Generic Fractions Research Articles

Evaluation of asphalt ageing degree based on asphalt color

To understand the relationship between the surface color and ageing of asphalt, the evaluation method for asphalt surface color was established with the color parameter of Munsell Value, then two asphalts were adopted to study the influence of asphalt ageing on its surface color, and the mechanism of whitening was investigated by the four generic fractions experiment, color spectrum tests and scanning electron microscopy (SEM) test. The results show that the surface color of asphalt will be changed by some factors, while ageing is an important factor. The thermal-oxidative ageing (TOA) of asphalt would lead to the asphalt to be darker in color due to the component migration caused by ageing, while the ultraviolet ageing (UVA) of asphalt will result in a grey or white asphalt surface because of the fact that UVA makes the surface wrinkled and rough which would cause the asphalt surface to change from specular reflection to diffuse reflection. Since the whitening of asphalt surface caused by UVA is much more serious than the blacking caused by TOA, the asphalt pavement always tends to appear grey or white during its service life. To verify the close relationship between the surface color and UVA degree of asphalt, two modified asphalts with anti-ultraviolet ageing agents, carbon black and layered double hydroxides, were suffered from UVA, and their ageing degrees were assessed with the parameters of Munsell Value and conventional physical properties, results indicate the two evaluations on UVA degree have much consistency, which means it is feasible to adopt Munsell Value, a parameter of asphalt surface color, to evaluate the UV ageing degree of asphalt.

Preparation and performance evaluation of different bitumens modified by antioxidant/PABA-LDHs composites

The para-aminobenzoic acid intercalated layered double hydroxides (PABA-LDHs) were prepared through intercalating ultraviolet absorbent para-aminobenzoic acid (PABA) into the layers of layered double hydroxides (LDHs) through anion exchange. Then the PABA-LDHs were compounded with antioxidants (Irganox 1076 and Irganox 1010, which are abbreviated as 1076 and 1010, respectively) to modify-two base bitumens with penetration grades of 70 and 90, respectively, and the physical properties, rheological properties, molecular weight distribution and four generic fractions of the modified bitumen before and after thermal- and photo-oxidative aging were analyzed to investigate the effects of antioxidant/PABA-LDHs on the aging resistance of bitumen. The results showed that PABA was successfully inserted into the interlayer of LDHs to form organic LDHs, and PABA-LDHs can effectively improve the aging resistance of both 70 and 90-base bitumens due to their excellent reflectance and absorption of ultraviolet (UV) rays and the blocking effect on oxygen. The composite modification of PABA-LDHs with 1076 and 1010 could further enhance the thermal- and photo-oxidative aging resistance of bitumen, exhibiting a complementary effect. In addition, 1076/PABA-LDHs modified bitumen presented superior anti-aging property in comparison with 1010/PABA-LDHs modified bitumen.

Properties and mechanism of Re-refined engine oil bottom rejuvenated aged asphalt

• 1. Re-refined engine oil bottom (REOB) is similar in composition to asphalt and contains more light components. • 2. The REOB can recover the physical and rheological properties of the aged asphalt. • 3. The REOB can restore the generic fractions and functional groups of the aged asphalt. • 4. REOB-1 has higher content of aromatics and higher permeability into aged asphalt of REOB-1 than those of REOB-2. The asphalts with different aging degrees (mildly, moderately and severely aging) were obtained by indoor aging test to estimate the rejuvenated effect of Re-refined engine oil bottom (REOB) on properties of asphalt with different aging extent. Two kinds of REOB (REOB-1 and REOB-2) with different contents were added into three aging asphalts respectively by melt blending method. The influences of different REOBs on the physical and rheological properties of asphalt with different aging degrees were studied. The thin-layer chromatography with flame ionization detection (TLC-FID), the Fourier transform infrared spectrometer (FTIR) and the permeability test were conducted to analyze the rejuvenated mechanism of REOB on properties of aged asphalt from the points of generic fractions, functional groups and diffusing ability. Results show that the REOB can partly recover the properties of aged asphalt, and the appropriate content of REOB is recommended to be around 15 wt%. Compared between the two REOBs, the REOB-1 has better rejuvenation effect on the aged asphalt than the REOB-2, which can be ascribed to higher content of aromatics and higher permeability into aged asphalt of REOB-1 than those of REOB-2.

FTIR analysis of UV aging on bitumen and its fractions

The ultraviolet (UV) aging of bitumen involves a series of complex chemical reactions due to its complicated chemistry and structure. To conduct the UV aging on simplified components of bitumen is very helpful to reveal the UV aging mechanism accurately. In this study, two bitumens were separated into four generic fractions (saturates, aromatics, resins and asphaltenes) respectively by solubility procedures and chromatographic techniques. Both bitumens and their fractions were processed to form a thin film and then aged under UV irradiation for a certain time. The Fourier transform infrared spectra of bitumens and their fractions before and after the UV aging were recorded and quantitatively analyzed based on four structural indexes to evaluate the effect of UV aging on chemical evolution of bitumens and fractions. The results show that the bitumens and their generic fractions all suffer from reactions of oxidation and aromatization during the UV aging. The single fraction separated from the bitumen suffers from more severe oxidation and is more vulnerable to the UV aging than the bitumen itself. Among the four generic fractions, saturates are the most unstable components to be oxidized by the UV aging.

Determination of the four generic fractions of aged bitumen by thin-layer chromatography with flame ionization detection

The aging process of bitumen has been paid more and more attention by the researchers. The four generic fractions (saturates, aromatics, resins and asphaltenes) of bitumen change significantly during the aging process. The analysis of the changes of the four generic fractions of bitumen is very helpful to reveal the bitumen aging mechanisms and guide its engineering applications. In this study, the bitumen was aged by thin film oven test (TFOT) , pressurized aging vessel (PAV) test and ultraviolet (UV) aging test, respectively. Then the four generic fractions of bitumen before and after aging were analyzed by thin-layer chromatography with flame ionization detection (TLC-FID) , which was further compared with the solubility procedures and chromatographic technique ( named as Corbett method). The compositions of the expanded solvents were also investigated. Finally, the correlation between the TLC-FID and Corbett method was further studied, which revealed a proper TLC-FID meth- od for detection of aged bitumen. The bitumen solution dissolved by dichloromethane was successively expanded by n-heptane, toluene/n-heptane (80 :20, v/v) and toluene/ethanol (55: 45, v/v) , followed by TLC-FID. This method is of great significance for the analysis of the four generic fractions of bitumen and for the exploration of bitumen aging mechanisms.

Curing and ageing of biofluxed bitumen: a physicochemical approach

Bitumen solutions, comprising of four bioflux-modified bitumens and one traditional slow-curing cut-back bitumen as a reference, were stabilised with two-phased process consisting of recovery and stabilisation parts. The oxidative long-term ageing (LTA) of the stabilised bitumen solutions was performed by a pressure ageing vessel (PAV). The generic fractions of the base bitumens were determined after LTA by thin-layer chromatographic method with flame-ionisation detector (IATROSCAN MK-6s). Complex shear moduli and phase angles of both base bitumens and bitumen solutions were examined with Physica 301 rheometer in oscillatory mode. The curing and ageing behaviour of the biofluxed bitumens differed notably from the traditional cut-back bitumen. Based on PAV and rheometer testing, the effects of ageing on the rheological properties of biofluxed binders may be solely bound to the evaporation of bioflux. Sigmoidal functions were introduced as an option for evaporation models with limited evaporation. However, interpretation of chemical composition of cut-back bitumens as analysed by thin layer chromatography-flame ionisation detector leaves a reasonable doubt for this method to give ultimate composition result.

Physicochemical properties of bitumens modified with bioflux

Five laboratory-produced cut-back bitumens with same target viscosity of 600 mm2/s at 60°C were investigated to determine the effect of chemical composition on the rheological properties. Studied cut-back bitumens comprised four bioflux-modified bitumens and one traditional slow-curing cut-back bitumen as a reference. The generic fractions (saturates, aromatics, resins and asphaltenes) of base bitumens (viscosities of about 1500, 3000, 6000 and 37,000 mm2/s at 60°C) were quantified by thin-layer chromatographic method with flame-ionisation detection (IATROSCAN MK-6s) and the rheological properties of the base bitumens and cut-back bitumens were studied with a Physica 301 rheometer. The soft base bitumens (viscosity≤6000 mm2/s at 60°C) and their biofluxed solutions proved to be rheologically complex, which was witnessed by wax crystallisation and melting phenomena observed at temperatures between 10 and 30°C. The harder base bitumens with higher asphaltene content did not exhibit noticeable crystallisation. The low polarity and low molecular weight of the bioflux solvent reduced the stiffnesses of cut-back bitumens remarkably under 30°C. Thus, the composition of cut-back bitumens had a significant effect on the rheology of blends, although the target viscosities at 60°C were the same.

The Relationship Between Colloidal Chemistry and Ageing Properties of Bitumen

The colloidal indices based on generic fractions, namely saturates (Sa), aromatics (Ar), resins (Re), and asphaltenes (As), were applied to evaluate the correlations between colloidal chemistry and ageing properties of bitumen. The results show that colloidal index Ip (value of Re/As) is positively correlated with penetration retention rate and ductility retention rate. The softening point increment is significantly influenced by colloidal index Is [value of As/(Sa + Ar + Re)]. The colloidal index Ic [value of (Ar + Re)/(Sa + As)] is obviously correlated with viscosity ageing index. Higher value of Ip and Ic, as well as lower value of Is, implies a better ageing resistance of bitumen.

Effect of chemical compositions on temperature susceptibility of bitumens

The viscosity of five bitumens was measured at different temperatures and the viscosity- temperature relationship was developed to evaluate the temperature susceptibility of different bitumens. The generic fractions (i e, saturates, aromatics, resins and asphaltenes) of the bitumens were separated and tested by thin-layer chromatography with flame ionization detection (TLC-FID) and the effect of chemical compositions on temperature susceptibility of bitumens was analyzed using the linear regression method. The experimental results show that the four generic fractions play an inconsistent role in the temperature susceptibility of bitumens and the correlation degree of each fraction is somewhat different. The existence of aromatics and asphaltenes can lower the sensitivity to temperature changes whereas saturates and resins may have an adverse impact on the temperature susceptibility of bitumens. As for the correlation degrees, resins show the closest correlation with the temperature susceptibility of bitumens, then asphaltenes and aromatics, and the correlation between temperature susceptibility and saturates is relatively weak.

2-Level Fractional Factorial Designs Which are the Union of Non Trivial Regular Designs

Each non regular fraction of a 2-level factorial design is a union of points, each of them being trivially a regular fraction. In order to find non-trivial decompositions of non regular fractions into regular fractions, in the first part of the paper we derive a condition for the inclusion of a regular fraction in a generic fraction. We use polynomial algebra arguments introduced by the authors and Maria Piera Rogantin (JSPI, 2000). The practical interest of the decomposition and its computational feasibility are discussed in the second part of the paper.

NMR Fingerprinting of Chemical Changes in Asphalt Fractions on Oxidation

The composition of asphalt has been the subject of much study because such data are required in determining its performance-related properties. A problem inherent in studying asphalt composition is its chemical complexity; however, the characterization of asphalt can be better achieved by separating into fractions. In this work, the chemical property of commercial-grade asphalt obtained from BAPCO refinery, Bahrain (BH), was carried out. The rolling thin-film oven (RTFO), used for short-term aging, and pressurized aging vessel (PAV), used for long-term aging, ASTM D4124 (1991) method was used to separate fresh and aged asphalt into four generic fractions such as asphaltenes, polar aromatics, naphthene aromatics, and saturates. The Corbett fractionation procedure was used to separate fresh and aged asphalt into four generic fractions such as asphaltenes, polar aromatics, naphthene aromatics, and saturates. Nuclear magnetic resonance (NMR) was employed to fingerprint the chemical changes that occurred in asphalt during the aging processes. NMR measurements of asphalt fractions showed that during aging, isomerization and dehydrogenation types of reactions took place. Significant differences were observed between the structure and composition of fresh and aged fractions of asphalt. Results from NMR spectrometry provided significant information concerning the chemical transformations that occurred during the aging processes.

NMR Finger Printing of Chemical Changes in Asphalt Fractions on Oxidation

The composition of asphalt has been the subject of much study because such data is required in determining its performance-related properties. A problem inherent in studying asphalt composition is its chemical complexity; however, the characterization of asphalt can better be achieved by separating it into fractions. In this work, the chemical property of commercial grade asphalt obtained from BAPCO refinery, Bahrain (BH) was studied. The rolling thin-film oven (RTFO), termed as short-term aging, and pressurized aging vessel (PAV), termed as long-term aging, tests were used to simulate the laboratory aging of this asphalt. The Corbett fractionation procedure was used to separate fresh and aged asphalt into four generic fractions such as asphaltenes, polar aromatics, naphthene aromatics, and saturates. Nuclear magnetic resonance (NMR) was employed to fingerprint the chemical changes that occurred in asphalt during the aging processes. NMR measurements of asphalt fractions showed that during aging, isomerization and dehydrogenation reactions took place. Significant differences were observed between the structure and composition of fresh and aged fractions of asphalt. The result from the NMR spectrometry has provided very significant information concerning the chemical transformations that occur during the aging processes.

