Influence of Chemical Composition on the Physical Characteristics of Paving Asphalts

Abstract

The simplest general compositional model considers asphalt to be made up of asphaltenes, heavy oils, and resins. In the present study the extent of similarity between the properties and composition of various types of asphalt obtained from different sources has been carefully explored. It shows how ductility, penetration, and softening point are related to the chemical nature of paving asphalts in the range 41–58 softening points. Asphalt properties are found to be a direct function of its chemical constituents. The relationship between softening point and asphaltene content was found to be linear while asphalts of the same softening point are easily distinguished by the content of the resins. Evaluation of the two asphalt indices—the asphaltene index (I _A ) and the Gaestel index (I _C ), reveals that they both vary linearly with the composition of asphaltenes and resins thus confirming their suitability in the characterization of asphalts. Comparison of the two indices shows that IC is more suitable in estimating the colloidal stability of different groups of asphalts. The observed correlations can be found useful in the areas of asphalt blending and rejuvenating through the appropriate selection of asphalt components.     

Effect of Chemical Nature on the Susceptibility of Asphalt to Aging

The knowledge of the factors affecting the susceptibility of asphalt to aging can be of help when selecting the asphalt binders for the construction of durable pavements. Investigated were the aging-induced changes in the chemical composition and colloidal nature of asphalts differing in origin and technology. It was shown that the course of the changes in the generic composition of asphalt upon aging under laboratory conditions depends on the chemical type of the feedstock from which the asphalt has been derived. During aging of the asphalts from the paraffin-naphthenic crudes, the resins undergo partial decomposition, which results in the increase of the cyclic fraction content. Although the increase of the asphaltene content in air-blown asphalts after the Thin Film Oven Test was found to be lower than that in the corresponding straight-run asphalts, the much higher value of the instability index and smaller size distribution of asphaltenes in the air-blown asphalts permit us to expect that their utilization as binders in pavement construction will lead to the reduction of pavement durability. It follows from the results of this study that not only the generic composition but also the structure of the fractions affect the resistance of asphalt to aging.     

Effect of Chemical Nature on the Susceptibility of Asphalt to Aging

Abstract

The knowledge of the factors affecting the susceptibility of asphalt to aging can be of help when selecting the asphalt binders for the construction of durable pavements. Investigated were the aging-induced changes in the chemical composition and colloidal nature of asphalts differing in origin and technology. It was shown that the course of the changes in the generic composition of asphalt upon aging under laboratory conditions depends on the chemical type of the feedstock from which the asphalt has been derived. During aging of the asphalts from the paraffin–naphthenic crudes, the resins undergo partial decomposition, which results in the increase of the cyclic fraction content. Although the increase of the asphaltene content in air-blown asphalts after the Thin Film Oven Test was found to be lower than that in the corresponding straight-run asphalts, the much higher value of the instability index and smaller size distribution of asphaltenes in the air-blown asphalts permit us to expect that their utilization as binders in pavement construction will lead to the reduction of pavement durability. It follows from the results of this study that not only the generic composition but also the structure of the fractions affect the resistance of asphalt to aging.     

网络结构理论在沥青改性研究中的应用

利用了网络结构理论解释了LDPE以及GMA-g-LDPE分别改性秦皇岛基质沥青、中海36-1基质沥青的软化点、低温延度、针入度指数以及高温稳定性随着改性剂含量变化而变化的规律。红外光谱研究表明，LDPE改性沥青体系中LDPE与沥青二者属于溶涨没有发生任何反应，GMA-g-LDPE改性沥青体系中GMA所含的C=O 的特征吸收峰仍然存在，但907.69cm - 1有环氧基吸收峰消失了，说明GMA-g-LDPE的侧链环氧环与沥青中的官能团发生了反应而形成网络结构。     

Study on Aging Kinetics of Panjin Paving Asphalt

In this paper, the changes of n-pentane asphaltene content, penetration, softening point, and ductility of two Panjin paving asphalts have been studied during aging. Further, based on the change of n-pentane asphaltene content, a study on aging kinetics of asphalt has been conducted. Some correlative kinetic parameters were calculated, and the aging kinetic equation of asphalt was gained. The value calculated, depending on the equation, was in accordance with the experimental data. In addition, the relationship between the composition of the high grade paving asphalt and its aging resistant performances was revealed. It showed that the aging of high grade paving asphalt was a first order reaction. Moreover, the kinetic model was proved to be reliable by investigating the changes of penetration, softening point, and ductility of asphalt during aging.     

