Application of rheological characteristics of modified bitumen to predict the fatigue life of asphalt mixtures

Fatigue is defined as a fracture phenomenon due to a repetitive load or a variable dynamic load that occurs at a lower load than the ultimate static load. Fatigue stability of an asphalt mixture is its ability of enduring the repetitive flexural loads. In this study, the carbon nanotubes are used as the bitumen modifier in the way that the prepared samples contain 0%, 0.3%, 0.6%, 0.9%, 1.2%, and 1.5% carbon nanotubes. Then, the classic and rheological experiments are conducted on these samples. This additive improves the classical properties of bitumen (softening point, penetration degree, and so on) and also the fatigue parameter of bitumen (i.e., G*Sinδ) in comparison to the standard bitumen. Using the rheological graphs, it can be predicted that adding the carbon nanotubes to bitumen might improve the fatigue life of the asphalt mixtures. To evaluate the accuracy of this prediction, the fatigue experiment are performed on the prepared beam samples using a four-point loading in the case of constant strain (600 microstrain) with a semi-sinusoidal wave at 20°C. The end of the samples’ fatigue life is 50% reduction in their initial rigidity. It is observed that with an increase in the percentage of carbon nanotube in fatigue samples, the fatigue life of asphalt mixtures remarkably increases.     

An aspect of bitumen emulsification by steam condensation: Effect of formation temperature and bitumen content

The experiments to form emulsions of bitumen including fine droplets of condensate water were carried out for an average formation temperature range; T_f = 38–69°C and bitumen content; C_B = 29–82%. It was observed that the water retention capacity or stability of the emulsions after mild agitation was significantly affected by formation temperature and content of the bitumen. The particle size of water droplets in emulsion decreased with increasing formation temperature. However, bitumen emulsions showed similar shear thinning non-Newtonian behavior in spite of the formation temperature, since water droplets in the emulsions changed under shear flow to smaller size similar to ones formed at the higher formation temperature.     

NEW EXPERIMENTAL AND THEORETICAL RELATION TO DETERMINE THE RESEARCH OCTANE NUMBER (RON) OF AUTHENTIC AROMATIC HYDROCARBONS COULD BE PRESENT IN THE GASOLINE FRACTION

ABSTRACT

Calculation of the octane number for aromatic hydrocarbons expected to be present in the gasoline range (40-200° C) was carried out by developing a new method using H-nmr spectroscopy and multiparametric regressional analysis. The additivity parameters suggested in the muliparametric regressional analysis are relevant to the chemical formula for mono, di, and poly alkyl substituted benzenes.

Two sets of relevant parameters in two different attempts were suggested to suit the calculation of the octane number of all the possible present aromatic in the gasoline range. The first attempt, gives rise to parametric equation (1) suitable to calculate the octane number for all mono substituted alkyl benzenes. However, application of the developed equation to di, tri, and poly substituted alkyl benzenes gives calculated octane number values, do not agree with the observed values. In the second attempt additional parameters were included in the regression analysis; they are resonance (R), steric (S), and inductive (I) effects. The new developed equation (2) gives calculated octane number values comparable to the observed ones for all the possible and hypothetical aromatics in gasoline.     

利用植物油脚合成油脚沥青的技术工艺

阐述了利用植物油脚制取沥青的原理及工艺,可解决油脚对环境的污染问题,且具有较好的经济效益.     

煤焦油与轮古稠油悬浮床加氢共炼工艺的研究

在间歇式高压反应釜中对轮古稠油和某煤焦油进行了悬浮床加氢裂化共处理改质的反应。反应条件为:煤焦油与稠油质量比1∶3 , 反应温度430 ℃, 室温下氢气初压7.0 M Pa , 反应时间60 min , 催化剂质量分数为200 μg/ g 。研究表明:在氢气和分散性催化剂存在下的反应有效地抑制了生焦及产气率, 增加了中间馏分油的收率。从生焦指数及生焦量来看, 镍催化剂的催化加氢性能优于铁催化剂, 油溶性的NiNaph 催化加氢性能明显高于水溶性的Ni(NO₃)₂ 。不同的原料配比改变了反应产物分布。对稠油与煤焦油共炼产物分离, 选取尾油切割点420 ～ 430℃, 可以作为接近于生产90^#道路沥青的原料。     

Experimental measurement of gas permeability through bitumen: results for H2, N2 and O2

This study reports experimental results concerning the transport of permanent gases (H₂, O₂, N₂) through bitumen between 15 and 25 °C. A pressure differential technique, already used in membrane science in order to determine the permeability of gases through dense polymeric films, has been attempted with bitumen samples. It is shown that reproducible permeability data can be obtained thanks to this strategy, providing that bitumen mechanical resistance is improved by a support paper and a low leak module is used. Experimental results are analyzed in terms of permeability value and temperature dependency (activation energy) in comparison with other dense and permeable organic solids (polymers). The limitations of the technique as well as its potential extension to diffusion coefficient determination are discussed.     

