of asphaltenes adsorption. The adsorption amount of asphaltenes increases with increasing the specific surface area of adsorbent (decreasing particle size) and increasing the initial concentration of asphaltenes, and decreases with the addition of water to the two-phase system. The static adsorption amount of asphaltenes in a two-phase system can be up to 90% higher than the adsorption amount in a three-phase system. Doubling the fluid flow rate in dynamic adsorption significantly (by about 20%) reduces the asphaltenes adsorption, which could be a sign of physical adsorption of asphaltenes on adsorbents. The structure and elemental composition of asphaltenes also have a significant effect on asphaltenes adsorption. The asphaltene sample, which had a more aromatic nature and high nitrogen content, had higher adsorption on reservoir rock minerals. Finally, fitting the adsorption equilibrium models with experimental data reveals that the adsorption isotherm model depends on the type and particle size of the adsorbents and the concentration and type of asphaltenes. Cited as : Mohammadi, M.R., Bahmaninia, H., Ansari, S., Hemmati-Sarapardeh, A., Norouzi-Apourvari, S., Schaffie, M., Ranjbar, M. Evaluation of asphaltene adsorption on minerals of dolomite and sandstone formations in two and three-phase systems. Advances in Geo-Energy Research, 2021, 5(1), 39-52, doi: 10.46690/ager.2021.01.05

Long-term aging performance study of asphalt with different composition

Thin film oven tests (TFOT), pressure aging tests (PAV) for 5 h, 10 h, 15 h, 20 h were carried out on asphalts from 6 crude oil resources. Conventional and dynamic shear rheological tests (DSR) were carried out on samples at different aging degrees, respectively to evaluate the aging performance of asphalt with different composition. The main conclusions are as follows: asphalt composition had obvious influence on the long-term aging performance, in which the asphaltene content of asphalt is negatively correlated with the long-term aging performance of asphalt. According to experimental results of aging process influence on storage modulus G', A3, A5 and A6 asphalts had worse anti-aging performance than A1, A2 and A4. Meanwhile based on test results of aging process influence on loss modulus G", A1, A2 and A4 asphalts had worse anti-aging performance than A3, A5 and A6 asphalt.

Study of the molecular structure of hexane-insoluble asphaltenes in coal tar pitch

A comprehensive study of the functional-group composition and structure of hexane-insoluble asphaltenes of coal tar pitch was carried out by methods of chemical elemental analysis, nuclear magnetic resonance (NMR), IR spectroscopy, scanning electron microscopy, X-ray diffraction (XRD), thermal analysis in combination with chromatography-mass spectrometry. It is shown that a hypothetical macromolecule of asphaltenes can be considered as a set of condensed aromatic nuclei of the peri-condensed type of 7 rings, which have alkyl substituents and connecting bridges consisting on average of 2 carbon atoms. The ratio of various structural units in the asphaltene powder is as follows: for one S-containing structure there are 4-5 N-and 1.3-1.7 O-containing structures. Sulfur atoms are contained in thiophene-like, thermally stable fragments of the structure and pass into the coke residue without decomposition. Oxygen is contained in thermally unstable carboxyl and phenolic groups, which decompose with the release of CO2, as well as in the composition of aromatic ethers that pass into the coke residue. The crystallographic characteristics of ordered structures formed by macromolecules of asphaltenes are studied. The average diameter of the packets is La of about 0.66 nm, with a thickness of Lc ≈ 1.30 nm, the distance between individual layers is d002 ≈ 0.34 nm, the average number of layers in the packages is n ≈ 5-7 pieces. In this case, the crystallinity of asphaltene powders does not exceed 30%. The data obtained by different methods are in good agreement and more fully characterize the structure of macromolecules of asphaltenes of coal tar pitch.

Computational and infrared spectroscopic investigations of N-substituted carbazoles.

The carbazole moiety is a commonly identified structural motif in the high-molecular-weight components of petroleum, known as asphaltenes. Detailed characterization of carbazoles is important for understanding the structure of asphaltenes and addressing challenges in the areas of heavy oil recovery, transportation, upgrading, and oil spills, arising from asphaltene properties and composition. In this work we study carbazole and the four N-substituted carbazoles 9-methylcarbazole, 9-ethylcarbazole, 9-vinylcarbazole and 9-phenylcarbazole. Experimental far- and mid-infrared spectra of these five carbazoles are measured using transmission and photoacoustic techniques. The molecular structures of the monomers and the respective dimers, optimized at the ωB97X-D/6-311++G(d,p) level of the density functional theory (DFT), are subjected to harmonic vibrational frequency calculations. The effect of changing substituents on the N-H bond, π-π stacking distances, and angles between monomers within the dimers, in addition to intermolecular interactions, is investigated. Noncovalent interaction analysis is employed to highlight the areas of attractive and repulsive interactions in the dimers. Thermochemistry calculations show that the formation of dimers of all carbazoles is spontaneous at 298 K. Comparison of the calculated vibrational spectra of these compounds with experimental spectra indicates that the existence of both monomers and dimers must be invoked to account for the observed bands in the infrared spectra. Excellent correlations between the experimentally-determined and calculated harmonic vibrational energies are obtained, with an experimental-to-calculated scaling factor of 0.95-0.96. These findings highlight the coupled computational-experimental approach for the interpretation of vibrational spectra and are essential for improving the spectroscopic characterization of N-substituted carbazoles.

Influence of the Chemical Composition of Asphalt and the 3D Morphology of the Aggregate on Contact Surface Adhesion

The influence of the chemical composition of asphalt, the aggregate lithology, and the morphological characteristics of the aggregate on the level of adhesion between the asphalt and the aggregate is investigated. A contactless three‐dimensional (3D) white‐light scanning technique is used to obtain point cloud data of the aggregate particles. Six independent feature parameters are used as evaluation indices to quantitatively describe the multilevel features of the 3D morphology of road aggregates. Methods for analyzing the feature parameters based on the point cloud data of the aggregate are presented. Subsequently, the process and evaluation standard of the adhesion test are improved to quantify the spalling degree of the asphalt film on the aggregate surface under boiling conditions. The influences of the chemical composition of the asphalt and the aggregate morphology on the level of adhesion between the asphalt and aggregate are analyzed, and the compatibility between aggregates with different lithologies and the asphalt is assessed. The results show that the shape factor (SF) can be used to characterize the needle‐flake shape of the particles, the ellipsoid index (E) is suitable to determine the angularity of the aggregate particles, and the 3D joint roughness coefficient (JRC3D) describes the roughness of the particle surface. The type of adhesion between the aggregate and the asphalt includes chemical and physical adsorption; chemical bonding is relatively strong, and the physical orientation force and mechanical interlocking force are relatively weak. Alkaline limestone aggregates should be used with asphalt with a high aggregate content of colloid and asphaltenes. Basalt aggregate with weak alkalinity should be used with asphalt with a high colloid content, and the use of angular aggregates should be avoided. Acidic aggregates with compact shapes, few edges and corners, and rough surfaces should be used prudently.

Абиотическая деградация нефтяных асфальтенов

This review is devoted to the generalization and systematization of the available literature data on the processes of abiotic degradation of asphaltenes, which can occur in natural conditions. In particular, it was shown that exposure to sunlight, and especially UV radiation, triggers photolysis and photooxidation reactions in asphaltenes, leading to an increase in the oxygen content in them, thereby shifting the hydrophilic-lipophilic balance towards hydrophilicity. At the same time the availability of reaction products for subsequent biotic degradation by microorganisms is increased. Exposure to ionizing radiation does not lead to a significant change in the molecular composition of asphaltenes, due to their high radiation resistance. As exception there is the irradiation of asphaltenes with intense electron beams, which leads to their significant degradation.