Study and Evaluation of Aging Performance of Petroleum Asphalts and Their Constituents During Oxygen Absorption. I. Oxygen Absorption Behaviors and Kinetics

The oxygen absorption behaviors and kinetics of Shanjiasi, Shengli, and Renqiu petroleum asphalts and their constituents including saturates, aromatics, resins, and asphaltenes were successfully studied at 50°C, 0.133 MPa (O₂) and 1 mm sample film in darkness by means of precise measurement of oxygen pressure changes in reactor. The experimental results that the resin and the asphaltene can easily absorb oxygen and they are more active constituents in petroleum asphalt, while the saturate hardly absorbs oxygen, which is the most stable constituent of petroleum asphalt. The better the antiaging performance of straight run petroleum asphalt, the more stable its constituents and the less oxygen they absorb generally. The oxygen absorption rate of asphaltene diluted with the lower viscous saturate is obviously higher than that of pure asphaltene. The resin constituent of Shanjiasi asphalt could remarkably improve the antiaging ability of Shengli asphalt by the constituent substitution. The kinetic model of maximum combined oxygen presented in this paper could satisfactorily explain the oxygen absorption behaviors of petroleum asphalts and their constituents, and the oxygen absorption quantities calculated by the model are very identified with the test ones.     

Plastic asphalts produced from residua of West Siberian crudes

Summary A study has been made of the physicochemical and rheological properties of oxidized asphalts obtained from residua of West Siberian crudes.It has been shown that the nature of the feedstock has a decisive influence on the properties of the oxidized asphalts. The asphalts produced from a straight-run long residuum from West Siberian crudes have wide ranges of plasticity (91 and 111°C), low brittle points (–20 and –30°C), and better heat resistance than do the oxidized asphalts produced from a solvent-precipitated asphalt obtained in Stage II deasphalting.It has been established that, as the degree of oxidation is increased, the asphaltene content of the asphalts increases sharply, and the amount of the most reactive bicyclic and polycyclic aromatic compounds decreases through conversion into resins and then asphaltenes; the amount of oxygen-containing groups increases, as evidenced by the IR spectra of the component groups of the asphalt.The oxidized asphalts produced from residua of West Siberian crudes are highly structured systems within the interval of temperatures that was investigated (from 60 to 180°C); for a given penetration, the asphalt produced from the straight-run long residuum is more highly structured than that produced from the solvent-precipitated Stage II asphalt, as a consequence of the higher asphaltene content of the former.Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 5, pp. 26–29, May, 1973.     

Studies on Nigerian Crudes IV. Improvement of Asphaltic Properties of Residual Asphalts

Residual asphalts obtained from 25 samples of Nigerian light, medium, and heavy crude oils were chemically treated by air-oxidation and sulfurization to improve their characteristic properties. The asphalt yield for light crudes varied from 27.7-33.7 wt% and 33.4-67.5 wt% for medium crudes. The chemical treatment brought about changes in chemical composition, increase in molecular mass and modification of consistency resulting in highly improved asphaltic properties. There were manifold increases in viscosity and softening points, which came as a result of the higher asphaltene content of the treated materials. The asphalts obtained meet quality specifications for typical commercial grade products thus confirming the suitability of Nigerian crude oils for the production of residual asphalts.     

RELATIONSHIPS BETWEEN ASPHALTENES,HEITHAUS COMPATIBILITY PARAMETERS,AND ASPHALT VISCOSITY

ABSTRACT

Historically, asphalt rheology has been described in terms of a colloidal model, which depicts asphalts as dispersions of asphaltenes in petrolenes (maltenes). The model leads to a classification of asphalts into sol, gel, or intermediate categories. Sol and gel type asphalts exhibit differences in physical and chemical behavior. Sol asphalts also are described as compatible, while gel asphalts are described as non-compatible. The relative viscosity of an asphalt, defined as the quotient of the viscosity of the whole asphalt divided by the viscosity of the n-heptane soluble maltene fraction at a given temperature and rate of shear is one measure of asphalt compatibility. Based on this definition of compatibility, asphalts with low values of relative viscosity are designated as compatible and higher values of relative viscosity are designated as incompatible. Asphalt compatibility is also related to the asphaltene content, where asphalts with low asphaltene content are designated as compatible. It is claimed that the Heithaus parameters also are measures of asphalt compatibility. Therefore there should be a relationship between relative viscosities (π_rel), Heithaus parameters, and n-heptane asphaltene volume fractions ( φn-heptane)- Such a relationship has been derived assuming that the Heithaus p_a parameter is numerically equivalent to α in the Pal-Rhodes equation.     

