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TRB Superpave Abstracts 200180th Transportation Research Board Annual Meeting

January 7- 11, 2001Washington, D. C.Table of Contents

1. Washington State Dot Superpave Implementation 2. Mechanistic Analysis of Asphalt Pavements Using Superpave Shear Tester and

Hamburg Wheel-Tracking Device3. Impact of Gradation Relative to the Superpave Restricted Zone on HMA

Performance4. Comparison of the Engineering Characteristics of Asphalt Mixes To Field Data and

Pavement Performance5. Effect of Superpave Gyratory Compactor Type on Compacted Hot Mix Asphalt

(HMA) Density6. Gradation Effects on HMA Performance 7. Effect of Aggregate Gradation on Permanent Deformation of Superpave HMA 8. Forensic Analysis of Arizona™s US-93 Superpave sections 9. Design, Construction, And Early Performance Of Virginia’s Hot-Mix Asphalt

Stabilizer And Modifier Test Sections10. Effect of Mix Gradation on Rutting Potential of Dense Graded Asphalt Mixtures 11. Evaluation of Laboratory Measured Crack Growth Rate for Asphalt Mixtures 12. Low-temperature Thermal Cracking of Asphalt Binders as Ranked by Strength and

Fracture Properties13. An Evaluation of Factors Affecting Permeability of Superpave Designed Pavements 14. Variability of Asphalt Mixtures Tests Using the Superpave Shear Tester Repeated

Shear at Constant Height Test15. Development of Performance-Based Mix Design for Cold In-Place Recycling of

Asphalt Mixtures16. Hydraulic Conductivity (Permeability) Of Laboratory Compacted Asphalt Mixtures 17. Effect of Short Term Oven Aging on Volumetrics And Selection of N-Design 18. Development of Critical Field Permeability and Pavement Density Values for

Coarse-Graded Superpave Pavements19. New Jersey’s Superpave Specification: The Next Generation 20. Development of a Void Pathway Test for Investigating Void Interconnectivity in

Compacted Hot-Mix Asphalt Concrete21. Asphalt Permeability Testing: Specimen Preparation and Testing Variability 22. Correlation of Imaging Shape Indices of Fine Aggregate with Asphalt Mixture

Performance23. A Comparison of Four Brands of Superpave Gyratory Compactors 24. Field Conditioning of Superpave Asphalt Mixes 25. A Mathematical Model for Calculating Pavement Temperatures, Comparisons

between Calculated and Measured Temperatures26. An Evaluation of Field Density Measuring Devices 27. Discrete Element Modeling of Asphalt Concrete: A Micro-Fabric Approach 28. Field Tests and Economic Analysis of High-Cure Crumb-Rubber Modified Asphalt

Binders in Dense-Graded Mixes29. Measurement of Flat and Elongation of Coarse Aggregate Using Digital Image

Processing30. Microstructure Study of WesTrack Mixes from X-ray Tomography Images

31. A Statistical Model Of Pavement Rutting In Asphalt Concrete Mixes 32. Potential of Using Stone Matrix Asphalt (SMA)For Thin Overlays 33. Repeated Triaxial Testing During Mix Design for Performance Characterization 34. A Procedure for Using an FWD to Determine the Structural Layer Coefficients for

Flexible Pavement Materials35. Construction and Performance of Ultra-Thin Bonded HMA Wearing Course 36. Effects of Sample Preconditioning on Asphalt Pavement Analyzer (APA) Wet Rut

Depths 37. Insitu Measurement and Empirical Modeling of Base Infiltration in Highway

Pavement Systems38. Advanced Characterization of Crumb Rubber Modified Asphalts Using Protocols

Developed for Complex Binders39. An Examination of Operator Variability for Selected Methods for Measuring Bulk

Specific Gravity of Hot-Mix Asphalt Concrete40. Effect of Flat and Elongated Coarse Aggregate on Field Compaction of Hot Mix

Asphalt41. Effect of Using Silicone Rubber Molds on the Low-Temperature Binder Grading

Parameters: BBR S(60) and m-Value42. Improvement in the Determination of Failure Stress of Asphalt Binder and Test

Repeatability through Sample Preparation in Direct Tension Testing43. Techniques for Determining Errors in Asphalt Binders Rheological Data 44. A Method to Construct Thermal Stress Relief Joints in Asphalt Pavement 45. A Quantitative Evaluation of Stripping Potential in Hot Mix Asphalt Using Ultrasonic

Energy for Moisture Accelerated Conditioning46. Assessing the Economic Benefits from the Implementation of New Pavement

Construction Methods47. Estimation of Rutting Models by Combining Experimental Data From Different

Sources48. Fatigue and Permanent Deformation Models for Polymer-Modified Asphalt

Mixtures49. Flexible Pavement Design in Michigan: Transition from Empirical to Mechanistic

Methods50. Long-Term Field Performance of Crack-and-Seat Rehabilitation Strategy 51. Propagation Mechanisms For Surface-Initiated Longitudinal Wheel Path Cracks 52. Quantitative Analysis of 3-D Images of Asphalt Concrete 53. Application of LTPP Seasonal Monitoring Data to Evaluate Volumetric Moisture

Predictions from the Integrated Climatic Model54. Data Collection and Management of The Instrumented Smart Road Flexible

Pavement Sections55. Low-Temperature Binder Specification Development: Thermal Stress Restrained

Specimen Testing of Asphalt Binders and Mixtures56. Measurement and Evaluation of Pavement Marking Retroreflectivity: South

Carolina’s Experience57. Modification of Binder with Acid Advantages and Disadvantages 58. Searching For Superior Performing Porous Asphalt Wearing Courses 59. Using Pavement Distress Data To Assess The Impact Of Construction On Pavement

Performance

Washington State DOT Superpave ImplementationPaper 01-0149

Rita B. Leahy, PhD, PEFugro-BRE, Inc. 8613 Cross Creek DriveAustin, TX 78754Phone (512) 977-1800Fax (512) 973-9565Email: [email protected]

Robert N. BriggsMaterials Quality Systems EngineerWashington State Department of TransportationP.O. Box 47365Olympia, WA 98504-7365Phone (360) 709-5411Fax (360) [email protected]

ABSTRACTWashington DOT (WSDOT) has aggressively investigated selected components and concepts of the SHRP/Superpave technology to include the following: Performance Grade (PG) binder usage and specification validation, gyratory mix design; the Superpave Shear Tester (SST); and field performance of Superpave mixes. The focus of this paper, however, is on field performance of Superpave mixes. Validation of the binder specification with respect to low temperature cracking was accomplished using binder and field performance data from 28 projects. The results were very encouraging: the original SHRP algorithm for binder selection correctly “predicted” field performance in 22 of 28 cases, whereas the LTPP algorithm SHRP algorithm for binder selection correctly “predicted” field performance in 26 of 28 cases. Since 1993, WSDOT has placed 44 projects that include some component of the Superpave technology. For 17 of these projects parallel Hveem and Superpave mix designs were conducted. In 13 of the 17 cases, the Superpave design asphalt content was equal to or greater than the Hveem design asphalt content, although the difference was usually no more than 0.2 percent. A conventional Hveem mix design was conducted for 18 of the original 44 projects placed using a PG binder (Hveem-PG). The remaining 26 projects were truly Superpave, i.e., the materials selection and mix design were established in accordance with the Asphalt Institute’s SP-2, Superpave Level 1 Mix Design. According to WSDOT practice the following numerical indices trigger maintenance: Pavement Structural Condition (PSC) =50, rutting =13 mm, or International Roughness Index (IRI) =500 cm/km. Although relatively “young,” all 44 projects are performing quite well. The average values of rutting, PSC and IRI (4, 91 and 121, respectively) are all well below the “trigger” values. With respect to rutting and PSC, the performance of Hveem-PG and Superpave projects is virtually identical. However, the ride quality of the Superpave projects is a bit rougher than that the Hveem-PG binder projects: IRI of 134 for the former and 103 for the latter. The higher values of IRI measured on the Superpave projects may be the result of the typically coarser aggregate gradation or differences in construction techniques.

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Mechanistic Analysis of Asphalt Pavements Using Superpave Shear Tester and Hamburg Wheel-Tracking DevicePaper No. 01-0138

Jian-Neng Wang*, Ph.D., Assistant ProfessorDepartment of Civil EngineeringChing-Yun Institute of Technology2F, 68, LN 422, SEC 2, Chung-Shan E RDChungli 320, TaiwanTel: (886-3) 456-8088Fax:(886-3) 466-4628E-mail:[email protected]* Corresponding Author

Chien-Kuo Yang, Senior EngineerConstruction Management DepartmentPublic Construction Commission9F, 4, SEC 1, Chung-Hsiao W RdTaipei 100, TaiwanTel: (886-2) 361-8661Fax: (886-2) 331-5808

E-mail: [email protected]

Tsair-Yi Luo, Associate EngineerDesign DivisionTaiwan Area National Expressway Engineering Bureau, 5F, 1, LN 1, Sec 3, Ho-Ping E RdTaipei 106, TaiwanTel: (886-2) 2701-8808FAX: (886-2) 2701-8891E-mail:[email protected]

ABSTRACTThe study presents the comparative evaluation of permanent deformation and moisture damage of asphalt mixtures using the Superpave Shear Tester (SST) and the Hamburg Wheel-Tracking Device (HWTD). The damage analysis of simulated asphalt pavements is also included. The selected materials were a PG 64-22 asphalt binder and a sandstone aggregate with or without an anti -stripping additive. Repeated Shear test at Constant Height (RSCH) and the HWTD tests were performed for the evaluation of permanent deformation. The results showed the Superpave mixtures were less susceptible to permanent deformation than the Marshall mixture. It was found that the results of the HWTD tests performed at 40 o C were consistent with those of the RSCH tests. Two permanent deformation models were compared to relate plastic strain accumulation with the number of load repetitions. One selected for use in the SHRP A-005 contract is generally better than the other model. For moisture susceptibility evaluation of these mixtures, the results of the AASHTO T283 tests were consistent with those of the HWTD tests at 40 o C. The creep compliances calculated from the Frequency Sweep tests at Constant Height (FSCH) were applied to the KENLAYER program for pavement damage analysis. Based on the data and analyses in this study, the simulated asphalt pavements are considered more of a material and mix design problem rather than a structural problem. The use of creep compliances of the above mixtures could not successfully predict the pavement performance in comparison with results of the RSCH and HWTD tests.


Impact of Gradation Relative to the Superpave Restricted Zone on HMA PerformanceTRB Paper Number: 01-0141

Adam J. Hand 1 Quality Systems Engineer, Granite Construction Incorporated, 1900 Glendale Avenue, Sparks,NV 89431, Office: (775) 352-1953, Fax: (775) 355-3431, email: [email protected]

Amy L. Epps 2Assistant Professor, Texas A&M University, 503F CE/TTI Building, College Station, TX77843-3136, Office: (979) 862-1750, FAX (979) 845-0278, email: [email protected]

ABSTRACTSignificant controversy has revolved around the Superpave gradation specifications, in particular the restricted zone, since the completion of the Strategic Highway Research Program (SHRP). The reason for this is simple, dense-graded mixtures which encroach on the restricted zone had historically provided good performance prior to SHRP. However, current Superpave guidelines recommend that gradations passing through the restricted zone not be used. The objective of this paper is to provide a synopsis of recent research related specifically to the impact of the Superpave restricted zone on performance of hot mix asphalt (HMA). The evolution and purpose of the Superpave restricted zone are presented along with findings of both recently completed and on-going research. Studies involving laboratory and full scale accelerated performance tests of mixtures with gradations plotting above (ARZ), through (TRZ) and below (BRZ) 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. Based on this it is suggested that the restricted zone recommendation be eliminated from the Superpave volumetric mixture design specifications.

Key Words: Superpave, aggregate specifications, restricted zone, gradation, HMA performance


Comparison of the Engineering Characteristics of Asphalt Mixes To Field Data and Pavement Performance

Jonathan E. CrinceStaff EngineerNTH Consultants, Ltd.

Gilbert Y. Baladi, Ph.D., P.E, Professor (corresponding author) andKarim Chatti, Ph.D., Assistant ProfessorMichigan State UniversityDept. of Civil and Environmental Engineering3546 Engineering BuildingEast Lansing, MI 48824Phone#: (517)-355-5147Fax#: (517)[email protected]

ABSTRACTOver the past few decades, State Highway Agencies have continually modified their specifications regarding bituminous mixtures and/or have established new asphalt mixes such as Superpave. The engineering properties of the modified and/or new Superpave mixes have impacted the durability and performance of the pavement structures and they are needed as inputs to the pavement structural design procedure. Based on this need, the Pavement Research Center of Excellence (PRCE) at Michigan State University (MSU) undertook a research project to develop, implement and verify test procedures to characterize the engineering properties of Superpave and other conventional mixes. The two-year project, which was sponsored by the Michigan Department of Transportation (MDOT), consisted of field and laboratory studies. The laboratory investigation program was undertaken to characterize the physical and the engineering properties of various asphalt mixes. The field program included coring and nondestructive deflection testing (NDT) using a Falling Weight Deflectometer (FWD). This paper summarizes the laboratory and field test procedures and presents a comparison between the field and the laboratory test results. It is shown that: „ The laboratory test procedures can be used to characterize the engineering properties of the asphalt mixes. „ The laboratory test results correspond well to the backcalculated modulus values. „ The laboratory classification of the fatigue and rut potentials of the asphalt mixes corresponds to the observed field-performance. „ All laboratory and field results indicate that most superpave mixes have higher resilient modulus values and lower fatigue and rut potentials than other asphalt mixes.


