The Experts below are selected from a list of 189 Experts worldwide ranked by ideXlab platform
Yiik Diew Wong - One of the best experts on this subject based on the ideXlab platform.
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the influence of Aggregate shape properties on Aggregate Packing in porous asphalt mixture pam
Construction and Building Materials, 2020Co-Authors: Dana Mutiara Kusumawardani, Yiik Diew WongAbstract:Abstract Aggregate shape properties is one of the factors that determine the Packing conditions of asphalt mixtures. The influence of Aggregate shape properties was evaluated by utilising Aggregates in three shapes, namely cubical, blade, and disk. Three shape parameters, namely sphericity, shape factor, and roundness, were defined to quantify the shape properties of the Aggregates. Herein, the influence of Aggregate shape on the Packing of porous asphalt mixture (PAM) was evaluated via comparative studies of PAM’s mechanical properties in laboratory measurements versus discrete element method (DEM) algorithmic simulations. PG-76 binder was used in the PAM, with compaction by a gyratory compactor. Simulation models of PAMs were built in Particle Flow Code in 3 Dimensions (PFC3D) algorithm simulation. The results showed that Aggregate Packing structure is greatly affected by Aggregate shape properties, in terms of volumetric properties and mechanical properties. Statistical analysis results indicated that cubical shape is the recommended shape to optimise the quality of Aggregate Packing structure of PAM. The research provided in-depth analysis of PAM Packing structure, in terms of volumetric and mechanical properties. The results of these experiments indicated that DEM simulation is an appropriate method to evaluate Aggregate Packing structure of PAM.
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evaluation of Aggregate gradation on Aggregate Packing in porous asphalt mixture pam by 3d numerical modelling and laboratory measurements
Construction and Building Materials, 2020Co-Authors: Dana Mutiara Kusumawardani, Yiik Diew WongAbstract:Abstract The Packing conditions of unbound Aggregate blends and porous asphalt mixture (PAM) are investigated via comparative studies between mechanistic laboratory measurements versus discrete element method (DEM) algorithmic simulations. Nine Aggregate gradations with variations in 2.36–4.75 mm and 6.3–9.5 mm fractions were studied. For PAM, PG-76 binder which is a polymer-modified asphalt was used in the mixture, with compaction by gyratory compactor. Simulation models of unbound Aggregate blends and PAMs were built in Particle Flow Code in 3 Dimensions (PFC3D) algorithm simulation. The simulation results were compared with the volumetric measurements of laboratory specimens. The results showed that the proportion of 6.3–9.5 mm fraction does not have notable influence on the Aggregate Packing structure, while 2.36–4.75 mm size fraction has notable influence. The 2.36–4.75 mm fraction has a tendency to either fill the voids of Aggregate Packing or affect re-orientation of stone-on-stone interlocking of the coarser fraction. DEM modelling provides a valuable aid to design feasible PAMs with a desired Packing condition, which shall be supplemented with limited laboratory verifications.
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evaluation of the development of Aggregate Packing in porous asphalt mixture using discrete element method simulation
Road Materials and Pavement Design, 2017Co-Authors: M J Chen, Yiik Diew WongAbstract:Packing in coarse Aggregates is the main factor for porous asphalt mixture's (PAM) resistance to external loading and deformation. Eight PAM gradations were designed, and Aggregate backbone generated in the Aggregate blend with particles larger than 2.36 mm was assessed through voids content in the Aggregates under dry-rodded condition (VADRC) for four types of unbound Aggregate blend (i.e. Blend-1∼Blend-4). Corresponding models, namely Model-1∼Model-4, were generated for each gradation design using discrete element method (DEM). Through the effect of sequentially adding increasingly finer particle components on the voids content, Aggregates larger than 2.36 mm were classified into three categories: main coarse, interceptor, and quasi-fine. The particle-to-particle contact can well explain the development of Packing structure in an assembly of particles via the DEM simulation parameter, mean coordination number in coarser fraction (MCNcr), and MCNcr of an intermediate value indicated adequate interaction ...