Characterization of hydration and dry shrinkage behavior of cement emulsified asphalt composites using deep learning

This paper introduces a study of characterizing hydration and dry shrinkage behavior of cement emulsified asphalt composites (CEACs) through a deep-learning framework. The deep-learning framework consisted of two parts: generative adversarial networks (GANs) and deep neural networks (DNNs). The GAN part was first developed to map the design parameters of a CEAC to its X-ray powder diffraction (XRD) spectrum and scanning electron microscope (SEM) images. The DNN part was then designed to predict the dry shrinkage behavior of the CEAC based on its design parameters and the outputs of the GAN part. Finally, the effectiveness of the deep-learning framework was tested by 36 groups of CEACs. The results showed that the outputs of the GAN part, synthetic XRD spectrums and SEM images, were close to the measured data. Thus, the synthetic data were capable of characterizing the hydration processes and the microstructure of the CEACs. The DNN predicted the dry shrinkage ratios of the 36 groups with a 2.70% average error, demonstrating its high and stable precision. The feature vectors in the DNN provided a new method to characterize the effects of the design parameters on the dry shrinkage ratios. From the distribution of the feature vectors in a two-dimension space, we found that the curing time had the most significant effects on the dry shrinkage ratios, followed by the aggregate grading and the contents of cement and emulsified asphalt.

Effect of amorphous rice husk silica addition on the structure of asphalt composite

In this study, modified asphalt composites were produced by adding silica extracted from rice husk. The mass ratios of asphalt to silica are 1:0, 1:1.6, 1:1.8, and 1:2 and calcined at the temperature of 150°C for 6 h. The structural and microstructural characteristics of asphalt composites were examined by x-ray diffraction (XRD), Scanning Electron Microscopy/Energy Dispersive x-ray (SEM-EDX) Spectroscopy and Differential Thermal Analysis (DTA-TGA), respectively. The XRD study revealed that the major phases were carbon and amorphous silica. The surface morphology of asphalt without silica addition presents a cluster of larger size than the cluster of asphalt with an addition of silica. The addition of silica significantly increased the thermal stability of the asphalt due to the formation of a physically cross-linked silica network structure. DTA/TGA analyses produced that temperature decomposition increased with the increasing silica addition from 230℃ to 315°C. Based on these characteristics, the samples are considered for the roof material, suggesting their potential use in substitute lightweight steel roof devices.

STUDY OF COMPOSITION OF HIGH-VISCOUS HEAVY OILS BY METHOD OF NUCLEAR MAGNETIC RESONANT SPECTROSCOPY

The work uses the nuclear magnetic resonance method to study the composition of heavy high-viscosity oils of various fields of the Volga Ural oil and gas basin. The spectra were recorded on a Bruker Avance III 500MHz high resolution NMR spectrometer with operating frequencies of 1H (500.1 MHz) and 13C (125.8 MHz) at a constant sample temperature in CDCl3. It is established that the oil of the studied field in its physical and chemical characteristics, structural group composition of resins, asphaltenes and oil components is a typical representative of aromatic oils. Oil samples are characterized by high density, a high content of tar-asphaltene compounds and sulfur. In the 1H NMR scale, methylene and methine signals appear in the range from 1.0 to 2.3 ppm: β-CH2, some β-CH groups in aromatic compounds and β-CH, CH2-groups in hydroaromatic compounds, and in the 13C NMR scale they are in the range from 22 to 60 ppm: methylene group (CH2-) in naphthenic fragments, etc. An analysis of the aromaticity coefficients obtained from the 1H and 13C NMR spectra shows a high convergence of the results and indicates a high degree of aromatic condensation in oil samples with a density of 950 kg/m3, a viscosity of 7200 mPa*s at 20 °C and a density of 948 kg/m3, viscosity 1000 mPa·s (FHA=0.046-0.081). With an increase in viscosity, there is a clear tendency to increase the aromaticity coefficient and the average chain length. It follows from the results of the 1H NMR spectra of oils with different origins, viscosities and processing that crude and refined oils may differ in water and olefin signals, and from 13C NMR analysis for oils the most important results were obtained when assessing the concentration of primary, tertiary and aromatic carbon.