Effect of Superpave Gyratory Compactor Type on Compacted Hot Mix Asphalt (HMA) Density

M. Shane BuchananNational Center for Asphalt Technology277 Technology ParkwayAuburn, AL 36830Phone: 334-844-6334FAX:334-844-6248e-mail:[email protected]

E. Ray BrownNational Center for Asphalt Technology277 Technology ParkwayAuburn, AL 36830Phone: 334-844-6228FAX:334-844-6248e-mail:[email protected]

ABSTRACTThe 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 asphalt (HMA) mixes. 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 is 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/assurance results from a state DOT. The data was then analyzed to determine the statistical (precision) and potential project implications which 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/assurance testing of a given mix.


Gradation Effects on HMA Performance

Adam J. Hand 1, James L. Stiady 2, Thomas D. White 3, A. Samy Noureldin 4 and Khaled Galal5

1 Quality Systems Engineer, Granite Construction Incorporated, 1900 Glendale Avenue Sparks, NV 89431, Office: (775) 358-8792, Fax: (775) 355-3431, email: [email protected]

2 Staff Engineer, Kleinfelder, 5015 Shoreham Place, San Diego, CA 92122, Office: (858) 320-2000, Fax: (858) 320-2001, email: [email protected]

3 Professor and Head, Mississippi State University, Mississippi State, MS(662) 325-7185, Fax (662) 325-7189, email: [email protected]

4 Pavement Research Engineer, Indiana DOT, Research Division, 1205 Montgomery Street,West Lafayette, Indiana 47906 Office: (765) 463-1521, Fax: (765) 497-1665, email:[email protected]

5 Material Research and Accelerated Pavement Testing Engineer, Indiana DOT, Research Division, 1205 Montgomery Street, West Lafayette, Indiana 47906Office: (765) 463-1521, Fax: (765) 497-1665, email: [email protected]

ABSTRACTThe effect of gradation on hot mix asphalt (HMA) performance has long been a contentious issue. One objective of National Pooled Fund Study No. 176 was to evaluate the impact of gradation on the rutting performance of HMA mixture. To this end twenty-one Superpave mixtures were designed employing a range of materials, aggregate nominal maximum aggregate sizes, and gradations typical of those used throughout the United States. A suite of tests that included both laboratory and prototype scale loading were then used to evaluate the permanent deformation characteristics of the mixtures. Analysis of the data revealed that adequate performance could be obtained with mixture gradations plotting above (ARZ), through (TRZ), and below (BRZ) the restricted zone. Laboratory tests suggested that ARZ and/or TRZ gradations might provide better deformation resistance than BRZ gradations. However, prototype scale accelerated pavement testing did not show any clear trends in performance relative to gradation alone with respect to the restricted zone. This means that the restricted zone alone is not adequate to characterize gradation to ensure acceptable rutting performance and should therefore be omitted from Superpave specifications.

Key Words: rutting performance, aggregate, gradation, restricted zone, Superpave





Effect of Aggregate Gradation on Permanent Deformation of Superpave HMAPaper No. 01-2786

ARIF CHOWDHURY (Corresponding Author)Engineering Research Associate, Texas Transportation Institute, 508H CE/TTI Building, Texas A&M University, College Station, Texas 77843-3135, Tel: 979-458-3350, Fax: 979-845-0278, Email: [email protected]

JOSE D. C. GRAUMinistry of Transportation, Spain, Email: [email protected]

JOE W. BUTTONSenior Research Engineer, Texas Transportation Institute, 508D CE/TTI Building, Texas A&M University, College Station, Texas 77843-3135, Tel: 979-845-9965, Fax: 979-845-0278, Email: [email protected]

DALLAS N. LITTLESenior Research Fellow, Texas Transportation Institute, 601 CE/TTI Building, Texas A&M University,College Station, Texas 77843-3135, Tel: 979-845-9963, Fax: 979-845-0278, Email: [email protected]

ABSTRACTThe restricted zone in aggregate gradation curve is one of the most controversial components of the Superpave mix design process. The restricted zone was adopted in order to reduce premature rutting in hot mix asphalt (HMA) pavements. The validity of the restricted zone requirement has been questioned by both the owner agencies and the paving and aggregate industries. The purpose of this paper is to examine the effect of the restricted zone on pavement rutting. Four different types of aggregate were studied: crushed granite, crushed limestone, partially crushed river gravel, and mixture of partially crushed river gravel as coarse aggregate with natural sand as fines. For each aggregate, HMA mixtures were designed using three different gradations: above the restricted zone, through the restricted zone, and below the restricted zone. Mixtures were tested using Superpave Shear Tester (SST). Four different tests were performed: simple shear at constant height, frequency sweep at constant height, repeated shear at constant stress ratio, and repeated shear at constant height. All twelve mixtures were also tested with Asphalt Pavement Analyzer (APA) to evaluate the rutting potential of those mixtures. From the analysis of the test results of SST and APA, we conclude that there is no relationship between restricted zone and permanent deformation. Further, these gradings passing below the restricted zone most often exhibited the greatest permanent deformation. Hardly ever did a gradation through the restricted zone yield the highest permanent deformation.


Forensic Analysis of Arizona™s US-93 Superpave sectionsPaper No. 01-0345

Naga ShashidharFHWA/Soil and Land Use Technology, Inc.6300 Georgetown PikeMcLean VA 22101Ph: (202) 493-3101Tel: (202) [email protected]

John D™AngeloFederal Highway Administration, HIPT-10400 7th Street, SWWashington DC 20590Tel. (202) 366-0121Fax: (202) [email protected]

George WayArizona Department of Transportation807 W. Keating Ave.Phoenix AZ 85210Tel: (602) 255-8085Fax: (602) [email protected]

Thomas HarmanFederal Highway Administration, HRDI-116300 Georgetown PikeMcLean VA 22101Ph: (202) 493-3072Tel: (202) [email protected]

AbstractIn 1993, State of Arizona placed Long Term Pavement Performance (LTPP) SPS-1 and SPS-9 sections that included three different pavements sections at US 93 in Kingman, AZ. These were two Superpave sections and an Arizona™s base mix. After four years, the Superpave sections began to show moisture damage, raveling and fatigue cracking, while the Arizona section performed well. To determine the cause of these failures, a forensic study was initiated. This study revealed that the absence of anti-strip additives could have been the cause of moisture damage. However, the reason for ravelling and fatigue cracking could not be explained other than the fact that these might be side effects to moisture damage. Three-dimensional images of the cores obtained by x-ray computed tomography (XCT) from these sections showed that the size and distribution of air-voids within the bulk of the pavements were such that the asphalt matrix did not hold the large aggregates tight. This would explain the propensity of the Superpave sections for raveling and fatigue cracking. Further, the larger average size of the air-voids in the Superpave sections possibly provided channels for easy access for water thereby providing the opportunity for moisture damage.



Design, Construction, and Early Performance of Virginia’s Hot-Mix Asphalt Stabilizer and Modifier Test SectionsPaper No. 01-2334

Brian D. ProwellSenior Research ScientistVirginia Transportation Research Council530 Edgemont RoadCharlottesville, VA 22903Telephone: (804) 293-1919Fax: (804) 293-1990

ABSTRACTThis study evaluated three modifiers and two types of fibers (stabilizers) for hot-mix asphalt (HMA) commonly available in Virginia. Ten test sections were built in 1995 on I-66, west of Manassas, Virginia. The modified asphalts complied with the specifications for performance grade (PG) 76-22 and were placed in both dense-graded Marshall and coarse-graded Superpave mixes. The fibers were placed only in the dense-graded Marshall mixes. During design, the dense-graded Marshall mix complied with all of the Superpave requirements except for the gradation, which passed through the restricted zone. Samples from the sections were tested for asphalt content, gradation, and Superpave and Marshall volumetrics and were rut tested using both the Georgia loaded-wheel tester and the asphalt pavement analyzer. Field samples generally passed Marshall volumetrics and generally failed Superpave volumetrics. Neither laboratory compaction method correlated with the ultimate field densities. Both tests indicated that the sections were rut resistant. All of the sections have been rut resistant and have performed well in the field after 45 months of service.


Effect of Mix Gradation on Rutting Potential of Dense Graded Asphalt MixturesTRB Paper No.:01-2051

Prithvi S. KandhalAssociate DirectorNational Center for Asphalt Technology (NCAT)277 Technology ParkwayAuburn, AL 36830Phone: 334-844-6242Fax: 334-844-6248Email: [email protected]

Rajib B. MallickAssistant ProfessorWorcester Polytechnic Institute (WPI)100 Institute RoadWorcester, MA 01609Phone: 508-831-5289Fax: 508-831-5808Email: [email protected]

ABSTRACTThe objective of this study was to evaluate the effect of mix gradations, both complying with and violating the Superpave restricted zone, on rutting potential of hot mix asphalt (HMA) mixtures. Superpave gyratory samples of mixes with granite, limestone, and gravel aggregates were used. The following gradations were used: gradation above the restricted zone, gradation through the restricted zone in close proximity to the maximum density line, and gradation below the restricted zone. Rut tests were conducted at 64EC with the Asphalt Pavement Analyzer (APA) under 689 kPa contact pressure and 45.2 kg wheel load. Rut depths were measured at the end of 8,000 cycles. Repeated shear tests at constant height were also conducted with the Superpave shear tester (SST). Statistical analysis of rut data generally indicates a significant difference between rut depths obtained in mixes using different aggregate types and different gradations. The gradations violating the restricted zone did not necessarily give relatively higher rut depths compared to the gradations in compliance with the zone.

KEY WORDS: asphalt mixtures, hot mix asphalt, gradation, Superpave, restricted zone,rutting, permanent deformation


Evaluation of Laboratory Measured Crack Growth Rate for Asphalt Mixtures

Zhiwang Zhang, Graduate Research AssistantReynaldo Roque, Professor, (Corresponding Author)Bjorn Birgisson, Assistant Professor

Department of Civil EngineeringUniversity of Florida345 Weil HallGainesville, FL 32611-6580Tel: (352)392-7368Fax: (352)392-3394e-mail: [email protected]

ABSTRACTA clear understanding of the cracking mechanisms of asphalt mixtures is needed to identify the most rational approach to analyze its cracking behavior. Asphalt mixture properties were determined for eight asphalt mixtures of known cracking performance. This included the determination of crack growth rates for each mixture using the method developed by Roque et al. (1). The crack growth rates determined in the laboratory were evaluated to determine: (1) the validity of the test results (2) the relationship, if any, between laboratory crack growth rates and field performance; (3) the relationship between the measured crack growth rates and other mixture properties; (4) the validity of Paris law of crack propagation for evaluating asphalt mixture performance in the field. Through this evaluation, it was found that Paris law does not appear to incorporate all aspects involved in the mechanism of cracking of asphalt mixtures subjected to generalized loading conditions, such as those encountered in pavements in the field. Therefore, a concept involving the use of fracture energy as a failure criterion for the initiation and propagation of cracks appears to be warranted. This concept appears to have the potential of explaining both laboratory measured crack growth rates and field cracking performance.

Key word: fatigue cracking, crack growth rate, fracture mechanics, asphalt mixtures


Low-temperature Thermal Cracking of Asphalt Binders as Ranked by Strength and Fracture Properties

Dr David A. Anderson: Professor, Penn State University201 Transportation Research Building,University Park, PA 16802Telephone: (814) 863-1912, E-mail: [email protected]

Dr. Laurence Champion-Lapalu Research Scientist, Elf-Antar FranceElf Research Center, BP22, 69360 Solaize, FRANCE

Dr. Mihai O. Marasteanu: Assistant Professor, University of Minnesota500 Pillsbury Drive S.E., Minneapolis, MN 55455Telephone: (612) 625-5522, E-mail: [email protected] Research Associate, Penn State University

Yann M. Le Hir: Visiting Researcher, Penn State - Elf201 Transportation Research Building, University Park, PA 16802Telephone: (814) 865-3188, E-mail: [email protected]

Dr. Jean-Pascal Planche: Research Project Manager on Asphalt, Elf-Antar FranceElf Research Center, BP22, 69360 Solaize, FRANCEE-mail: [email protected]

Didier Martin Research Study Leader on Asphalt, Elf-Antar FranceElf Research Center, BP22, 69360 Solaize, FRANCEE-mail: [email protected]

ABSTRACTThe original Superpave low-temperature specification for asphalt binders placed limits on the low temperature stiffness (S) and m-value (m). A recently approved alternative to the original Superpave asphalt binder low temperature specification makes use of the measured stiffness and tensile strength of the binder to determine a critical cracking temperature. In this paper the thermal cracking temperatures are presented for 42 plain and modified asphalt binders. Thermal cracking temperatures determined by the original and recently approved alternative Superpave specification are compared. The fracture toughness, KIC, can also be used to evaluate low-temperature cracking properties of asphalt binders. Fracture properties obtained for fourteen asphalt binders are compared to the thermal cracking temperatures as determined by the original and recently adopted alternative Superpave specification. The set of fourteen binders were produced from a common base material but modified by different means. For the set of fourteen binders there is little difference in their ranking according to both the original and recently proposed alternative Superpave low temperature criteria. However, their ranking is quite different based on the fracture properties as measured by KIC. KIC appears to provide a much more discriminating ranking of the binders than either of the Superpave specification criteria.