Dana Mutiara Kusumawardani - One of the best experts on this subject based on the ideXlab platform.
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the influence of Aggregate shape properties on Aggregate Packing in porous asphalt mixture pam
Construction and Building Materials, 2020Co-Authors: Dana Mutiara Kusumawardani, Yiik Diew WongAbstract:Abstract Aggregate shape properties is one of the factors that determine the Packing conditions of asphalt mixtures. The influence of Aggregate shape properties was evaluated by utilising Aggregates in three shapes, namely cubical, blade, and disk. Three shape parameters, namely sphericity, shape factor, and roundness, were defined to quantify the shape properties of the Aggregates. Herein, the influence of Aggregate shape on the Packing of porous asphalt mixture (PAM) was evaluated via comparative studies of PAM’s mechanical properties in laboratory measurements versus discrete element method (DEM) algorithmic simulations. PG-76 binder was used in the PAM, with compaction by a gyratory compactor. Simulation models of PAMs were built in Particle Flow Code in 3 Dimensions (PFC3D) algorithm simulation. The results showed that Aggregate Packing structure is greatly affected by Aggregate shape properties, in terms of volumetric properties and mechanical properties. Statistical analysis results indicated that cubical shape is the recommended shape to optimise the quality of Aggregate Packing structure of PAM. The research provided in-depth analysis of PAM Packing structure, in terms of volumetric and mechanical properties. The results of these experiments indicated that DEM simulation is an appropriate method to evaluate Aggregate Packing structure of PAM.
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evaluation of Aggregate gradation on Aggregate Packing in porous asphalt mixture pam by 3d numerical modelling and laboratory measurements
Construction and Building Materials, 2020Co-Authors: Dana Mutiara Kusumawardani, Yiik Diew WongAbstract:Abstract The Packing conditions of unbound Aggregate blends and porous asphalt mixture (PAM) are investigated via comparative studies between mechanistic laboratory measurements versus discrete element method (DEM) algorithmic simulations. Nine Aggregate gradations with variations in 2.36–4.75 mm and 6.3–9.5 mm fractions were studied. For PAM, PG-76 binder which is a polymer-modified asphalt was used in the mixture, with compaction by gyratory compactor. Simulation models of unbound Aggregate blends and PAMs were built in Particle Flow Code in 3 Dimensions (PFC3D) algorithm simulation. The simulation results were compared with the volumetric measurements of laboratory specimens. The results showed that the proportion of 6.3–9.5 mm fraction does not have notable influence on the Aggregate Packing structure, while 2.36–4.75 mm size fraction has notable influence. The 2.36–4.75 mm fraction has a tendency to either fill the voids of Aggregate Packing or affect re-orientation of stone-on-stone interlocking of the coarser fraction. DEM modelling provides a valuable aid to design feasible PAMs with a desired Packing condition, which shall be supplemented with limited laboratory verifications.
Shihui Shen - One of the best experts on this subject based on the ideXlab platform.
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impact of Aggregate Packing on dynamic modulus of hot mix asphalt mixtures using three dimensional discrete element method
Construction and Building Materials, 2012Co-Authors: Shihui ShenAbstract:Abstract Aggregates are the major component of hot mix asphalt (HMA) mixtures. The properties of Aggregates and the way of Aggregate Packing have important influence on the performance of HMA mixtures. Because the dynamic modulus is considered as the most important HMA property influencing the field fatigue and rutting performance of a flexible pavement and are used in the mechanistic-empirical pavement design guide for determining the stress–strain responses of the pavements, a study of the impact of Aggregate Packing on dynamic modulus will provide insight on the HMA mix design and the material performance evaluation. This paper studies the effect of Aggregate size distribution and angularity distribution on dynamic modulus using a 3D discrete element method (DEM). Angular particles are generated using an image-based ball-clumping approach which requires significantly reduced number of balls and is capable of capturing the particle shape and angularity effect. These particles are assigned to the DEM dynamic modulus specimen based on the angularity distributions of the actual experimental specimen. A 3D DEM dynamic modulus model is thus established and calibrated using experimental data. This calibrated model is further used to evaluate how the different Aggregate Packing due to the change of the proportions of Aggregate particles and the change of Aggregate angularities can result in the change of dynamic modulus.
