Precision Estimates of AASHTO T283: Resistance of Compacted Hot-Mix Asphalt (HMA) to Moisture-Induced Damage (2010)

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ACKNOWLEDGMENT This work was sponsored by the American Association of State Highway and Transportation Officials (AASHTO), in cooperation with the Federal Highway Administration, and was conducted in the National Cooperative Highway Research Program (NCHRP), which is administered by the Transportation Research Board (TRB) of the National Academies. COPYRIGHT INFORMATION Authors herein are responsible for the authenticity of their materials and for obtaining written permissions from publishers or persons who own the copyright to any previously published or copyrighted material used herein. Cooperative Research Programs (CRP) grants permission to reproduce material in this publication for classroom and not-for-profit purposes. Permission is given with the understanding that none of the material will be used to imply TRB, AASHTO, FAA, FHWA, FMCSA, FTA, Transit Development Corporation, or AOC endorsement of a particular product, method, or practice. It is expected that those reproducing the material in this document for educational and not-for-profit uses will give appropriate acknowledgment of the source of any reprinted or reproduced material. For other uses of the material, request permission from CRP. DISCLAIMER The opinions and conclusions expressed or implied in this report are those of the researchers who performed the research. They are not necessarily those of the Transportation Research Board, the National Research Council, or the program sponsors. The information contained in this document was taken directly from the submission of the author(s). This material has not been edited by TRB.

iii CONTENTS LIST OF TABLES .................................................................................................................................... VI LIST OF FIGURES ................................................................................................................................ VII ACKNOWLEDGEMENTS ..................................................................................................................... IX ABSTRACT ............................................................................................................................................... XI CHAPTER 1- INTRODUCTION AND RESEARCH APPROACH ..................................................... 1 1.1 Background............................................................................................................................. 1 1.2 Background of the test protocol ............................................................................................ 2 1.3 Problem Statement ................................................................................................................. 3 1.4 Research Objectives ............................................................................................................... 3 1.5 Scope of Study ........................................................................................................................ 3 CHAPTER 2- DESIGN AND CONDUCT OF THE ILS ........................................................................ 5 2.1 Materials Selection ................................................................................................................. 5 2.2 Design Selection ...................................................................................................................... 5 2.3 Preliminary Testing ............................................................................................................... 6 2.3.1 Results of Preliminary Testing ................................................................................. 6 2.3.1.1 Volumetric measurements ........................................................................ 7 2.3.1.2 Indirect Tensile Strength Test Results .................................................... 7 2.3.1.3 Hamburg Wheel Tracking Test Results .................................................. 8 2.4 Selection of Participating Laboratories ............................................................................... 9 2.5 Sample Preparation ............................................................................................................... 9 2.6 Instructions for Interlaboratory Study .............................................................................. 10 CHAPTER 3- INTERLABORATORY TEST RESULTS AND ANALYSIS ..................................... 11 3.1 Test Data ............................................................................................................................... 11 3.2 Method of Analysis ............................................................................................................... 11

iv 3.3 Analysis of Results of Limestone Mixtures ........................................................................ 12 3.3.1 Superpave Gyratory Compacted Specimens ........................................................ 12 3.3.2 Marshall Compacted Specimens ............................................................................ 14 3.4 Analysis of Results of Sandstone Mixtures ........................................................................ 16 3.4.1 Superpave Gyratory Compacted Specimens ........................................................ 16 3.4.2 Marshall Compacted Specimens ............................................................................ 19 3.5 Statistical Comparison of TSR Results of Different Materials and Different Compaction Methods ........................................................................................................... 20 3.5.1 Comparison of Average TSR Values ..................................................................... 21 3.5.2 Comparison of Within-Laboratory Standard Deviations of TSR ...................... 22 3.5.3 Comparison of Between-laboratory Standard Deviations of TSR ..................... 23 3.6 Precision Estimates for AASHTO T283 ............................................................................. 24 CHAPTER 4- IDENTIFICATION OF THE PARAMETERS CAUSING VARIABILITY IN AASHTO T283 .......................................................................................................................................... 26 4.1 X-Ray Tomography Scanning ............................................................................................. 26 4.2 X-Ray Measurement Test Results ...................................................................................... 27 4.2.1 Inside and outside porosity ..................................................................................... 27 4.2.2 Vacuum Induced Micro-Cracking ........................................................................ 29 4.2.3 Distribution of inside porosity ............................................................................... 30 4.3 Moisture Infiltration Simulation ........................................................................................ 32 4.4 Mechanical Aspects of the Indirect Tension Test .............................................................. 35 4.5 Moisture Induced Damage in the Field .............................................................................. 37 4.6 Variability Due to Other Factors ........................................................................................ 38 CHAPTER 5- CONCLUSIONS AND RECOMMENDATIONS ......................................................... 39 5.1 Conclusions ........................................................................................................................... 40 5.2 Recommendations ................................................................................................................ 41 REFERENCES .......................................................................................................................................... 43

