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Effect of carbon black on the dynamic moduli of asphalt mixtures and its master curves

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Frontiers of Structural and Civil Engineering 2019年第4期13卷 918-925页

作者： Chuangmin LI Fanbo NING Yuanyuan LI Engineering Laboratory of Spatial Information Technology of Highway Geological Disaster Early Warning in Hunan Province Changsha University of Science & Technology Changsha 410114 China School of Traffic and Transportation Engineering Changsha University of Science &Technology Changsha 410114 China State Key Laboratory of Silicate Materials for Architectures Wuhan University of Technology Wuhan 430070 China

modulus is one of the main parameters during the design of asphalt pavement structure, the newest specifications of China gives the dynamic moduli ranges of commonly used asphalt mixtures with base asphalt (BA) or styrene-butadiene-styrene modified asphalt (SBS MA), while the moduli ranges of mixtures with carbon black modified asphalt (CB MA) are not recommended. To investigate the CB effect on the dynamic moduli of CB MA mixtures, one commonly used asphalt mixture (AC-20) was designed with BA, SBS MA, and CB MA, respectively. Then, the uniaxial compression dynamic modulus tests were conducted at different temperatures and loading frequencies, the master curves of asphalt mixtures were analyzed based on the time-temperature equivalence principle. The results show that with increasing loading frequency, the temperature dependence of dynamic moduli of all asphalt mixtures tend to be less obvious. Both SBS and CB can decrease the temperature sensitivity of asphalt mixture, the SBS MA mixture has the lowest temperature sensitivity, followed by CB MA and BA mixture. In addition, CB and SBS can obviously improve the dynamic modulus of the BA mixture, enhance the anti-deformation performance of pavement structure, and the improvement effect of CB is almost the same with SBS.

关键词： dynamic modulus carbon black master curve modified asphalt asphalt mixture

Surface microtopography and micromechanics of various rank coals

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International Journal of Minerals,Metallurgy and Materials 2019年第11期26卷 1351-1363页

作者： Xiang-hui Tian Da-zhao Song Xue-qiu He Hui-fang Liu Wei-xiang Wang Zhen-lei Li Key Laboratory of Ministry of Education for Efficient Mining and Safety of Metal Mine University of Science and Technology BeijingBeijing 100083China School of Civil and Resources Engineering University of Science and Technology BeijingBeijing 100083China School of Civil Mining and Environmental EngineeringUniversity of WollongongWollongong NSW 2522Australia

For a long time,coalbed gas has brought about various problems to the safety of coal mine production.In addition,the mining of gas and coalbed methane(CBM)has attracted much attention.The occurrence and migration of CBM are believed to be closely related to the micro-surface properties of coal.To further explore the characteristics of CBM occurrence and migration,in this study,the micro-surface topography,adhesion,and elastic modulus of five metamorphic coals were measured by atomic force microscopy(AFM).The results show that the microtopography of coal fluctuates around 40 nm,reaching a maximum of 66.5 nm and the roughness of the surface decreases with the increase of metamorphism.The elastic modulus of coal micro-surface varies from 95.40 to 9626.41 MPa,while the adhesion varies from 15.08 to 436.22 nN,and they both exhibit a trend of"M"shape with the increase of metamorphism.Furthermore,a high correlation exists between adhesion and microtopography fluctuation.In most cases,the adhesion is larger in the concavity area and smaller in the convexity area.The research results may provide a new method for revealing the occurrence and migration of CBM and ensure efficient and safe CBM exploitation.

关键词： coal atomic force microscopy microtopography adhesion elastic modulus

Experimental characterization of the 3D linear viscoelastic behavior of cold recycled bitumen emulsion mixtures

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Journal of Traffic and Transportation Engineering(English Edition) 2019年第4期6卷 324-336页

作者： Andrea Graziani Carlotta Godenzoni Francesco Canestrari Dipartimento di Ingegneria Civile Edile e Architettura Università Politecnica delle Marche

Cold mixtures with bitumen emulsion are produced at ambient temperature, leading to substantial reductions of energy consumption and atmospheric emissions. In cold recycling applications, cement is normally used to improve the mixture performance. Thus, the rheological behavior of cold recycled mixtures is different from that of conventional hot mixtures because it is due to the interaction of fresh bitumen, aged bitumen and cementitious bonds. In this study, we investigated the three-dimensional(3 D) linear viscoelastic(LVE) behavior of a cement-bitumen treated material(CBTM) mixture fabricated using bitumen emulsion and cement. For comparison, we also investigated the 3 D LVE behavior of hot-mix asphalt containing 25% of reclaimed asphalt and fabricated using polymermodified binder. Sinusoidal axial tests on cylindrical specimens, were carried out at various temperatures(from 0℃ to 50℃) and frequencies(from 0.1 to 12 Hz). The complex Young’s modulus E~*and the complex Poisson’s ratio v~*were determined through the measurement of axial and transverse strain. We show that when considering E*, CBTM mixtures may be considered thermo-rheologically simple and the Huet-Sayegh model can be used to simulate the frequencyetemperature dependence. On the other hand, when considering v*the behavior of CBTM mixtures is very different from that of hot mix asphalt. In particular, its absolute value is almost constant and very close to 0.15.