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analysis of Aggregate gradation and Packing for easy estimation of hot mix asphalt voids in mineral Aggregate
Journal of Materials in Civil Engineering, 2011Co-Authors: Shihui ShenAbstract:The voids in mineral Aggregate (VMA) design parameter is one of the most important in the current Superpave mix design procedure that links hot-mix-asphalt (HMA) mix properties to field performance. The success of achieving the appropriate VMA at an early stage of the mix-design process not only significantly impacts the design time and effort but also can produce an economical and reasonable design with good field performance. Although several current mix and gradation design methods have provided some guidance on adjusting gradation to achieve target VMA, these approaches still have to rely on initial experimental results with some degree of trial and error, and provide no direct correlation between Aggregate gradation and VMA. This paper presents an analysis of Aggregate Packing and discrete-element modeling (DEM) simulation to link the Aggregate gradation property to the VMA of HMA. A new definition is proposed for characterizing traditional dense-graded Aggregate gradations into three types: coarse-g...
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Characterize Packing of Aggregate particles for paving materials: Particle size impact
Construction and Building Materials, 2011Co-Authors: Shihui Shen, Huanan YuAbstract:Abstract Aggregate Packing directly affects the way of Aggregate particles forming a skeleton to transmit and distribute traffic loads, thus influencing the stability and mechanical performance of the mixtures. Although some efforts have been conducted to evaluate the quality of a designed Aggregate structure, such as the Bailey’s method for hot mix asphalt (HMA) mixture, there is a lack of fundamental understanding of the Aggregate Packing properties. Also how the Packing and degree of Aggregate interlock can be related to mixture performance is not clear. Major reason is because the Aggregate structure is a very complicated system whose Packing characteristics can be affected by both particle size distributions and the particle shape (angularities) distribution. To understand this complex Packing system, our study developed a two-step procedure. As the first step, the size distribution effect is evaluated and the results are presented in this paper. The second step will investigate the combined effect of size distribution and shape impact and the results will be presented in a later paper. Specifically, in this paper we conducted a particle Packing analysis using a discrete element modeling (DEM) simulation method. An HMA mixture gradation typically used in the State of Washington was utilized as a case study example for the analysis. By correlating the gradation parameter to the volumetric properties of the structure, this paper theoretically demonstrated the roles of Aggregate particles with different sizes in an HMA mixture. Contact force chains and mean contact force were calculated using PFC 3 D DEM simulation, which provided an indication of the capability of the Aggregate structure to transmit stresses through Aggregate skeleton, and thereby, to resist permanent deformation. The study conducted here demonstrated the Aggregate size distribution played a significant role in the Packing characteristics, affecting both volumetrics and the contact characteristics of a packed structure. Such findings are critical for evaluating the combined effect of size and shape distribution on Packing, and achieving a performance based Aggregate gradation design.