Mechanical and anticorrosive properties of non toxic coal-tar epoxy alternative coating

Coal tar epoxy (CTE) coating system has been widely used for protection of steel structures under atmospheric, buried and immersion conditions because of their low water vapour permeability, high electrolyte resistance and good antibacterial properties. However, coal tar has been classified as carcinogen, mutagen and toxic for reproduction (CMR) as per International guideline (REACH, IARC and GS 11). It is now banned in the developed nations like US, Europe, Japan, etc. As the use of coal tar is being restricted, there is an urgent need to formulate a coal tar free epoxy product for corrosion protection of structures. In the present study, alternative approaches have been proposed to replace coal tar such as bitumen (BIT), hydrocarbon resin (HR), flexibilizer (FL) and curing agents like polyamide (PAD) or polyamine (PAM). Four different coal tar free formulations were formulated separately by using these approaches. The standard CTE and coal tar free epoxy compositions were evaluated for mechanical properties such as elongation at break, tensile strength, adhesion strength and resistance to abrasion, impact and flexibility. The resistance to corrosion of optimized composition (epoxy-HR-FL-PAD-PAM) and coal tar epoxy coating was evaluated by exposing to different environments. The corrosion resistance property was also evaluated by cathodic disbondment and electrochemical impedance spectroscopy (EIS) technique. Results indicate that epoxy-hydrocarbon resin-flexibilizer composition cured with blend of polyamide and polyamine has comparable mechanical and corrosion protection properties to that of standard CTE.     

Stability of the edge of a SAGD steam chamber in a bitumen reservoir

Steam-Assisted Gravity Drainage (SAGD) is a key in-situ recovery process being used today to extract oil from bitumen reservoirs. In SAGD, an oil-depleted chamber of steam grows within the oil sands formation along a pair of horizontal wells and heats bitumen-laden oil sands at its edge. The viscosity of bitumen drops by up to five orders of magnitude when heated to above 200 °C and mobilized bitumen at the chamber edge flows under gravity to a production well located at the base of the chamber. If the steam chamber does not grow uniformly along the wellpair, then bitumen recovery is less than ideal. To raise the thermal efficiency, and consequently the economics, of the process, efficient heat transfer from chamber to the oil sands must occur and the chamber must grow uniformly along the entire length of the wellpair. If steam fingers develop at the edge of the chamber, then the heat transfer area enlarges and raises the thermal efficiency of the process since more heat is directed to the oil sands. In this research, the stability of the interface between the steam chamber and oil sands is examined by using linear stability theory. The results show that the stability is controlled by the difference between the energy content-weighted Darcy–Rayleigh numbers of the steam/water phases (displacing fluid) and the oil phase (displaced fluid). Also, the results show that at typical SAGD steam saturation temperatures, the chamber edge is unstable providing the steam quality at the edge exceeds about 50%.     

The Use of Microscopic Bitumen Froth Morphology for the Identification of Problem Oil Sand Ores

Oil sand, which is found in various deposits around the world, consists mostly of sand, surrounded by up to 18 wt% bitumen. The largest deposits known are situated in northern Alberta, Canada, where reserves of bitumen are estimated to be 1.7 trillion barrels. Bitumen is similar to heavy oil, but with much higher viscosity and density. The two main commercial oil sand operations in Alberta are surface mines and use aqueous flotation of the bitumen to separate it from the rest of the oil sand. Under optimal conditions up to 95% of the bitumen can be recovered, but occasionally ores are mined that create problems in extraction, and recovery can drop to 70% or less. This article discusses the microscopic morphologies of various bitumen and heavy oil streams and their relationship to processing problems. The results of extensive microscopic work have demonstrated that the bitumen in an oil sand ore is the phase most susceptible to oxidation and that the resulting changes manifest themselves in particular microscopic structures. The presence and type of these structures can be related to the processing behavior of oil sand ores. Morphological features found in froths from commercial operations are similar to those found in froths from laboratory-prepared samples. The morphological features found in froths of oxidized ores have been categorized and quantified for a variety of samples and are referred to as degraded bitumen structures. Experiments in which fresh oil sand ores were subjected to low-temperature oxidation showed that bitumen froth morphology changed dramatically compared to that of nonoxidized ores for identical bulk compositions and extraction water chemistries.     

沥青混合料最大理论密度确定方法的比较

最大理论密度的确定方法一般有两种;计算法和实测法,通过对沥青混合料最大理论密度几种确定方法的比较分析,认为采用实测法最为合理,对实测法的一些注意事项提出了有益的建议,当实测条件不具备时,推荐了江苏地区适用的计算方法。