摘要:

Thermodynamic behaviour of bitumens - threefresh, one oxydative aged - relative to two different penetration classes, has been studied by isobaric calorimetry and isochoric thermobarometry to lay down caracterisation criteria of bitumens from transformation temperatures. The thermiobarograms are analysed in terms of phases transitions; and compared to thermograms. A Pressure - Temperature phase diagram is determined for each bitumen. Five transformations are observed on the usual temperature range. The transition that occurs at lower temperature seems to be glass type ; generaly, the other transformations are attended with weak enthalpy changes. For the Van der Waals state equation applied to bitumens, the free volumes are determined from the slopes of thermobarograms. Transformations temperatures under atmospheric pressure are always higher forsoftbitumens than for harder ones. It occurs that aging increases transformations temperatures. Thermobarometrk analysis of afreshbitumen show that a progressive densifica-tion appears during thermail cycles

ISSN:0884-3759    

DOI:10.1080/08843759208916024

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Eight asphalts selected for intensive study in the Strategic Highway Research Program have been separated into neutral, basic, and acidic fractions by means of ion exchange chromatography. Each asphalt exhibits a characteristic fractionation pattern into neutral, acidic, and basic components. The separations into chemical types were verified by elemental analysis and infrared methods. Separations were reasonably repeatable, and recoveries were acceptable. Large enough amounts of asphalts could be separated so that properties of interest of the fractions could be studied.

ISSN:0884-3759    

DOI:10.1080/08843759208916025

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Nuclear Magnetic Resonance (NMR) spectroscopy has been used to partially characterize eight selected asphalts. This report describes the initial efforts in this endeavor. Proton and carbon spectra have been collected and analyzed for percent aromatic content as well as aromatic substitution. DEFT results, chemical shifts and literature precedent have been used to assign the major resonances in the aliphatic region to chemical entities. Finally, using elemental analysis data, molecular weight data and NMR results, average structures for the eight asphalts have been derived

ISSN:0884-3759    

DOI:10.1080/08843759208916026

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Fluorescence microphotometry has been used as a technique for the characterization of asphalt binder quality and the deterioration of asphalt cements. The technique employs optical microscopy for the in situ identification of asphalt binder from aggregate materials in cements, thereby eliminating the need to solvent extract the binder for evaluation. It may also obviate the possibility of solvent interaction or interference with the physical and chemical properties of asphalt binders that have developed in-service.

ISSN:0884-3759    

DOI:10.1080/08843759208916027

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The purpose of this work was to identify chemical compound types produced at or near the asphalt/aggregate interface during oxidative aging. Diffuse reflectance infrared Fourier transform (DRIFT) spectrometry was used to analyse samples of asphalt that had been oxidatively aged in contact with aggregate for various periods of time. Aging products were studied as a function of time, distance from the aggregate surface, asphalt composition, and aggregate composition. Three compound types were observed to form upon aging—sulfoxides, ketones, and carboxylic acids. All three compounds types are thought to cause hardening and cracking of asphalts. The composition of the virgin asphalt was a key factor in determining the kind and amounts of aging products formed. The amount of products formed was also related to aging time. Evidence for the concentration of any one aging product on or near the asphalt/aggregate interface was not found