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impact of Aggregate Packing on dynamic modulus of hot mix asphalt mixtures using discrete element method
Transportation Research Board 90th Annual MeetingTransportation Research Board, 2011Co-Authors: Shihui ShenAbstract:Aggregates are the major component of hot mix asphalt (HMA) mixtures. The properties of Aggregates and the way of Aggregate Packing have important influence on the performance of HMA mixtures. Because the dynamic modulus is considered as the most important HMA property influencing the field fatigue and rutting performance of a flexible pavement, a study of the impact of Aggregate Packing on dynamic modulus will provide insight on the HMA mix design and the material performance evaluation. This paper studies the effect of Aggregate size distribution and angularity distribution on dynamic modulus using a 3D discrete element method (DEM). Angular particles are generated using an image-based ball-clumping approach. These particles are assigned to the DEM dynamic modulus specimen based on the angularity distributions of the actual experimental specimen. A 3D DEM dynamic modulus model is thus established and calibrated using experimental data. Based on the simulation, it is found that the Aggregate Packing, influenced by the Aggregate particle size distribution and angularity distribution, have important impact on dynamic modulus. In general, Aggregates with higher angularity will have higher dynamic modulus. The proportions of particles passing 2.36mm, 4.75mm, and 9.5mm also affect dynamic modulus.
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investigation of Aggregate Packing using discrete element modeling
GeoShanghai 2010 International ConferenceShanghai Society of Civil EngineeringChinese Institute of Soil Mechanics and Geotechnical EngineeringAmerican, 2010Co-Authors: Shihui ShenAbstract:The Packing of Aggregate skeleton directly affects the capability of a mixture to transmit and distribute loads. It has significant impact on the performance hot mix asphalt (HMA) mixtures. This paper conducted an analysis of Aggregate Packing characteristics using a Discrete Element Modeling (DEM) simulation. A Washington typical HMA gradation is used as an example for the analysis. By using the PFC3D DEM simulation to relate the gradation parameter to the volumetric properties of the structure, this paper theoretically demonstrated the different roles of Aggregate particles in an HMA mixture. A new criterion to differentiate "coarse" and "fine" Aggregates is developed, which is consistent with the Bailey’s method definition. Aggregate contacts and contact force are also studied in this paper to evaluate the capability of the Aggregate structure to transmit stresses through Aggregate skeleton, and thereby, to resist permanent deformation. It is suggested that the method described in this paper based on the analysis of Aggregate Packing and DEM simulation provide a promising direction to theoretically understand the characteristics of a packed Aggregate structure, as well as to guide the Aggregate gradation design.
Hussain U. Bahia - One of the best experts on this subject based on the ideXlab platform.
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mechanisms of failure in uniaxial repeated creep test and the relationship to Aggregate Packing
2016Co-Authors: Nima Roohi Sefidmazgi, Hussain U. BahiaAbstract:Rutting performance characterization of asphalt mixtures has attracted lots of attentions after the Strategic Highway Research Program (SHRP). The main reason is the lack of a stability or strength test in the Superpave volumetric criteria. Different test methods and analysis have been proposed with a goal of accurately as well as simply predicting the rutting performance of designed mixtures. A uniaxial repeated creep and recovery test is recommended in NCHRP 456 report (i.e. Flow number test) as a performance characterization test method, and it is currently being used by researchers extensively. This study is focused on comparing the mechanisms and fundamental properties that control the performance of asphalt mixtures throughout the uniaxial flow number testing. It is shown that Aggregate Packing, as measured using an image analysis method, is the key property affecting deformation characteristics in uniaxial testing. Additionally, it is shown that the main cause of tertiary flow of mixtures in the flow number test is structural instability and bulging (dilation) of Aggregate skeleton. Aggregate skeleton discontinuities at outer layers of samples are observed after failure in the tertiary zone. It is observed that mixtures with better Aggregate Packing showed a better rutting performance due to lower stress level within the binder phase due to Aggregate skeleton serving as the main stress path, and the Aggregates in proximity or contact showed a supporting structure, which delays the tertiary flow in material, and reduces the rate of permanent deformation. Based on these observations, it is shown that applying confinement has a very significant effect in preventing tertiary flow conditions by maintaining the Aggregate Packing, thus improving rutting resistance of asphalt mixtures.