General fractional models for linear viscoelastic characterization of asphalt cements

Rheological models based on fractional order derivatives have been applied to characterize the linear viscoelasticity of asphalt cements for a long time. Such models provide continuous spectra which are fundamentally related to the molecular characteristics and facilitate analytical investigations as compared to discrete representations. With the increasing complexity in asphalt composition to satisfy various purposes, however, the inadequacy of existing fractional models has been noted. This paper proposed a generalized fractional Maxwell-dashpot (GFMD) model as a general framework for describing the modulus behaviors of asphalt cements. The generalized fractional Voigt (GFV) model was considered the counterpart for the compliances. The material functions given by each model are primarily the superposition of its constituent fractional Maxwell-dashpot or fractional Voigt (FV) elements. Geometric features of these elements were investigated such that a proper initial guess of model parameters can be obtained graphically with relative ease. For computational efficiency, the continuous spectra were discretized to provide the Prony representations of the material functions. To demonstrate the model capability, the dynamic mechanical data of a neat asphalt showing the typical behavior and a heavily polymer-modified asphalt exhibiting strong cross-linking were utilized. For the typical behavior, the GFMD and GFV models containing two fractional elements yielded excellent descriptions. A third fractional unit was necessitated in both models to account for the cross-linking mechanism for the modified asphalt. A relaxation/retardation mode density of two points equidistantly per decade produced material functions with negligible waviness and almost the same accuracy as compared to the use of the continuous spectra.

Crack-Healing Investigation in Asphalt Mixture with Modified Thermoplastic-Bitumen Composite

This study aims to investigate the crack-healing of asphalt mixture by induction heating of bitumen-thermoplastic binder. This system employs a heterogeneous mixture, in which different percentages (2, 4, 6, and 8% by weigh) of thermoplastic healing agent (polyethylene (PE) and polypropylene (PP)) dissolve with the bitumen, respectively. Healing was achieved by heating the fractured asphalt composite to a specific temperature; in which heterogeneous blend has undergone random molecule diffusion and volumetric thermal expansion of healing agent within the matrix. The thermal properties in the bitumen-thermoplastic were characterized by means of dynamic mechanical thermal analysis (DMTA); in which the glass transition temperature (Tg ) has been used as a reference for the healing process. The FTIR shows no chemical reaction between bitumen and thermoplastic. Three-point bending test was conducted to demonstrate details crack-healing capability in asphalt composite. The results show that 6% of PE and PP to the mixture of bitumenthermoplastic has the highest tensile strength. The percentage of recovery was also measured through the healing cycle process using a three-point bending test. Overall, within the third healing cycle, asphalt composite with modified bitumen (with PP or PE) shows 98-55% of healing recovery. The best percentage recovery is using bitumen-PP mixture with a ratio of 94:6. The crack-healing process was also proven through the surface and cross-section asphalt morphology analyses using optical microscopy and scanning electron microscope (SEM).

Evaluating the Suitability of Nanoclay-Modified Asphalt Binders from 10°C to 70°C

This study presents the results of laboratory experiments and analyses carried out to evaluate the rheological performance of nanoclay (NC) modified asphalt binders from 10°C to 70°C. A viscosity graded binder, VG-30, was modified using 2%, 4%, and 6% NC by weight of the base binder. The suitability of the NC modification was ascertained using a series of rheological evaluations, including a frequency sweep test (10°C–70°C), linear amplitude sweep (LAS) test (10°C, 20°C, and 30°C), and multiple stress creep and recovery (MSCR) test (40°C, 50°C, 60°C, and 70°C). Scanning electron microscopy (SEM) was carried out on the unmodified and modified asphalt binders to assess the microscopic dispersion of NC in the base asphalt binder. The SEM images demonstrated that with an increase in the percentage of NC, the physical dispersion of the modifier in the base asphalt binder changes. Six percent of the NC was found to form an interlocked phase within the composite asphalt binder matrix. It was found that the h-parameter obtained from Cole-Cole plots at individual temperatures offers a better and clearer comparison between the asphalt binders in comparison to the master curves and combined Cole-Cole plots. The analysis using h-parameter indicated a higher elasticity and lower temperature susceptibility offered by the NC modified binders. With an increase in the percentage of nanoclay, both the fatigue and rutting performance improved. The value of the Jnr decreased while the value of the percentage recovery (R) increased with an increase in the percentage of the NC. At the temperature of 70°C, only a 6% NC modified asphalt binder was found to be suitable for standard traffic conditions. The LAS test resulted in a higher value of A and an insignificant increase in the value of B for NC modified binders in comparison to the values obtained for VG-30. No specific trend was observed in the value of A at different CSRs, and it suggested from this study that an average value may be used. The number of cycles to failure for NC modified binders was found to be higher than VG-30. A statistical analysis carried out for different parameters revealed that the NC modification has a significant effect on the performance parameters of asphalt binders at all the test temperatures. A simple framework for the cost-benefit analysis has been proposed in this study, which revealed a 6% NC modification to be the optimum dosage for attaining a higher benefit in comparison to the cost.