Key Words: Asphalt binder, Bitumen, Superpave, thermal cracking, KIC, stiffness, m-value, fracture,failure strain, fracture toughness, direct tension, specifications, morphology.




An Evaluation of Factors Affecting Permeability of Superpave Designed Pavements

Authors: Rajib B. Mallick, Assistant ProfessorWorcester Polytechnic InstituteCEE Department, 100 Institute Road, MA 01609Phone: (508) 831 5289, Fax: (508) 831 5808,e-mail: [email protected]

L. Allen Cooley, Jr., Research EngineerNational Center for Asphalt Technology277 Technology Parkway, Auburn, AL 36830Phone: (334) 844 6336, Fax: (334) 844 4485,e-mail: [email protected]

Matthew R. Teto, Asphalt Research EngineerWorcester Polytechnic InstituteCEE Department, 100 Institute Road, MA 01609

Phone: (508) 831 6034, Fax: (508) 831 5808, e-mail: [email protected]

Richard L. Bradbury, EngineerMaine Department of Transportation219 Hogan Road, PO Box 1208, Bangor, ME 04402Phone: (207) 941 4597, Fax: (207) 287 3392,e-mail: [email protected]

Dale Peabody, Maine Department of Transportation16 State House Station, Augusta, ME 04333-0016Phone: (207) 287 5662, Fax: (207) 287 3292,e-mail: [email protected]

ABSTRACTIt can be expected that the life of a permeable pavement would be shorter than that of an impermeable pavement, due to deterioration of mix through water and air infiltration, and subsequent stripping and oxidation and hardening of binder. Recent work has indicated that coarse graded Superpave mixes can be excessively permeable to water at air void levels around 6 percent. The objectives of this study were to evaluate the permeability of Superpave designed mixes used by Maine Department of Transportation and determine the effect of gradation, lift-thickness, and in-place density on the permeability of these mixes. Five Superpave projects were selected for this study. These projects included coarse-graded 9.5 mm, 12.5 mm, 19.0 mm, and 25.0 mm nominal maximum aggregate size (NMAS) mixes and one fine-graded 9.5 mm NMAS mix. Based on the National Center for Asphalt Technology permeameter, a field permeameter was developed at the Worcester Polytechnic Institute (WPI) laboratory. This permeameter was used for testing at ten locations per project. One core was obtained at each of these test locations. The cores were used to determine in-place density at each of the test locations. Field testing was done at random locations, immediately behind the finish roller. Loose mixes were also obtained from each project. The loose mixes were compacted to 5 percent air voids, and to different thickness to evaluate the effect of thickness on permeability. On the basis of results obtained in this study, the following conclusions can be made: 1. Air void content (as measured by voids in total mix) of dense graded HMA has a significant effect on in-place permeability of pavements, 2. There is a significant effect of NMAS on the permeability of coarse-graded Superpave designed mixes. It was shown that at a given in-place air void content the permeability increased by one order of magnitude as the NMAS increased, 3. Samples with different thicknesses showed that there is a decrease in permeability with an increase in thickness. It is recommended that State DOTs consider designing mixes to be placed 100 mm below the pavement surface on the fine side of the maximum density line. By designing base mixes on the fine side of the maximum density line, these mixes could be made less permeable than coarse graded mixes at similar void levels and thus less susceptible to allowing moisture or moisture vapor to propagate upward through the pavement structure. This in turn should reduce the potential for moisture damage within pavement structures.

Key words: Superpave, coarse-graded, permeability, air voids, gradation


Variability of Asphalt Mixtures Tests Using the Superpave Shear Tester Repeated Shear at Constant Height TestPaper 01-2098

Pedro Romero, Ph.D., P.E.Assistant Professor of Civil EngineeringThe University of Utah122 South Central Campus Drive, Suite 104Salt Lake City, UT 84112-0561Ph: 801-581-6931Fax: 801-585-5477e-mail: [email protected]

R. Michael Anderson, P.E.Director of ResearchThe Asphalt InstituteReseach Park DriveLexington, KY 40512-4052Ph: 606-288-4984Fax: 606-288-4999e-mail: [email protected]

ABSTRACTAnalyses were conducted on data obtained from the Superpave Shear Tester Repeated Shear at Constant Height Test (RSCH). The data indicated that, even under the most controlled experimental conditions, the resulting parameters showed high variability. Up to six replicates samples were tested using an extra shear LVDT. The coefficient of variation of the permanent strain at 5,000 load cycles for six samples was between 10 and 20 percent in most cases. Out of different options studied to decrease variability, the trimmed-mean method provided the greatest decrease in the coefficient of variation without affecting the mean of the results. In this method, five specimens are tested, the high and low values eliminated, and the remaining three are used to obtain the mean and standard deviation of the results. Since the suggested trimmed-mean method requires an increase in the number of samples tested to five, it is proposed that the number of load cycles used in the RSCH be reduced for materials to be placed in low volume roads.

KEYWORDSAsphalt Mixtures, Superpave Shear Tester, Repeated Shear at Constant Height, Mean, Coefficient of Variation.


Development of Performance-Based Mix Design for Cold In-Place Recycling of Asphalt Mixtures

Todd E. BraytonBryant Associates, Inc.12 Breakneck Hill RoadLincoln, RI 02865Tel: (401) 722-7660 Fax: (401) 722-7530e-mail: [email protected]

K. Wayne Lee, Ph.D., P.E.Professor and Director of Research & Development, Transportation CenterBliss Hall #212University of Rhode IslandTel: (401) 874-2695 Fax: (401) 874-2297e-mail: [email protected]

David Gress, Ph.D., P.E.Professor, Department of Civil EngineeringUniversity of New Hampshire235 Kingsbury HallDurham, NH 03824Tel: (603) 862-1410 Fax: (603) 862-2364e-mail: [email protected]

Jason HarringtonFederal Highway Administration, Pavement Division400 Seventh Street, S.W.Washington, D.C. 20590Tel: (202) 366-1576 Fax: (202) 366-9981e-mail: [email protected]

ABSTRACTThe high cost and environmental impact of pavement rehabilitation has led to an increase in the use of Cold In-Place Recycling (CIR) as an effective alternative to other rehabilitation strategies. However, currently there is not a universally accepted or standard mix-design for CIR. Therefore, the project is being undertaken with the objective to develop a performance-based mix-design procedure for CIR through laboratory evaluation and limited field verification. The present project focuses on partial-depth CIR using asphalt emulsions as the recycling agent. After evaluating the modified Marshall mix-design recommended by the AASHTO Task Force No. 38, a new volumetric mix-design has been developed utilizing the Superpave gyratory compactor and technology. It requires that specimens are prepared at densities similar to those found in the field. It also suggests that specimens should be cured at 140 0 F for 24 hours. This will allow for the most consistent specimens, while at the same time, most effectively utilizing the time of laboratory personnel. The performance of CIR mixtures prepared and constructed in accordance with the new mix-design is being evaluated in the laboratory as well as in the field. The resistance characteristics, in relation to rutting and fatigue cracking, were predicted using the computer program, VESYS. Creep compliance and strength were determined using the Indirect Tensile Tester (IDT) to evaluate the resistance against the low-temperature cracking.


Hydraulic Conductivity (Permeability) Of Laboratory Compacted Asphalt MixturesPaper No. 01299

Kunnawee Kanitpong, Craig H. Benson, Hussain U. BahiaDepartment of Civil and Environmental Engineering2210 Engineering Hall, 1415 Engineering Dr.The University of Wisconsin-Madison, Madison, WI, [email protected], [email protected], [email protected]

ABSTRACTA flexible-wall permeameter was used to study the hydraulic conductivity (also referred to as “permeability”) of asphalt mixtures commonly used in Wisconsin. Effects of saturation, hydraulic gradient, and side-wall leakage were studied to determine an appropriate testing procedure. The test procedure was then used to study how mixture design variables affect hydraulic conductivity. Four aggregate gradations were tested to develop relationships between hydraulic conductivity and volumetric properties. Two mixtures were also compacted to different heights (ranging from 37.5 mm to 110.0 mm) to evaluate how lift thickness affects hydraulic conductivity. Results of the tests indicate that the backpressure saturation procedure can be used to ensure that specimens are saturated and that the saturated hydraulic conductivity is measured. Sidewall leakage was eliminated by using bentonite clay as a sealing agent and the hydraulic gradient was selected based on a parametric experiment showing how gradient affects hydraulic conductivity. Tests on the various mixtures showed that a power law relationship exists between air voids content and hydraulic conductivity, but that the hydraulic conductivity also depends on the gradation. Lift thickness is also important, with lower hydraulic conductivity obtained with greater lift thickness at a given air voids content. The results show that hydraulic conductivity cannot be controlled only by limiting air voids and that a hydraulic conductivity test is necessary for a mixture design that includes hydraulic conductivity as a criterion.

Key Words: hydraulic conductivity, permeability, asphalt, Superpave, air voids, mineral aggregate, hot mix asphalt


Effect of Short Term Oven Aging on Volumetrics and Selection of N-DesignTRB Paper Id – 01-3122

Bradley J. McMullen, EngineerApplied Pavement Technology, Inc.17W703 Butterfield Rd, Suite AOakbrook Terrace, IL 60181Phone: 630-268-8483Fax: [email protected]

William R. Vavrik , Senior Engineer ERES Consultants Applied Research Associates, Inc. 505 W. University Ave. Champaign, Illinois 61820 (217) 356-4500 (217) 356-3088 fax

[email protected]

Samuel H. Carpenter, Professor University of Illinois Urbana-ChampaignDepartment of Civil Engineering205 N. Mathews Ave., MC-250Urbana, Illinois 61801(217) 333-4188 (217) 333-1924 fax [email protected]

ABSTRACTThis report presents findings on the effect of conditioning time on the volumetric properties of Superpave Gyratory Compactor (SGC) prepared asphalt mixtures. Field mixtures were sampled from the producing plants and then recreated in the laboratory following 3 different short-term conditioning procedures to measure the effect on the N-design value of the mixture. The projects selected represent three different N-design levels, have different nominal maximum aggregate size, aggregate sources, and asphalt binder types. Bulk Specific Gravity (Gmb) samples were aged at compaction temperature for 1-hr, 2-hr, and 4-hr. Maximum Specific Gravity (Gmm) samples were also aged at compaction temperature for 0-hr, 2-hr, and 4-hr. The short-term aging times are based off of Illinois Department of Transportation aging procedures, current National Center for Asphalt Technology recommendations, and the original Superpave conditioning specifications. It was observed in this study that increased conditioning time has a greater impact on the volumetric properties of polymer-modified binder mixes than on neat binder mixes. Also, noticed is that the presence of polymers in the binder appears to have greater effect than the higher temperatures used for conditioning polymer-modified HMA.

Key Words: Short-term-Oven-Aging, Polymers, air voids, density, volumetrics.




Development of Critical Field Permeability and Pavement Density Values for Coarse-Graded Superpave PavementsTRB Paper No.: 01-0344

L. Allen Cooley, Jr.,Research EngineerNational Center for Asphalt Technology (NCAT)277 Technology ParkwayAuburn, AL 36830Phone: 334-844-6336Fax: 334-844-6248Email: [email protected]

E. Ray Brown,DirectorNational Center for Asphalt Technology (NCAT)277 Technology ParkwayAuburn, AL 36830

Phone: 334-844-6202Fax: 334-844-6248Email: [email protected]

Saeed Maghsoodloo, ProfessorIndustrial Systems Engineering210 Dunstan HallAuburn University, AL 36849Phone: 334-844-1045Fax: 334-844-1381Email: [email protected]

ABSTRACTWithin the hot mix asphalt (HMA) community, it is generally accepted that the proper compaction of HMA is vital for a stable and durable pavement. Low in-place air voids have been shown to lead to rutting and shoving while high in-place air voids have been shown to reduce a pavement’s durability through moisture damage and excessive oxidation of the asphalt binder. Recent research has suggested that coarse-graded Superpave designed mixes are more permeable than conventionally designed pavements at a given air void content. This higher permeability can lead to durability problems. This study was conducted to evaluate at what pavement density coarse- graded Superpave mixes become permeable using a field permeability device. Based upon the data collected, 9.5 and 12.5 mm nominal maximum size mixtures (NMAS) become excessively permeable at approximately 7.7 percent in-place air voids, which corresponded to a field permeability value of 100×10 -5 cm/sec. Mixtures having a 19.0 mm NMAS became permeable at an in-place air void content of 5.5 percent air voids, which provided a field permeability value of 120×10 -5 cm/sec. Coarse-graded mixes having an NMAS of 25.0 mm became permeable at 4.4 percent air voids, which corresponded to a field permeability value of 150×10 -5 cm/sec.