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low temperature mechanics of hot recycled mixtures through asphalt thermal cracking analyzer atca
Construction and Building Materials, 2015Co-Authors: Arianna Stimilli, Pouya Teymourpour, Francesco Canestrari, Hussain U. BahiaAbstract:Abstract Thermal cracking is recognized as a critical failure mode for bituminous mixtures and good fracture properties are a key factor to obtain long lasting asphalt pavements in cold climate. Investigating this aspect in hot recycled mixtures with high amount of Reclaimed Asphalt Pavement (RAP) is fundamental due to the stiffening effect of aged bitumen that can emphasize the cracking aptitude of the mixture when subjected to thermal stresses. An innovative tool for characterizing the low-temperature cracking behavior of asphalt mixtures is the new developed Asphalt Thermal Cracking Analyzer (ATCA). It allows the evaluation of several parameters (e.g. glass transition temperature, coefficients of contraction, cracking temperature) directly related to the mechanics of low-temperature performance. In this study, four recycled asphalt mixtures were produced in laboratory with 40% of RAP using the Bailey Method as tool to optimize the Aggregate structure. Different binder contents and modified bitumens (with various level of polymer modification) were employed. An additional mixture with 25% of RAP was used as control mixture. All the mixes were tested using the ATCA device. Moreover, an original image analysis was performed to assess at a microscale level the effects of compaction properties and Aggregate structure on thermal cracking response. Results show that mixtures with 40% of RAP can behave better than the control mixture at low temperature if an accurate mix design is performed. Careful selection of RAP material and type and quantity of virgin bitumen can enhance low temperature performance and Aggregate Packing although high amount of RAP Aggregates.
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mechanisms controlling shearing resistance of mixtures in the superpave gyratory compactor
Transportation Research Board 94th Annual MeetingTransportation Research Board, 2015Co-Authors: Nima Roohi Sefidmazgi, Hussain U. BahiaAbstract:Rutting performance characterization of asphalt mixtures has attracted a lot of attention after the implementation of the Superpave Volumetric Mixture design method due to the lack of a stability or strength test in the volumetric design criteria. Different test and analysis methods have been proposed with a goal of accurately, as well as simply, predicting the rutting performance of designed mixtures. The simplicity and cost effectiveness of using the Superpave Gyratory Compactor (SGC) made many researchers interested to find a fundamental and practical way for rutting characterization during compaction. One of the promising tools used for characterization of asphalt mixture internal friction and stability during compaction in SGC is the Gyratory Pressure Distribution Analyzer (GPDA). This study is focused on understanding the mechanisms and fundamental material characteristics that control the shearing resistance of asphalt mixtures throughout the compaction in SGC. The main cause of reduction in internal friction of some mixtures during compaction is shown to be the buildup of pore binder pressure and static liquefaction at lower air voids although some other factors may affect this phenomenon as well. It is shown that the mixtures with lower Aggregate Packing, measured using an image analysis method in this study, are more prone to reduction in internal friction. It is thus necessary to ensure that higher Packing and more contact points be formed by selection of gradation to reduce the risk of instability resulting from liquefaction (loss of internal friction). Measuring internal friction is a necessary compliment to volumetric mixture design.
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Effect of compaction conditions on Aggregate Packing using 2-dimensional image analysis and the relation to performance of HMA
Materials and Structures, 2014Co-Authors: Nima Roohi Sefidmazgi, Hussain U. BahiaAbstract:Characterization of the asphalt mixture microstructure using two dimensional (i.e., 2-D) imaging techniques could be an economically efficient approach. However, the features that have been captured and quantified using 2-D imaging techniques in most published research are limited to simplistic analyses of Aggregate structure. This paper focuses on introducing a more elaborate method for characterization of the internal structure of Aggregates to define performance related parameters that could be used as quality indicators of mixes. These indicators are proposed as important properties that complement the volumetric properties so wide relied on for acceptance of mixture designs. The results of the study show that Aggregate structure can be characterized using a combination of newly developed image analysis indices namely: number of Aggregate-to-Aggregate proximity zones, total proximity zone length, and proximity zone plane orientation. A software developed in a previous study and significantly modified for this study, is used to process digital images of a set of asphalt mixtures with different gradations, binder contents, types of modification, compaction efforts, compaction temperatures, and methods. The results demonstrate that the internal structure indices correlate well with rutting performance, as well as with low temperature thermal contraction of asphalt mixtures. Additionally, the indices can be successfully used to show the effects of compaction effort, compaction method and temperature, gradation of Aggregates, and binder modification on the mixture internal structure. The results indicate potential for using this method for quality control of mixtures during production.