Study on Aging Kinetics of Saudi Arabian Paving Asphalt

The changes of n-pentane asphaltene content, penetration, softening point, and ductility of two Saudi Arabian paving asphalts have been studied during aging. Further, aging kinetics of asphalt, based on the change of n-pentane asphaltene content, has been studied. Some correlative kinetic parameters were calculated and the aging kinetics equation of asphalt was gained. The value calculated depending on the equation was in accordance with the experimental data. And the relationship between the composition of the high grade paving asphalt and its aging resistant performances was revealed. It showed that the aging of high grade paving asphalt was a first-order reaction. AH-70 paving asphalt has the following characteristics: higher reaction active energy, less reaction velocity constant, lower aging velocity, and better aging resistance performance compared with AH-90 paving asphalt. The changes of penetration, softening point, and ductility of asphalt during aging further proved that the kinetic model is reliable.     

Studies on Nigerian Crudes IV. Improvement of Asphaltic Properties of Residual Asphalts

Abstract

Residual asphalts obtained from 25 samples of Nigerian light, medium, and heavy crude oils were chemically treated by air-oxidation and sulfurization to improve their characteristic properties. The asphalt yield for light crudes varied from 27.7–33.7 wt% and 33.4–67.5 wt% for medium crudes. The chemical treatment brought about changes in chemical composition, increase in molecular mass and modification of consistency resulting in highly improved asphaltic properties. There were manifold increases in viscosity and softening points, which came as a result of the higher asphaltene content of the treated materials. The asphalts obtained meet quality specifications for typical commercial grade products thus confirming the suitability of Nigerian crude oils for the production of residual asphalts.     

Study on Aging Kinetics of Saudi Arabian Paving Asphalt

Abstract

The changes of n-pentane asphaltene content, penetration, softening point, and ductility of two Saudi Arabian paving asphalts have been studied during aging. Further, aging kinetics of asphalt, based on the change of n-pentane asphaltene content, has been studied. Some correlative kinetic parameters were calculated and the aging kinetics equation of asphalt was gained. The value calculated depending on the equation was in accordance with the experimental data. And the relationship between the composition of the high grade paving asphalt and its aging resistant performances was revealed. It showed that the aging of high grade paving asphalt was a first-order reaction. AH-70 paving asphalt has the following characteristics: higher reaction active energy, less reaction velocity constant, lower aging velocity, and better aging resistance performance compared with AH-90 paving asphalt. The changes of penetration, softening point, and ductility of asphalt during aging further proved that the kinetic model is reliable.     

Study on Aging Capability of Paving Asphalt

The changes of softening point, penetration, and ductility of two asphalts after aging were studied. Two methods are simultaneously used to study the aging kinetics of two asphalts and some kinetic parameters are given in this paper. The results show that the softening points increase while penetration and ductility values decrease after aging. It was concluded that the aging capability of AH-70 asphalt is better than AH-90 asphalt. The aging kinetic models of two asphalts based on softening points are compared with a pentane asphaltene aging kinetic model and the results are consistent. A new and easy method for studying the aging of asphalt was developed.     

高等级道路沥青老化动力学研究

在实验室研究了AH－70和AH－90两种高等级道路沥青在老化过程中,正戊烷沥青质及针入度、软化点、延度等指标的变化,并根据老化过程中,正戊烷沥青质的变化,进行了沥青老化动力学研究,计算得出了有关动力学参数,得到了沥青老化动力学方程,其计算值与试验数据相吻合。表明高等级道路沥青老化属于一级动力学反应。实际老化过程中针入度、软化点及延度的变化进一步证明了所得动力学模型是可靠的。     

Study on Aging Capability of Paving Asphalt

Abstract:

The changes of softening point, penetration, and ductility of two asphalts after aging were studied. Two methods are simultaneously used to study the aging kinetics of two asphalts and some kinetic parameters are given in this paper. The results show that the softening points increase while penetration and ductility values decrease after aging. It was concluded that the aging capability of AH-70 asphalt is better than AH-90 asphalt. The aging kinetic models of two asphalts based on softening points are compared with a pentane asphaltene aging kinetic model and the results are consistent. A new and easy method for studying the aging of asphalt was developed.     