New Jersey’s Superpave Specification: The Next GenerationPAPER 01-0268

Richard M. WeedNew Jersey Department of Transportation

ABSTRACTThe testing of New Jersey’s first acceptance procedure for hot-mix asphalt (HMA) pavement designed by the Superpave method began in 1998 with the construction of a series of pilot projects. A distinct feature of the prototype specification was the use of a composite pay equation that expressed the pay factor as a function of the average of the quality levels for air voids, thickness, and riding quality. Although the quality received under this specification has ranged from good to excellent, a national survey recently conducted by the NJDOT suggests that pavement performance is more appropriately characterized by an additive function rather than by the average of the individual quality measures. A new pay schedule, developed from a combination of performance and analytical data and the opinion survey, produces larger bonuses for superior quality and larger pay reductions for poor quality. NJDOT engineers also realized that the original RQL provision based on individual quality measures did not properly account for the combined effect of deficient quality in two or more quality measures. It was also discovered that the use of a composite quality measure not only corrects these deficiencies, it also makes it possible to key the pay equation more directly to performance while substantially reducing the complexity of the acceptance procedure as a whole. Consequently, the new procedure is much closer to a true performance-related specification and, at the same time, is far simpler to understand and apply than its predecessors. The new version of the specification was developed cooperatively through a task force representing the NJDOT, FHWA, and several Industry associations, and is currently under test on a series of pilot projects.

KEY WORDS, Hot-Mix Asphalt Pavement, Superpave Design Method, Statistical Quality Assurance, Construction Acceptance Procedures, Adjusted Pay Schedules, Composite Quality Measures


Development of a Void Pathway Test for Investigating Void Interconnectivity in Compacted Hot-Mix Asphalt ConcretePaper 01-2810

Kevin D. Hall, Ph.D., P.E.Hooi G. Ng

ABSTRACTIn response to reports of moisture “weeping” out of hot-mix asphalt concrete (HMAC) pavements, research was initiated relating to the permeability of coarse-graded Superpave mixes. Tests using a falling-head permeameter yielded inconsistencies in the relationship between air voids and permeability. It was hypothesized that the inconsistencies related to the inability of the permeability device and procedures to account for the void characteristics in a compacted specimen – void size, arrangement, and interconnectivity. A testing apparatus and methodology termed the “Void Pathway Test” (VPT) was developed to attempt to characterize such void characteristics. The VPT forces air (under pressure) through an HMAC specimen; a soap solution “painted” on the surfaces of the specimen create bubbles at exit points for the air flow. Void pathways and characteristics in the specimen are related to the number and size of bubbles mapped on specimen surfaces. Results from 43 HMAC specimens indicated that significantly more void openings occur on perimeter surfaces than on cross-sectional surfaces. The majority of perimeter openings occurred within 25 mm of the cross-sectional surface through which air was input. No discernable pattern was evident in the number, arrangement, or interconnectivity of voids mapped on both cross-sectional surfaces of a specimen. The results suggest that void pathways are not relatively straight and vertical, but convoluted – and most tend towards the perimeter of a compacted specimen. These findings could significantly affect permeability testing using falling-head permeameters by challenging the basic assumptions relating to the flow necessary for using Darcy’s Law to calculate permeability.


Asphalt Permeability Testing: Specimen Preparation and Testing VariabilityPaper No. 01-2076

G. W. Maupin, Jr.Principal Research ScientistVirginia Transportation Research Council530 Edgemont RoadCharlottesville, VA 22903Telephone: (804) 293-1948Fax: (804) 293-1990e-mail: [email protected]

ABSTRACTThe concern over asphalt mixtures allowing surface water to enter has led to an interest in developing a reliable permeability test. Over the last several years, several studies related to permeability testing have been conducted, and the American Society for Testing and Materials (ASTM) is currently developing a falling head test method to determine asphalt permeability. The Virginia Department of Transportation became interested in testing its pavements and using permeability as a design consideration. As a member of the ASTM task group, the author investigated the effect of sawing specimens, a technique that is often used to separate the asphalt layers. Sawing was found to cause a reduction in permeability. Since a falling head test might be used in acceptance and design specifications, it was important to determine its associated variability. Permeability variability was computed from test data derived from field cores and specimens prepared in the laboratory. Repeat tests by different operators indicated differences that warrant additional investigation.


Correlation of Imaging Shape Indices of Fine Aggregate with Asphalt Mixture PerformancePaper No. 01-2132

Eyad Masad, Assistant Professor (Corresponding Author)Dana Olcott and Laith Tashman Graduate Research AssistantDepartment of Civil and Environmental EngineeringWashington State UniversityPullman, WA 99164Phone: 509 335 9147Fax: 509 335 7632E-mail: [email protected]

Thomas White, ProfessorDepartment of Civil EngineeringMississippi State University204 McCain Engineering BuildingP.O. Box 9546, MSU, MS 39762Phone: 662-325-7185E-mail: [email protected]

ABSTRACTThis study addresses the relationship between fine aggregate shape properties and the performance of hot mix asphalt (HMA). Aggregate shape was expressed in terms of three independent properties: form, angularity, and texture. Image analysis procedures and indices were developed to capture these properties. The indices were measured for twenty-two aggregate samples. Then, they were related to the HMA rutting resistance measured under wet and dry conditions in the Purdue wheel-tracking device (PURWheel). Among the different aggregate shape properties, the texture had the strongest correlation with the rutting resistance. The resistance to rutting increased exponentially with an increase in aggregate texture.

KEY WORDS: Image Analysis, Fine Aggregate, Asphalt Mixture, Performance


A Comparison of Four Brands of Superpave Gyratory Compactors

John HinrichsenIowa Department of TransportationMaterials Department800 Lincoln WayAmes, Iowa 50010515-239-1601FAX [email protected]

ABSTRACTFour different brands of gyratory compactors were chosen for an experiment to determine if the devices would produce comparable results. For this experiment, a Troxler model 4140, a Test Quip Brovold Gyratory, a Pine model AFGC 125X and an Interlaken model #1 were used. The four brands of gyratory compactors were compared on four different plant produced Superpave mixtures. Three of the four mixtures were coarse graded (below the restricted zone), the other was fine graded (above the restricted zone). All the gyratory compactors were calibrated according to the manufacturers recommendations. Testing was randomized to reduce bias. Comparison of results between the brands indicates that distinct differences exist between the different devices. The same trend was observed for all four mixtures, however, the magnitude of the differences was mix dependent. The coarse mixtures showed greater differences than the fine mixture. Under the conditions of this experiment, the Interlaken produced lower densities than the other devices.

Key words: Gyratory Compactor, calibration, Superpave, correlation.


Field Conditioning of Superpave Asphalt MixesPaper No. 01-0395

James A. MusselmanFlorida Department of Transportation(352) [email protected]

Gale C. Page(352) [email protected]

Gregory A. Sholar(352) [email protected]

ABSTRACTFailing volumetric properties (low air voids and VMA) have been a common occurrence in the production of Superpave mixes in Florida and nationally. There are several potential causes of this problem including the effect of asphalt absorption as related to conditioning time. The intent of this study was to determine 1) if the two hour force-draft oven conditioning adequately simulates actual roadway conditions, and 2) how can actual roadway conditions best be simulated when the asphalt mixture is sampled and tested immediately following production at the plant. The results of this study indicate: 1) three hours of conditioning during design best correlated with roadway conditions, 2) a one-hour conditioning time at the asphalt plant will resulted in maximum specific gravity values that best correlated with roadway conditions, 3) one hour of conditioning at the asphalt plant increased the air voids of the mix by 0.5% for absorptive materials and 0.25% for non-absorptive materials and 4) conditioning had minimal effect on bulk density values.


A Mathematical Model for Calculating Pavement Temperatures, Comparisons between Calculated and Measured Temperatures.Paper number: 01-3543

Åke Hermansson. Researcher,Highway Engineering, Swedish National Road and Transport Research Institute, VTI,SE-581 95 Linköping, SwedenandDept. of Civil and Mining Eng. Luleå University of Technology, SE-971 87 Luleå, Sweden.

Åke HermanssonVTISE-581 95 LinköpingSwedenPhone: +4613204072Fax: +4613141436Email: [email protected]

ABSTRACTA simulation model has been developed to calculate the temperatures of the pavement during summer condition. Input data to the model are hourly values for solar radiation, air temperature and wind velocity. Longwave radiation incident to and outgoing from the pavement surface, is calculated from the air and pavement surface temperatures, respectively. The portion of the incident shortwave radiation absorbed by the pavement surface is calculated from the albedo of the surface. By means of a finite difference approximation of the heat transfer equation, the temperatures under the surface are calculated. Apart from radiation and heat transfer, convection losses from the pavement surface are also calculated based on wind velocity, air temperature and surface temperature. The model is validated by using data from 12 different sections in the LTPP program, where hourly measurements are made of weather as well as of pavement temperatures at different depths. One set of parameter values for albedo, emissivity, longwave counter radiation and convection losses giving a good correspondence for asphalt concrete and one for cement concrete are given. The formulas used in “Superpave” to calculate maximum pavement temperatures are based on the assumption that there is an equilibrium when a maximum temperature is reached. Such an equilibrium assumption can strongly be questioned. The author instead suggests, that the proposed simulation model can be used to calculate a maximum temperature of a pavement. Either by calculating a maximum solar radiation, or, as is suggested in the present paper, by using weather data. Then, sets of calculation parameters are used for asphalt concrete and cement concrete pavements respectively. The parameters are obtained by analyzing several years weather data and the corresponding pavement temperature information.

Key words: Pavement temperatures, Maximum temperature, Simulation model, Superpave, LTPP


An Evaluation of Field Density Measuring DevicesPaper No. 01-0390

Gregory A. Sholar(352) [email protected]

Gale C. Page(352) [email protected]

James A. Musselman(352) [email protected]

Patrick B. Upshaw(352) [email protected]

ABSTRACTThe use of non-destructive devices for the measurement of in-place density of a compacted asphalt mat would be beneficial in that it would save time and money compared to cutting roadway cores for the determination of pay factors by Florida Department of Transportation (FDOT) Acceptance personnel. However, the use of non-destructive devices was discontinued by the FDOT in 1997 during the onset of Superpave construction because it was found that the gauges were not providing accurate readings when compared to the core densities. The recent development of non-nuclear density measuring devices has prompted the need for research studies that would again compare core density values to gauge density values for both coarse and fine graded Superpave mixes. This study compared core and gauge densities for two separate test sections (one coarse and one fine graded Superpave mix). Nuclear gauges from Troxler and CPN and non-nuclear gauges from Transtech were used in the study. The results indicate that when comparing standard deviations and means of the gauge densities to the core densities, the CPN MC3 gauge outperformed all of the other gauges used in this study. The Transtech gauges had comparably equivalent mean density values but had very high standard deviations. The Troxler gauges (three models were tested) had mixed results. In general, all of the gauges did not perform better on the fine graded mix as compared to the coarse graded mix. Although the CPN MC3 gauge used in this study provided results very close to the core density values, use of the gauge for Acceptance is not recommended at this time since these results are based on one gauge and there are issues related to requiring a specific manufacturer™s gauge to be used. It is recommended that the Transtech gauges be allowed for use as a Quality Control tool since their variability is not necessarily worse than an allowable nuclear gauge.


Discrete Element Modeling of Asphalt Concrete: A Micro-Fabric Approach

William G. Buttlar, Ph.D., P.E.Assistant Professor, Department of Civil and Environmental EngineeringUniversity of Illinois at Urbana-Champaign205 North Mathews Avenue1212 Newmark Laboratory205 North Mathews AvenueUrbana, IL 61801Ph: (217) 333-5966Fax: (217) [email protected]

Zhanping You, M.S.C.E.Graduate Research Assistant, Department of Civil and Environmental EngineeringUniversity of Illinois at Urbana-Champaign3214 Newmark Laboratory205 North Mathews AvenueUrbana, IL 61801Ph: (217) 333-6974Fax: (217) [email protected]

ABSTRACTMicromechanical modeling has tremendous potential benefits in the field of asphalt technology, for reducing or eliminating costly tests to characterize asphalt-aggregate mixtures for the design and control of flexible pavement structures and materials. In time, these models could provide a crucial missing link for the development of true Performance-Related Specifications for hot-mix asphalt (HMA). A microfabric discrete element modeling (MDEM) approach is presented for modeling asphalt concrete microstructure. The technique is a straightforward extension of a traditional DEM analysis, where various material phases (e.g., aggregates, mastic) are modeled with clusters of very small discrete elements. The MDEM method has all the benefits of traditional DEM, e.g., the ability to handle complex, changing contact geometries, large displacements and crack propagation, and the ability to simulate specimen assembly (e.g., laboratory compaction of the asphalt mixture). By modeling inclusions such as aggregates with a “mesh” of small discrete elements, it is also possible to model complex aggregate shapes and the propagation of cracks around or through aggregates during a strength test. A commercially available DEM package was used to demonstrate the usefulness of the MDEM approach. A method was also presented to obtain the properties of the matrix material in an asphalt mixture, which is typically difficult to determine experimentally. This study was limited to two-dimensional analysis techniques and involved the simulation of small test specimens. Follow-up studies involving larger specimen models and three-dimensional modeling capabilities are underway.