Joint- or Crack-Opening Resistance Evaluation of Waterproofing Material and System for Structural Sustainability in Railroad Bridge Deck.

A joint- or crack-opening resistance evaluation method for the selection of optimal waterproofing material for a railroad bridge deck is proposed. The joint opening range (mm) for the evaluation, and a typical load case of a high-speed double-track railroad bridge structure deck, is analyzed through the finite element method (FEM) and the results of analysis are used to calculate the minimum opening range. The evaluation method is then demonstrated with 4 commonly used waterproofing types of cementitious membrane system: a polyurethane coating system, self-adhesive asphalt sheet system and synthetic polymerized rubber gel composite asphalt sheet system. Five specimens of each type are subjected to continuous joint opening under 4 different joint width range conditions (1.5, 3.0, 4.5, and 6.0 mm), and the joint-opening resistance performance is compared. The proposal for the evaluation criteria and the specimen test results demonstrate how the evaluation method is pertinent for future selection of waterproofing membranes for the sustainability of high-speed railroad bridge deck structures.

Crude oil fingerprint heterogeneity assessment by investigation of asphaltene subfractions: Implementation for reservoir continuity evaluation

Asphaltenes are being a proxy of kerogen in the reservoir oil, which they have structural similarity. This characteristic provides an invaluable tool for obtaining oil fingerprints from the structural composition of asphaltenes. Since these compounds are classically defined as a solubility class, they constitute a large number of compound types with similar solubility features, instead of chemical characteristics. An effective strategy for the comprehensive characterization of these complex compounds is the fractionation of asphaltenes into several solubility subfractions. In this paper, asphaltenes were fractionated into three subfractions via adsorption of asphaltene onto CaCO3. The three obtained subfractions were entirely distinguishable, in which the FR-3 has the highest aromatic content, lowest aliphatic content, and the highest polarity among three subfractions. The FTIR spectroscopy was used for achieving structural composition information from each subfraction. Ninety peak ratios (10 × 9) based on ten characteristic bands were calculated for each subfraction, and a total of 270 peak ratios (90 × 3) were generated for each asphaltene sample. The modified moving window correlation coefficient technique was employed on generated peak ratios to obtain oil fingerprints for each sample and then the pairwise comparison between different samples. As exemplified, ten samples from the Asmari and Bangestan reservoirs in the Rag-e Sefid field were studied by the proposed procedure. The thresholds of MMWR and AMWR were determined as 0.9494 and 0.9894, respectively, in the Rag-e Sefid field. The similarity matrix was constructed based on a comparison of calculated MMWR and AMWR for all pairs of samples and thresholds to distinguish homogeneous and heterogenous oil fingerprints. However, the Bangestan reservoir has fingerprint homogeneity, some heterogeneities were observed in the Asmari reservoir. The investigation of migration pathways revealed initial heterogeneity in the reservoir, in which these fingerprints dissimilarities were removed in connected wells during geological times. The examination of heterogeneities revealed three compartmentalized regions in the Asmari reservoir.

Multi-walled carbon nanotubes enhanced the property of epoxy asphalt composite

In order to decrease the agglomeration of carbon nanotubes (CNTs) and enhance the interaction between CNTs and epoxy asphalt (EA), CNTs were modified by epoxy resin (ER) after treated with mixture acid, and then CNTs-EA was synthesized via mechanical stirring method. Experimental results confirmed that ER was decorated on the surface of CNTs. Moreover, the softening point and anti-ultraviolet aging of matrix asphalt were significantly improved by introducing modified CNTs, which increased about 48.7% for softening point and the variety ratio of UV aging (UAI) value was close to 1. The enhancement is mainly attributed to the excellent property of CNTs and the effective synergistic effect between CNTs and ER.