v APPENDIX A- INSTRUCTIONS AND DATA SHEET FOR INTERLABORATORY STUDY ..... 44 APPENDIX B- RESULTS OF INDIRECT TENSILE STRENGTH TEST OF LIMESTONE GYRATORY SPECIMENS ..................................................................................................................... 54 APPENDIX C- RESULTS OF INDIRECT TENSILE STRENGTH TEST OF LIMESTONE MARSHALL SPECIMENS ..................................................................................................................... 58 APPENDIX D- RESULTS OF INDIRECT TENSILE STRENGTH TEST OF SANDSTONE GYRATORY SPECIMENS ..................................................................................................................... 62 APPENDIX E- RESULTS OF INDIRECT TENSILE STRENGTH TEST OF SANDSTONE MARSHALL SPECIMENS ..................................................................................................................... 66 APPENDIX F- RECOMMENDED PRECISION ESTIMATES FOR AASHTO T283 ..................... 70

vi LIST OF TABLES Table 2-1- Percent passing of the limestone and sandstone aggregates ................................................. 6 Table 2-2- Measured air void and water absorption. MAR stands for Marshall; GYR stands for gyratory, Va % stands for percent air voids, and Abs. % stands for percent absorption . 7 Table 2-3- Measured tensile strength values (kPa) .................................................................................. 8 Table 3-1-Statistics of dry and wet indirect tensile strength and tensile strength ratio (TSR) of gyratory compacted limestone mixtures ............................................................................... 14 Table 3-2-Statistics of dry and wet indirect tensile strength and indirect tensile strength ratios of Marshall compacted limestone specimens ............................................................................ 16 Table 3-3-Statistics of dry and wet indirect tensile strength and indirect tensile strength ratios of gyratory compacted sandstone mixtures .............................................................................. 18 Table 3-4-Statistics of dry and wet indirect tensile strength and indirect tensile strength ratio of Marshall compacted sandstone specimens ........................................................................... 20 Table 3-5- Statistical compar ison of the average TSR values of the two mater ial types and two compaction methods ............................................................................................................... 22 Table 3-6- Statistical compar ison of the repeatability standard deviations of TSR values for the two mater ial types and the two compaction methods ................................................................. 23 Table 3-7- Statistical compar ison of the reproducibility standard deviations of TSR values of the mater ial types and compaction methods .............................................................................. 24 Table 3-8- Precision estimates of TSR ..................................................................................................... 25 Table 4-1- Inside, outside, and overall air voids (porosity) of specimens from X-Ray scans ............. 28 Table 4-2- Comparison of initial absorption and outside connected porosity ..................................... 30

vii LIST OF FIGURES Figure 2-1- Deformation of limestone and sandstone mixture in Hamburg wheel tracking test ......... 9 Figure 3-1- Average dry and wet indirect tensile strength values of gyratory compacted limestone mixtures ................................................................................................................................... 13 Figure 3-2- Average TSR values of gyratory compacted limestone mixtures ..................................... 13 Figure 3-3- Average dry and wet indirect tensile strength values of Marshall compacted limestone specimens ................................................................................................................................. 15 Figure 3-4- Average TSR values of Marshall compacted limestone specimens .................................. 15 Figure 3-5- Average dry and wet indirect tensile strength values of gyratory compacted sandstone specimens ................................................................................................................................. 17 Figure 3-6- Average TSR values of gyratory compacted sandstone specimens .................................. 18 Figure 3-7- Average dry and wet strength values of Marshall compacted sandstone specimens ...... 19 Figure 3-8- Average TSR values of Marshall compacted sandstone mixtures specimens .................. 19 Figure 3-9- Compar ison of the average TSR values of gyratory and Marshall compacted limestone and sandstone specimens ........................................................................................................ 21 Figure 3-10- Comparison of the within-laboratory standard deviation of TSR values of gyratory and Marshall compacted limestone and sandstone specimens ........................................... 22 Figure 3-11- Comparison of the between-laboratory standard deviations of TSR values of gyratory and Marshall compacted limestone and sandstone specimens ........................................... 24 Figure 4-1- Typical X-ray tomography images of 6” gyratory and 4” Marshall compacted specimens ................................................................................................................................. 27 Figure 4-2- Schematic of inside and outside pore-space ........................................................................ 29 Figure 4-3- Pore space distr ibution in gyratory compacted limestone (LMST) specimens (a) inside porosity (b) outside porosity .................................................................................................. 31 Figure 4-4- Pore space distr ibution in Marshall compacted limestone (LMST) specimens (a) inside porosity (b) outside porosity .................................................................................................. 32 Figure 4-5- Finite element infiltration in Gyratory compacted limestone (LMS) specimen (a) finite element mesh (b) moisture conditioning (c) moisture infiltration in mid-plane for different conditioning times t, in which θ is the moisture content (or normalized moisture concentration) ......................................................................................................... 33