Field Tests and Economic Analysis of High-Cure Crumb-Rubber Modified Asphalt Binders in Dense-Graded Mixes

Jason F. Chipps, Richard R. Davison, Cindy K. Estakhri, and Charles J. Glover* Dept. of Chemical Engineering Texas Transportation InstituteTexas A&M University College Station, TX 77843-3122 * Corresponding Author - Phone 979-845-3361 - Fax 979-845-6446 - E-mail: [email protected]

ABSTRACTThis paper reports field implementation of laboratory research. Laboratory work assessed several production methods for blending ground tire rubber with asphalt and also the resulting binder properties, especially as they relate to Superpave performance specifications and durability. Field work included commercial-scale production of high-cure crumb-rubber binders at asphalt supplier sites and monitoring of contractor placement. This was carried out at sites in Bryan, Texas, (July, 1998) and in League City, Texas, south of Houston (June 2000). Both of these implementation tests utilized dense graded mixes and demonstrated the ability of high-cure crumb-rubber materials to be used in conventional settings with no hot-mix or pavement contractor adjustments. Binder rubber content varied from 8 to nearly 18 weight percent while binder content in the mix was under 5 weight percent. Long-term laboratory aging of these binders indicates a reduced hardening rate compared to the non-rubber base AC that would provide more than enough improvement to support its use, according to a capitalized cost life-cycle analysis.


Measurement of Flat and Elongation of Coarse Aggregate Using Digital Image Processing

Norbert H. Maerz, Department of Geological Engineering, University of Missouri-Rolla, 1006 Kingshighway, Rolla MO, 65409, USATel: (573) 341-6714, Fax: (573) 341-4368, e-mail: [email protected].

Mike Lusher, Department of Civil Engineering,University of Missouri-Rolla,111 Bultler-Carlton Hall, Rolla, MO, 65409-0660, USA Tel: (573) 341-4457, Fax: (573) 341-4729, e-mail: [email protected].

ABSTRACTCoarse aggregate shape (flat and elongated) and angularity are important issues in the highway industry. Elongated aggregates tend to break down during the asphalt emplacement process, or align themselves, resulting in anisotropic pavements. The use of angular aggregate results in a greater interlock and strength of the asphalt product. Measurement of particle shape is a tedious subjective procedure, resulting in a great deal of uncertainty about the results, and indeed of the ability of the tests to reasonably characterize the population of aggregates being produced. Digital image processing is a new approach to measuring these characteristics of aggregates. A new measuring system called WipShape has recently been developed. It images each particle separately, and from two views. A mini-conveyor system has been developed to parade individual fragments past two orthogonally oriented synchronized cameras, fed by aggregates from a hopper. This system designed for continuous automated operation, measures flat and elongated aggregates at ratios of 5:1, 4:1, 3:1, and 2:1. It also has the potential to report various shape factors, including principal axis ratios, roundness, sphericity and angularity. Simultaneously it will produce size distribution curves, and shape measurement summaries by size classes. Research will be conducted to determine if the percentage of fractured faces can also be measured.

KEYWORDSFlat and elongated, Coarse aggregate angularity, Digital image processing, Automated measurements


Microstructure Study of WesTrack Mixes from X-ray Tomography ImagesPaper No. 01-2632

L.B.Wang, Assistant ProfessorDepartment of Civil and Environmental EngineeringLouisiana State University and Southern University, Baton Rouge, LA 70803Tel: (225)388-4821, Fax: (225)578-8652, Email:[email protected]

Dr. J. D. Frost, Professor (Author to Contact)School of Civil and Environmental EngineeringGeorgia Institute of Technology, Atlanta, GA 30332

Tel: (404)894-2280, Fax: (404)894-2281, Email: [email protected]

Dr. Naga Shashidhar, Material ScientistSoil and Land Use Technology, Inc., Under Contract with Federal Highway Administration6300 Georgetown Pike, Federal Highway Administration, McLean, VA 22101Tel: (202)493-3101, Fax:(202)493-3161, Email:[email protected]

ABSTRACTAsphalt concrete is a composite comprised of aggregates, air voids, and micro cracks of various sizes and shapes. The property of asphalt mixes is not only affected by the volume fractions of these components such as Voids in Mineral Aggregates (VMA, the complementary volume fraction of aggregates), and the Air Void (AV) content but also the size and spatial distributions of these components. However, both conventional and Superpave volumetric mix designs specify only the bulk values of VMA and AV, which may not be able to capture all the critical factors of a mix. The unexpected WesTrack mixes’ premature failure may reflect this limitation in the design specifications. The paper presents the results of a study to statistically evaluate the spatial and size distribution of the void systems of the mixes and to find other possible parameters that might be better or complementary to the current parameters to characterize the mixture internal structure and performance. In this study, the void systems of the three original WesTrack mixes were evaluated using X-ray tomography images and stereology methods. The spatial void content variation, and the void size distribution for six specimens of the three mixes were quantified. In addition, the specific damaged surfaces (void surfaces), the damage tensor, the mean solid path among the damaged surfaces, and the mean solid path tensor, which indicate the damage level and the interaction of the damage, were also quantified. The results indicate a consistent conclusion: the coarse graded mix is more severely inherently damaged. It was also found that this set of parameters gave a performance ranking of the three mixes consistent with field observations. Moreover, the quantified tensors are also applicable in Continuum Damage Mechanics (CMD) for fatigue and rutting modeling.

Key Words: X-ray tomography image, void size and spatial distribution, continuum damage mechanics, damage tensor and mean solid path tensor, image interpolation.



A Statistical Model of Pavement Rutting In Asphalt Concrete MixesPaper No. 01-0128

Authors: Adrián Ricardo Archilla 1 and Samer Madanat 21. Profesor Titular, Escuela de Ingeniería de Caminos de Montaña,Universidad Nacional de San Juan,Av. Libertador San Martín 1109 (O), San Juan, 5400, Argentina2. Associate Professor, Department of Civil and Environmental Engineering,University of California, Berkeley, CA 94720

ABSTRACTPavement deterioration models are an important input for the efficient management of pavement systems, the allocation of cost responsibilities to various vehicle classes for their use of the highway system, and the design of pavement structures. This paper is concerned with the development of an empirical rutting progression model using an experimental data set from WesTrack. The salient features of the model specification are: 1) three properties of the mix are sufficient to model the performance of the asphalt concrete pavement at WesTrack accurately, 2) the model captures the effects of high air temperatures at WesTrack, and 3) the model predicts rut depths by adding predicted values of the increment of rut depth for each time period, which is particularly advantageous in a pavement management context. The three mix properties are a gradation index, which is obtained from the aggregate gradation, the voids filled with asphalt obtained for the construction mix in the Superpave gyratory compactor, and the initial in-place air voids. The specified model is non-linear in the variables and the parameters, and is estimated using a random effects specification to account for unobserved heterogeneity. The estimation results and prediction tests show that the model replicates the observed pavement behavior at WesTrack well.


Potential of Using Stone Matrix Asphalt (SMA) For Thin OverlaysTRB Paper No.:01-0367

L.Allen Cooley,Jr., Research Engineer and E.Ray Brown, DirectorNational Center for Asphalt Technology (NCAT)277 Technology ParkwayAuburn,AL 36830Phone:334-844-6202, Fax:334-844-6248, Email:[email protected]

ABSTRACTStone matrix asphalt (SMA)has been used within the U.S.since 1991. To date almost all of the SMA mixes have had either a 12.5 or 19.0 mm nominal maximum aggregate size (NMAS). These two NMASs have been predominant because they conform to information obtained from European experiences with SMA. However, the existence of a “fine ”SMA mix could be beneficial because it can be placed in thinner lifts and should be more workable. For the purpose of this study, a “fine ”SMA is defined as a SMA with either a 4.75 or 9.5 mm NMAS. This research study was conducted to evaluate the potential of fine SMAs and to compare these fine SMAs to more conventional SMA mixes (larger NMAS).Data accumulated from this study showed that these fine SMAs could be successfully designed to have stone-on-stone contact. Rut testing with the Asphalt Pavement Analyzer confirmed that the designed fine SMA mixes were rut resistant. Permeability testing indicated that these fine SMA mixes were less permeable than conventional SMA mixes, at similar void levels, and thus should be more durable. Based upon all information from this study, it was concluded that fine SMAs are a viable option for thin overlays.


Repeated Triaxial Testing During Mix Design for Performance CharacterizationTRB PAPER ID 01-3129 -

Samuel H. Carpenter , Professor,University of Illinois Urbana-Champaign Department of Civil Engineering 205 N. Mathews Ave., MC-250.Urbana, Illinois 61801 (217) 333-4188, (217) 333-1924 fax, [email protected]

William R. Vavrik, Senior Engineer, ERES Consultants DivisionApplied Research Associates, Inc505 W. University AveChampaign, Illinois 61820(217) 356-3088, fax (217) 356-4500, [email protected]

ABSTRACTThe advancement of the Superpave Gyratory Compactor (SGC) has lead to a recognized need for a simple test that preferably can be performed on SGC samples during mix design that would rank performance potential of the mixtures if used in a pavement. While it has proven difficult to find one test that can rate mixture potential for rutting and fatigue cracking and modulus, this paper presents the results of a limited study on Illinois mixtures that provides evidence that a simple test performed during mix design has the potential to predict a diverse set of performance characteristics. This paper presents the results of ten Illinois dense graded mixtures of surface and binder (9.5 and 12,5 mm) gradations that were tested in the Asphalt Pavement Analyzer (APA), flexural beam fatigue, and unconfined repeated load permanent deformation testing, and diametral resilient modulus testing. The mixtures were further tested in a Rapid Triaxial Test (RaTT) procedure using SGC compacted samples as taken from the SGC machine, and tested at 50 C in a triaxial stress reversal mode. The triaxial testing provides data that predicts resilient modulus, APA rutting results, fatigue coefficients, and permanent deformation characteristics of accumulated strain at tertiary failure, loads to tertiary failure, and the exponent to the standard logarithmic permanent deformation curve. The excellent correlations obtained from this study provide direct evidence that this test protocol may provide for a structural evaluation procedure to supplement the volumetric mix design process and warrants further study.

Key Words: Rutting, fatigue, APA, triaxial


A Procedure for Using an FWD to Determine the Structural Layer Coefficients for Flexible Pavement MaterialsPaper Number: 01-2259Michael PologrutoVermont Agency of TransportationNational Life Building, Drawer 33Montpelier, Vermont 05633(802) 828-3876(802) [email protected]

ABSTRACTThe American Association of State Highway and Transportation Officials (AASHTO) pavement design model is one of the most widely used empirical design models for flexible pavement design. A factor complicating its utility is the use of an abstract quality, the structural number (SN), to quantify the strength of the total pavement structure. A consequence of the SN is the need for structural layer coefficients (ai) to characterize the component materials of the pavement structure. These layer coefficients are difficult to assess directly. However, this paper presents a method for determining layer coefficients using a falling weight deflectometer (FWD) that are representative of the in situ behavior of the pavement materials. This method is based on a model provided in the 1993 edition of the AASHTO Guide for Design of Pavement Structures for assessing the effective SN. The Vermont Agency of Transportation (VTrans) has established a procedure using FWD data, and the AASHTO effective SN model, to characterize layer coefficients for Vermont pavement materials: 0.074 for sand subbase, 0.144 for crushed stone subbase, 0.569, 0.563, and 0.655 for Marshall ACC base, binder, and surface, respectively, and 0.334, 0.522, and 0.686 for Superpave ACC base, binder, and surface, respectively. A statistical comparison of these findings with an elastic layer simulation of the final structure was performed. The statistical findings of this study indicate p>0.05 when comparing FWD derived layer coefficients to layer coefficients estimated for the final structure using an elastic layer simulation.

Key words: Layer coefficient, FWD, Effective SN


Construction and Performance of Ultra-Thin Bonded HMA Wearing CourseTRB Paper No.: 01-2296

Douglas I. Hanson, PENational Center for Asphalt Technology277 Technology ParkwayAuburn, AL 36830Telephone: 334/844-6240Fax: 334/844-6248e-mail: [email protected]

ABSTRACTIn recent years the need for preserving our investment in the Nation’s highway system has received increased emphasis. An effective pavement preservation program includes a number of maintenance strategies that are applied in a cost-effective and efficient manner. There have been a number of new technologies developed to address these problems. One of the more promising technologies is the use of an ultra-thin bonded HMA wearing course (UTBWC). It consists of a layer of hot mix asphalt (HMA) laid over a heavy asphalt emulsion layer or membrane. The thickness of the ultra-thin surface ranges from 9.5 mm (3/8 in) to 19 mm (3/4 in). The system is placed on a structurally sound rigid or flexible pavement, which may exhibit minor surface distresses. The process was developed in France in 1986 and has been in use in the United States since 1992. Both a review of published experimental project reports and inspections of recently completed projects in many locations indicate good performance of the UTBWC. The UTBWC provides a surface with excellent macro texture qualities, good aggregate retention, and excellent bonding of the very thin surfacing to the underlying pavement.


