Nuclear-Electron Overhauser Effect in MC800 Liquid Asphalt Solutions

Experimental results on the extrapolated ultimate enhancement factors of o-, m-, and p-xylene protons at 1.53 mT are obtained for MC800 asphalt solutions. The ultimate enhancement factors are found such as ?26.9, ?25.7, and ?11.7 for o-, m-, and p-xylene, respectively. These results show that the solvent proton Overhauser effect cannot reach the extrapolated enhancement of ?330 in the extreme narrowing case because of occurrence of small scalar interactions in addition to the dipole–dipole interactions between solvent protons and asphalt electrons. The ortho, meta, and para positions of the –CH₃ group change the nature of the interactions. The nuclear magnetic resonance (NMR) signal enhancements exhibit a sensitive behavior depending on the chemical environment differing from isomer to isomer. The solvation or association of asphalt in xylene isomers at room temperature is revealed. Quantum chemical calculations for the xylene isomers with the electronic and optical properties; absorption wavelengths, excitation energy, atomic charges, dipole moment and frontier molecular orbital energies, molecular electrostatic potential; are carried out using the density functional theory (DFT) method (B3LYP) with the 6-311G(d,p) basis set by the standard Gaussian 09 software package program. The relative importance of scalar and translational dipolar interaction parameters determined in dynamic nuclear polarization experiments is explained by the electronic structure of HOMO–LUMO of the xylene isomers.     

Microwave-assisted one-pot conversion from deoiled asphalt to green fluorescent graphene quantum dots and their interfacial properties

High-quality graphene quantum dots (GQDs) were prepared through a facile route of microwave-assisted one-step mild oxidation of cheap deoiled asphalt (DOA). The as-prepared DOA-derived GQDs dissolved in water with a much smaller and thinner size than most of the reported GQDs, and luminesced bright green light by excitation of 365 nm. Furthermore, the GQDs possessed excellent properties of excitation-tuned fluorescence behavior with a high quantum yield up to 16.4%. In addition, the GQDs showed amphipathic properties and could significantly reduce the interfacial tension, which give them great potential as surfactants for asphalt emulsion.     

Elastodynamic analysis of a thin layer bonded on a visco-elastic medium under combined in-plane and lateral pulse loads

An analytic solution of a thin layer bonded on a visco-elastic medium under the action of in-plane and lateral pulse loads is presented. The analysis is based on double integral transforms with respect to space and time. Representative examples are studied and discussed to determine the influence of the (a) damping and elastic coefficients of visco-elastic medium, and (b) in-plane compression and stretching of the thin layer on wave propagation.     

Spectral Analysis of Some Distillates from Asphalt Cracking and Evaluation of UTIMAC as Cracking Catalyst

This paper demonstrates the spectral analysis of some distillates obtained from asphalt cracking in the presence of a conventional expensive catalyst, i.e., HZSM‐5, and local cheap and readily available clay, i.e., UTIMAC. Each distillate was fractionated into pentane soluble (PI) and pentane insoluble (PI) fractions based on solubility in n, pentane. Both PS and PI obtained in the case of HZSM‐5 and UTIMAC were analyzed by ¹H‐NMR spectrophotometry using CDCl₃ as dissolving solvent and tetramethylsilane (TMS) as internal standard. It is evident from the profiles that both catalysts caused the generation of some peaks ascribed to methylene and methene configurations in the aliphatic region. Bands corresponding to aromatic configurations were also generated. The results indicate that the cheap local catalyst used has comparable suitability with the conventional expensive catalyst in terms of asphalt cracking.     

飞机－道面－土基动力耦合系统有限元分析

本文将飞机－道面－土基作为一个相互作用的动力系统，对飞机滑行情况下，弹性半空间地基上刚性道面板的动响应，采用有限元法进行了计算分析。结果表明，本文计算结果与现场实测值吻合很好。由于考虑了飞机和道面之间的耦合作用，避免了实测飞机对道面作用荷载的繁琐工作，因此本文方法具有明显的实用意义。     