关键词： Bitumen emulsion Cold recycling Complex modulus Complex Poisson’s ratio Huet-Sayegh model

Influence of polyolefin fibers on the strength and deformability properties of road pavement concrete

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Journal of Traffic and Transportation Engineering(English Edition) 2019年第4期6卷 407-417页

作者： Olga Smirnova Alexey Kharitonov Yuriy Belentsov Department of Constructing Mining Enterprises and Underground Structures Saint-Petersburg Mining UniversitySaint Petersburg 199106Russia Department of Technology of Building Materials and Metrology Saint-Petersburg State University of Architecture and Civil EngineeringSaint Petersburg 190005Russia Department of Building Materials and Technologies Emperor Alexander I St.Petersburg State Transport UniversitySaint Petersburg 190031Russia

Influence of the type and quantity of polyolefin fibers on the strength properties(compression strength, tensile strength in bending, strength in uniaxial tension), the deformation properties(elastic modulus, Poisson’s coefficient) and the abrasion resistance of cement concrete with water-to-cement ratio within 0.31 e0.55 were stated in the paper.The ways of fibers introduction into fresh concrete were investigated. It was shown that the fibers introduction method and procedure of mixing are the ways to improve the fibers uniform distribution in fresh concrete. The increase of the bending tensile strength and the uniaxial tensile strength of concrete with fibers reinforcement in comparison with the reference concrete was observed with the water-to-cement ratio decrease. The increase of uniaxial tensile strength at age of 28 days for concrete with macrofibers in amount of4.5 kg/m^3 was 23% and 29%;for macrofibers in quantity of 3 kg/m^3 was 19% and 26% with water-cement ratio equal to 0.49 and 0.31, respectively. The maximum reduction of abrasion in the range of 7.5%e10% was observed in concrete with water-to-cement ratio within0.44 e0.55 for all investigated types of fibers. The influence of fibers on the concrete abrasion with lower W/C ratio was negligible. The results can contribute to the rational use of modified polyolefin fibers in road pavement concrete.

关键词： Road pavement concrete Polyolefin fibers Strength Elastic modulus Abrasion Water-to-cement ratio

Surface segregation of hydrogen in free-standing Pd-H alloy nanofilms

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Science China(Technological Sciences) 2019年第10期62卷 1735-1746页

作者： CAI Hong MAI JiaWei GAO YingXin HUANG He SUN Sheng ZHANG TongYi Materials Genome Institute Shanghai University

The interaction between mechanics and chemistry plays an essential and critical role in the behaviors and properties of materials,especially in nanoscale alloys. Based on the classical Gibbs and Mc Lean adsorption isotherms, the present study takes the freestanding nanometer thick films of Pd-H solid solutions as a typic example to investigate surface segregation of hydrogen. The surface eigenstress model is further developed here to give analytic formulas, which have the capability to quantitatively predict the size-dependent surface segregation. Molecular dynamics(MD) simulations are conducted on free-standing Pd-H nanofilms.The MD simulations verify the theoretical analytic results and determine the values of parameters involved in the theoretical analysis. The integrated theoretical and numerical study exhibits that both surface excess H concentration and apparent biaxial Young’s modulus of Pd-H thin films depend on the nominal H concentration and the film thickness. The MD simulations determine the values of three parameters involved in the theoretical analysis. Especially, the parameter of the differentiation in reference chemical potential behaves like the molar free energy of segregation in the Mc Lean adsorption isotherm.

关键词： palladium-hydrogen nanofilms the biaxial Young’s modulus concentration

Insight into the role of cholesterol in modulation of morphology and mechanical properties of CH0-K1 cells: An in situ AFM study

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Frontiers of Chemical Science and Engineering 2019年第1期13卷 98-107页

作者： Lei Zhang Lisha Zhao Ping-Kai Ouyang Pu Chen Department of Chemical Engineering and Waterloo Institute for Nanotechnology University of Waterloo Ontario N2L 3G1 Canada College of Biotechnology and Pharmaceutical Engineering Nanjing Tech University Nanjing 211816 China Department of Agricultural Food and Nutritional Science University of Alberta Alberta T6G 2P5 Canada

Cholesterol plays a significant role in the organization of lipids and modulation of membrane dynamics in mammalian cells. However, the effect of cholesterol depletion on the eukaryotic cell membranes seems controversial. In this study, the effects of cholesterol on the topography and mechanical behaviors of CHO-K1 cells with manipulated membrane cholesterol contents were investigated by atomic force microscopy (AFM) technique. Here, we found that the depletion of cholesterol in cell membranes could increase the membrane stiffness, reduce the cell height as well as promote cell retraction and detachment from the surface, whereas the cholesterol restoration could reverse the effect of cholesterol depletion on the membrane stiffness. Increased methyl-β-cyclodextrin levels and incubation time could significantly increase Young’s modulus and degree of stiffing on cell membrane and cytoskeleton. This research demonstratede importance of cholesterol in regulating the dynamics of cytoskeleton-mediated processes. AFM technique offers excellent advantages in the dynamic monitoring of the change in membranes mechanical properties and behaviors during the imaging process. This promising technology can be utilized in studying the membrane properties and elucidating the underlying mechanism of distinct cells in the near-native environment.