Effects of Sample Preconditioning on Asphalt Pavement Analyzer (APA) Wet Rut Depths TRB Paper No. 01-0392

Stephen A. Cross, Ph.D., P.E.Associate ProfessorCivil and Environmental Engineering DepartmentUniversity of KansasLawrence, Kansas 66045Tel: (785) 864-4290Fax: (785) 864-3199e-mail: [email protected]

Michael D. Voth, P.E.Pavement EngineerFederal Highway Administration3300 SW Topeka Blvd. Suite 1Topeka, Kansas 66111-2237Tel: (785) 267-7286Fax: (785) 267-7290e-mail: [email protected]

ABSTRACTMoisture damage of asphalt mixes, better known as stripping, is a major distress affecting pavement performance. AASHTO T 283 has historically been used to detect moisture susceptible pavements through the determination of a tensile strength ratio (TSR). Results from AASHTO T 283 have been inconsistent. As a result there has been increased interest in finding an alternative test. Preliminary indications reveal that loaded wheel rut testers, such as the Asphalt Pavement Analyzer (APA), have the potential to detect moisture susceptible mixtures. To date no standard test methodolgy has been developed. The objective of this study was to evaluate the effects of sample preconditioning on APA rut depths and to further evaluate the APA’s suitability for predicting moisture susceptible mixtures. Eight different mixes from seven project sites were evaluated with the APA. Samples were tested using four different preconditioning procedures: dry, soaked, saturated, and saturated with a freeze cycle. The results were compared with TSR values as well as the methylene blue and sand equivalent tests. Samples were also tested using three additive states: no additive, with lime and with liquid anti-strip. The results were evaluated to determine the viability of using the APA to predict moisture damage. The results indicate that the APA can be utilized to evaluate the moisture susceptibility of asphalt mixes. Additionally, the results indicate that the harsher preconditioning of saturation and saturation with a freeze cycle did not result in increased wet rut depths. Using only dry and soaked conditioning appears to be adequate.


Insitu Measurement and Empirical Modeling of Base Infiltration in Highway Pavement SystemsTRB # 01-2868N. Randy Rainwater, Gang Zuo, Eric C. Drumm, Wesley C. Wright, Ronald E. Yoder

N. Randy Rainwater, P.E.The University of Tennessee, Department of Civil and Environmental Engineering223 Perkins HallKnoxville, TN 37996-2010865-974-3355, 865-974-2669 (fax), [email protected]

Gang ZuoThe University of Tennessee, Department of Civil and Environmental Engineering223 Perkins HallKnoxville, TN 37996-2010865-974-2608, 865-974-2669 (fax), [email protected]

Eric C. Drumm, P.E., Ph.D.The University of Tennessee, Department of Civil and Environmental Engineering223 Perkins HallKnoxville, TN 37996-2010865-974-7715, 865-974-2608 (fax), [email protected]

Wesley C. Wright and Ronald E. Yoder, Ph.D.The University of Tennessee, Department of Agricultural and Biosystems EngineeringP O Box 1071Knoxville, TN 37901-1071865-974-7266, 865-974-4514 (fax)

ABSTRACTFree-drainage lysimeters, commonly used in agriculture to monitor evapotranspiration and solute transport, were installed at three highway test sites in Tennessee. The lysimeters were installed below flexible pavement systems just beneath the coarse-graded asphalt stabilized base. The lysimeters collect water infiltrating the unbound aggregate (stone base) and monitor the quantity of infiltration by diverting the flow into tipping bucket rain gages. One test site indicated infiltration beneath the longitudinal joint in the first several months of monitoring. A second test site, where the dense surface layer was not in place, indicated infiltration correlating well with rainfall. Data from this site was used to develop a model to predict the measured infiltration based on the recorded rainfall. The monitoring method and modeling approach may be applicable in the investigation of pavement permeability, drainage system efficiency, and the role of infiltration in the seasonal variation of water content of unbound pavement layers.


Advanced Characterization of Crumb Rubber Modified Asphalts Using Protocols Developed for Complex BindersPaper No. 01-2986

Sohee Kim, Ssu-Wei Loh, Huachun Zhai, Hussain U. BahiaThe Asphalt Pavement Research Group2210 Engineering Hall, 1415 Engineering Dr.The University of Wisconsin-Madison, Madison, WI, [email protected]

ABSTRACTThis study is focused on the evaluation of using crumb rubber modifier (CRM) to modify asphalt binders. Crumb rubber was mixed with two base asphalts of grades PG 70-22 and PG 64-22. Varying grades of asphalt binders resulted from the blending of these 2 base asphalt binders with 3 sizes of crumb rubber modifier at 2 rubber contents. In addition to these binders, 2 binders modified with reacted crumb rubber using a patented process are included in the study. Testing was conducted at different temperatures, testing frequencies, and strain conditions using methods recently developed as part of the NCHRP 9-10 project (Superpave Protocols for Asphalt Binders) for complex binders. The new testing includes the PAT (Particulate Additives Test), used for determining the volume of particulate material greater than 75....m present in the asphalt, and the LAST (Laboratory Asphalt Stability Test), which measures the potential for separation and degradation of additives in asphalt. Strain sweeps, fatigue testing, and low temperature failure and creep properties are also measured and presented in this paper. The results indicate that the concentration and size of crumb rubber influence viscosity significantly. The results using PAT show that the rubber size has a significant effect on the volume of residue collected. It is found that both fatigue and strain dependencies are highly sensitive to asphalt binder type, rubber size and rubber content. The failure properties of CRM measured using the Direct Tension Test (DTT) indicate that the failure stress and strain reduce with increasing rubber size and concentration. It is also found that concentration and size of rubber are not important compared to other factors in the LAST and that keeping the binders agitated during storage can reduce separation significantly.

Key Words: Crumb Rubber, Asphalt, Superpave, Storage Stability, Direct Tension, Dynamic Shear Rheometer, Bending Beam Rheometer, Complex binders.


An Examination of Operator Variability for Selected Methods for Measuring Bulk Specific Gravity of Hot-Mix Asphalt ConcreteTRB Paper - 01-2933

Kevin D. Hall, Ph.D., P.E.Frances T. GriffithStacy G. Williams

ABSTRACTThe ability of different operators to obtain similar results when performing laboratory tests on the same material is vital for producing accurate testing results. By conducting trials in triplicate for each of three different testing methods, a measurement of the bulk specific gravity (Gmb) of compacted Hot Mix Asphalt Cement (HMAC) cores was obtained. An analysis of the variability between operators was investigated using a total of almost 1300 test results, using hot-mix asphalt concrete sampled from six projects in Arkansas. Three methods were used to determine the bulk specific gravity of compacted HMAC samples, including SSD (as per AASHTO T-166), height / diameter (as per AASHTO T-269), and vacuum sealing (using the Corelok vacuum sealing device). In almost all cases, Gmb values determined using the height/diameter method were statistically different from those determined using the SSD and Corelok methods; further, statistical differences were noted in paired analyses between the SSD and Corelok methods. The Corelok method exhibited a lower degree of variability than the other two methods used, based on the standard deviation of test results obtained by different operators. In direct comparison with the SSD method, the Corelok exhibited a lower variability (standard deviation) in 81 percent of the cases. Overall, the Corelok method appears to offer a viable alternative for determining the bulk specific gravity of compacted hot-mix asphalt concrete. However, agencies seeking to use the Corelok must consider the effect of an apparent shift in Gmb values obtained on resulting HMAC volumetric and compaction properties.


Effect of Flat and Elongated Coarse Aggregate on Field Compaction of Hot Mix Asphalt

Brian D. AhoProject Engineer, ERES Consultants DivisionApplied Research Associates, Inc.505 W. University Ave.Champaign, Illinois 61820(217) 356-4500, (217) 356-3088 fax, [email protected]

William R. VavrikSenior Engineer, ERES Consultants DivisionApplied Research Associates, Inc.505 W. University Ave.Champaign, Illinois 61820(217) 356-4500, (217) 356-3088 fax, [email protected]

Samuel H. CarpenterProfessor, University of Illinois Urbana-ChampaignDepartment of Civil Engineering205 N. Mathews Ave., MC-250Urbana, Illinois 61801(217) 333-4188, (217) 333-1924 fax, [email protected]

ABSTRACTIt has long been believed that coarse aggregates that have a flat and elongated (F&E) shape are detrimental to the properties of hot mix asphalt. Several attempts have been made to establish a relationship between coarse flat and elongated aggregate particles and performance. It is believed that decreased performance may result from either aggregate breakage or less-than-optimum particle orientation. This study set aside the question of mixture performance and focused on the constructability of asphalt mixtures with high percentages of flat and elongated aggregate. Research on F&E aggregate shows that, for a given gradation and aggregate type, increasing the percentage of F&E particles will increase the amount of aggregate breakdown. One focus of this study was to determine if the same relationship between percentage of F&E particles and breakdown that has been documented in laboratory settings could be observed in the field. An additional portion of this study compared the aggregate breakdown caused by the gyratory compactor to the aggregate breakdown in the field. The major results of this research show the need for adequate lift thickness in the construction of asphalt pavements. Using thin lifts will increase the amount of broken aggregate particles. Other major findings show the importance of aggregate hardness in aggregate breakdown during construction and the breakdown caused in the laboratory by the Superpave Gyratory Compactor.

Key Words: Flat and Elongated, Aggregate, Consensus Properties, Superpave, Asphalt Mixture, Compaction


Effect of Using Silicone Rubber Molds on the Low-Temperature Binder Grading Parameters: BBR S(60) and m-Value

Raj Dongré , Ph. D., ConsultantFederal Highway Administration6300 Georgetown Pike, McLean, VA-22101(703) [email protected]

John D’ Angelo,Federal Highway Administration400 Seventh Street, NWWashington, D.C. 20590(202) 366-0121

John.D’ [email protected]

Charles Antle, Professor Emeritus of Statistics, Penn State University2302 West Branch RoadState College, PA 16801(814) [email protected]

ABSTRACTA study was conducted to determine if test specimen produced using the Silicone rubber molds affect the Superpave low-temperature grading parameters, S(60) and the m-value determined using the Bending Beam Rheometer (AASHTO-TP1). Six laboratories participated in this study. Four unmodified asphalt binders with low-temperature PG grades between – 6 o C and –30 o C were tested. The thickness of each test specimen was measured using the flip technique. The results show that the Silicone rubber molds produce significantly thinner beams than the required 6.35 ± 0.05 mm thickness. This affects the calculated S(60) values but not the m-value. Aluminum molds were also used in this study according to AASHTO-TP1. It was found that the stiffness values S(60) calculated in the BBR test are significantly lower when Silicone Rubber Molds are used to produce test specimen as compared to those test beams produced using Aluminum molds. The cause of this is due to the peculiarity of the calculation process specified in AASHTO-TP1. AASHTO-TP1 requires that the thickness of the test beam must always be assumed to be 6.35 mm for computing S(60). This study suggests that the test beams produced using the Silicone Rubber molds are significantly thinner, therefore, assuming a thickness of 6.35 mm to calculate S(60) for these beams produces a negative bias. It shown here that when thickness is measured using the “flip” technique, and the measured thickness is then used to calculate S(60), there is no statistically significant difference between the S(60) values of the test beams produced using either the Aluminum or Silicone Rubber molds.


Improvement in the Determination of Failure Stress of Asphalt Binder and Test Repeatability through Sample Preparation in Direct Tension TestingPaper No. 01-2277

Susanna Ho and Ludo ZanzottoBituminous Materials LaboratoryFaculty of Engineering,University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, CANADA

ABSTRACTWe found that during Superpave direct tension testing (DTT) of asphalt binder materials, the failure stress and failure strain values were highly dependent on the DT mold temperature and the rate of cooling of these samples. A sample preparation method in DTT of asphalt binder materials was developed. In this method, aged asphalt binder was allowed to stay fluid in the DT molds for a short period of time to allow the molecules inside the asphalt to form a uniform network. Ceramic tiles holding the direct tension molds were heated in an oven with controlled temperatures specific to the Performance Grade (PG) of the binder. These heated ceramic tiles provided a means for the poured asphalt to stay fluid and to cool slowly and uniformly. The detailed method development and the sample preparation method are described. It was found that with this method, the failure stress of asphalt binder determined by the DT method increased as compared to those samples prepared without controlled cooling. With this sample preparation method, the variability of failure stress and failure strain values of the 6 specimens within the same run is usually less than 15% for the softer asphalt, e.g., 200/300 asphalt, and somewhat higher for the harder asphalt, e.g., 85/100 asphalt. The average results of the best 4 out of 6 specimens usually agreed with another run within 10-15%, regardless of asphalt type. The theory of this method is discussed. Important points to follow or to avoid during preparation of DT samples are discussed. The incorporation of the details of this sample preparation method in the DT procedure will lead to better agreement of direct tension results between different laboratories.


Techniques for Determining Errors in Asphalt Binders Rheological Data

Dr. Mihai O. MarasteanuAssistant Professor, University of Minnesota500 Pillsbury Drive S.E., Minneapolis, MN 55455Telephone: (612) 625-5558E-mail: [email protected] Research Associate, Pennsylvania State University

Dr. David A. AndersonProfessor, Pennsylvania State University201Research Office BuildingUniversity Park, PA 16802Telephone: (814) 863-1912, E-mail: [email protected]

ABSTRACTA number of new methods for specifying asphalt binders, based on more complex theoretical approaches, have emerged in the past years and researchers are increasingly using these methods for studying asphalt binders. These methods require an increased degree of accuracy and precision in the laboratory data. This paper details a number of simple techniques that can be successfully used to identify errors in rheological data obtained for asphalt binders. Asphalt binders do not exhibit sudden changes in their behavior with respect to time or temperature. Therefore, any discontinuities revealed by the visual inspection of the test data in graphical format can be attributed to testing errors. A powerful yet simple tool in identifying potential problems with the DSR test data is the Black diagram. Black diagram is a plot of phase angle versus log |G*| which, unlike master curves, does not require shifting of the data generated at different temperatures. However, pseudo Black diagrams should not be used with the BBR data due to the errors in calculating m-values associated with the use of the polynomial approximation. “c” coefficient can be used for a Quick check of the BBR data based on the fact that the slope of the m-values decreases as the test temperature decreases. For the DT the secant modulus calculated from the stress-strain data provides a better tool in identifying errors in the test data.


