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The maintenance management decisions of network-level asphalt pavements have long been a challenge to highway agencies, and a great amount of factors have been involved. In this study, a network-level optimization method was established by integrating the maintenance benefits into the zero-one programming optimization model. An optimized performance evaluation method of asphalt pavement was proposed which contains 11 different kinds of combinations. The benefit model quantifies the cost savings of user travel time and vehicle fuel consumption to the pavement condition index (PCI) and ride quality index (RQI), respectively. Based on the simplified evaluation method as well as the quantified maintenance benefit model, an optimization model was established by employing the zero-one programming. This optimization model aimed to maximize the improvements/price ratio of pavement maintenance for the whole pavement network. The calculation results present the optimal strategies of maintenance for every road section in the network. The applicability of the newly proposed model was validated by a case study. The methodology developed in this study helps to offer guidelines to highway agencies in managing and making decisions about network-level pavement maintenance.
Leilei Chen; Zepeng Fan; Pengfei Liu; Zhendong Qian. Optimization Model of Network-Level Pavement Maintenance Decision considering User Travel Time and Vehicle Fuel Consumption Costs. Advances in Civil Engineering 2021, 2021, 1 -9.
AMA StyleLeilei Chen, Zepeng Fan, Pengfei Liu, Zhendong Qian. Optimization Model of Network-Level Pavement Maintenance Decision considering User Travel Time and Vehicle Fuel Consumption Costs. Advances in Civil Engineering. 2021; 2021 ():1-9.
Chicago/Turabian StyleLeilei Chen; Zepeng Fan; Pengfei Liu; Zhendong Qian. 2021. "Optimization Model of Network-Level Pavement Maintenance Decision considering User Travel Time and Vehicle Fuel Consumption Costs." Advances in Civil Engineering 2021, no. : 1-9.
The aggregate skeleton significantly influences the deformation resistance of asphalt mixtures. A stable skeleton has good interlocking effects and load transfer ability to resist deformation of mixtures during loading. Therefore, the methodology to accurately evaluate the morphology of aggregate skeleton based on the mechanism of load transfer inside mixtures is of great value to predict the mixture stability. The objective of this study is to predict and validate mixture stability from the perspective of evolutional morphologies of the skeleton. The methodology has three main steps, which are as follows: (1) the initial morphology of the aggregate skeleton is characterized and evaluated; (2) the topological and non-topological evolutions of the skeleton morphology during external loading are characterized; and (3) the strain energy of the mixture and the stress distribution on contact regions in the skeleton are used to analyze and validate the prediction of the mixture's stability. Simulations of uniaxial displacement-controlled tests of three cylindrical specimens drilled in a field-compacted test track were conducted, and 7.5, 15, 22.5, and 30 s were selected as time points in the simulation to analyze mixture stability. Results indicate that a mixture has a better load-bearing capacity when its initial skeleton contains more chains with higher evaluation indices, which proves the reliability of the stability prediction using the proposed method.
Can Jin; Xiaodong Wan; Pengfei Liu; Xu Yang; Markus Oeser. Stability prediction for asphalt mixture based on evolutional characterization of aggregate skeleton. Computer-Aided Civil and Infrastructure Engineering 2021, 1 .
AMA StyleCan Jin, Xiaodong Wan, Pengfei Liu, Xu Yang, Markus Oeser. Stability prediction for asphalt mixture based on evolutional characterization of aggregate skeleton. Computer-Aided Civil and Infrastructure Engineering. 2021; ():1.
Chicago/Turabian StyleCan Jin; Xiaodong Wan; Pengfei Liu; Xu Yang; Markus Oeser. 2021. "Stability prediction for asphalt mixture based on evolutional characterization of aggregate skeleton." Computer-Aided Civil and Infrastructure Engineering , no. : 1.
The properties of pavement materials strongly affect the service performance of the pavement. Although technical standards are commonly referenced to filter out unqualified materials, the method of deciding the optimal material remains unclear. This study proposes a decision-making framework based on the fuzzy comprehensive evaluation (FCE) and analytic hierarchy process (AHP). In this framework, several experiment-based indexes have been adopted to evaluate the service performance of pavement materials from different perspectives. Each index was quantitatively graded into five grades according to the fuzzy mathematics theories. The weights of the involved indexes were determined using AHP. The proposed decision-making framework was applied to selecting the optimal mineral filler from four types of mineral fillers for the pavement structure in a selected region. The proposed method combined the qualitative and quantitative factors and thus improved the credibility of the material applicability evaluation.
Zeyu Zhang; Pengfei Liu; Mrinali Rochlani; Gustavo Canon Falla; Sabine Leischner; Markus Oeser. A fuzzy comprehensive evaluation method to select the optimal mineral filler for optimization of the performance of asphalt mastics. Construction and Building Materials 2021, 298, 123847 .
AMA StyleZeyu Zhang, Pengfei Liu, Mrinali Rochlani, Gustavo Canon Falla, Sabine Leischner, Markus Oeser. A fuzzy comprehensive evaluation method to select the optimal mineral filler for optimization of the performance of asphalt mastics. Construction and Building Materials. 2021; 298 ():123847.
