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Tom Scullion - One of the best experts on this subject based on the ideXlab platform.
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RDD Data Interpretation and Its Application on Evaluating Concrete Pavements for Asphalt Overlays
Journal of Performance of Constructed Facilities, 2012Co-Authors: Fujie Zhou, Sheng Hu, Darhao Chen, Tom ScullionAbstract:The placement of an Asphalt Overlay is the most common method to rehabilitate existing concrete pavements. Reflective cracking, however, has been a serious problem with Asphalt Overlays for a long time. To prevent reflective cracking, it is critical to evaluate existing concrete pavements and identify the joints/cracks with poor load-transfer efficiency (LTE) before placing an Asphalt Overlay. The most common equipment for this evaluation is a falling weight deflectometer (FWD). However, FWD testing is conducted only at discrete points and is time consuming. It is desirable to use the rolling dynamic deflectometer (RDD) that can continuously characterize each slab and all joints and cracks (e.g., LTE). The RDD was developed in the 1990s at the Center for Transportation Research in Austin, Texas. The RDD is one of the few operational rolling deflection systems that provide continuous data to make project level decisions on rehabilitating concrete pavements. In contrast to the FWD, no RDD data analysis software is available. This paper discusses RDD data interpretation and its application on evaluating existing concrete pavement for Asphalt Overlays. First of all, some basics of RDD deflection data interpretation are discussed. Several common patterns within the RDD data are identified, and associated interpretation and limited verification are presented in this paper. The RDD deflection data measured before an Asphalt Overlay on Interstate Highway-20, Texas, and the observed Asphalt Overlay performance (in terms of reflective cracking) are then presented, and the relationship between RDD deflection and reflective cracking rate is further investigated. Finally, guidelines for evaluating existing concrete pavements using RDD are proposed.
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Reflection Cracking–Based Asphalt Overlay Thickness Design and Analysis Tool:
Transportation Research Record, 2010Co-Authors: Sheng Hu, Fujie Zhou, Tom ScullionAbstract:An Asphalt Overlay is one of the primary options for rehabilitating existing Asphalt and concrete pavements. Reflection cracking, however, has been a serious concern associated with Asphalt Overlays for a long time. Currently, reflection cracking is not considered in most existing Asphalt Overlay thickness design programs, including the Mechanistic-Empirical Pavement Design Guide developed under the NCHRP Project 1-37A. Therefore, there is an urgent need to develop a reflection cracking-based Asphalt Overlay thickness design and analysis tool for routine use. Three reflection cracking mechanisms (bending, shearing, and thermal stress) and mechanistic modeling are discussed according to fracture mechanics concepts. A mechanistic-empirical reflection cracking model is first proposed and then developed into an Asphalt Overlay thickness design and analysis framework. This framework is further implemented into a Windows-based design program, making it more convenient for pavement engineers to optimize Asphalt ...
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reflection cracking based Asphalt Overlay thickness design and analysis tool
Transportation Research Record, 2010Co-Authors: Sheng Hu, Fujie Zhou, Tom ScullionAbstract:An Asphalt Overlay is one of the primary options for rehabilitating existing Asphalt and concrete pavements. Reflection cracking, however, has been a serious concern associated with Asphalt Overlays for a long time. Currently, reflection cracking is not considered in most existing Asphalt Overlay thickness design programs, including the Mechanistic-Empirical Pavement Design Guide developed under the NCHRP Project 1-37A. Therefore, there is an urgent need to develop a reflection cracking-based Asphalt Overlay thickness design and analysis tool for routine use. Three reflection cracking mechanisms (bending, shearing, and thermal stress) and mechanistic modeling are discussed according to fracture mechanics concepts. A mechanistic-empirical reflection cracking model is first proposed and then developed into an Asphalt Overlay thickness design and analysis framework. This framework is further implemented into a Windows-based design program, making it more convenient for pavement engineers to optimize Asphalt ...
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advanced Asphalt Overlay thickness design and analysis system
Journal of the Association of Asphalt Paving Technologists, 2010Co-Authors: Fujie Zhou, Sheng Hu, Tom ScullionAbstract:The placement of an Asphalt Overlay is the most common method used by many state Departments of Transportation (DOT) to rehabilitate existing flexible and rigid pavements. To perform well, an Asphalt Overlay must have a good balance of rutting and reflective cracking performance. The main objective of this paper is to present a comprehensive mechanistic-empirical (M-E) Asphalt Overlay thickness design system to assist pavement engineers to design a balanced Asphalt Overlay based on traffic loadings, climate, the existing pavement conditions, and the engineering properties of the Asphalt Overlay mix. The design system developed incorporates models for both reflective cracking and rutting of the proposed Asphalt Overlay. The Paris’ law-based reflective cracking model was chosen and further developed for predicting reflective cracking development. The required fracture properties of an Asphalt Overlay can be easily determined using the Overlay Tester. The proposed reflective cracking model was calibrated using a variety of Overlay test sections including the LTPP-SPS5 sections on US175 near Dallas, Texas, and then verified using the California Heavy Vehicle Simulator test results. To predict Asphalt Overlay rutting, the well-known VESYS layer rutting model was adopted and later calibrated using the field rutting data from the National Center for Asphalt Technology ( NCAT) test track 2006 and LTPP-SPS5 on US175. The material properties required for this model were obtained from repeated load tests. The reliability and accuracy of the calibrated rutting model was further validated using one set of independent rutting data from NCAT test track 2000. The calibrated reflective cracking and rutting models were then integrated into an Asphalt Overlay thickness design and analysis program. A sensitivity analysis was conducted to identify the significant parameters influencing the predicted levels of reflective cracking and rutting. It was found that the six most important input parameters are 1) traffic loading level, 2) climate, 3) Asphalt Overlay thickness, 4) Overlay mix type, 5) Asphalt binder type, 6) load transfer efficiency (LTE). Furthermore, it was also noticed that Asphalt Overlay life in terms of reflective cracking is not linearly proportional to Overlay thickness. A four in. Asphalt Overlay can have more than twice the life of a 3 in. Overlay. The proposed Asphalt Overlay thickness design and analysis program provides the designer with a tool to compute pavement life in terms of rutting and reflective cracking. The system permits the designer to use up to two different Overlay mixes such as a crack relief layer and a wearing surface. The system is fully operational and undergoing implementation within the Texas Department of Transportation (TxDOT).
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mechanistic empirical Asphalt Overlay thickness design and analysis system
2009Co-Authors: Fujie Zhou, Sheng Hu, Xiaodi Hu, Tom ScullionAbstract:The placement of an Asphalt Overlay is the most common method used by the Texas Department of Transportation (TxDOT) to rehabilitate existing Asphalt and concrete pavements. The type of Overlay and its required thickness are important decisions that TxDOT engineers make on a daily basis. To perform well, an Asphalt Overlay must have a balance of both good rut and crack resistance. Furthermore, Overlay performance is highly influenced by many factors, such as existing pavement conditions, traffic loading, and environmental conditions. It has also recently become common practice to use two different materials in an Overlay, the first being a crack resistant level up course and the second being a wearing surface. The properties of both Overlay types have a big impact on performance. The main objective of the Research Project 0-5123 was to develop a comprehensive mechanistic-empirical (M-E) Asphalt Overlay design system to assist TxDOT engineers to make these design decisions. The design system developed incorporates models for both rutting and reflection cracking of the proposed Overlay. The Paris’ law-based reflection cracking model was evaluated and recommended for use in this study. This model requires the use of both stress intensity factors (SIF) and fracture properties (A and n) for predicting crack propagation caused by both traffic loading and thermal effects. For practical implementation of the SIF concept, a total of 34 SIF regression equations were developed based on more than 1.6 million finite element computations. The required fracture properties can be easily determined using the Overlay Tester. The proposed reflective cracking model was calibrated using performance data from three HMA Overlay field case studies and then verified using the California’s Heavy Vehicle Simulator test results. To predict Asphalt Overlay rutting, the well-known VESYS layer rutting model was used and later calibrated using the field rutting data from the National Center for Asphalt Technology (NCAT) test track 2006. The material properties required for this model are obtained from repeated load tests. The reasonableness and accuracy of the calibrated rutting was further verified by the field rutting data from NCAT test track 2000. Finally, the calibrated reflective cracking and rutting models were integrated into an Asphalt Overlay thickness design and analysis program. To assist in implementation, default values of material properties have been provided for all the Overlay types currently used in Texas. The program provides the designer with a tool to evaluate on a project-level basis the impact of load transfer efficiency (LTE) on predicted life and to determine what level of LTE must be repaired in order to achieve adequate performance. In summary, this study has developed a comprehensive Overlay thickness design and analysis system based on solid engineering principles. The software package developed in this study has been provided to TxDOT. Based on the evaluations made in this study its predictions appear rational and reasonable. This system is ready for state-wide pilot implementation.
Shan Zhao - One of the best experts on this subject based on the ideXlab platform.
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Super-Resolution of 3-D GPR Signals to Estimate Thin Asphalt Overlay Thickness Using the XCMP Method
IEEE Transactions on Geoscience and Remote Sensing, 2019Co-Authors: Shan Zhao, Imad L. Al-qadiAbstract:The extended common midpoint (XCMP) method can be used on multichannel 3-D ground-penetrating radar (GPR) to estimate the Asphalt pavement thickness and dielectric constant without the need for calibration by taking cores. The XCMP method requires accurate time delay determination of pavement reflection. However, for thin Asphalt Overlay, the range resolution of 3-D GPR signal is insufficient to resolve the overlapped pulses of Asphalt concrete (AC). The objective of this paper is to use multiple signal classification (MUSIC) algorithm to increase the resolution of 3-D GPR signals, such that thin Asphalt Overlay thickness can be accurately estimated. An evaluation of the MUSIC algorithm at a full-scale test section and a comparison with regularized deconvolution algorithm showed the MUSIC algorithm is an effective approach for increasing the 3-D GPR signal range resolution when the XCMP method is applied on thin AC Overlay.
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development of regularization methods on simulated ground penetrating radar signals to predict thin Asphalt Overlay thickness
Signal Processing, 2017Co-Authors: Shan Zhao, Imad L AlqadiAbstract:The range resolution of ground-penetrating radar (GPR) signal is important in thin Asphalt Overlay thickness estimation. In this paper, regularized deconvolution is utilized to analyze simulated GPR signals to increase their range resolution. Four types of regularization methods, including Tikhonov regularization and total variation, were applied on noisy GPR signals; and their performance was evaluated in terms of accuracy in estimating distance of close impulses. The L-curve method was used to choose the appropriate regularization parameter. The total variation regularization method and zeroth-order Tikhonov regularization outperform first-order and second-order Tikhonov regularization in terms of average Asphalt layer thickness estimation error and the standard deviation of the error. An example of the field GPR data is provided to validate the proposed algorithm. The study shows that the algorithm based on regularization is a simple and effective approach to increase the GPR signal range resolution with presence of noise in the case of thin Asphalt Overlay thickness prediction. Deconvolution can be used to increase GPR signal resolution.Tikhonov and total variation regularization can make deconvolution robust to small reflection and noise.Simulation and field example show that accurate layer thickness can be obtained when the duration between two pulses is larger than 0.51ns.
Imad L Alqadi - One of the best experts on this subject based on the ideXlab platform.
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development of regularization methods on simulated ground penetrating radar signals to predict thin Asphalt Overlay thickness
Signal Processing, 2017Co-Authors: Shan Zhao, Imad L AlqadiAbstract:The range resolution of ground-penetrating radar (GPR) signal is important in thin Asphalt Overlay thickness estimation. In this paper, regularized deconvolution is utilized to analyze simulated GPR signals to increase their range resolution. Four types of regularization methods, including Tikhonov regularization and total variation, were applied on noisy GPR signals; and their performance was evaluated in terms of accuracy in estimating distance of close impulses. The L-curve method was used to choose the appropriate regularization parameter. The total variation regularization method and zeroth-order Tikhonov regularization outperform first-order and second-order Tikhonov regularization in terms of average Asphalt layer thickness estimation error and the standard deviation of the error. An example of the field GPR data is provided to validate the proposed algorithm. The study shows that the algorithm based on regularization is a simple and effective approach to increase the GPR signal range resolution with presence of noise in the case of thin Asphalt Overlay thickness prediction. Deconvolution can be used to increase GPR signal resolution.Tikhonov and total variation regularization can make deconvolution robust to small reflection and noise.Simulation and field example show that accurate layer thickness can be obtained when the duration between two pulses is larger than 0.51ns.
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field and laboratory evaluation of fracture resistance of illinois hot mix Asphalt Overlay mixtures
Transportation Research Record, 2009Co-Authors: William G Buttlar, Jongeun Baek, Imad L AlqadiAbstract:A major study of reflective cracking of Asphalt Overlays that are used in conjunction with interlayer systems for reflective-crack control was recently completed. In this cooperative study at the Illinois Center for Transportation, three field projects in central Illinois were selected and extensive coring was performed. Six fundamentally different types of hotmix Asphalt Overlay mixtures, which were expected to demonstrate significantly different levels of fracture resistance, were obtained from coring. To evaluate the fracture resistance of these mixtures in the field and the laboratory, visual field crack surveys and a series of advanced laboratory tests were conducted. This paper presents field performance evaluation results for the performance-benefit ratio and laboratory performance evaluation results for creep stiffness (St), complex modulus (E*), and diskshaped compact tension fracture energy (Gf). Field performance of pavement sections with premium Overlay mixtures was found to be superior to tho...
Fujie Zhou - One of the best experts on this subject based on the ideXlab platform.
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OPTIMAL THICKNESS OF Asphalt Overlay FOR COMPOSITE PAVEMENTS
2020Co-Authors: Fujie ZhouAbstract:Reflective cracking is a big problem for Asphalt Overlays on existing concrete pavements (AC/PCC). It is uneconomical to completely prevent reflective cracking from occurring only by increasing the thickness of Asphalt Overlay, and in fact the method is not practical. Therefore, it is necessary to study the optimal thickness of Asphalt Overlay. The paper analyzed the effect of thickness of Asphalt Overlay on reflective cracking utilizing the three-dimensional finite element. Based on the result of the mechanistic analysis, the critical thickness between the single reflective cracking and couple reflective cracking was recommended, and the concepts of "optimal width of delamination" and "optimal thickness of Asphalt Overlay" are introduced. Furthermore, the results of test roads not only validate the above mechanistic analysis, but also show that the width of couple reflective cracking is equal to the thickness of Asphalt Overlays. Based on the results of both mechanistic analysis and test roads, the optimal thickness of Asphalt Overlay is suggested. For the covering abstract see ITRD E109276.
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RDD Data Interpretation and Its Application on Evaluating Concrete Pavements for Asphalt Overlays
Journal of Performance of Constructed Facilities, 2012Co-Authors: Fujie Zhou, Sheng Hu, Darhao Chen, Tom ScullionAbstract:The placement of an Asphalt Overlay is the most common method to rehabilitate existing concrete pavements. Reflective cracking, however, has been a serious problem with Asphalt Overlays for a long time. To prevent reflective cracking, it is critical to evaluate existing concrete pavements and identify the joints/cracks with poor load-transfer efficiency (LTE) before placing an Asphalt Overlay. The most common equipment for this evaluation is a falling weight deflectometer (FWD). However, FWD testing is conducted only at discrete points and is time consuming. It is desirable to use the rolling dynamic deflectometer (RDD) that can continuously characterize each slab and all joints and cracks (e.g., LTE). The RDD was developed in the 1990s at the Center for Transportation Research in Austin, Texas. The RDD is one of the few operational rolling deflection systems that provide continuous data to make project level decisions on rehabilitating concrete pavements. In contrast to the FWD, no RDD data analysis software is available. This paper discusses RDD data interpretation and its application on evaluating existing concrete pavement for Asphalt Overlays. First of all, some basics of RDD deflection data interpretation are discussed. Several common patterns within the RDD data are identified, and associated interpretation and limited verification are presented in this paper. The RDD deflection data measured before an Asphalt Overlay on Interstate Highway-20, Texas, and the observed Asphalt Overlay performance (in terms of reflective cracking) are then presented, and the relationship between RDD deflection and reflective cracking rate is further investigated. Finally, guidelines for evaluating existing concrete pavements using RDD are proposed.
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reflection cracking based Asphalt Overlay thickness design and analysis tool
Transportation Research Record, 2010Co-Authors: Sheng Hu, Fujie Zhou, Tom ScullionAbstract:An Asphalt Overlay is one of the primary options for rehabilitating existing Asphalt and concrete pavements. Reflection cracking, however, has been a serious concern associated with Asphalt Overlays for a long time. Currently, reflection cracking is not considered in most existing Asphalt Overlay thickness design programs, including the Mechanistic-Empirical Pavement Design Guide developed under the NCHRP Project 1-37A. Therefore, there is an urgent need to develop a reflection cracking-based Asphalt Overlay thickness design and analysis tool for routine use. Three reflection cracking mechanisms (bending, shearing, and thermal stress) and mechanistic modeling are discussed according to fracture mechanics concepts. A mechanistic-empirical reflection cracking model is first proposed and then developed into an Asphalt Overlay thickness design and analysis framework. This framework is further implemented into a Windows-based design program, making it more convenient for pavement engineers to optimize Asphalt ...
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Reflection Cracking–Based Asphalt Overlay Thickness Design and Analysis Tool:
Transportation Research Record, 2010Co-Authors: Sheng Hu, Fujie Zhou, Tom ScullionAbstract:An Asphalt Overlay is one of the primary options for rehabilitating existing Asphalt and concrete pavements. Reflection cracking, however, has been a serious concern associated with Asphalt Overlays for a long time. Currently, reflection cracking is not considered in most existing Asphalt Overlay thickness design programs, including the Mechanistic-Empirical Pavement Design Guide developed under the NCHRP Project 1-37A. Therefore, there is an urgent need to develop a reflection cracking-based Asphalt Overlay thickness design and analysis tool for routine use. Three reflection cracking mechanisms (bending, shearing, and thermal stress) and mechanistic modeling are discussed according to fracture mechanics concepts. A mechanistic-empirical reflection cracking model is first proposed and then developed into an Asphalt Overlay thickness design and analysis framework. This framework is further implemented into a Windows-based design program, making it more convenient for pavement engineers to optimize Asphalt ...
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advanced Asphalt Overlay thickness design and analysis system
Journal of the Association of Asphalt Paving Technologists, 2010Co-Authors: Fujie Zhou, Sheng Hu, Tom ScullionAbstract:The placement of an Asphalt Overlay is the most common method used by many state Departments of Transportation (DOT) to rehabilitate existing flexible and rigid pavements. To perform well, an Asphalt Overlay must have a good balance of rutting and reflective cracking performance. The main objective of this paper is to present a comprehensive mechanistic-empirical (M-E) Asphalt Overlay thickness design system to assist pavement engineers to design a balanced Asphalt Overlay based on traffic loadings, climate, the existing pavement conditions, and the engineering properties of the Asphalt Overlay mix. The design system developed incorporates models for both reflective cracking and rutting of the proposed Asphalt Overlay. The Paris’ law-based reflective cracking model was chosen and further developed for predicting reflective cracking development. The required fracture properties of an Asphalt Overlay can be easily determined using the Overlay Tester. The proposed reflective cracking model was calibrated using a variety of Overlay test sections including the LTPP-SPS5 sections on US175 near Dallas, Texas, and then verified using the California Heavy Vehicle Simulator test results. To predict Asphalt Overlay rutting, the well-known VESYS layer rutting model was adopted and later calibrated using the field rutting data from the National Center for Asphalt Technology ( NCAT) test track 2006 and LTPP-SPS5 on US175. The material properties required for this model were obtained from repeated load tests. The reliability and accuracy of the calibrated rutting model was further validated using one set of independent rutting data from NCAT test track 2000. The calibrated reflective cracking and rutting models were then integrated into an Asphalt Overlay thickness design and analysis program. A sensitivity analysis was conducted to identify the significant parameters influencing the predicted levels of reflective cracking and rutting. It was found that the six most important input parameters are 1) traffic loading level, 2) climate, 3) Asphalt Overlay thickness, 4) Overlay mix type, 5) Asphalt binder type, 6) load transfer efficiency (LTE). Furthermore, it was also noticed that Asphalt Overlay life in terms of reflective cracking is not linearly proportional to Overlay thickness. A four in. Asphalt Overlay can have more than twice the life of a 3 in. Overlay. The proposed Asphalt Overlay thickness design and analysis program provides the designer with a tool to compute pavement life in terms of rutting and reflective cracking. The system permits the designer to use up to two different Overlay mixes such as a crack relief layer and a wearing surface. The system is fully operational and undergoing implementation within the Texas Department of Transportation (TxDOT).
Sheng Hu - One of the best experts on this subject based on the ideXlab platform.
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RDD Data Interpretation and Its Application on Evaluating Concrete Pavements for Asphalt Overlays
Journal of Performance of Constructed Facilities, 2012Co-Authors: Fujie Zhou, Sheng Hu, Darhao Chen, Tom ScullionAbstract:The placement of an Asphalt Overlay is the most common method to rehabilitate existing concrete pavements. Reflective cracking, however, has been a serious problem with Asphalt Overlays for a long time. To prevent reflective cracking, it is critical to evaluate existing concrete pavements and identify the joints/cracks with poor load-transfer efficiency (LTE) before placing an Asphalt Overlay. The most common equipment for this evaluation is a falling weight deflectometer (FWD). However, FWD testing is conducted only at discrete points and is time consuming. It is desirable to use the rolling dynamic deflectometer (RDD) that can continuously characterize each slab and all joints and cracks (e.g., LTE). The RDD was developed in the 1990s at the Center for Transportation Research in Austin, Texas. The RDD is one of the few operational rolling deflection systems that provide continuous data to make project level decisions on rehabilitating concrete pavements. In contrast to the FWD, no RDD data analysis software is available. This paper discusses RDD data interpretation and its application on evaluating existing concrete pavement for Asphalt Overlays. First of all, some basics of RDD deflection data interpretation are discussed. Several common patterns within the RDD data are identified, and associated interpretation and limited verification are presented in this paper. The RDD deflection data measured before an Asphalt Overlay on Interstate Highway-20, Texas, and the observed Asphalt Overlay performance (in terms of reflective cracking) are then presented, and the relationship between RDD deflection and reflective cracking rate is further investigated. Finally, guidelines for evaluating existing concrete pavements using RDD are proposed.
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Reflection Cracking–Based Asphalt Overlay Thickness Design and Analysis Tool:
Transportation Research Record, 2010Co-Authors: Sheng Hu, Fujie Zhou, Tom ScullionAbstract:An Asphalt Overlay is one of the primary options for rehabilitating existing Asphalt and concrete pavements. Reflection cracking, however, has been a serious concern associated with Asphalt Overlays for a long time. Currently, reflection cracking is not considered in most existing Asphalt Overlay thickness design programs, including the Mechanistic-Empirical Pavement Design Guide developed under the NCHRP Project 1-37A. Therefore, there is an urgent need to develop a reflection cracking-based Asphalt Overlay thickness design and analysis tool for routine use. Three reflection cracking mechanisms (bending, shearing, and thermal stress) and mechanistic modeling are discussed according to fracture mechanics concepts. A mechanistic-empirical reflection cracking model is first proposed and then developed into an Asphalt Overlay thickness design and analysis framework. This framework is further implemented into a Windows-based design program, making it more convenient for pavement engineers to optimize Asphalt ...
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reflection cracking based Asphalt Overlay thickness design and analysis tool
Transportation Research Record, 2010Co-Authors: Sheng Hu, Fujie Zhou, Tom ScullionAbstract:An Asphalt Overlay is one of the primary options for rehabilitating existing Asphalt and concrete pavements. Reflection cracking, however, has been a serious concern associated with Asphalt Overlays for a long time. Currently, reflection cracking is not considered in most existing Asphalt Overlay thickness design programs, including the Mechanistic-Empirical Pavement Design Guide developed under the NCHRP Project 1-37A. Therefore, there is an urgent need to develop a reflection cracking-based Asphalt Overlay thickness design and analysis tool for routine use. Three reflection cracking mechanisms (bending, shearing, and thermal stress) and mechanistic modeling are discussed according to fracture mechanics concepts. A mechanistic-empirical reflection cracking model is first proposed and then developed into an Asphalt Overlay thickness design and analysis framework. This framework is further implemented into a Windows-based design program, making it more convenient for pavement engineers to optimize Asphalt ...
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advanced Asphalt Overlay thickness design and analysis system
Journal of the Association of Asphalt Paving Technologists, 2010Co-Authors: Fujie Zhou, Sheng Hu, Tom ScullionAbstract:The placement of an Asphalt Overlay is the most common method used by many state Departments of Transportation (DOT) to rehabilitate existing flexible and rigid pavements. To perform well, an Asphalt Overlay must have a good balance of rutting and reflective cracking performance. The main objective of this paper is to present a comprehensive mechanistic-empirical (M-E) Asphalt Overlay thickness design system to assist pavement engineers to design a balanced Asphalt Overlay based on traffic loadings, climate, the existing pavement conditions, and the engineering properties of the Asphalt Overlay mix. The design system developed incorporates models for both reflective cracking and rutting of the proposed Asphalt Overlay. The Paris’ law-based reflective cracking model was chosen and further developed for predicting reflective cracking development. The required fracture properties of an Asphalt Overlay can be easily determined using the Overlay Tester. The proposed reflective cracking model was calibrated using a variety of Overlay test sections including the LTPP-SPS5 sections on US175 near Dallas, Texas, and then verified using the California Heavy Vehicle Simulator test results. To predict Asphalt Overlay rutting, the well-known VESYS layer rutting model was adopted and later calibrated using the field rutting data from the National Center for Asphalt Technology ( NCAT) test track 2006 and LTPP-SPS5 on US175. The material properties required for this model were obtained from repeated load tests. The reliability and accuracy of the calibrated rutting model was further validated using one set of independent rutting data from NCAT test track 2000. The calibrated reflective cracking and rutting models were then integrated into an Asphalt Overlay thickness design and analysis program. A sensitivity analysis was conducted to identify the significant parameters influencing the predicted levels of reflective cracking and rutting. It was found that the six most important input parameters are 1) traffic loading level, 2) climate, 3) Asphalt Overlay thickness, 4) Overlay mix type, 5) Asphalt binder type, 6) load transfer efficiency (LTE). Furthermore, it was also noticed that Asphalt Overlay life in terms of reflective cracking is not linearly proportional to Overlay thickness. A four in. Asphalt Overlay can have more than twice the life of a 3 in. Overlay. The proposed Asphalt Overlay thickness design and analysis program provides the designer with a tool to compute pavement life in terms of rutting and reflective cracking. The system permits the designer to use up to two different Overlay mixes such as a crack relief layer and a wearing surface. The system is fully operational and undergoing implementation within the Texas Department of Transportation (TxDOT).
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mechanistic empirical Asphalt Overlay thickness design and analysis system
2009Co-Authors: Fujie Zhou, Sheng Hu, Xiaodi Hu, Tom ScullionAbstract:The placement of an Asphalt Overlay is the most common method used by the Texas Department of Transportation (TxDOT) to rehabilitate existing Asphalt and concrete pavements. The type of Overlay and its required thickness are important decisions that TxDOT engineers make on a daily basis. To perform well, an Asphalt Overlay must have a balance of both good rut and crack resistance. Furthermore, Overlay performance is highly influenced by many factors, such as existing pavement conditions, traffic loading, and environmental conditions. It has also recently become common practice to use two different materials in an Overlay, the first being a crack resistant level up course and the second being a wearing surface. The properties of both Overlay types have a big impact on performance. The main objective of the Research Project 0-5123 was to develop a comprehensive mechanistic-empirical (M-E) Asphalt Overlay design system to assist TxDOT engineers to make these design decisions. The design system developed incorporates models for both rutting and reflection cracking of the proposed Overlay. The Paris’ law-based reflection cracking model was evaluated and recommended for use in this study. This model requires the use of both stress intensity factors (SIF) and fracture properties (A and n) for predicting crack propagation caused by both traffic loading and thermal effects. For practical implementation of the SIF concept, a total of 34 SIF regression equations were developed based on more than 1.6 million finite element computations. The required fracture properties can be easily determined using the Overlay Tester. The proposed reflective cracking model was calibrated using performance data from three HMA Overlay field case studies and then verified using the California’s Heavy Vehicle Simulator test results. To predict Asphalt Overlay rutting, the well-known VESYS layer rutting model was used and later calibrated using the field rutting data from the National Center for Asphalt Technology (NCAT) test track 2006. The material properties required for this model are obtained from repeated load tests. The reasonableness and accuracy of the calibrated rutting was further verified by the field rutting data from NCAT test track 2000. Finally, the calibrated reflective cracking and rutting models were integrated into an Asphalt Overlay thickness design and analysis program. To assist in implementation, default values of material properties have been provided for all the Overlay types currently used in Texas. The program provides the designer with a tool to evaluate on a project-level basis the impact of load transfer efficiency (LTE) on predicted life and to determine what level of LTE must be repaired in order to achieve adequate performance. In summary, this study has developed a comprehensive Overlay thickness design and analysis system based on solid engineering principles. The software package developed in this study has been provided to TxDOT. Based on the evaluations made in this study its predictions appear rational and reasonable. This system is ready for state-wide pilot implementation.