A Method to Construct Thermal Stress Relief Joints in Asphalt PavementReport 01-0266

Thomas Amon P. E.B. R. Amon and Sons, Inc.W2950 Highway 11Elkhorn, WI 53121Phone: 262-723-2547Fax: 262-723-2666E-mail: [email protected]

AbstractDiscussed in this paper is a method to construct joints in hot mix asphalt during the paving by cutting the hot mat before the initial rolling. By spacing transverse joints at small intervals, the joints remain tight during low temperatures. With proper spacing, random transverse cracking will be controlled by the joints and will reduce the need for the chemical properties of the asphalt cement to resist the low temperature cracking.

Keywords: Transverse cracking, low temperature, asphalt cement and pavement design.


A Quantitative Evaluation of Stripping Potential in Hot Mix Asphalt Using Ultrasonic Energy for Moisture Accelerated ConditioningPaper No. 01-0251

Martin McCann, MS, PE.Candidate for Ph.D. – University of Nevada, RenoCivil Engineering Dept. Mail Stop 258Reno, NV 89557Phone: 775-324-2571Fax: 775-784-1429E-mail: [email protected]

Dr. Peter Sebaaly, PE.Professor – University of Nevada, RenoCivil Engineering Dept. Mail Stop 258Reno, NV 89557Phone: 775-784-6565Fax: 775-784-1429E-mail: [email protected]

ABSTRACTThe ultrasonic moisture accelerated conditioning process is a quantitative analysis to establish the moisture sensitivity of any given hot mix asphalt (HMA) pavement. While holding a waterbath temperature at a constant 60 C, a sample from a HMA mix is conditioned by ultrasonic energy for a specified period of time. Within the waterbath, the repeated cycle of compression then cavitation accelerates the detachment and displacement of the asphalt binder from the aggregate’s surface. The proportion of separated particles versus conditioning time has been statistically shown to have a unique linear relationship for each HMA mix. The test procedure was implemented on a variety of pavement mixtures and found to distinguish between aggregate sources, different asphalt binders, specimens containing lime versus no-lime, and variability in asphalt binder content. Simplicity of the ultrasonic moisture accelerated conditioning process is attributed to the ease in which a sample is prepared and conditioned. Samples can be derived from pavement cores or utilized from briquettes after establishing the job mix formula. When submerged in the waterbath and subjected to ultrasonic moisture accelerated conditioning, the samples are subjected only to variables associated with moisture sensitivity; aggregate, asphalt binder, water, temperature, and energy.

Key Words:Stripping, Conditioning, Ultrasonic, Asphalt, Moisture



Assessing the Economic Benefits from the Implementation of New Pavement Construction MethodsDavid Gillen, Research EconomistInstitute of Transportation Studies115 McLaughlin HallUniversity of CaliforniaBerkeley, CA 94720(510) 643 [email protected]

John HarveyAssociate Research Engineer,Pavement Research CenterInstitute of Transportation StudiesBldg 480 Richmond Field Station1353 South 46 th StreetRichmond, CA 94804(510) 231 [email protected]

Douglas CooperInstitute of Transportation Studies109 McLaughlin HallUniversity of CaliforniaBerkeley, CA 94720(510) 642 [email protected]

David HungAssistant Development Engineer,Institute of Transportation StudiesBldg 480 Richmond Field Station1353 South 46 th StreetRichmond, CA 94804(510) 231 [email protected]

ABSTRACTThe benefits of pavement research are often presented in measures of interest to pavement engineers and managers. These pavement measures must be rationally converted to monetary measures so that the public and managers without pavement training can evaluate the return on their investment in pavement research. This paper presents the evaluation of the economic costs and benefits of implementation of three recommendations for changes in flexible pavement design and construction made by the CAL/APT pavement research program to the California Department of Transportation (Caltrans). The analysis was performed using a full cost model developed for transportation projects, that includes direct agency costs, user costs and safety costs. The analysis procedure was applied to a generic Caltrans rehabilitation project, the results of which were extrapolated to the state network. The results indicate potential savings of direct agency costs of hundreds of millions of dollars. The results were also applied to a set of rural Caltrans highway rehabilitation projects. The projected cost savings from these three recommendations are many times greater than the total cost of the entire 6-year CAL/APT project.

Key Words: pavement research, cost-benefit analysis, accelerated pavement testing, CAL/APT, rehabilitation


Estimation of Rutting Models by Combining Experimental Data from Different SourcesPaper No. 01-0126

Adrián Ricardo Archilla 1 and Samer Madanat 21Profesor Titular, Escuela de Ingeniería de Caminos de Montaña,Universidad Nacional de San Juan,Av. Libertador San Martín 1109 (O), San Juan, 5400, Argentina,[email protected] Associate Professor, Department of Civil and Environmental Engineering,University of California, Berkeley, CA 94720

ABSTRACTThe accurate prediction of rutting development is an essential element for the efficient management of pavement systems. In addition, progression models of highway pavement rutting can be used to study the effects of different loading levels, and thus in allocating cost responsibilities to various vehicle classes for their use of the highway system. Further, such models can be used for evaluating different strategies for design, maintenance and rehabilitation. Finally, if the models contain information about asphalt concrete mixes, they can also provide directions in the proportioning of aggregate, asphalt and air in the mix. The objective of this paper is to demonstrate the effectiveness of the estimation of rutting models by combining the information from two data sources. The data sources considered are the AASHO Road Test and the WesTrack Road Test. Combined estimation with both data sources is used to identify parameters that are not identifiable from one data source alone. In addition, this estimation approach also yields more efficient parameter estimates. The results presented in this paper demonstrate that joint estimation produces more realistic parameter estimates than those obtained by using either data set alone. Furthermore, joint estimation allows us to account for the effects of pavement structure, axle load configuration, asphalt concrete mix properties, freeze-thaw cycles and hot temperatures in a single model. Finally, it allows to us to predict the relative contributions of rutting originating both in the asphalt concrete and in the unbound layers in the same model.


Fatigue and Permanent Deformation Models for Polymer-Modified Asphalt MixturesTRB ID Number: 01-2813

Mohammad J. Khattak, Ph.D. (Corresponding Author)Assistant ProfessorDepartment of Civil EngineeringUniversity of Louisiana at LafayetteLafayette, LA 70504-2291Phone #: (337) 482-5356Fax#: (337) 482-6688And

Gilbert Y. Baladi, Ph.D., P.E, ProfessorPavement Research Center of ExcellenceDept. of Civil and Environmental Engineering3546 Engineering BuildingMichigan State UniversityEast Lansing, MI 48824Phone#: (517)-355-5147Fax#: (517)-432-1827

ABSTRACTFor the past two decades significant research has been conducted on polymer modified asphalt (PMA) mixtures. Polymers can successfully improve the performance of asphalt pavements at low, intermediate and high temperatures by increasing mixture resistance to fatigue cracking, thermal cracking and permanent deformation. Most of the research has been concentrated on the characterization and relative comparison of neat and polymer modified asphalt (PMA) mixtures and little work has done towards the development of fatigue and permanent deformation models for PMA mixtures. A three-year study that was sponsored by the Michigan Department of Transportation (MDOT) was conducted at Michigan State University to characterize PMA mixtures. It was found that the rheological and engineering properties of PMA mixtures largely depend on the polymer type and content. The improvements in the fatigue lives and resistance to permanent deformation are mainly due to the improvements in the rheological properties of the binders. Fatigue life and permanent deformation models were developed. These models show that the laboratory fatigue life and permanent deformation are strongly related to the rheological properties of binders and the engineering properties of the PMA mixtures.

Key Words: Flexible pavements, Polymers, Modified asphalt mixtures, Fatigue, Rutting, Permanent deformation, Models.


Flexible Pavement Design in Michigan: Transition from Empirical to Mechanistic MethodsPaper No. 01-2817

Ronald S. Harichandran,Neeraj Buch, andGilbert Y. Baladi, Michigan State University

ABSTRACTMichigan is rapidly moving toward the adoption and use of mechanistic-empirical design for flexible pavements. To facilitate the transition from empirical to mechanistic design methods, the Michigan Department of Transportation (MDOT) contracted the development of the software named the Michigan Flexible Pavement Design System (MFPDS). This software provides a holistic framework for the analysis and design of flexible pavements. MFPDS includes modules for AASHTO design, linear and nonlinear mechanistic analysis, backcalculation, and mechanistic design (including overlay design). The software incorporates enhanced elastic layer and finite element models within an easy-to-use Windows user-interface, and can be used on a routine basis. New response models to predict fatigue life and rut depth also were developed as part of this effort and are included in MFPDS. New pavements and overlays may be designed to limit predicted distresses to user-specified threshold values. The features of the mechanistic analysis and design approaches used are presented.

Keywords: mechanistic, flexible pavement, analysis, design, elastic layer, finite element, backcalculation


Long-Term Field Performance of Crack-and-Seat Rehabilitation Strategy

Bouzid Choubane1 , Harold F. Godwin1 , Bjorn Birgisson2 , Adenour Nazef1 , and James A. Musselman1

1 FDOT State Materials Office, 2006 N.E. Waldo Road, Gainesville, FL 32609Phone: (352) 337-3132, E-mail: [email protected]

2 Civil Engineering Department, University of Florida, Gainesville, FL 32611Phone: (352) 846-3429, E-mail: [email protected]

ABSTRACTIn 1993 and 1994, Florida initiated the construction of seven crack-and-seat projects. They were all two-lane rehabilitation projects located on different parts of I-10, both in the East and West directions. The primary intent was to obtain long-term field performance data to allow for a more rational assessment of the effectiveness of the crack-and-seat technique in minimizing reflection cracking in asphalt overlays. As a supplementary strategy to further reduce reflective cracks, the projects also included an asphalt-rubber membrane interlayer (ARMI). The performance of a total of 14 two-lane sections was monitored, at the time of construction and periodically thereafter. After approximately seven years of service, all the projects still have very good to good ride characteristics while the majority of the sections exhibited less than 6-mm (0.25 in.) of rutting. In addition, the overall performance of the Florida crack-and-seat projects is still highly rated in terms of cracking and patching. Visual surveys indicated that the amount of cracking was still relatively insignificant in most of the tests sections. All the present performance indications are that the crack-and-seat technique, when used in conjunction with an ARMI as in these projects, could be an effective rehabilitation strategy of PCC pavements.



Propagation Mechanisms for Surface-Initiated Longitudinal Wheel Path CracksPaper 01-0433

Leslie Ann Myers, Graduate Research AssistantReynaldo Roque, ProfessorBjorn Birgisson, Assistant ProfessorDepartment of Civil EngineeringUniversity of Florida345 Weil HallP. O. Box 116580Gainesville, FL 32611-6580Tel: (352) 392-1033Fax: (352) 392-3394

ABSTRACTField observation of cores and trench sections extracted from asphalt concrete highway pavements exhibited propagation of surface-initiated longitudinal wheel path cracks. The initiation for these cracks was explained by high contact stresses induced under radial truck tires; however, the mechanisms for surface crack propagation have not been explained. A combination of finite element modeling and fracture mechanics was selected for physical representation and analysis of a pavement with a surface crack. An approach was developed to model a cracked pavement and predict pavement response in the vicinity of the crack and throughout the depth of the asphalt layer. Analysis of pavement response showed the mechanism for crack propagation was primarily tensile. Shear stresses were not significant to control crack growth, regardless of load position. Effects of pavement structure and load spectra (magnitude and position) were evaluated in a comprehensive parametric study of the cracked pavement. Load positioning was shown to have the most effect on crack propagation, along with asphalt and base layer stiffness. The direction of crack growth was computed and was shown to change with increasing crack length. Therefore, identification of a tensile failure mechanism for crack propagation was accomplished, along with demonstration of the importance of defining load spectra and inspection of the change in direction of crack growth. Most importantly, the mechanism defined offered an explanation for crack propagation and confirmed observations of crack growth in the field.

Keywords: top-down cracking, propagation, pavement modeling


Quantitative Analysis of 3-D Images of Asphalt ConcretePaper No. 01-0321

Richard A. KetchamDepartment of Geological SciencesUniversity of Texas at AustinAustin TX 78712Ph: (512) 471-0260Fax: (512) [email protected]

Naga ShashidharMaterials ScientistFHWA/Soil and Land Use Technology, Inc.6300 Georgetown PikeMcLean VA 22101Ph: (202) 493-3101Tel: (202) [email protected]

Three-dimensional images of asphalt concrete are very useful for the study of the aggregate structure in hot mix asphalt (HMA). Because the aggregate skeleton is the component that carries load and resists shear, study of its structure will lead to the development of means for its optimization, enhancing the performance of pavements. The volumetric images permit study of various aspects of asphalt concrete such as the structure of the aggregate skeleton, the orientation of particles, any lack of homogeneity (segregation) in aggregate sizes, distribution of air-voids, presence of cracks, the distribution of asphalt, etc. Thus, a comprehensive analysis of all aspects of HMA is possible. Henceforth, these characteristics of HMA will collectively be called the “internal structure.” This is equivalent to the term “microstructure” used in materials science. Because we are dealing with characteristics that are not “micro” the more appropriate term seems to be “internal structure.”


