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.     

Studies of the microstructure of polymer-modified bitumen emulsions using confocal laser scanning microscopy

Polymer-modified bitumen emulsions present a safer and more environmentally friendly binder for enhancing the properties of roads. Cationic bitumen emulsion binders containing polymer latex were investigated using confocal laser scanning microscopy. The latex was incorporated into the bitumen emulsion by using four different addition methods and all emulsions were processed with a conventional colloid mill. The emulsion binder films were studied after evaporation of the emulsion aqueous phase. We show how the microstructure and distribution of the polymer varies within the bitumen binder depending on latex addition method, and that the microstructure of the binder remains intact when exposed to elevated temperature. It was found that a distinctly fine dispersion of polymer results when the polymer is blended into the bitumen before the emulsifying process (a monophase emulsion). In contrast, bi-phase emulsion binders produced by either post-adding the latex to the bitumen emulsion, or by adding the latex into the emulsifier solution phase before processing, or by comilling the latex with the bitumen, water and emulsifier all resulted in a network formation of bitumen particles surrounded by a continuous polymer film. The use of emulsified binders appears to result in a more evenly distributed polymer network compared to the use of hot polymer-modified binders, and they therefore have greater potential for consistent binder cohesion strength, stone retention and therefore improved pavement performance.     

休息期和聚合物改性剂对疲劳寿命的影响

研究了在相对低温时均匀分散的填料对沥青结合料和沥青混凝土混合料复原的影响,通过对两种级配明显不同的磨碎石灰石作为填料组成的结合料系统进行研究,得出了填料颗粒尺寸对沥青玛脂复原的影响.     

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.     

Geochemical characteristic and origin of solid bitumen in the Jurassic and Triassic sandstone reservoir of Santai Area,Junggar Basin,NW China

Solid bitumen was identified in the pore spaces of the Jurassic and Triassic sandstone reservoir in the Santai Area, Junggar Basin, NW China, which limits economic petroleum production, even influencing hydrocarbon accumulation. Organic geochemical techniques were figured out the origin of bitumen and its formation mechanisms. Carbon isotope characteristics of the crude oil and bitumen-reservoir extracts suggests the bitumen mainly derived from sapropelic-type source rock of Pingdiquan Formation, which was deposited in the semideep and deep lacustrine environment. Biomarker date indicates bitumen was formed from petroleum in low thermally mature stage and biodegradation was responsible for formation of the bitumen.     

黔中隆起震旦系灯影组高热演化沥青地球化学特征及差异分析

黔中隆起地区震旦系灯影组白云岩的溶蚀孔洞、构造裂缝等储集空间中发现有白云石、石英和黑色炭质沥青的充填,其中沥青的形成晚于白云石但早于石英。研究采集了贵州开阳县双流镇白马洞新桥剖面（双流白马）和金沙县岩孔镇箐口村剖面（金沙岩孔）2处沥青样品。沥青样品都具有较高的热演化程度,扫描电镜下呈块状或小球状;根据碳同位素组成,认为沥青来源于下寒武统烃源岩。但2处沥青又具有显著的差异。双流白马沥青与金沙岩孔沥青相比,具有较低的热演化程度,2处沥青反射率平均值分别为4.30%和5.17%;具有相对较高的N、O、S含量和相对较高的H/C值以及相对较轻的碳同位素组成。流体包裹体测温和沥青反射率表明2处埋藏热演化过程的差异导致了沥青在元素组成和同位素组成上的差异。     

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。