Chicago/Turabian StyleZeyu Zhang; Pengfei Liu; Mrinali Rochlani; Gustavo Canon Falla; Sabine Leischner; Markus Oeser. 2021. "A fuzzy comprehensive evaluation method to select the optimal mineral filler for optimization of the performance of asphalt mastics." Construction and Building Materials 298, no. : 123847.
Currently, recovering the natural hydrological cycle and lowering urban flood risk are global challenges. A permeable pavement with void-rich pavement materials, such as porous asphalt (PA), is one feasible and effective measure. Due to the specific gradation, fillers can considerably influence the performance of PA mixtures. In this study, the effect of four different fillers (limestone, dolomite, rhyolite, and granodiorite) on the mechanical responses of PA mixtures was investigated by the numerical method. X-ray computer tomography (X-ray CT) and digital image processing (DIP) were applied to detect and reconstruct the microstructure of PA specimens. Finite-element (FE) analysis was conducted to simulate an indirect tensile test and by this means the mechanical responses of the PA mixtures (load-bearing capacity, von Mises stress, and creep strain) were computed and compared. The results show that the different fillers have significant influence on the mechanical responses of PA mixtures. Based on the computational results, the correlation between the mechanical responses of PA mixtures and filler properties was analyzed. In addition, the performance of PA mixtures with different fillers was ranked. Based on this ranking, it is possible to select an optimal filler to facilitate the improvement of permeable pavement design.
Pengfei Liu; Guoyang Lu; Xu Yang; Can Jin; Sabine Leischner; Markus Oeser. Influence of Different Fillers on Mechanical Properties of Porous Asphalt Mixtures Using Microstructural Finite-Element Analysis. Journal of Transportation Engineering, Part B: Pavements 2021, 147, 04021004 .
AMA StylePengfei Liu, Guoyang Lu, Xu Yang, Can Jin, Sabine Leischner, Markus Oeser. Influence of Different Fillers on Mechanical Properties of Porous Asphalt Mixtures Using Microstructural Finite-Element Analysis. Journal of Transportation Engineering, Part B: Pavements. 2021; 147 (2):04021004.
Chicago/Turabian StylePengfei Liu; Guoyang Lu; Xu Yang; Can Jin; Sabine Leischner; Markus Oeser. 2021. "Influence of Different Fillers on Mechanical Properties of Porous Asphalt Mixtures Using Microstructural Finite-Element Analysis." Journal of Transportation Engineering, Part B: Pavements 147, no. 2: 04021004.
To investigate the damage behavior of asphalt pavements under the combination of temperature fields and traffic loadings, a two-dimensional (2D) mesostructure-based finite-element method was developed. Temperature fields in an asphalt pavement at midday and midnight of summer and winter seasons were considered according to real air temperature data of an inland city in China. The mesostructure of the asphalt concrete layer was established based on digital image processing (DIP) technology from the cross-section image of an asphalt mixture specimen. A multiscale simulation approach was employed to link the mechanical behaviors of the asphalt concrete layer at different length scales. During the simulation, the traffic and temperature loadings were applied to the macroscale pavement model; subsequently, the strain responses and temperature distributions were extracted from critical positions of the pavement and transferred to the mesoscale model. In addition, the thermal expansion/contraction behavior of the asphalt mixture was taken into account. In this way, the stress distributions and damage behavior of the asphalt pavement induced by both the traffic tire loadings and temperature variations were well simulated while considering the heterogeneous features of the asphalt mixture. The results showed that the thermal expansion/contraction induced by the temperature changes had a significant influence on the maximum principal stress distributions within the asphalt layer, which further can influence the damage behavior of the asphalt pavements. In particular, significant thermal stress caused by the temperature variation appeared on the top of the asphalt concrete (AC) layer in the winter, and the thermal expansion/contraction can affect remarkably the pavement responses at midnight in the winter.
Cong Du; Yiren Sun; Jingyun Chen; Changjun Zhou; Pengfei Liu; Dawei Wang; Markus Oeser. Coupled Thermomechanical Damage Behavior Analysis of Asphalt Pavements Using a 2D Mesostructure-Based Finite-Element Method. Journal of Transportation Engineering, Part B: Pavements 2021, 147, 04021012 .
AMA StyleCong Du, Yiren Sun, Jingyun Chen, Changjun Zhou, Pengfei Liu, Dawei Wang, Markus Oeser. Coupled Thermomechanical Damage Behavior Analysis of Asphalt Pavements Using a 2D Mesostructure-Based Finite-Element Method. Journal of Transportation Engineering, Part B: Pavements. 2021; 147 (2):04021012.
Chicago/Turabian StyleCong Du; Yiren Sun; Jingyun Chen; Changjun Zhou; Pengfei Liu; Dawei Wang; Markus Oeser. 2021. "Coupled Thermomechanical Damage Behavior Analysis of Asphalt Pavements Using a 2D Mesostructure-Based Finite-Element Method." Journal of Transportation Engineering, Part B: Pavements 147, no. 2: 04021012.
The microstructure variation plays an essential role in the micro-mechanical performance of the bitumen and the macro-mechanical behavior of asphalt mixtures. This research aims to reveal the influence of the microstructure changes of bitumen on its micromechanical responses. Based on atomic force microscopy (AFM) technology, the microstructure (bee structure: bee, peri, and interstitial phases) of the bitumen was detected. With the self-developed microstructural finite element (FE) models, the micromechanical responses of bitumen with different bee structures were comprehensively simulated. The results show that the computational load-bearing capacity of the bitumen increases with an increase of the peri phase content, but the difference is not significant. The development of high stresses within the bee phase is mainly due to the inhomogeneity of the material. Additionally, the distribution of the tensile strain becomes more homogeneous with the increase of the peri phase content. This research contributes to establishing a better understanding of the relationship between the microstructure of the bitumen and its micromechanical properties.
Cong Du; Pengfei Liu; Kaloyan Ganchev; Guoyang Lu; Markus Oeser. Influence of microstructure evolution of bitumen on its micromechanical property by finite element simulation. Construction and Building Materials 2021, 293, 123522 .
AMA StyleCong Du, Pengfei Liu, Kaloyan Ganchev, Guoyang Lu, Markus Oeser. Influence of microstructure evolution of bitumen on its micromechanical property by finite element simulation. Construction and Building Materials. 2021; 293 ():123522.
Chicago/Turabian StyleCong Du; Pengfei Liu; Kaloyan Ganchev; Guoyang Lu; Markus Oeser. 2021. "Influence of microstructure evolution of bitumen on its micromechanical property by finite element simulation." Construction and Building Materials 293, no. : 123522.
In micromechanical simulations of asphalt mixtures, complex shapes of asphalt mortar and coarse aggregates require numerous elements in the finite element (FE) representation. This makes simulation time‐consuming with a high risk of failure. To conduct simulations with acceptable accuracy and low computational cost, an approach is proposed to simplify the geometry of mixture microstructures with error assessment due to simplification. The methodology comprises four main steps, as follows: (1) coarse aggregates in a specimen are three‐dimensionally reconstructed to conduct surface triangulation; (2) surface triangles are then clustered with a predefined fitting accuracy using the least square method; (3) coarse aggregates are simplified as polyhedrons based on triangle clusters, and the asphalt mortar is then reconstructed using Boolean operations; and (4) the simulation error caused by simplification is assessed based on FE interpolation theory to ensure the reliability of the simulation. Two samples were prepared and then reconstructed for the simulation of a cyclic indirect tensile test. The volume difference for more than 95% aggregates was less than 5% for the two specimens. The difference of stress and strain curves of original and simplified models of the two specimens ranged from 2% to 4%, which indicates that the simulation solutions of the simplified and original microstructures were very close. Furthermore, computational time was significantly reduced due to the simplification of the aggregates. This method facilitates the reliable and highly efficient simulation of asphalt mixtures using the FE method.
Can Jin; Wuxing Zhang; Pengfei Liu; Xu Yang; Markus Oeser. Morphological simplification of asphaltic mixture components for micromechanical simulation using finite element method. Computer-Aided Civil and Infrastructure Engineering 2021, 1 .
AMA StyleCan Jin, Wuxing Zhang, Pengfei Liu, Xu Yang, Markus Oeser. Morphological simplification of asphaltic mixture components for micromechanical simulation using finite element method. Computer-Aided Civil and Infrastructure Engineering. 2021; ():1.
Chicago/Turabian StyleCan Jin; Wuxing Zhang; Pengfei Liu; Xu Yang; Markus Oeser. 2021. "Morphological simplification of asphaltic mixture components for micromechanical simulation using finite element method." Computer-Aided Civil and Infrastructure Engineering , no. : 1.
Cold-mixed epoxy bitumen (CEB) has been presented as an eco-friendly paving material used for steel bridge deck pavements. This study performed an investigation on three preparation methods of CEBs, which includes one kind of three-component and two kinds of two-component methods. The curing process was characterized through the viscosity measurement. Meanwhile, the microstructure of CEBs was observed using fluorescence microscopy. Mechanical properties of CEBs prepared with different methods were characterized by employing direct tensile tests and dynamic mechanical analysis (DMA). Finally, thermogravimetric analysis (TGA/DTG) was conducted to feature the thermal stability of CEBs. The results indicated that the preparation methods significantly affected the performance of cured CEBs, although the same mix design was adopted. The curing temperature determined the curing rate of CEBs, while the preparation methods dominated the morphological characteristic of cured CEBs. The three-component preparation method can achieve acceptable mechanical performance for engineering requirements. As for two-component methods, the curing agent is supposed to be mixed with bitumen to obtain satisfying microstructures of CEBs.
Quan Liu; Chonghui Wang; Zeyu Zhang; Cong Du; Pengfei Liu; Markus Oeser. Influence of preparation methods on the performance of cold-mixed epoxy bitumen. Materials and Structures 2021, 54, 1 -13.
AMA StyleQuan Liu, Chonghui Wang, Zeyu Zhang, Cong Du, Pengfei Liu, Markus Oeser. Influence of preparation methods on the performance of cold-mixed epoxy bitumen. Materials and Structures. 2021; 54 (2):1-13.
Chicago/Turabian StyleQuan Liu; Chonghui Wang; Zeyu Zhang; Cong Du; Pengfei Liu; Markus Oeser. 2021. "Influence of preparation methods on the performance of cold-mixed epoxy bitumen." Materials and Structures 54, no. 2: 1-13.
The piezoelectric energy harvester (PEH) is a device for recycling wasted mechanical energy from pavements. To evaluate energy collecting efficiency of PEHs with various piezoelectric unit distributions, finite element (FE) models of the PEHs were developed in this study. The PEH was a square of 30 cm × 30 cm with 7 cm in thickness, which was designed according to the contact area between tire and pavement. Within the PEHs, piezoelectric ceramics (PZT-5H) were used as the core piezoelectric units in the PEHs. A total of three distributions of the piezoelectric units were considered, which were 3 × 3, 3 × 4, and 4 × 4, respectively. For each distribution, two diameters of the piezoelectric units were considered to investigate the influence of the cross section area. The electrical potential, total electrical energy and maximum von Mises stress were compared based on the computational results. Due to the non-uniformity of the stress distribution in PEHs, more electrical energy can be generated by more distributions and smaller diameters of the piezoelectric units; meanwhile, more piezoelectric unit distributions cause a higher electrical potential difference between the edge and center positions. For the same distribution, the piezoelectric units with smaller diameter produce higher electrical potential and energy, but also induce higher stress concentration in the piezoelectric units near the edge.
Cong Du; Pengfei Liu; Hailu Yang; Gengfu Jiang; Linbing Wang; Markus Oeser. Finite Element Modeling and Performance Evaluation of Piezoelectric Energy Harvesters with Various Piezoelectric Unit Distributions. Materials 2021, 14, 1405 .
AMA StyleCong Du, Pengfei Liu, Hailu Yang, Gengfu Jiang, Linbing Wang, Markus Oeser. Finite Element Modeling and Performance Evaluation of Piezoelectric Energy Harvesters with Various Piezoelectric Unit Distributions. Materials. 2021; 14 (6):1405.
Chicago/Turabian StyleCong Du; Pengfei Liu; Hailu Yang; Gengfu Jiang; Linbing Wang; Markus Oeser. 2021. "Finite Element Modeling and Performance Evaluation of Piezoelectric Energy Harvesters with Various Piezoelectric Unit Distributions." Materials 14, no. 6: 1405.
A locally homogeneous finite element (FE) model is proposed to account for the heterogeneous internal structures of asphalt mixtures in this study. For this model, the internal structure of the asphalt mixture was divided into several homogeneous parts based on digital image processing (DIP) technology. Within each part, one aggregate or air void inclusion was embedded in asphalt mortar, and the integral material properties were homogenized. By comparison with the currently used mesoscale heterogeneous FE models, the proposed locally homogeneous model was proven to be able to effectively consider the local enhancement of the aggregates especially at low frequencies and also consume much less computational time. In addition, the locally homogeneous asphalt mixtures were coupled into the macroscale asphalt pavement model to analyze the load-bearing capacity of the pavements. Comparing with a fully homogeneous pavement model, the computational results showed that the proposed locally homogeneous model can effectively represent the loading-bearing responses of asphalt pavements. This study indicates that this proposed FE simulation approach is able to balance the computational time and simulation effectivity and thus form a base for providing an efficient and robust platform for future development in the multiscale simulation of asphalt pavements.
Cong Du; Pengfei Liu; Quan Liu; Sabine Leischner; Yiren Sun; Jingyun Chen; Markus Oeser. Development of locally homogeneous finite element model for simulating the mesoscale structure of asphalt mixture. Computers & Structures 2021, 248, 106517 .
AMA StyleCong Du, Pengfei Liu, Quan Liu, Sabine Leischner, Yiren Sun, Jingyun Chen, Markus Oeser. Development of locally homogeneous finite element model for simulating the mesoscale structure of asphalt mixture. Computers & Structures. 2021; 248 ():106517.
Chicago/Turabian StyleCong Du; Pengfei Liu; Quan Liu; Sabine Leischner; Yiren Sun; Jingyun Chen; Markus Oeser. 2021. "Development of locally homogeneous finite element model for simulating the mesoscale structure of asphalt mixture." Computers & Structures 248, no. : 106517.
Porous asphalt (PA) pavements are widely employed in areas with wet climates. As particle enhancement inclusions in asphalt mastic, mineral fillers play essential roles in improving the performance of PA pavements. This study developed a coupled multiscale finite element (FE) model, involving the mesostructure of PA mixture and PA pavement. Four types of mastic properties were employed with four mineral fillers (Granodiorite, Limestone, Dolomite, and Rhyolite) in the mesoscale portion of the pavement model to analyse the effects of filler types on the performance of pavements. The performances (load-bearing capacity, rutting resistance, and ravelling resistance) of pavements with different fillers were identified and ranked, and their correlations with the chemical components of the four fillers were analysed. The computational results showed that pavements with Rhyolite and Granodiorite fillers have higher load-bearing capacities and rutting resistance, while the Limestone and Dolomite fillers can improve the ravelling resistance of the PA pavements. In the correlation analysis, the chemical components Al2O3 and SiO2 play dominant roles in improving the load-bearing capacities and rutting resistance of the PA pavements, and the fillers with high percentages of CaO can improve the ravelling resistance of the PA pavements.
Cong Du; Guoyang Lu; HaoPeng Wang; Yiren Sun; Pengfei Liu; Dawei Wang; Sabine Leischner; Markus Oeser. Effect of filler on performance of porous asphalt pavement using multiscale finite element method. International Journal of Pavement Engineering 2021, 1 -11.
AMA StyleCong Du, Guoyang Lu, HaoPeng Wang, Yiren Sun, Pengfei Liu, Dawei Wang, Sabine Leischner, Markus Oeser. Effect of filler on performance of porous asphalt pavement using multiscale finite element method. International Journal of Pavement Engineering. 2021; ():1-11.
Chicago/Turabian StyleCong Du; Guoyang Lu; HaoPeng Wang; Yiren Sun; Pengfei Liu; Dawei Wang; Sabine Leischner; Markus Oeser. 2021. "Effect of filler on performance of porous asphalt pavement using multiscale finite element method." International Journal of Pavement Engineering , no. : 1-11.
Aggregates in contact constitute the skeleton of the asphalt mixture and affect load transmission in the mixture, which determines its deformation resistance. The objective of this study is to characterize the aggregate skeleton for the evaluation of the stability of the asphalt mixture. The methodology has four main steps: (1) aggregates in specimens are three-dimensionally (3D) reconstructed before surface triangulation; (2) the geometry and orientation of contact areas between aggregates are detected to obtain the contact network of aggregates; (3) effective contacts are identified to determine force chains represented by a weighted directed graph; and (4) all force chains constitute the aggregate skeleton, which is then evaluated for load transfer efficiency by the characterization of the skeleton. Simulations of compression tests on three virtual specimens with different skeletons were conducted to obtain the stress and strain distribution within the mixture. The results indicate that a skeleton with a higher evaluation index has a more uniform stress and strain distribution, which indicates that the mixture bears the load better to resist deformation. The proposed method also facilitates the study of the correlation between the mixture stability and the gradation and morphology of aggregates.
Can Jin; Xiaodong Wan; Xu Yang; Pengfei Liu; Markus Oeser. Three-Dimensional Characterization and Evaluation of Aggregate Skeleton of Asphalt Mixture Based on Force-Chain Analysis. Journal of Engineering Mechanics 2021, 147, 04020147 .
AMA StyleCan Jin, Xiaodong Wan, Xu Yang, Pengfei Liu, Markus Oeser. Three-Dimensional Characterization and Evaluation of Aggregate Skeleton of Asphalt Mixture Based on Force-Chain Analysis. Journal of Engineering Mechanics. 2021; 147 (2):04020147.
Chicago/Turabian StyleCan Jin; Xiaodong Wan; Xu Yang; Pengfei Liu; Markus Oeser. 2021. "Three-Dimensional Characterization and Evaluation of Aggregate Skeleton of Asphalt Mixture Based on Force-Chain Analysis." Journal of Engineering Mechanics 147, no. 2: 04020147.
Titanium dioxide (TiO2) is widely used to purify air pollutants in environmental engineering, but it is only activated by ultraviolet (UV) light. The metal or nonmetal single doping of TiO2 cannot observably improve the purification efficiency of TiO2 under visible light. To further increase the photocatalytic activity and purification efficiency of TiO2 on vehicle exhaust under visible light, nitrogen (N)-vanadium (V) co-doped TiO2 was first prepared. The influences of N–V co-doping on phase structures, morphology, microstructures, electronic structures, and photo-absorption performances were then observed and examined using X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and UV–visible light diffuse reflectance spectra. Purification efficiency and reaction rates of N–V co-doped TiO2 on NOx, HC, CO and CO2 in vehicle exhaust were studied using a purification test system under UV and visible light irradiations, respectively. Results indicate that N and V are synchronously doped into the crystal structures of TiO2 to replace O and Ti, respectively. N and V show the synergistic co-doping effect to suppress the grain growth of TiO2 and improve the dispersity and specific surface area of TiO2. Also, the N–V co-doping introduces more lattice distortions and defects in the crystal lattices of TiO2. Further, N presents in the form of Ti–O–N and O–Ti–N bonds, and V exists in the form of V5+ and V4+. These form the impurity energy level in the band gap to narrow the energy band of TiO2. Additionally, the N–V co-doping broadens the photoabsorption threshold of TiO2 from 387 nm to 611 nm. These results show that N–V co-doping increases the photocatalytic activity of TiO2. Finally, the N–V co-doped TiO2 shows higher catalytic purification efficiency on NOx and HC under UV and visible light. The N–V co-doping obviously increases the purification efficiency of TiO2 on CO and CO2 when exposed to visible light, and their reversible reactions are not found. The N–V co-doping of TiO2 is a feasible approach to purify vehicle exhaust under visible light irradiations.
Zhihui Hu; Tao Xu; Pengfei Liu; Markus Oeser. Microstructures and optical performances of nitrogen-vanadium co-doped TiO2 with enhanced purification efficiency to vehicle exhaust. Environmental Research 2020, 193, 110560 .
AMA StyleZhihui Hu, Tao Xu, Pengfei Liu, Markus Oeser. Microstructures and optical performances of nitrogen-vanadium co-doped TiO2 with enhanced purification efficiency to vehicle exhaust. Environmental Research. 2020; 193 ():110560.
Chicago/Turabian StyleZhihui Hu; Tao Xu; Pengfei Liu; Markus Oeser. 2020. "Microstructures and optical performances of nitrogen-vanadium co-doped TiO2 with enhanced purification efficiency to vehicle exhaust." Environmental Research 193, no. : 110560.
The interfacial behavior between bitumen and aggregate is not well understood so far since it is sensitive to various factors including chemistry of the components, morphology of the interface, and the environmental and loading conditions. Moreover, the mechanisms of action for different factors occur at distinct time and length scales. The multi-factor and multi-scale natures bring great challenge to the interfacial behavior between bitumen and aggregate. This study aims to exploit a deep understanding of the interfacial behavior from the perspective of aggregate mineralogy at the molecular scale and relate this fundamental understanding to affinity between bitumen and aggregate. For this, the affinity between bitumen and six kinds of aggregates were evaluated by the rolling bottle test, and adhesion mechanisms between bitumen and component minerals were investigated through molecular dynamics simulations. The rolling bottle test results show that the diabase has the best moisture damage resistance, followed by the greywacke I, basalt and greywacke II. The two granite aggregates show the worst moisture damage resistance. The molecular dynamics simulation indicates the existence of competitive adsorption between bitumen and water molecules at the mineral surface, and the penetration capacity of bitumen molecule is greatly affected by the mineral property. Aggregates with higher content of nepheline, chlorite, pyroxene and olivine minerals are more likely exhibit better moisture damage resistance while aggregates with higher content of quartz, plagioclase and calcite minerals do the opposite. The findings from this research provide insights into the underlying mechanism of aggregate mineralogy influence on affinity between bitumen and aggregate.
Zepeng Fan; Jiao Lin; Zixuan Chen; Pengfei Liu; Dawei Wang; Markus Oeser. Multiscale understanding of interfacial behavior between bitumen and aggregate: From the aggregate mineralogical genome aspect. Construction and Building Materials 2020, 271, 121607 .
AMA StyleZepeng Fan, Jiao Lin, Zixuan Chen, Pengfei Liu, Dawei Wang, Markus Oeser. Multiscale understanding of interfacial behavior between bitumen and aggregate: From the aggregate mineralogical genome aspect. Construction and Building Materials. 2020; 271 ():121607.
Chicago/Turabian StyleZepeng Fan; Jiao Lin; Zixuan Chen; Pengfei Liu; Dawei Wang; Markus Oeser. 2020. "Multiscale understanding of interfacial behavior between bitumen and aggregate: From the aggregate mineralogical genome aspect." Construction and Building Materials 271, no. : 121607.
To reduce the thermal-oxidative aging of asphalt and the release amount of harmful volatiles during the construction of asphalt pavement, a new composite anti-aging agent was developed. Since the volatiles were mainly released from saturates and aromatics during the thermal-oxidative aging of asphalt, expanded graphite (EG) was selected as a stabilizing agent to load magnesium hydroxide (MH) and calcium carbonate (CaCO3) nanoparticles for preparing the anti-aging agents of saturates and aromatics, respectively. Thermal stability and volatile constituents released from saturates and aromatics before and after the thermal-oxidative aging were characterized using the isothermal Thermogravimetry/Differential Scanning Calorimetry-Fourier Transform Infrared Spectrometer test (TG/DSC-FTIR test). Test results indicate that anti-aging agents of EG/MH and EG/CaCO3 effectively inhibit the volatilization of light components in asphalt and improve the thermal stability of saturates and aromatics. Then, the proportions of EG, MH, and CaCO3 added in the developed composite anti-aging agent of EG/MH/CaCO3 are 2:1:3 by weight. EG/MH/CaCO3 plays a synergetic effect on inhibiting the thermal-oxidative aging of asphalt, and reduces the release amount of harmful volatiles during the thermal-oxidative aging after EG/MH/CaCO3 is added into asphalt at the proposed content of 10 wt.%. EG plays a synergistic role with MH and CaCO3 nanoparticles to prevent the chain reactions, inhibiting the thermal-oxidative aging of asphalt.
Zhihui Hu; Tao Xu; Pengfei Liu; Markus Oeser; HaoPeng Wang. Improvements of Developed Graphite Based Composite Anti-Aging Agent on Thermal Aging Properties of Asphalt. Materials 2020, 13, 4005 .
AMA StyleZhihui Hu, Tao Xu, Pengfei Liu, Markus Oeser, HaoPeng Wang. Improvements of Developed Graphite Based Composite Anti-Aging Agent on Thermal Aging Properties of Asphalt. Materials. 2020; 13 (18):4005.
Chicago/Turabian StyleZhihui Hu; Tao Xu; Pengfei Liu; Markus Oeser; HaoPeng Wang. 2020. "Improvements of Developed Graphite Based Composite Anti-Aging Agent on Thermal Aging Properties of Asphalt." Materials 13, no. 18: 4005.
This study aims to understand the damage evolution of water-saturated asphalt mixture under freeze-thaw cyclic loading from the perspective of continuum damage mechanics (CDM). The connective void content of three types of asphalt mixtures was employed to characterize the damage to the corresponding asphalt mixture sample under freeze-thaw cyclic loading. The variation of connective void content revealed the nonlinear characteristics of asphalt mixture damage accumulation. A CDM-based model was built to describe the damage evolution law of asphalt mixture. The results predicted by this model agreed with the experimental data, validating its feasibility.
Zeyu Zhang; Quan Liu; Qi Wu; Huining Xu; Pengfei Liu; Markus Oeser. Damage evolution of asphalt mixture under freeze-thaw cyclic loading from a mechanical perspective. International Journal of Fatigue 2020, 142, 105923 .
AMA StyleZeyu Zhang, Quan Liu, Qi Wu, Huining Xu, Pengfei Liu, Markus Oeser. Damage evolution of asphalt mixture under freeze-thaw cyclic loading from a mechanical perspective. International Journal of Fatigue. 2020; 142 ():105923.
Chicago/Turabian StyleZeyu Zhang; Quan Liu; Qi Wu; Huining Xu; Pengfei Liu; Markus Oeser. 2020. "Damage evolution of asphalt mixture under freeze-thaw cyclic loading from a mechanical perspective." International Journal of Fatigue 142, no. : 105923.
Spatial variations of soil properties occur even within nominally homogeneous soil layers. To perform a reliable geotechnical design, it is necessary to consider local variations of soil properties. A varying soil stiffness leads to spatially variable settlements which imply increasing dynamic forces on passing vehicles. Higher dynamic forces result in additional settlements and simultaneously reduce driving comfort. This process continues steadily until a repair of the asphalt pavement is required. The aim of this paper is to provide a new mechanically reasoned method in order to derive the permissible spatial variation of Continuous Compaction Control data from driving comfort requirements. Therefore, a numerical model is presented which allows for modeling the long-term evenness of asphalt pavements due to passing vehicles taking into account a spatial variation of the subsoil stiffness. The numerical model is based on subgrade reaction method modeling surface and subjacent base courses by a series ofspring elements. Thereby, a depth-dependent stress distribution and interaction of base courses are considered. The initial stiffness of the spring elements is derived from oedometer tests. Depending on traffic load and utilisation period, the long-term evenness of the asphalt pavement and effects of a spatially varying subsoil stiffness are investigated.
Anne Stark; Tom Törzs; Jürgen Grabe. Permissible spatial variation of CCC data from driving comfort requirements over time. Proceedings of the Institution of Civil Engineers - Geotechnical Engineering 2020, 173, 319 -326.
AMA StyleAnne Stark, Tom Törzs, Jürgen Grabe. Permissible spatial variation of CCC data from driving comfort requirements over time. Proceedings of the Institution of Civil Engineers - Geotechnical Engineering. 2020; 173 (4):319-326.
Chicago/Turabian StyleAnne Stark; Tom Törzs; Jürgen Grabe. 2020. "Permissible spatial variation of CCC data from driving comfort requirements over time." Proceedings of the Institution of Civil Engineers - Geotechnical Engineering 173, no. 4: 319-326.
Emulsified asphalt (EA) is an environment-friendly paving material that is commonly used as the binder of the interlay stress-absorbing composite (ISAC) layer. Roughening the surface of glass fiber by chemical treating is an effective approach to improve the adhesion between glass fiber and EA. However, the effects of the fiber treatment method on the performance of fiber-reinforced EA (FEA) still remain unclear. In this study, glass fiber, which is commonly used in the ISAC layer, was firstly treated with six methods (three etchants in two concentrations). Fibers were then incorporated into EA to prepare FEA samples. Finally, laboratory tests, including Scanning electron microscope (SEM) test, Fourier-transform infrared spectroscopy (FTIR) test, contact angle test, surface tension test, dynamic shear rheometer (DSR) test, and direct tensile test, were performed to evaluate the changes in the physical and chemical properties of glass fiber, EA, and FEA. The experimental results indicated that etching roughened the surface of glass fiber, increased the adhesion work of EA-glass fiber and the fracture strength of FEA. In addition, it was found that the interaction between glass fiber and EA was physical bonding and the performance of FEAs depended on the glass fiber treatment method. Sulfuric acid with a concentration of 2 mol/L was recommended as the optimal glass fiber etchant.
Yanyan Liu; Zeyu Zhang; Lijuan Tan; Yong Xu; Chonghui Wang; Pengfei Liu; Huayang Yu; Markus Oeser. Laboratory evaluation of emulsified asphalt reinforced with glass fiber treated with different methods. Journal of Cleaner Production 2020, 274, 123116 .
AMA StyleYanyan Liu, Zeyu Zhang, Lijuan Tan, Yong Xu, Chonghui Wang, Pengfei Liu, Huayang Yu, Markus Oeser. Laboratory evaluation of emulsified asphalt reinforced with glass fiber treated with different methods. Journal of Cleaner Production. 2020; 274 ():123116.
Chicago/Turabian StyleYanyan Liu; Zeyu Zhang; Lijuan Tan; Yong Xu; Chonghui Wang; Pengfei Liu; Huayang Yu; Markus Oeser. 2020. "Laboratory evaluation of emulsified asphalt reinforced with glass fiber treated with different methods." Journal of Cleaner Production 274, no. : 123116.
To reveal the influencing factors and changing rules for the hydrothermal interaction process of highway subgrade, the field measurements of Shiwei-Labudalin Highway in Inner Mongolia, China was conducted for 3 years, based on which the freezing-thawing rules and water content changing characteristics were analyzed. The main results show the subgrade presents a frequent freezing-thawing alternation, and the water content of subgrade exhibits an obvious seasonal alternation. The subbase has the maximum water content, while the base has the minimum water content. The change of water flux is concentrated in the thawing period and consistent with the change of temperature gradient. The subbase layer has the most active water flux due to the heat absorption and impermeability of pavement that easily causes the water accumulation in this layer. Therefore, the prevention and treatment for the freezing-thawing disease should be started from heat insulation and water resistance.
Hong-Wei Zhang; Xue-Ying Wang; Xin Zhao; Peng-Fei Liu. In-situ experiment investigations of hydrothermal process of highway in deep seasonal frozen soil regions of Inner Mongolia, China. Journal of Central South University 2020, 27, 2082 -2093.
AMA StyleHong-Wei Zhang, Xue-Ying Wang, Xin Zhao, Peng-Fei Liu. In-situ experiment investigations of hydrothermal process of highway in deep seasonal frozen soil regions of Inner Mongolia, China. Journal of Central South University. 2020; 27 (7):2082-2093.
Chicago/Turabian StyleHong-Wei Zhang; Xue-Ying Wang; Xin Zhao; Peng-Fei Liu. 2020. "In-situ experiment investigations of hydrothermal process of highway in deep seasonal frozen soil regions of Inner Mongolia, China." Journal of Central South University 27, no. 7: 2082-2093.
Permeable pavements are widely recognized as an effective way to improve the environmental and ecological aspects of conventional dense pavements. Based on traditional pavement materials, permeable pavements are often designed to be partially permeable or to consist of merely permeable surfaces. Recently, the development of novel polyurethane-bound pervious mixtures (PUPM) has made the widespread application of fully permeable pavement (FPP) structures possible, which will increase the environmental benefits of permeable pavements. In this case, the saturation of a pavement has a major influence on the performance of FPP. The generation and dissipation of pore pressure is recognized as a critical factor, influencing the bearing capacity of permeable pavement structures. In literature, only few studies focus on the pore pressure in permeable pavements under traffic loading. This study aims to measure and characterize the changes in pore pressure in a full-scale permeable pavement under various saturation conditions under traffic loading. To achieve this objective, pore pressure data was collected from laboratory testing as well as from a full-scale test track constructed with a polyurethane-bounded pervious mixture (PUPM) wearing course. Based on this study, it is found that when permeable pavement material is subjected to cyclic loading, the pore water pressure is much larger than the pore air pressure; in fact, the latter is found to be negligible. During the irrigation process and dynamic vehicle loading, the pore water pressure increases as the saturation increases. The changes of pore water pressure are not obvious in the PUPM surface layer when comparing the results to the pervious layers below the wearing course. Under cyclic vehicle loading, the accumulated pore water pressure of each layer increases with the number of loading cycles and also increases as the saturation increases. These findings support the quest for an in-depth understanding of the stress state and the degradation mechanisms in FPP. The results provide practical conclusions and recommend optimized design properties for a wide application of FPP.
Guoyang Lu; Tom Törzs; Pengfei Liu; Zeyu Zhang; Dawei Wang; Markus Oeser; Jürgen Grabe. Dynamic Response of Fully Permeable Pavements: Development of Pore Pressures under Different Modes of Loading. Journal of Materials in Civil Engineering 2020, 32, 04020160 .
AMA StyleGuoyang Lu, Tom Törzs, Pengfei Liu, Zeyu Zhang, Dawei Wang, Markus Oeser, Jürgen Grabe. Dynamic Response of Fully Permeable Pavements: Development of Pore Pressures under Different Modes of Loading. Journal of Materials in Civil Engineering. 2020; 32 (7):04020160.
Chicago/Turabian StyleGuoyang Lu; Tom Törzs; Pengfei Liu; Zeyu Zhang; Dawei Wang; Markus Oeser; Jürgen Grabe. 2020. "Dynamic Response of Fully Permeable Pavements: Development of Pore Pressures under Different Modes of Loading." Journal of Materials in Civil Engineering 32, no. 7: 04020160.