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role of asphalt modification in achieving better Aggregate Packing structure and performance
PROCEEDINGS OF THE FIFTY-EIGHTH ANNUAL CONFERENCE OF THE CANADIAN TECHNICAL ASPHALT ASSOCIATION (CTAA): ST. JOHN'S NEWFOUNDLAND AND LABRADOR NOVEMBER , 2013Co-Authors: Pouya Teymourpour, Sm Hacker, Hussain U. BahiaAbstract:Asphalt modifiers have been widely used to improve the engineering characteristics of asphalt mixtures. It has been commonly assumed that the main cause of this improvement is the change in binder rheological characteristics. Furthermore, use of modifiers has been known to affect compaction temperatures. However, what has not been considered in the past is the influence of asphalt modifiers on changing the Aggregate structure of the mix during compaction. Recently, a number of studies using image analysis tools have shown that Aggregate Packing has a significant impact on mixture performance. In this study, an image analysis tool ("iPas2") has been used in combination with binder, mastic and mixture tests to study the effect of selecting a modifier and a combination of modifiers (elastomeric and plastomeric) on the Performance Grade (PG), as well as the effect on Aggregate structure and performance for a number of mixtures compacted at different temperatures. The results allowed the identification of the relative importance of binder PG and Aggregate skeleton changes on the high and low temperature response of asphalt mixtures. Results show that careful selection of modifiers can enhance performance of binders as well as Aggregate structure when compaction is conducted at optimum temperatures. (A) For the covering abstract of this conference see ITRD record number 201402RT334E.
Qiao Dong - One of the best experts on this subject based on the ideXlab platform.
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evaluation of Aggregate Packing based on thickness distribution of asphalt binder mastic and mortar within asphalt mixtures using multiscale methods
Construction and Building Materials, 2019Co-Authors: Jiwang Jiang, Linyi Yao, Qiao DongAbstract:Abstract Aggregate Packing is a key factor controlling the durability of asphalt mixtures. Considering the complex system of the Aggregate structures, multiscale method was utilized by dividing asphalt mixtures into four scales, including asphalt binder, mastic, mortar and asphalt mixtures. Six asphalt mixtures with different gradation types and nominal maximum Aggregate size (NMAS) were prepared and the corresponding mastics or mortars were also designed. Comprehensive image analysis methods, including high-resolution scanning, Scanning Electron Microscope (SEM), and Laser Diffraction Analyzer (LDA), were utilized to obtain the 2D images of asphalt mixtures, mortars and mastics. Then, the distribution curves of the binder within mastics, mastic within mortars, and mortar within asphalt mixtures were calculated and compared. New Packing indexes were proposed, such as: expected value (E binder ) and peak value (P binder ) of the binder distribution at mastic scale, expected value (E mastic ) and peak value (P mastic ) of the mastic distribution at mortar scale, expected value (E mortar ) and peak value (P mortar ) of the mortar distribution at mixture scale. By comparing with volumetric parameters, it was found that E binder and P binder could correlate well with the volume ratio of filler to mastic. E mastic could correlate with the volume fraction of fine Aggregate within the mortar, but the P mastic may also influence by the fine Aggregate gradation. The void filled with asphalt (VFA) has weak correlation with both Packing indexes, E mortar and P mortar , which indicates that VFA has limitation for evaluation of the Packing properties of asphalt mixtures, and more indexes from the internal structure need to be considered.