ISSN:0884-3759    

DOI:10.1080/08843759208916028

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Sorption flow microcalorimetry methods were developed for measuring the amounts and heats of adsorption and desorption at the asphalt-aggregate interface. Model studies of the amounts and heats of phenylsulfoxide sorption on SHRP aggregates RH-greywacke and RC-McAdams limestone indicated strong and irreversible bonding of a large fraction of adsorbed phenylsulfoxide that resisted displacement by cyclohexane and water. In addition, the microcalorimetry results indicated that intermolccular interactions between adsorbed phenylsulfoxide molecules were very strong at submonolayer coverages. This suggests that phenylsulfoxide adsorbs with the sulfoxide directly attached and oriented perpendicular to the surface with strong face-to-face interactions of the phenyl groups. Similar experiments conducted on the sorption of SHRP asphalts AAD-1 and AAM-1 from solution on the RC and RH aggregates indicated significant differences in the sorption of these four asphalt-aggregate pairs. Similar to phenylsulfoxide, a large fraction of both asphalts adsorbed irreversibly with respect to cyclohexane and water-saturated cylohexane desorption. Surface analysis by laser ionization (SALI) was used to measure surface compositions of the aggregates and to monitor temperature programmed desorption (TPD) of adsorbed phenylsulfoxide. SALI analysis indicated that a significant fraction of die RC aggregate is covered with an aluminosilicate layer although bulk analysis indicates that this aggregate is predominantly limestone. TPD studies confirmed the microcalorimetry results that a large fraction of phenylsulfoxide irreversibly binds to silicate and aggregate surfaces and moreover that this irreversible binding leads to deoxygenation of the sulfoxide to sulfide at relatively low temperatures

ISSN:0884-3759    

DOI:10.1080/08843759208916029

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Three different fractions derived from each of eight SHRP asphalts were analysed by means of supercritical fluid chromatography. The three fractions were a low molecular weight neutral fraction obtained by ion exchange chromatography, a low molecular weight fraction obtained by size exclusion chromatography, end maltenes obtained by precipitation with hydrocarbon solvents. For a given asphalt, these fractions contain much of the same material and all comprise over one-half of the bulk of the asphalts. The ion exchange chromatography neutral fractions contain minimal amounts of polar materials. Based on the microstructural model of asphalt structure, any one of the three fractions might be considered to represent the solvent phase of an asphalt.

ISSN:0884-3759    

DOI:10.1080/08843759208916030

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Eight core asphalts and eleven other asphalts selected for study in the Strategic Highway Research Program have been separated into two or more fractions by means of preparative size-exclusion chromatography. The first fraction obtained by this technique is believed to consist of materials that form associations and correspond roughly to asphalt dispersed phases. This phase is polar, aromatic, and of high apparent molecular weight. Subsequent fractions obtained by size exclusion chromatography of the asphalts are of progressively lower molecular weight. When the asphalts were separated into nine fractions, the weights of each fraction were plotted versus elution volume to give distinctive bimodal chromatograms, with one exception.

ISSN:0884-3759    

DOI:10.1080/08843759208916031

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A novel experimental method developed for the measurement of the transport properties such as the diffusion coefficient, D, solubility, S, and permeability, P, for oxygen Into asphalt materials using an electrodynamic balance Is described. Both imaged and aged rolling thin-film oven test (RTFOT) asphalt particle samples In the 12 to 62 pm size range were suspended contactless and weighed In the balance to measure D, S, and P In the temperature range 17°C to 66°C. Volatilization rate data were obtained from the particle mass measurements made prior to the start of the sorption experiments. Sorption curves obtained in this study for unweathered asphalt samples showed a non-Pickian, two-stage type sorption behavior indicating the possibility of an additional mechanism other than diffusion. Analogous behavior in sorption was observed for weathered samples

ISSN:0884-3759    

DOI:10.1080/08843759208916032

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

We have delineated similarities and differences in chemical composition among neat asphalt samples obtained from the Strategic Highway Research Program (SHRP) Materials Reference Library in Austin, TX, and oxidized materials prepared by SHRP contractors using thermal chromatography (TC). This unique method for disassembling complex materials for analysis using precise temperature programming in a controlled and well characterized environment was combined with flamie ionization detection (FID) and with gas chromatographic (GC) separation and mass spectral (MS) detection. Our TC/FID analyses provided thermal profiles of materials under study-quantity of evolved species as a function of temperature--, while our TC/MS studies allowed structures to be assigned to the various components evolved from the asphalt matrix. Distinct differences among neat samples and between neat samples and their oxidized counterparts were easily discerned, both in comparisons of thermal profiles and of compound-specific identifications of components

ISSN:0884-3759    

DOI:10.1080/08843759208916033

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor