摘要:

Structure, Interaction, and phase transition of a vacuum residue fractions In various apolar solvents were Investigated, using viscosity measurements and small angle neutron scattering. Both light and heavy ended fractions form colloidal particles of spherical shape with average sizes of -40 and -60 A respectively. The size distributions follow a Schultz distribution function approximately. Rheological studies of these fractions indicated significant particle solvation. The solvation mechanism is through association of the solvent molecules with individual VR colloids, instead of through solvent entrapment between agglomerated colloids. The viscosity, as a function of temperature, suggested a glass-like transition at approximately 254 K for the heavy ended fraction at 0.5 volume fraction. The small angle neutron scattering measurements confirmed the colloidal structure determined from rheological study. It also provided the information about the total colloids/solvent Interfacial area, from which we found that VR colloids have a rough surface

ISSN:0884-3759    

DOI:10.1080/08843759208916014

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Absorption is the process in which asphalt flows into a porous aggregate, under the driving force of capillary pressure. Asphalt absorption is of interest because it represents an economic loss of effective binder, and because it may change the properties of the resulting asphalt film and lead to premature pavement distress. Incorrect air voids estimation may also result from failure to properly account for asphalt absorption in pavement design. The objective of this research was to determine the temporal dependence of absorption upon asphalt and aggregate properties and to test a rational model for this dependence.

ISSN:0884-3759    

DOI:10.1080/08843759208916015

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Component type compositions were changed by blending with fractionated materials and the effects of these changes on the Theological properties were studied. Thus, saturated hydrocarbons, naphthene aromatics, propane precipitated asphalts and waxes were blended with both good and poor paving asphalts. Changes in penetration index, low temperature stiffness, ductility and glass transition temperature were examined. The composition of a number of asphalts including air blown and visbroken asphalts and their Theological properties were also examined in these studies to obtain correlations

ISSN:0884-3759    

DOI:10.1080/08843759208916016

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Single- and multi-component adsorption of compounds representing highly polar functional groups in asphalt onto SI-1000 silica has been performed at 25 °C using cyclohexane as a solvent. The asphalt functionalities used are benzoic acid (strong acid), 1-naphthol (weak acid), phenanthridine (strong base), and phenyisulfoxide (weak base). The bi-, tri-, and quadh-component adsorption behaviors demonstrated that the competitive adsorptive affinities of the asphalt functionalities for the silica are ranked as 1-naphthol < benzoic acid » phenanthridine < phenyisulfoxide. The prediction of multi-component adsorption equilibria has been made by applying the Langmuir Competitive Model (LCM) and the Ideal Adsorbed Solution Theory (LAST) to single-component adsorption data. Both the LCM and the LAST provided a good prediction for benzoic acid/1-naphthol and phenanthridine/phenyisulfoxide combinations. In the cases that involved acid-base combinations, however, both the LCM and the LAST yielded predictions that deviated from actual behavior. This deviation was most likely caused by the nonideal behavior of strong adsorbate-adsorbate interaction in the adsorbed phase

ISSN:0884-3759    

DOI:10.1080/08843759208916017

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Petroleum asphalt contains asphaltene which is peptized with resin fraction molecules and is dispersed in an intermicellar medium consisting of saturates and aromatics (gas oil fraction). The single sheet of asphalcic molecules, determined by a variety of instrumental methods, has an average size of 0.5 × 1.5 nm. These mesomorphic units as evaluated by x-ray diffraction contain ordered nuclei of Lcwith 1.0 - I.S nm and Lcof 2.0 nm. The micellar structure can be evaluated from petroleum, asphalt, or asphattene suspended in any medium by small angle x-ray or neutron scattering to yield a morphological diameter measuring ca. 10 nm. The tendency of these units to be associated has been investigated by a number of investigators, for example, electron microscopic techniques such as freeze-fracture, holycarbon and metal shadowing have indicated a cluster diameter of 100 - 1000 nm. The upper range of these clusters (super-micelles) can again agglomerate into a giant size of agglomerate on the order of 2 - 10 μm, which corresponds to a typical floe weight. At high temperature these supermicelles can form two-dimensional liquid crystalline mesophase spherules with sizes varying from 2 to 5 μm

ISSN:0884-3759    

DOI:10.1080/08843759208916018

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Numerous thcrmoanalyttcal methods can be used to evaluate asphalt cements. Optical thermomicroscopy techniques such as phase contrast microscopy and polarized light microscopy have been used to directly observe the in situ crystallization of aliphatic, waxy fractions, and to monitor any changes in structure that occur with temperature. These visual changes are then correlated with enthalpy changes resulting from precipitation/dissolution as measured by Differential Scanning Calorimetry (DSC) to better understand their thermal behavior. Temperature cycling studies show the phenomenon of crystallization to be completely reversible.

ISSN:0884-3759    

DOI:10.1080/08843759208916019

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Supercritical extraction with n-pentane was used to separate asphalt into distinct fractions having different physical and compositional properties. A pilot-scale supercritical unit capable of processing thirty kilograms of asphalt per day was designed and fabricated specifically for asphalt fractionation. The operation and design of the unit is similar to the ROSE (Residuum Oil Supercritical Extraction) process of Keer-McGee. This unit was used to separate asphalt into five different fractions ranging from soft greases to asphaltene-like solids. Supplemental room-temperature solvent fractionation of the hardest of these five using binary pentane/cyclohexane mixtures produces, a total of eight fractions. A variety of analyses provide chemical and physical ctauracterization of the fractions. These include: (1) Corbett Fractionation, (2) FT-IR spectroscopy, (3) size exclusion chromatography, (4) nickel and vanadium atomic absorption, and (5) viscosity

ISSN:0884-3759    

DOI:10.1080/08843759208916020

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Infrared analysis is an extremely valuable tool for investigating the chemical functionality of asphalts. The attenuated total reflection (ATR) FT-IR method is especially useful for the study of this intractable material. Quick and easy sample preparation, natural state analysis, and clean and reproducible spectra are advantages of the ATR method over conventional transmission methods. Comparisons of this procedure to potassium bromide pellet and solution methods support the method's use. Asphalt oxidative and solvent aging studies employed the ATR method to track hardening of asphalt in various solvents as indicated by increased carbonyl absorbances. Also. standard laboratory tests for simulating the hot-mix aging of asphalts, compared using this method as well as other chemical and physical properties, sbow significant differences from actual hot-mix aging

ISSN:0884-3759    

DOI:10.1080/08843759208916021

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

High performance gel permeation chromatography (HP-GPC) studies using a multiple wavelength ultraviolet-visible detector have been carried out on a number of asphalts as well as on strong acids and neutrals fractions from some of them. Some findings are summarized in terms of three representative asphalts which differ in molecular size distribution, in presence of large size molecules and large assemblies of smaller molecules, in the absorption due to conjugated molecules or portions of molecules and in the size of the conjugated units responsible for that absorption. The nature of the strong acids appears to be linked to the presence of large molecules and assemblies ir the whole asphalt

ISSN:0884-3759    

DOI:10.1080/08843759208916022

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Combining supercritical fluid chromatography and Fourier transform infrared spectroscopy has been described in a number of reports. This work is concerned with developing an automated combined micro Fourier transform infrared spectroscopy with a micro extractor SFC interface. The instrument is described in detail. Basically it consists of a computer driven collector drum complete with cooling assembly that is attached to the exit of an SFC extractor which can be controlled as to temperature and pressure. This permits some preliminary fractionation. The interface is then moved to micro FTIR. The computer then is used to position the collected areas successively under the FTIR and multiple scans are made to any desired level. Examples are given of the performance on extracts from asphalts

ISSN:0884-3759    

DOI:10.1080/08843759208916023

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor