scholarly journals Investigation on the Micro Deformation Mechanism of Asphalt Mixtures under High Temperatures Based on a Self-Developed Laboratory Test

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1791
Author(s):  
Jilu Li ◽  
Wei Guo ◽  
Anxin Meng ◽  
Meizhao Han ◽  
Yiqiu Tan
Keyword(s):  
Current Flow ◽  
Asphalt Mixture ◽  
Asphalt Mixtures ◽  
Particle Flow Code ◽  
Mechanism Of Formation ◽  
Coarse Aggregates ◽  
Load Location ◽  
Micro Deformation ◽  
Aggregate Amount ◽  
Reduced Scale

Rutting has always been considered the main disease in asphalt pavement. Dealing with rutting disease would be benefitted by understanding the formation of rutting and testing the rutting performance of mixtures more reasonably. The objective of this paper is to systematically investigate the rutting mechanism by employing a self-designed rutting tester along with the corresponding numerical simulations. The deformation of different positions of the existing tracking tester was found to be inconsistent, and the loading was not in line with reality. Accordingly, a more practical tester was proposed: the reduced scale circular tracking (RSCT) tester integrates the functions of asphalt mixture fabrication and rutting monitoring. The results demonstrated that the loading of the new tester is closer to the actual situation. In addition, determining the stress and displacement characteristics of particles in the asphalt mixture was found to be difficult due to the limitations of the testing methods. Therefore, a two-dimensional virtual rutting test based on the RSCT was built using PFC2D (Particle Flow Code 2 Dimension) to investigate the mechanism of formation in rutting and to obtain the corresponding guidance. The numerical simulation showed that all particles of the specimen tended to move away from the load location. The main cause of rutting formation was the eddy current flow of asphalt mastic driven by coarse aggregates. The aggregates with diameters ranging from 9.5 to 4.75 mm were observed to have the greatest contribution to rutting deformation. Therefore, the aggregate amount of these spans should be focused on in the design of mixture grading.

scholarly journals Laboratory Evaluation of the Use of Florida Washed Shell in Open-Graded Asphalt Mixtures

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7060
Author(s):  
Mohammad Alharthai ◽  
Qing Lu ◽  
Ahmed Elnihum ◽  
Asad Elmagarhe
Keyword(s):  
Tensile Strength ◽  
Asphalt Mixture ◽  
Asphalt Mixtures ◽  
Indirect Tensile Strength ◽  
Laboratory Evaluation ◽  
Void Content ◽  
Coarse Aggregates ◽  
Significant Difference ◽  
Indirect Tensile ◽  
Marshall Stability

This study investigates the substitution of conventional aggregate with a Florida washed shell in open-graded asphalt mixtures and evaluates the optimal substitution percentage in aggregate gradations of various nominal maximum aggregate sizes (NMASs) (i.e., 4.75, 9.5, and 12.5 mm). Laboratory experiments were performed on open-graded asphalt mixture specimens with the coarse aggregate of sizes between 2.36 and 12.5 mm being replaced by the Florida washed shell at various percentages (0, 15, 30, 45, and 100%). Specimen properties relevant to the performance of open-graded asphalt mixtures in the field were tested, evaluated, and compared. Specifically, a Marshall stability test, Cantabro test, indirect tensile strength test, air void content test, and permeability test were conducted to evaluate the strength, resistance to raveling, cracking resistance, void content, and permeability of open-graded asphalt mixtures. The results show that there is no significant difference in the Marshall stability and indirect tensile strength when the coarse aggregates are replaced with Florida washed shell. This study also found that the optimum percentages of Florida washed shell in open-graded asphalt mixture were 15, 30, and 45% for 12.5, 9.5, and 4.75 mm NMAS gradations, respectively.

scholarly journals Pavement Analysis and Design by Multiphysics Reconstructing Algorithm for the Virtual Asphalt Mixture Based on the Discrete-Element Method

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Danhua Wang ◽  
Xunhao Ding ◽  
Tao Ma ◽  
Weiguang Zhang ◽  
Deyu Zhang
Keyword(s):  
Asphalt Mixture ◽  
Two Dimensions ◽  
Shape Modeling ◽  
Particle Flow Code ◽  
Stochastic Algorithm ◽  
Analysis And Design ◽  
Coarse Aggregates ◽  
Simulation Efficiency ◽  
Actual Ratio ◽  
Compressive Tests

Based on the Particle Flow Code in Two dimensions (PFC2D), an algorithm for modeling the two-dimensional virtual asphalt mixture was proposed in this study. By combining the AIMS scanning technology (Aggregate Imaging Measurement System) with the designed stochastic algorithm, the virtual coarse aggregates could be generated rapidly and precisely. Different from the conventional methods, the contour shapes of the coarse aggregates were rebuilt only to balance the shape modeling precision and simulation efficiency. Then by distributing the coarse particles within container, virtual skeletons were formed firstly. An innovate algorithm was proposed afterwards to distinguish the external and internal area of the coarse aggregates and then model the mastic part by filling the irregular hollow shape with uniformly arranged balls. By deleting the mastic balls randomly, the voids were reconstructed consistent with the actual ratio. In the end, the virtual uniaxial compressive tests of AC-16 were simulated within PFC2D and the dynamic modulus at different load frequencies was predicted. The results indicated that the proposed algorithm could not only model the asphalt mixture precisely but also characterized its mechanical behavior as well.

scholarly journals Shear Deformation Behavior of a Double-Layer Asphalt Mixture Based on the Virtual Simulation of a Uniaxial Penetration Test

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3700
Author(s):  
Changjiang Kou ◽  
Xiaohui Pan ◽  
Peng Xiao ◽  
Aihong Kang ◽  
Zhengguang Wu
Keyword(s):  
Shear Deformation ◽  
Double Layer ◽  
Deformation Behavior ◽  
Lower Layer ◽  
Asphalt Mixture ◽  
Element Model ◽  
Discrete Element ◽  
Asphalt Mixtures ◽  
Penetration Test ◽  
Coarse Aggregates

This paper aims to clarify the shear deformation behavior of double-layer asphalt mixtures using the virtual uniaxial penetration test (UPT) with a discrete element method. For this purpose, asphalt mixtures with two different nominal maximum aggregate sizes were designed for the preparation of double-layer wheel tracking test specimens. Then, the cylindrical cores were prepared from the specimens and were cut for capturing the longitudinal profile images. These images were used to reconstruct a two-dimensional discrete element model (DEM) of the uniaxial penetration test specimen. The results indicate that the shear deformation behavior of the asphalt mixtures showed corresponding changes under the virtual loading. The tensile and compressive stress were distributed unevenly within the upper layer after the test, and both coarse aggregates and asphalt mortars bore a greater shear stress. Therefore, cracks were more likely to occur in the upper layer, leading to the failure of the specimens. This process enhanced the bonding between the asphalt mortars and the mineral aggregates. The aggregate particles in the upper layer moved more vertically, while those in the lower layer generally moved more laterally under the virtual loading. This behavior reveals the rutting mechanism of asphalt pavement.

scholarly journals The Effect of Morphological Characteristic of Coarse Aggregates Measured with Fractal Dimension on Asphalt Mixture’s High-Temperature Performance

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Hainian Wang ◽  
Yin Bu ◽  
Yanzhe Wang ◽  
Xu Yang ◽  
Zhanping You
Keyword(s):  
Fractal Dimension ◽  
High Temperature ◽  
Los Angeles ◽  
Coarse Aggregate ◽  
Asphalt Mixture ◽  
Great Influence ◽  
Asphalt Mixtures ◽  
Morphological Properties ◽  
Coarse Aggregates ◽  
Temperature Performance

The morphological properties of coarse aggregates, such as shape, angularity, and surface texture, have a great influence on the mechanical performance of asphalt mixtures. This study aims to investigate the effect of coarse aggregate morphological properties on the high-temperature performance of asphalt mixtures. A modified Los Angeles (LA) abrasion test was employed to produce aggregates with various morphological properties by applying abrasion cycles of 0, 200, 400, 600, 800, 1000, and 1200 on crushed angular aggregates. Based on a laboratory-developed Morphology Analysis System for Coarse Aggregates (MASCA), the morphological properties of the coarse aggregate particles were quantified using the index of fractal dimension. The high-temperature performances of the dense-graded asphalt mixture (AC-16), gap-graded stone asphalt mixture (SAC-16), and stone mastic asphalt (SMA-16) mixtures containing aggregates with different fractal dimensions were evaluated through the dynamic stability (DS) test and the penetration shear test in laboratory. Good linear correlations between the fractal dimension and high-temperature indexes were obtained for all three types of mixtures. Moreover, the results also indicated that higher coarse aggregate angularity leads to stronger high-temperature shear resistance of asphalt mixtures.