Application of LTPP Seasonal Monitoring Data to Evaluate Volumetric Moisture Predictions from the Integrated Climatic ModelPaper No. 01-3106

Cheryl Allen Richter, P.E.Federal Highway AdministrationOffice of Infrastructure Research and Development6300 Georgetown Pike McLean, VA 22101-2296Tel: (202) 493-3148FAX: (202) 493-3161Email: [email protected]

M.W. Witczak, PhD, ProfessorArizona State UniversityP. O. Box 875306Tempe, AZ 85287-5306TEL: (480) 965-2759FAX: (480) 965-0557

ABSTRACTData collected as a part of the Long Term Pavement Performance Program (LTPP) Seasonal Monitoring Program were applied to evaluate the moisture prediction capabilities of the Integrated Climatic Model (ICM). Two versions of the ICM were considered in this evaluation: Version 2.1 (August 1999), and Version 2.6 (February 2000). Overall agreement between monitored moisture contents, and those predicted using ICM Version 2.1 was poor. Evaluation of these results lead to the identification of several potential improvements to the model, and the application thereof. ICM Version 2.6 is the product of efforts to implement the improvements that were identified. Overall agreement between the monitored moisture contents and those predicted with ICM Version 2.6 of the ICM is deemed acceptable. The model revisions embodied in Version 2.6 greatly enhance the applicability of the ICM to routine pavement engineering practice.


Data Collection and Management of The Instrumented Smart Road Flexible Pavement SectionsPaper No. 01-2668

Amara Loulizi, Senior Research AssociateVirginia Tech Transportation Institute3500 Transportation Research PlazaBlacksburg, VA 24061Tel: 540 231-1504, Fax: 540 231-1555e-mail: [email protected]

Imad L. Al-Qadi, ProfessorThe Via Department of Civil and Environmental Engineering, 200 Patton HallVirginia Polytechnic Institute and State UniversityBlacksburg, VA 24061-0105Tel: 540 231-5262, Fax: 540 231-7532e-mail: [email protected]

Samer Lahouar, Graduate Research AssistantVirginia Tech Transportation Institute3500 Transportation Research PlazaBlacksburg, VA 24061Tel: 540 231-1568, Fax: 540 231-1555e-mail: [email protected]

Thomas E. Freeman, Senior Research ScientistVirginia DOT530 Edgemont RoadCharlottesville, VA 22903Tel: (804) 293 1957, Fax: (804) 293 1990e-mail: [email protected]

ABSTRACTThe flexible pavement research facility at the Virginia Smart Road consists of twelve different designs. All sections are closely monitored through a complex array of sensors located beneath the roadway that were embedded during construction. The environmental sensors include thermocouples for temperature measurements, time domain reflectometry (TDR) probes to measure moisture content in the base layers, and resistivity probes to measure frost penetration. The dynamic sensors include pressure cells and strain gages to measure stresses and strains, respectively, induced at different layers from truck loading. Currently, environmental data is collected daily every 15 minutes for temperature, every hour for moisture, and every six hours for frost penetration. Truck testing is performed every week with different loading configurations. The loading variables include three load levels, three wheel inflation pressures, and four different speeds. The loading is performed using the same truck and wheels to eliminate variability due to wheel configuration and tire type. Data is managed by saving environmental data from different instruments separately based on date and section number. Truck loading data is saved by test type (based on loading configuration, inflation pressure, and speed), date of test, and section number. A database is being generated for all twelve sections to study the effect of all tested variables on the different flexible pavement designs. This paper presents the performance of the used instruments and collected data, and discusses the techniques used to manage the overwhelming data.

Keywords: Flexible Pavements, Instrumentation, data collection, data management.


Low-Temperature Binder Specification Development: Thermal Stress Restrained Specimen Testing of Asphalt Binders and MixturesPaper No. 01-2027

Sushanta D. Roy and Simon A.M. HespDepartment of Chemistry, Queen’s UniversityKingston, Ontario, K7L 3N6 CanadaTel. +1-613-533-2615 and Fax +1-613-533-6669E-mail: [email protected]

ABSTRACTThis paper discusses the results of the low-temperature testing of Bow River asphalt binders and concrete mixtures (MRL code AAN), unmodified as well as modified with three different commercially used polymers (diblock SB, radial SBS and EVA). Thermal stress restrained specimen tests, at a cooling rate of 10ºC per hour, were used to evaluate the performance of both binders and mixtures. Binders were restrained as direct tension specimens with and without a sharp starter crack. Notching of the samples resulted in lower failure loads for all systems. However, only three of the four binders failed at warmer temperatures. The fourth binder, an exceptionally tough radial SBS-modified system, remained unaffected in this regard. Changes in failure temperatures due to the notching of the binder samples ranged from 0ºC (radial SBS) to as much as +12ºC (diblock SB). Comparing binder results with those obtained for the mixture yields additional insights. It appears that there are distinct differences between binder and mixture failure modes. The higher stress levels encountered in the mixture give rise to energy dissipating mechanisms such as yielding, that do not occur at the much lower stress levels in the binder test. It is unlikely that a specification based on binder failure stress or strain is ever going to predict performance in polymer-modified systems. Three-point bend tests on notched asphalt binder or mastic beams may provide more realistic conditions for measuring materials properties such as Young’s modulus, fracture toughness and fracture energy. A compression test on the binder or mastic may be used to determine additional important parameters, such as both Young’s modulus and yield stress in compression, which combined with the failure properties will likely produce an improved fracture mechanics-based low-temperature binder specification system.


Measurement and Evaluation of Pavement Marking Retroreflectivity: South Carolina’s ExperienceTRB Paper Number: 01-3491

David B. Clarke, Wayne A. Sarasua, J. Clifton Collins, Jennifer L. Tropea, Amanda J. PfallerDepartment of Civil EngineeringClemson UniversityClemson, SC 29634

William J. DavisDepartment of Civil and Environmental EngineeringThe CitadelCharleston, SC 29409

ABSTRACTIn anticipation of federal retroreflectivity standards for pavement markings, the South Carolina Department of Transportation initiated a research project in 1999 to develop a systematic methodology that quantitatively evaluates the retroreflectivity of pavement markings of South Carolina roads and interstates. One of the primary tasks was to evaluate the effectiveness of the different types of retroreflectometer devices. This paper presents the findings of field test data and compares results obtained from three models of handheld retroreflectometers and a vehicle mounted unit. Comparisons were made between the devices at over 160 sites on the interstate system throughout South Carolina as well as two off-interstate test sites. A review of some relevant research on pavement retroreflectivity issues is given as well as a summary of the results of a survey of the current practices of highway departments throughout the United States. The paper includes an overview of an innovative geographic information system application that was developed to specifically manage the unique characteristics of pavement marking retroreflectivity data. This paper should be of interest to state highway departments as well as anyone interested in implementing a pavement marking inventory and management system.


Modification of Binder with Acid Advantages and Disadvantages

S. W. Bishara, Donna Mahoney, and R.L. McReynoldsKansas Department of Transportation2300 Van BurenTopeka, Kansas 66611-1152Telephone (785) 291-3851; Fax (785) 296-2526

G.N. King Koch Materials Company,4027 East 37th StreetNorth Wichita, Kansas 67201Telephone (316) 828-8492; Fax (316) 828-7385E-Mail [email protected]

ABSTRACTModification (hardening) of binder by an acid extends the upper application limit, and protects from possible rutting of a mix. Antistripping agents, ASAs, on the other hand, have active amino hydrogens that, on mixing with a binder, help the latter adhere to aggregate surface, and minimize moisture damage. It is not uncommon that the two effects are simultaneously sought: a higher upper limit, and a suitable protection from moisture attack. That is, both types of modifiers – acid and ASA, may be present in the same binder. Although each of the 2 types of modifiers, separately, has advantages, it is not known whether their coexistence in the same binder would enhance each other's benefits, or would limit the individual advantages of each, and may even be detrimental? Is there an optimum amount of each modifier type when both are used together? To address these questions, two parameters were followed. 1- The high critical temperature, high TC of the binder alone and in presence of each modifier type separately then combined, and, 2- The pH value of the aqueous layer obtained after extraction with water from the binder toluene solution. The pH measurements are, similarly, carried out on the binder alone and in presence of each modifier type separately then combined. The pH value provides a quantitative measure of the acidity (or alkalinity) of the water-soluble constituents of a binder. This information might serve 2 purposes. 1. An alkaline pH value denotes presence of an ASA; an acidic value denotes an acid, and 2. A low pH value points to possible field interactions with an alkaline environment such as a limestone aggregate.


Searching For Superior Performing Porous Asphalt Wearing Courses

P. E. BOLZANPavement Engineering ServicesCalle 5 # 319, 1900 La Plata ARGENTINATel No. (54) 221-4217405, Fax No. (54) 221-4259835, E-mail: [email protected]

J. C. NICHOLLSPrincipal Research Engineer, Infrastructure DivisionTransport Research LaboratoryOld Wokingham RoadCrowthorne, Berkshire RG45 6AU ENGLANDTel No. (44) 1344 770004, Fax No. (44) 1344 770356, E-mail: [email protected]

G. A. HUBERAssociate Director of ResearchHeritage Research Group7901 West Morris St., Indianapolis, IN 46231Tel No. (317) 390 3141, Fax No (317) 486 2985, E-mail: [email protected]

ABSTRACTPorous asphalt can be considered as the safest wearing course available to prevent wet-pavement accidents. The primary goal is to obtain a durable and safe wearing course that also reduces the risk of aquaplaning, the spray in wet weather and the noise generated. At the same time, improved comfort can be achieved in terms of rideability. A challenge for a porous asphalt mixture is to keep the surface drainable for the longest time possible. The durability of these open-graded mixtures depends on many important factors such as aggregate gradation, binder type, hydraulic conductivity and climatic conditions. The search for a durable superior performing porous asphalt mixture has become a major goal for the asphalt industry, particularly after some premature failures found. This paper summarizes the extensive British experience since 1967, the performance of a new generation OGFC in the US, and the recent successful road applications carried out in Argentina. From these experiences, the most important factors that should be allowed for in the design of porous asphalt has been identified to provide superior performance. The use of a thick polymer modified binder film, additives, and high quality gap-graded aggregates (19 mm maximum size, 20 % initial air voids) along with well-supervised methods of construction and a sound quality control / quality assurance system are the main ingredients for a successful formula.


Using Pavement Distress Data to Assess The Impact Of Construction On Pavement PerformancePaper Number: 01-2576

Chieh-Min Chang, Graduate Research AssistantDepartment of Civil and Environmental EngineeringMichigan State University3546 Engineering BuildingEast Lansing, MI 48824-1226Phone: (517) 355-5107, Fax: (517) 432-1827E-Mail: [email protected]

Gilbert Y. Baladi, Ph.D., P.E.(Corresponding Author)Director of Pavement Research Center of ExcellenceDepartment of Civil and Environmental EngineeringMichigan State University3553 Engineering BuildingEast Lansing, MI 48824-1226Phone: (517) 355-5147, Fax: (517) 432-1827 E-Mail: [email protected]

Thomas F. Wolff, Ph.D., P.E.Associate Dean of College of Engineering for Undergraduate StudiesDepartment of Civil and Environmental EngineeringMichigan State University1410 Engineering BuildingEast Lansing, MI 48824-1226Phone: (517) 355-5128, Fax: (517) 432-1356, E-Mail: [email protected]

ABSTRACTMost State Highway Agencies specify incentives/ disincentives or acceptance criteria based on one or more attributes that can be measured during or immediately after construction (smoothness, early completion of construction, and nuclear density). In many scenarios where contractors have been awarded incentives, the pavement showed premature distress after construction. Furthermore, the magnitude of the incentives/disincentives is typically determined based on intuition and past practice without assessing the impact of the incentive’ s attribute on pavement performance. In a study sponsored by the Michigan Department of Transportation and conducted by the Pavement Research Center of Excellence (PRCE) at Michigan State University, the impact of segregation on pavement performance was assessed and an expedient test to detect segregation was developed so that incentives/disincentives or acceptance criteria could be established by MDOT. The study included seventeen segregated pavement projects and two non-segregated projects. Two types of segregation-related distress were observed; raveling, which was observed on eleven projects and cracking, which was observed on seven projects. Three projects showed both raveling and cracking. For each project, the raveled areas and the length of the cracks were measured over time and their rates of growth were assessed. Based on the results, the reductions in the pavement service life due to raveling and cracking were estimated. It is shown that areas with heavy and medium degrees of segregation experience on the average 73 and 56 percent reduction in the pavement service life, respectively due to raveling and 46 percent due to segregation-related cracks.

KEY WORDS: pavement performance, pavement management, segregation, prediction, model, pavement service life


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