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E R Brown - One of the best experts on this subject based on the ideXlab platform.
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Effect of Superpave Gyratory Compactor Type on Compacted Hot-Mix Asphalt Density
Transportation Research Record, 2001Co-Authors: M S Buchanan, E R BrownAbstract:The SUperior PERforming Asphalt PAVEments (Superpave) gyratory compactor was developed as a tool in the Superpave mix design system to better simulate the field compaction of hot-mix asphalts. All Superpave gyratory compactors are designed to meet the specification criteria found in AASHTO TP4. At the present time, AASHTO TP4 does not contain a precision statement. Furthermore, many agencies have reported differences in the bulk specific gravity of compacted samples from different Superpave gyratory compactors, which have been properly calibrated. Data are presented and analyzed from three gyratory compactor proficiency sample testing programs, from field project Superpave gyratory compaction comparisons, and from mix design and quality control and assurance results from a state department of transportation. The data were then analyzed to determine the statistical (precision) and potential project implications that result from the observed differences. The results indicate that the precision of the Superpave gyratory compactor is better than the mechanical Marshall hammer. However, there were significant differences between the bulk specific gravity of mixes compacted in different gyratory compactors. These differences could potentially lead to discrepancies during the mix design verification and quality control and assurance testing of a given mix.
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Superpave GYRATORY COMPACTION GUIDELINES
NCHRP Research Results Digest, 1999Co-Authors: E R Brown, M S BuchananAbstract:This digest summarizes key results of NCHRP Project 9-9, "Refinement of the Superpave Gyratory Compaction Procedure." Of particular interest, it presents a recommended reduction in the Ndesign table in AASHTO PP28, "Practice for Designing Superpave HMA," from the original 28 traffic and climate combinations to 4, provides specific Ndesign levels for base mixes, and recommends setting the Superpave short-term aging mix temperature equal to the equiviscous compaction temperature. The Superpave gyratory compaction procedure, developed under the Strategic Highway Research Program (SHRP), is the method required for all Superpave mix designs and mixture process control. The gyratory compactor must provide a density in the compacted laboratory specimen that closely approximates the ultimate density of the hot mix asphalt (HMA) mixture obtained in the pavement when subjected to traffic loads and climate conditions so that an appropriate optimum asphalt content can be selected during the laboratory mix design process.
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AN INITIAL EVALUATION FOR NDESIGN Superpave GYRATORY COMPACTOR
1998Co-Authors: E R Brown, R B MallickAbstract:Mix design is the first step in the construction of a high quality HMA mixture. The single most important step in the mix design procedure is laboratory compaction of specimens. One of the most important outcomes of the Strategic Highway research Program (SHRP) was the introduction of the Superpave gyratory compactor. For this compactor, Superpave specifies the rate of gyration, the compaction pressure, and the angle of gyration. Different gyration levels are also specified for different traffic levels. Researchers on the basis of laboratory compaction and in-place density data determined these gyration numbers. Due to the limited data collection by the researchers the established compactive efforts need to be verified. The objective of this study is to evaluate Ndesign for the Superpave gyratory compactor. Loose mix obtained during the construction of six test sections in the US was compacted with the Superpave gyratory compactor. Specimens were also compacted with the Superpave gyratory compactor, using aggregates and asphalt cement used in construction of test sections. These cores were also tested for density. The cumulative traffic levels for the test sections at different times were determined. Correlations were obtained between Ndesign and cumulative traffic levels. Ndesign values obtained from this study are less than the Superpave specified values by approximately 30 gyrations. At 1 million ESALs, the Superpave specified Ndesign is 76, whereas the Ndesign obtained from this study is 46. The results of this study alone should not be used to modify the compaction table. However, the study does indicate that the number of gyrations required, especially for low traffic level, should be reduced. A detailed study is needed to thoroughly valuate the Ndesign table.
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Applicability of Superpave to the Design of Airfield Asphalt Pavements
1997Co-Authors: E R Brown, M S BuchananAbstract:The Strategic Highway Research Program (SHRP) has developed a new mix design procedure for hot mix asphalt (HMA). This new procedure is referred to as Superpave. Many State DOTs have begun to adopt this new procedure and most State DOTs will certainly adopt it by the year 2000. Very little effort has been spent to determine if Superpave should be adopted for airfields. This paper presents a comparison of the Marshall and Superpave design procedures and makes recommendations concerning adoption of Superpave. Some of Superpave should be adopted immediately and while other parts should be evaluated in more detail prior to adoption.
Donald E. Watson - One of the best experts on this subject based on the ideXlab platform.
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verification of Superpave number of design gyration compaction levels for georgia
Transportation Research Record, 2008Co-Authors: Donald E. Watson, Jason R Moore, Justin Heartsill, David Mark JaredAbstract:The objective of this project was to evaluate the performance of Georgia's mixes designed by using the Superpave® gyratory compactor. Mixes designed with numbers of design gyrations that are too high would be rut resistant but may be difficult to compact adequately in the field and may lack sufficient durability because of reduced asphalt binder content. The following conclusions were made on the basis of an evaluation of field projects and from laboratory volumetric and performance testing with various aggregate sources and gyration levels: (a) It is unlikely that Superpave mixtures will reach the design air voids of 4.0% during the life of the pavement. After nearly 5 years, the average air voids measured in the wheelpaths were 5.7% for Superpave projects and 3.8% for Marshall projects. On the basis of volumetric comparisons, 66 gyrations with the laboratory-produced mix gave approximately the same density achieved on the Superpave projects in the field. (b) The difference between 4-in.-diameter Marshal...
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Comparison of Superpave and Marshall Mix Performance in Alabama
Transportation Research Record: Journal of the Transportation Research Board, 2005Co-Authors: Donald E. Watson, E. Ray Brown, Jason MooreAbstract:The Alabama Department of Transportation specifies the Superpave® design system for most of its dense-graded HMA mixes. However, there is concern that the number of design gyrations ( NDesign) may be too high for specified traffic levels. Mixes designed with an NDesign level that is too high would be rut resistant but may be difficult to compact in the field and may suffer from durability problems such as premature cracking and raveling. The objective of this project is to evaluate the performance of Alabama's mixes designed according to Superpave criteria and compare them to the performance of Alabama's Marshall-designed mixes to determine whether current NDesign levels should be adjusted. The following conclusions are based on an evaluation of 25 Marshall and Superpave projects placed about the same time and serving under approximately the same traffic conditions: ( a) Generally, both Marshall and Superpave mixtures are performing quite well with little rutting and cracking after a period of about 4 years. ( b) It is likely that most Marshall and Superpave mixtures will not reach the design air voids of 4.0% during the life of the pavement. After 4 years, the average air voids measured in the wheelpaths was 5.3% for Marshall mixes and 5.9% for Superpave mixtures. ( c) It appears that the durability of Superpave mixtures can be improved, without adversely affecting the rutting resistance, by increasing the asphalt content. Practitioners, however, are cautioned to monitor rutting indicators closely during mixture design, production, and construction.
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Comparison of Superpave and Marshall Mix Performance in Alabama
Transportation Research Record: Journal of the Transportation Research Board, 2005Co-Authors: Donald E. Watson, E. Ray Brown, Jason R MooreAbstract:The Alabama Department of Transportation specifies the Superpave® design system for most of its dense-graded HMA mixes. However, there is concern that the number of design gyrations (NDesign) may be too high for specified traffic levels. Mixes designed with an NDesign level that is too high would be rut resistant but may be difficult to compact in the field and may suffer from durability problems such as premature cracking and raveling. The objective of this project is to evaluate the performance of Alabama's mixes designed according to Superpave criteria and compare them to the performance of Alabama's Marshall-designed mixes to determine whether current NDesign levels should be adjusted. The following conclusions are based on an evaluation of 25 Marshall and Superpave projects placed about the same time and serving under approximately the same traffic conditions: (a) Generally, both Marshall and Superpave mixtures are performing quite well with little rutting and cracking after a period of about 4 years...
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Updated Review of Stone Matrix Asphalt and Superpave® Projects
Transportation Research Record: Journal of the Transportation Research Board, 2003Co-Authors: Donald E. WatsonAbstract:Stone matrix asphalt (SMA) and Superpave® represent relatively new mix design technologies in the United States. Therefore, a condition survey was conducted of mixes that had been in service for several years to evaluate the long-term performance of SMA and Superpave projects. This study is a follow-up to a 1995 review of SMA projects and a 1998 review of Superpave projects. Both SMA and Superpave are acknowledged to be rut-resistant mixes, and this resistance was shown to be the case during this project review. However, a significant amount of cracking occurred early in the life of some of these mixtures. Overall, the SMA mixtures appeared to be more durable than the Superpave mixtures evaluated. The SMA mixtures have been in place about 2½ years longer than the Superpave mixtures, but the overall condition is about the same. Some of the primary conclusions from the survey are as follows: both SMA and Superpave mixtures were shown to be rut-resistant even when placed on facilities with high traffic volume; much of the observed cracking, especially load cracking, appeared to be more related to problems other than mix design or material properties; and SMA mixtures can be expected to last longer than Superpave mixtures before reaching the same condition level.
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Updated review of stone matrix asphalt and Superpave® projects
Transportation Research Record, 2003Co-Authors: Donald E. WatsonAbstract:Stone matrix asphalt (SMA) and Superpave® represent relatively new mix design technologies in the United States. Therefore, a condition survey was conducted of mixes that had been in service for several years to evaluate the long-term performance of SMA and Superpave projects. This study is a follow-up to a 1995 review of SMA projects and a 1998 review of Superpave projects. Both SMA and Superpave are acknowledged to be rut-resistant mixes, and this resistance was shown to be the case during this project review. However, a significant amount of cracking occurred early in the life of some of these mixtures. Overall, the SMA mixtures appeared to be more durable than the Superpave mixtures evaluated. The SMA mixtures have been in place about 2 1/2 years longer than the Superpave mixtures, but the overall condition is about the same. Some of the primary conclusions from the survey are as follows: both SMA and Superpave mixtures were shown to be rut-resistant even when placed on facilities with high traffic vo...
Chris Wagne - One of the best experts on this subject based on the ideXlab platform.
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use of reclaimed asphalt pavement in Superpave hot mix asphalt applications
Transportation Research Record, 1999Co-Authors: Mary Stroupgardine, Chris WagneAbstract:Implementation of the Superpave mix design method has encouraged the use of coarser hot-mix asphalt (HMA) mixtures, which require tight control of both the overall gradation and the percent passing the 0.075-mm (No. 200) screen. There is some concern that use of reclaimed asphalt pavement (RAP) in Superpave mixtures may be seriously limited because stockpiles of RAP may have widely variable gradations as well as high percentages of minus 0.075-mm material. The possibility of splitting RAP stockpiles by using the coarser RAP fraction in a typical 12.5 mm below-the-restricted-zone Superpave gradation has been evaluated. The finer RAP fraction was used in an above-the-restricted zone 12.5-mm Superpave gradation. Two sources of RAP (Georgia and Minnesota) were used so that a wide range of asphalt and aggregate properties would be represented. Screening the RAP allowed up to 40 percent of the coarse RAP fraction to be used and still meet below-the-restricted zone Superpave gradation requirements. This was main...
Amy L Epps - One of the best experts on this subject based on the ideXlab platform.
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impact of gradation relative to Superpave restricted zone on hot mix asphalt performance
Transportation Research Record, 2001Co-Authors: Adam J. T. Hand, Amy L EppsAbstract:Significant controversy has revolved around the Superpave gradation specifications, in particular the restricted zone, since the completion of the Strategic Highway Research Program (SHRP). Historically, dense-graded mixtures that encroach on the restricted zone had provided good performance prior to SHRP. However, current Superpave guidelines recommend that gradations passing through the restricted zone not be used. A synopsis of recent research related specifically to the impact of the Superpave restricted zone on performance of hot-mix asphalt (HMA) is provided. The evolution and purpose of the Superpave restricted zone are presented, along with findings of both recently completed and ongoing research. Studies involving laboratory and full-scale accelerated performance tests of mixtures with gradations plotting above (ARZ), through (TRZ), and below the restricted zone were considered. The research reviewed clearly suggests that good performance can be achieved with fine-graded (ARZ and TRZ) mixtures and that no relationship exists between the Superpave restricted zone and HMA rutting or fatigue performance. It is suggested on the basis of this research that the restricted zone recommendation be eliminated from the Superpave volumetric mixture design specifications.
M S Buchanan - One of the best experts on this subject based on the ideXlab platform.
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Effect of Superpave Gyratory Compactor Type on Compacted Hot-Mix Asphalt Density
Transportation Research Record, 2001Co-Authors: M S Buchanan, E R BrownAbstract:The SUperior PERforming Asphalt PAVEments (Superpave) gyratory compactor was developed as a tool in the Superpave mix design system to better simulate the field compaction of hot-mix asphalts. All Superpave gyratory compactors are designed to meet the specification criteria found in AASHTO TP4. At the present time, AASHTO TP4 does not contain a precision statement. Furthermore, many agencies have reported differences in the bulk specific gravity of compacted samples from different Superpave gyratory compactors, which have been properly calibrated. Data are presented and analyzed from three gyratory compactor proficiency sample testing programs, from field project Superpave gyratory compaction comparisons, and from mix design and quality control and assurance results from a state department of transportation. The data were then analyzed to determine the statistical (precision) and potential project implications that result from the observed differences. The results indicate that the precision of the Superpave gyratory compactor is better than the mechanical Marshall hammer. However, there were significant differences between the bulk specific gravity of mixes compacted in different gyratory compactors. These differences could potentially lead to discrepancies during the mix design verification and quality control and assurance testing of a given mix.
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Superpave GYRATORY COMPACTION GUIDELINES
NCHRP Research Results Digest, 1999Co-Authors: E R Brown, M S BuchananAbstract:This digest summarizes key results of NCHRP Project 9-9, "Refinement of the Superpave Gyratory Compaction Procedure." Of particular interest, it presents a recommended reduction in the Ndesign table in AASHTO PP28, "Practice for Designing Superpave HMA," from the original 28 traffic and climate combinations to 4, provides specific Ndesign levels for base mixes, and recommends setting the Superpave short-term aging mix temperature equal to the equiviscous compaction temperature. The Superpave gyratory compaction procedure, developed under the Strategic Highway Research Program (SHRP), is the method required for all Superpave mix designs and mixture process control. The gyratory compactor must provide a density in the compacted laboratory specimen that closely approximates the ultimate density of the hot mix asphalt (HMA) mixture obtained in the pavement when subjected to traffic loads and climate conditions so that an appropriate optimum asphalt content can be selected during the laboratory mix design process.
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Applicability of Superpave to the Design of Airfield Asphalt Pavements
1997Co-Authors: E R Brown, M S BuchananAbstract:The Strategic Highway Research Program (SHRP) has developed a new mix design procedure for hot mix asphalt (HMA). This new procedure is referred to as Superpave. Many State DOTs have begun to adopt this new procedure and most State DOTs will certainly adopt it by the year 2000. Very little effort has been spent to determine if Superpave should be adopted for airfields. This paper presents a comparison of the Marshall and Superpave design procedures and makes recommendations concerning adoption of Superpave. Some of Superpave should be adopted immediately and while other parts should be evaluated in more detail prior to adoption.