scholarly journals Investigating the Functions of Particles in Packed Aggregate Blend using a Discrete Element Method

Materials ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 556 ◽  
Author(s):  
Yinghao Miao ◽  
Weixiao Yu ◽  
Yue Hou ◽  
Liyan Guo ◽  
Linbing Wang
Keyword(s):  
Discrete Element Method ◽  
Mechanical Characteristics ◽  
Asphalt Mixture ◽  
Discrete Element ◽  
Asphalt Mixtures ◽  
Coarse Aggregates ◽  
And Function ◽  
Skeleton Structure ◽  
Element Method ◽  
Aggregate Particles

In asphalt mixture, aggregates account for up to 90% of the total volume and play an important role in the mechanical characteristics of asphalt mixture. The proportions of fine and coarse aggregates in gradation, as well as the function of aggregate particles, are important factors for the skeleton structure performance of asphalt mixtures. However, the existing asphalt mixture design methods are mostly based on empirical methods, where the non-uniformity and complexity of the composition of asphalt mixtures are not fully studied. In this study, the skeleton structure of aggregate mixture and function of aggregate are studied and analyzed using the Discrete Element Method (DEM). The Particle Flow 3D (PFC3D) DEM program is used to perform the numerical simulation. The average contact number and interaction forces by aggregate particles of different sizes are obtained and studied. The skeleton structure of aggregate mixture and function of aggregate particles are further analyzed from the meso-structural perspective.

scholarly journals Effect of Gradation Segregation on Mechanical Properties of an Asphalt Mixture

2019 ◽  
Vol 9 (2) ◽  
pp. 308 ◽  
Author(s):  
Wenliang Wu ◽  
Zhixian Tu ◽  
Zihan Zhu ◽  
Zeyu Zhang ◽  
Yongjie Lin
Keyword(s):  
Mechanical Properties ◽  
Asphalt Pavement ◽  
Contact Point ◽  
Asphalt Mixture ◽  
Asphalt Mixtures ◽  
Service Performance ◽  
Particle Flow ◽  
Particle Flow Code ◽  
Vertical Load ◽  
Aggregate Distribution

Gradation segregation strongly affects the service performance of asphalt pavement. However, rare studies focus on the influences of segregation on asphalt mixture as it is difficult to simulate segregation in a laboratory. This paper presents a research aiming to evaluate the effects of gradation segregation using the two dimensional (2D) discrete element method (DEM). To achieve this objective, the gradation segregation levels are defined according to the differences between control and segregated gradations. Based on this, asphalt mixtures with three gradations at three segregation levels were selected. The corresponding 2D DEM models were then built using Particle Flow Code 2D (PFC 2D). The aggregate skeletons in the asphalt mixture were determined separately by means of the contact point and contact force. Based on this, the variations on the aggregate skeleton, aggregate distribution, and mechanical properties of the asphalt mixture under vertical load were studied at three different segregation levels. This study indicates that the aggregate skeleton in asphalt mixture can be affected by the gradation segregation. The correlation between gradation segregation and mechanical property is also determined in this study.

Research on Asphalt Mixture Force Chains Identification Criteria Based on Computational Granular Mechanics

2020 ◽  
Author(s):  
Guoqiang Liu ◽  
Yuanyuan Pan ◽  
Yongli Zhao ◽  
Jian Zhou ◽  
Jing Li ◽  
...  
Keyword(s):  
Contact Force ◽  
Asphalt Concrete ◽  
Asphalt Mixture ◽  
Threshold Value ◽  
Asphalt Mixtures ◽  
Force Chains ◽  
Particle Flow Code ◽  
External Loading ◽  
The Difference ◽  
Skeleton Structure

The difference of force chains can be used to evaluate asphalt mixture skeleton structure. In this study, different asphalt mixture discrete element method (DEM) models were established via the two dimensional particle flow code (PFC2D) software to analyze force chains identification criteria. And then, the force chains lengths of different asphalt mixtures were quantified preliminarily. Results indicate that the average contact force <F> need to be set as the contact force threshold value. 45o is recommended as the angle threshold value. For asphalt mixtures, less than 50% aggregate content is involved in transferring external loading. Whether the aggregate is located on the force chains should be regarded as an important criterion to judge whether the aggregate is involved in the asphalt mixture skeleton composition. Although dense-graded asphalt concrete (AC) will generate many force chains, most of them are short length force chains that are not conducive to transferring loading.