viii Figure 4-6- Finite element infiltration in Marshall compacted KST specimen (a) finite element mesh (b) moisture conditioning (c) moisture infiltration in mid-plane for different conditioning times t, in which θ is the moisture content (or normalized moisture concentration) ...... 34 Figure 4-7- Finite element continuum analysis of dry indirect tension test (22) ................................. 36 Figure 4-8- Compar ison of laboratory indirect tensile test data and CAPA-3D simulation at different loading rates ............................................................................................................ 37

ix ACKNOWLEDGMENTS The research reported herein was performed under NCHRP Project 9-26 A by the AASHTO Materials Reference Laboratory (AMRL). Dr. Haleh Azari was the principal investigator on the study. The authors are very thankful to the AMRL technicians from Proficiency Sample Program and Laboratory Assessment Program who provided help in processing the materials and preparing the samples for distribution to the laboratories. The authors gratefully acknowledge the support of the Turner-Fairbank Highway Research Center in preparing and testing the specimens in the preliminary stage of the study and for making the X-Ray system available for scanning of the specimens. The support of Maryland State Highway and Hanson Quarry in providing the aggregate and NuStar Asphalt Refining for providing the asphalt for this study is greatly appreciated. The authors wish to acknowledge the laboratories that participated in this interlaboratory study. Their willingness to volunteer their time and conduct the testing under tight time constraints at no cost to the study is most appreciated. The laboratories include: A.G. Wassenaar, Inc., Denver, CO AMEC Earth & Environmental Limited, Dartmouth, Canada Asphalt Testing Lab, Crestwood, IL Brooks Construction Company, Inc., Fort Wayne, IN Federal Highway Administration, Lakewood CO Turner-Fairbank Highway Research Center, Mclean VA Florida Department of Transportation, Gainesville, FL Garco Testing Laboratories, Fresno, CA Heritage Research Group, Indianapolis, IN Iowa Department of Transportation, Iowa Kleinfelder Inc., Reno, NV KS Dept. of Transportation, Topeka, KS Lafarge QA/QC Laboratory, Albuquerque, NM Landmark Testing & Engineering, St. George, UT MACTEC, San Diego, CA Maryland State Highway, Hanover, MD Milestone Contractors, LP, Indianapolis, IN MODOT, Jefferson City, MO Nebraska Department of Road Materials and Resources, Lincoln, NE ODOT Central Materials Laboratory, Salem, OR South Carolina DOT, Office of Materials and Research, Columbia, S.C. Ohio Dept of Transportation, Columbus, OH Oklahoma Department of Transportation, OKC, OK OMNNI Associates, Appleton, WI Rieth-Riley Construction Co., Inc., Indianapolis, IN Rieth-Riley Construction Co., Inc., South Bend, IN RMA Group, Rancho Cucamonga, CA Rutgers University, Dept. of Civil and Environ. Eng., Piscataway, NJ Saint Louis County Highways and Traffic, Maryland Heights, MO Shelly & Sands, Inc. / Mar-Zane Materials Inc., Zanesville, OH

x Sloan Construction Co., Duncan, CA Sully-Miller Contracting Company, Irwindale, CA Terracon, Fort Collins, CO Testing Service Corporation, Carol Stream The Port Authority of NY & NJ, Jersey City, NJ Tilcon CT Inc., North Branford, CT Vermont Agency of Transportation, Berlin, VT Virginia Transportation Research Council, Charlottesville, VA Vulcan Materials Company, Birmingham, AL Vulcan Materials Company, Western Division., Irwindale, CA Walsh & Kelly, Inc., Griffith, IN Western Regional Superpave Center, Reno, NV

xi ABSTRACT This work presents an interlaboratory study (ILS) resulting in a precision and bias statement for AASHTO T283, “Resistance of Compacted Hot Mix Asphalt (HMA) to Moisture-Induced Damage.” To gain insight into the variability of the T283 test results, a micro-scale finite element analysis using X-ray images of the test specimens was conducted. The ILS included preparing and testing 6 replicate specimens according to AASHTO T283 using two different aggregate sources and two compaction methods. The two aggregate sources were selected based on their moisture susceptibility. A sandstone aggregate representing moisture susceptible and a limestone aggregate representing moisture resistance were selected for the study. Marshall and Superpave gyratory compactors were selected as means of compaction to create test specimens with different structures. The statistical analysis of the ILS results indicated that the average tensile strength ratios (TSR) of the Marshall and gyratory specimens and that of limestone and sandstone mixtures were significantly different. Despite the difference in the average TSR values, the variability of TSR of Marshall and gyratory compacted specimens of limestone and sandstone mixtures were not significantly different. In this respect, the TSR statistics of the four specimen types (two mixture types and two compaction methods) were combined to prepare the precision estimates for AASHTO T283. The simulation of moisture infiltration in the X-ray images of gyratory and compacted specimens indicated that moisture penetrates to the center of Marshall specimens much faster than to the center of gyratory specimens. The reason for this was found to be the difference in size and distribution of outside and inside pore spaces in gyratory and Marshall specimens. Additionally, the conditioning procedure, as described in the current T-283 standard was found to not represent the actual moisture infiltration time frame that produced damage in the field. This could explain the often encountered discrepancy between laboratory and field moisture performance.