THE EVOLUTION OF THE DEAD SEA FLOATING ASPHALT BLOCKS: SIMULATIONS BY PYROLYSIS

The asphalts found as floating blocks on the Dead Sea and deep-seated in wells differ from all other asphalts of the area, mostly by their more abundand and much better preserved n-alkance. Since biodegradation was found to be the main alteration process through which crude oil was alterd into aphalts, such well-preserved n-alkanes are unexpected. A hypothesis of secondary generation of theise alkanes was tested bny pyrolysis simulations of asphalt at 300C during periods ranging up to 60 days. The abundance and distrubution pattern of the n-alkanes in the simulated asphalts after 14 days of heating resembles that of the floating asphalt blocks and that found at a depth of 3,500 m. In addiation to saturated hydrocarbons, aromatics and gases were also formed at the expense of resins and asphaltenes. The H/C ratio was balanced by the formation of pyrobitumen and by a gradual decrease of the H/C ratio in the residual resins and asphaltenes. The gas formed contained about 60 to 80% methane with an isotopic composition of-41 to 42%%. The hydrocarbon content of the simulated asphalt (gas and liquids) increased from about 15% at the stariting material to about 60% after 60 days of heating.
The recognition that asphalts in the Dead Sea basin are secondarily subjected to alteration upon burial might be of economic importance. Asphalts buried to a depth at which maturation conditions are close to that reached in the pyrolysis simulation at 300C after about 60 days may be counted on as source material for hydrocarbons.     

碱性物质对沥青热老化的影响

对两种沥青进行薄膜烘箱试验（ＴＦＯＴ）和掺加碱性物质的ＴＦＯＴ试验，用沥青蒸发损失率随ＴＦＯＴ时间的变化、沥青化学组成的变化和沥青红外光谱的变化阐述沥青热老化的原因，时比沥青抗老化性能的优劣，考察线性物质对沥青热老化的影响．结果发现：碱性物质使沥青蒸发损失率降低，可能是碱性物质促进沥青吸氧所致；碱性物质促进沥青中重胶质和沥青质的生成，使沥青在１７Ｏｃｍ－１附近的红外吸收强度明显增强，进一步说明碱性物质促进沥青吸氧．沥青ＴＦＯＴ后其重胶质和沥青质增加程度及其在１７０ｃｍ－１处的红外吸收强度变化程度能够表征其抗吸氧老化性能优劣，反映沥青胶体体系变化程度．     

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

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.     

Study and Evaluation of Aging Performance of Petroleum Asphalts and Their Constituents During Oxygen Absorption. I. Oxygen Absorption Behaviors and Kinetics

Abstract

The oxygen absorption behaviors and kinetics of Shanjiasi, Shengli, and Renqiu petroleum asphalts and their constituents including saturates, aromatics, resins, and asphaltenes were successfully studied at 50°C, 0.133 MPa (O₂) and 1 mm sample film in darkness by means of precise measurement of oxygen pressure changes in reactor. The experimental results that the resin and the asphaltene can easily absorb oxygen and they are more active constituents in petroleum asphalt, while the saturate hardly absorbs oxygen, which is the most stable constituent of petroleum asphalt. The better the antiaging performance of straight run petroleum asphalt, the more stable its constituents and the less oxygen they absorb generally. The oxygen absorption rate of asphaltene diluted with the lower viscous saturate is obviously higher than that of pure asphaltene. The resin constituent of Shanjiasi asphalt could remarkably improve the antiaging ability of Shengli asphalt by the constituent substitution. The kinetic model of maximum combined oxygen presented in this paper could satisfactorily explain the oxygen absorption behaviors of petroleum asphalts and their constituents, and the oxygen absorption quantities calculated by the model are very identified with the test ones.     

国内外典型道路沥青抗车辙性能的对比研究

通过采用灰色相关理论法和SHRP动态剪切法对国内外19种典型重交通道路沥青的抗车辙性能进行研究,并对影响抗车辙性能的几个因素进行讨论。研究结果表明,软化点、动力粘度、沥青质含量指标与沥青的抗车辙性能直接相关。软化点高、动力粘度大并且沥青质含量高的沥青具有较好的抗车辙性能,同时沥青彼此间的抗车辙性能差异较大,其中国产的沥青具有较好的抗车辙性能。