A Hybrid Model to Predict the Gyratory Compaction of Hot Mixed Asphalt

2019 ◽  
Author(s):  
Teng Man
Keyword(s):  
Hybrid Model ◽  
Asphalt Binder ◽  
Asphalt Mixture ◽  
Aggregate Size ◽  
Asphalt Mixtures ◽  
Compaction Process ◽  
Particle Rearrangement ◽  
Compaction Behavior ◽  
Grain Size Distributions ◽  
Gyratory Compaction

The compaction of asphalt mixture is crucial to the mechanical properties and the maintenance of the pavement. However, the mix design, which based on the compaction properties, remains largely on empirical data. We found difficulties to relate the aggregate size distribution and the asphalt binder properties to the compaction behavior in both the field and laboratory compaction of asphalt mixtures. In this paper, we would like to propose a simple hybrid model to predict the compaction of asphalt mixtures. In this model, we divided the compaction process into two mechanisms: (i) visco-plastic deformation of an ordered thickly-coated granular assembly, and (ii) the transition from an ordered system to a disordered system due to particle rearrangement. This model could take into account both the viscous properties of the asphalt binder and grain size distributions of the aggregates. Additionally, we suggest to use the discrete element method to understand the particle rearrangement during the compaction process. This model is calibrated based on the SuperPave gyratory compaction tests in the pavement lab. In the end, we compared the model results to experimental data to show that this model prediction had a good agreement with the experiments, thus, had great potentials to be implemented to improve the design of asphalt mixtures.

Utilization of Dacite as Alternative Aggregate in Asphalt Mixture

2012 ◽  
Vol 509 ◽  
pp. 209-214
Author(s):  
Shao Peng Wu ◽  
Pan Pan ◽  
Ming Yu Chen
Keyword(s):  
Asphalt Mixture ◽  
Asphalt Mixtures ◽  
Major Objective ◽  
Widespread Application ◽  
Bending Tests ◽  
Three Point Bending ◽  
Large Numbers ◽  
Asphalt Content ◽  
The Cost ◽  
Cost Of Construction

With the widespread application of asphalt mixture, current demand from transportation managers for construction and maintenance of their pavement network consumes large numbers of aggregates. If agencies excessively favor to some certain kinds of excellent aggregates, the cost of construction could be considerably expensive. The major objective of this study is to determine the feasibility of utilizing dacite in asphalt mixtures. By means of Marshall, freeze-thaw, rutting and three-point bending tests, the performances of dacite and basalt asphalt mixture are compared. The results of the testing illustrate that dacite asphalt mixture is more susceptible to gradation and asphalt content than basalt asphalt mixture. Meanwhile it is showed that the performances of dacite asphalt mixture can be improved greatly with the involvement of additives including active mineral powder and cement. Furthermore, it is validated that dacite can be used as alternative aggregate in asphalt mixture.

scholarly journals Chemical and Physical Properties of Limestone Powder as a Potential Microfiller of Polymer Composites

2017 ◽  
Vol 63 (2) ◽  
pp. 67-78 ◽  
Author(s):  
M. Kępniak ◽  
P. Woyciechowski ◽  
W. Franus
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Physical Properties ◽  
Polymer Composites ◽  
Asphalt Mixture ◽  
Limestone Powder ◽  
Coarse Aggregates ◽  
Mineral Powder ◽  
Materials Used ◽  
Scanning Electron

Abstract The preliminary stage of asphalt mixture production involves the drying and dedusting of coarse aggregates. The most common types of coarse aggregates used are limestone and basalt. In the process of drying and dedusting the dryer filter accumulates large quantities of waste in the form of mineral powder. This paper introduces an investigation into limestone powder waste as a potential microfiller of polymer composites. Physical characteristics such as the granulation the of powder collected from the filter - in terms of the season of its collection and the type of input materials used - were analysed. A scanning electron microscope (SEM) was used for the investigation described within this paper. The obtained results were compared against those of other materials which can be used as polymer composites microfillers.

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