Role of Gasoline Specifications in the Control of Environmental Pollution

Gasoline is a mixture of about 100 hydrocarbon compounds. Molecular carbon numbers range from C6–C12 and evaporating between ambient temperatures to about 220°C. Gasoline is used in spark ignition engines (cars and motorcycles). The grades and types of gasoline are usually defined in terms of octane numbers. The specifications of gasoline is based mainly on physical properties, which can be related to performance such as volatility and octane number. Chemical components such as oxygen, sulfur, lead, and benzene are also significant. The present trend is to incorporate generic fractions such as aromatics and olefinics in the specifications. How these parameters (specifications) relate to the various fuel requirements and subsequently affect the environment is described in this article.

Spin glass models with ferromagnetically biased couplings on the Bethe lattice: analytic solutions and numerical simulations

We derive the zero-temperature phase diagram of spin glass models with a generic fraction of ferromagnetic interactions on the Bethe lattice. We use the cavity method at the level of one-step replica symmetry breaking (1RSB) and we find three phases: A replica-symmetric (RS) ferromagnetic one, a magnetized spin glass one (the so-called mixed phase), and an unmagnetized spin glass one. We are able to give analytic expressions for the critical point where the RS phase becomes unstable with respect to 1RSB solutions: we also clarify the mechanism inducing such a phase transition. Finally we compare our analytical results with the outcomes of a numerical algorithm especially designed for finding ground states in an efficient way, stressing weak points in the use of such numerical tools for discovering RSB effects. Some of the analytical results are given for generic connectivity.

Mass‐Directed Normal‐Phase Preparative HPLC with Atmospheric Pressure Chemical Ionization Detection

A novel approach to auto‐purification of a wide variety of organic compounds is described. It is based on normal‐phase (NP) gradient high performance liquid chromatography (HPLC), performed on a 2 × 15 cm cyano column hyphenated with atmospheric pressure chemical ionization (APCI) source, and a single quad mass spectrometer (MS). A commercially available preparative HPLC–MS system, equipped with mass‐directed fraction collection capabilities, has been successfully used for NP purification of neutral, acidic, and basic pharmacologically active compounds. Samples of 10–100 mg were chromatographed in gradients of methanol in hydrophobic organic solvents, and collected using generic chromatographic, detection and fraction collection experimental parameters. “Smart” collection—one component–one collection vessel—with 90–95% recovery, was achieved by controlling injection volume and gradient slope and by adding acetic acid and diethylamine to the mobile phase to keep peak elution volumes below 50 mL. Auto‐collection of a solute was based on the main ion in its APCI–MS spectrum. The technique described has been also successfully used for chiral preparative HPLC applications and purification of non‐UV‐active compounds.

Investigation of chemical transformations by NMR and GPC during the laboratory aging of Arabian asphalt

In this work, the chemical properties of a commercial grade Saudi Arabian asphalt procured from Ras Tanura refinery were evaluated. The rolling thin film oven (RTFO), termed as short-term aging, and pressurized aging vessel (PAV), termed as long-term aging, tests were used to simulate the laboratory aging of this asphalt. It was found that PAV has more severe effects on the chemical properties of asphalt than RTFO method. The Corbett fractionation procedure was used to separate fresh and aged asphalts into four generic fractions namely; asphaltenes, polar aromatics, naphthene aromatics, and saturates and various analytical techniques were applied to evaluate the chemical changes that occurred during the aging processes. High pressure-gel permeation chromatography (HP-GPC) molecular weight and size distributions suggested that molecular rearrangement occurs predominantly on aging. Carbon and proton NMR measurements of generic fractions showed that isomerization, internal cross-linking, and dehydrogenation were the main chemical reactions of hydrocarbon groups following aging. Coupling the results from the GPC and NMR techniques have led to some interesting information concerning the chemical reaction types during the aging processes. Significant differences were observed between the structure and composition of fresh and aged generic fractions of Ras Tanura asphalt.