基于数字图像的土、岩和混凝土内部结构定量分析和力学数值计算的研究进展

土、岩及混凝土是一种内部结构极其复杂的材料,内部细观组成和结构决定了它们在外力作用下内部应力和应变等物理场的分布状态,在很大程度上控制了它们的宏观力学响应和破坏机理和过程。自1995年以来,数字图像处理技术作为一种材料细观空间结构及几何形态的精确量测和数字表述手段快速地被应用于沥青混凝土、水泥混凝土、土和岩体材料细观结构定量分析中来。本文在研究相关文献的基础上,分析和研究了数字图像技术在土、岩及混凝土内部结构定量分析和力学数值计算中的发展过程和研究成果,内容包括:单个骨料颗粒形态特征定量分析;土、岩和混凝土内部结构定量分析;岩体结构定量分析中的应用;基于数字图像处理的土、岩和混凝土细观结构力学计算。在此基础上,本文进一步对数字图像技术在岩土领域中的应用进展及未来的发展趋势进行了探讨,认为数字图像作为一种空间分布测量手段和数字表述方法使得它具有巨大的潜力,特别是在岩土领域的纵深发展过程中,它可能实现考虑细微观结构性的岩土力学和工程分析和预测的、新的方法和理论。     

Disk-shaped compact tension test for asphalt concrete fracture

A disk-shaped compact tension (DC(T)) test has been developed as a practical method for obtaining the fracture energy of asphalt concrete. The main purpose of the development of this specimen geometry is the ability to test cylindrical cores obtained from in-place asphalt concrete pavements or gyratory-compacted specimens fabricated during the mixture design process. A suitable specimen geometry was developed using the ASTM E399 standard for compact tension testing of metals as a starting point. After finalizing the specimen geometry, a typical asphalt concrete surface mixture was tested at various temperatures and loading rates to evaluate the proposed DC(T) configuration. The variability of the fracture energy obtained from the DC(T) geometry was found to be comparable with the variability associated with other fracture tests for asphalt concrete. The ability of the test to detect changes in the fracture energy with the various testing conditions (temperature and loading rate) was the benchmark for determining the potential of using the DC(T) geometry. The test has the capability to capture the transition of asphalt concrete from a brittle material at low temperatures to a more ductile material at higher temperatures. Because testing was conducted on ungrooved specimens, special care was taken to quantify deviations of the crack path from the pure mode I crack path. An analysis of variance of test data revealed that the prototype DC(T) can detect statistical differences in fracture energy resulting for tests conducted across a useful range of test temperatures and loading rates. This specific analysis also indicated that fracture energy is not correlated to crack deviation angle. This paper also provides an overview of ongoing work integrating experimental results and observations with numerical analysis by means of a cohesive zone model tailored for asphalt concrete fracture behavior.     

Research on nonlinear constitutive relationship of permanent deformation in asphalt pavements

To predict correctly the rut depths in asphalt pavements, a new nonlinear viscoelastic-elastoplastic constitutive model of permanent deformation in asphalt pavements is presented. The model combines a generalized Maxwell model with an elastoplastic one. Then from the creep theory, the linear and nonlinear constitutive equations of the generalized Maxwell model are obtained. From the nonlinear finite element method for the rutting of the asphalt pavement, the rut depths of 4 asphalt-aggregate mixtures are obtained. And the results are compared with the ones from the finite element method by SHRP and the experiments by SWK/UN. The results in this paper are better than the ones by SHRP, and agree with the ones of the experiment by SWK/UN. This shows that the nonlinear viscoelastic-elastoplastic constitutive model, which is presented in this paper for the rutting of the asphalt pavement, is effective. The properties, such as nonlinear elasticity, plasticity, viscoelasticity and nonlinear viscoelasticity, which affect the rutting of an asphalt pavement, can be shown in the model. And the characteristics of the permanent deformation of the asphalt pavement can be presented entirely in the model.     

Traffic noise reduction due to the porous road surface

Porous road surfaces reduce road traffic noise. A new method of noise reduction assessment is proposed. The noise generated by a few vehicles was measured two times: on an old surface with the dense asphalt and on a new surface with the porous asphalt. Subjective assessments of drive-by noise suggest that the sound exposure and the road surface coefficient can be used as the acoustical characteristics of a road surface. Their average values, with the average number of vehicles passing the receiver during a day or night, makes it possible to predict the equivalent continuous A-weighted sound pressure level for the new road surface. This is the main objective of this paper.     

An application of vertex packing to data analysis in the evaluation of pavement deterioration

The analysis of data concerning the deterioration of pavement over time yielded a problem of aggregating the data in a manner that preserved independence of the aggregated data points and maximized the number of points. We show that this problem can be modeled as a maximum cardinality vertex packing problem on a proper internal graph and thus can be solved very efficiently by a greedy algorithm.