关键词： cholesterol methyl-β-cyclodextrin atomic force microscopy Young's modulus CHO-K1 cell

A novel chemical composition estimation model for cement raw material blending process

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Chinese Journal of Chemical Engineering 2019年第11期27卷 2734-2741页

作者： Yaoyao Bao Yuanming Zhu Weimin Zhong Feng Qian Key Laboratory of Advanced Control and Optimization for Chemical Processes of Ministry of Education East China University of Science and TechnologyShanghai 200237China

Raw material blending process is an essential part of the cement production process. The main purpose of the process is to guarantee a certain oxide composition for the raw meal at the outlet of the mill by regulating the four raw materials. But the chemical compositions of raw materials vary from time to time, resulting in difficulties to control the oxide compositions to a predefined value. Therefore, a novel algorithm to estimate the chemical compositions of the raw materials is developed. The paper mainly consists of two parts. In model construction part, a novel constrained least square model is proposed to overcome the deviation introduced by long-term drift of the material components, and the model parameters are estimated with an online strategy. And in validation part, the approach is implemented to two examples including datasets from simulation model and the actual industrial process. The final results show the effectiveness of the proposed method.

关键词： Raw material blending process Chemical component estimation modulus prediction System identification

Effects of existing concrete pavement condition on performance of unbonded jointed plain concrete overlay

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Journal of Traffic and Transportation Engineering(English Edition) 2019年第6期6卷 567-576页

作者： Gauhar Sabih Rafiqul A.Tarefder Department of Civil Engineering University of New MexicoAlbuquerqueNM 87131USA

Unbonded concrete overlay(UBCO) is the most used pavement rehabilitation technique across United States with an overall usage of 47% amongst all the rehabilitation methods.It is aimed to improve the performance of any deteriorated/cracked jointed plain concrete pavement(JPCP).Unbonded JPCP overlay involves placement of a separation layer of hot mix asphalt(HMA),which acts as a stress relief layer between the existing concrete pavement and the overlay.There are numerous factors that affect the design and performance of UBCOs and out of these,existing pavement condition or the severity of damage of existing pavement is a prime factor.The severity of damage is described by the distressed elastic modulus thus,accurate determination of the distressed elastic modulus of the existing concrete pavement is essential for predicting the accurate performance of the unbonded overlay.This study focuses on analyzing the impact of distressed modulus by conducting simulations in the AASHTOWare pavement ME design software version 2.3 and evaluating the predicted performance of JPCP overlay for two different climatic regions.The results indicated that the distressed modulus of existing concrete pavement affects the performance of the overlay with regards to transverse cracking,joint faulting and pavement roughness.Transverse cracking is the most affected performance parameter with a change of 0.27% 2.31% with a unit change in distressed modulus.The impact of climatic conditions on the performance of unbonded overlay was also observed.The adverse effects of distressed modulus can be minimized by reducing the joint spacing or increasing the overlay slab thickness.

关键词： Unbonded concrete overlay Transverse cracking Joint faulting International roughness index Distressed Elastic modulus

Nanoindentation of circular multilayer graphene allotropes

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Science China(Technological Sciences) 2019年第2期62卷 269-275页

作者： HUO ZhanLei GUO ZhengRong LENG JianTao CHANG TienChong Shanghai Institute of Applied Mathematics and Mechanics Shanghai Key Laboratory of Mechanics in Energy EngineeringShanghai University

Nanoindentaion has been proposed as an efficient technique to measure mechanical single-layer two-dimensional(2D) materials via combining the membrane theory with the indentation data. However, for multilayered structures of 2D materials, significant discrepancy exists between the Young's modulus obtained from the existing membrane model and those from other methods.Here we develop a multilayer indentation model by taking the multilayer effect into account in the previous membrane model.We show that the present model can accurately predict the Young's modulus of multilayered 2D carbon materials. For few layer graphene and twin graphene structures, the deviation of the Young's moduli obtained by the present model are both within a reasonable range, while the error caused by the direct use of the previous single-layer membrane model increases with the number of layers. The present model provides an efficient tool to extract the mechanical properties of 2D materials from the nanoindentation data of their multilayered structures.

关键词： nanoindentaion two-dimensional materials Young’s modulus molecular dynamics