OXIDATION KINETICS OF ASPHALT CORBETT FRACTIONS AND COMPOSITIONAL DEPENDENCE OF ASPHALT OXIDATION

ABSTRACT This paper investigates the oxidation kinetics of asphalt generic fractions and the contribution of each individual fraction to the oxidation of the whole asphalt. Polar aromatic (PA) and naphthene aromatic (NA) fractions of five Strategic Highway Research Program (SHRP) core asphalts (AAA-1, AAD-1, AAF-1, AAG-1 and AAM-1) were prepared and aged at multiple conditions to obtain their kinetic parameters. Aromatics/saturates/asphaltenes blends of four of the five asphalts were also aged to deduce the influence of saturates and asphaltenes. Carbonyl growth in the PA and NA fractions as a result of oxidation follows a similar profile as the whole asphalts. The kinetic parameters of the NA fractions occur in two groups, one with high reaction order and activation energy, and the other with low values of each. The kinetic parameters of the PA fractions all fall into the low-values group. Although the PA fraction is the most reactive portion in an asphalt, its kinetic parameters (reaction order and activation energy) may be much different from those of its parent asphalt. Saturates have only a dilution effect. The data indicate that the addition of asphaltene increases the oxidation rate. The data also indicate that the PA and NA fractions age faster in a separated state than in a mixed state. This study shows that the kinetic characteristics of an asphalt are determined not only by the kinetic characteristics of the fractions but also by the interactions and molecular associations between the fractions.

THE EFFECT OF ASPHALT COMPOSITION ON THE FORMATION OF ASPHALTENES AND THEIR CONTRIBUTION TO ASPHALT VISCOSITY

ABSTRACT Interactions among asphalt components have significant effects on the performance of asphalt binder. To understand those interactions, four asphalts, SHRP AAA-I, AAD-I, AAF-I, and AAG-I, were fractionated into three generic fractions according to Corbett's procedure and reblended into asphaltenes/aromatics/saturates ternary mixtures in various ratios. Mixtures were oxidatively aged with atmospheric air at temperatures of 87.7, 93.3, and 98.8°C for 5 to 33 days. The changes in chemical composition and physical properties were monitored using fourier transform infrared spectroscopy (FT-IR) and dynamic mechanical rheometry The formation of asphaltenes is a major factor in the hardening of asphalt with aging. The data collected in this study indicate that the saturate content in the maltene phase has a profound impact on the contribution that asphaltenes have on the viscosity of aged asphalt. The data also suggest that the aromatics fraction is solely responsible for the formation of asphaltenes as an asphalt oxidizes.

Total bandwidth for Harper equation: correction to renormalization analysis

This paper studies the correction to the effective Hamiltonian of the Harper equation in respect of the total bandwidth. The effective Hamiltonian describes the further splitting from the spectrum of a lower-order fraction when the spectrum of a higher-order fraction is considered. The total bandwidth for a split sub-band is given by the Thouless scaling law modified by the curvature of the effective Hamiltonian at its saddle points. In this paper, it is shown that the leading term of the effective Hamiltonian is exactly solvable. Moreover the correction to the curvature of the effective Hamiltonian is obtained numerically, and the explicit analytical expression is also found. This gives the second sum rule, which is of importance in deriving the Thouless scaling law for a generic fraction.

UV/VIS SPECTROPHOTOMETRY FOR THE EVALUATION OF BINDER-AGGREGATE INTERACTIONS

ABSTRACT UV/VIS absorption spectra of a few bitumens and their main generic fractions obtained by liquid chromatography have been recorded. Major or minor differences have been found depending on the nature of the bitumen and the generic fraction considered. Those differences are a valuable help in interpreting measurements of binder-aggregate affinity. A spectrophotometry technique has been tried in order to assess this affinity from a physicochemical point of view. It is baaed on the adsorption equilibria in solution between the bitumen or one of its generic fractions and a ‘and’ grading fraction of the aggregate. Both the asphaltenes of the bitumen and the nature of the aggregate play a considerable part in binder-aggregate interactions. The influence of the nature of the aggregate depends mainly on the specific surface of the ‘sand’ fraction used in the tests: with a 0.15 to 0.4 mm fraction this specific surface may vary by a factor up to more than 10, according to the nature of the original aggregate. Orientation tests to obtain more information about the generic fractions have been positive. The asphaltenes can be separated into cyclic-like and resin-like asphaltenes and the resins can be divided into resins with an ‘acid’ or ‘basic’ behaviour