Variability of Ignition Furnace Correction Factors (2017)

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2017 N A T I O N A L C O O P E R A T I V E H I G H W A Y R E S E A R C H P R O G R A M NCHRP RESEARCH REPORT 847 Variability of Ignition Furnace Correction Factors Carolina Rodezno NatioNal CeNter for asphalt teChNology auburN uNiversity Auburn, AL Ray Brown NatioNal CeNter for asphalt teChNology auburN uNiversity Auburn, AL Grant Julian NatioNal CeNter for asphalt teChNology auburN uNiversity Auburn, AL Brian Prowell advaNCed Materials serviCes Auburn, AL Subscriber Categories Materials Research sponsored by the American Association of State Highway and Transportation Officials in cooperation with the Federal Highway Administration

NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM Systematic, well-designed research is the most effective way to solve many problems facing highway administrators and engineers. Often, highway problems are of local interest and can best be studied by highway departments individually or in cooperation with their state universities and others. However, the accelerating growth of highway transportation results in increasingly complex problems of wide inter- est to highway authorities. These problems are best studied through a coordinated program of cooperative research. Recognizing this need, the leadership of the American Association of State Highway and Transportation Officials (AASHTO) in 1962 ini- tiated an objective national highway research program using modern scientific techniques—the National Cooperative Highway Research Program (NCHRP). 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C O O P E R A T I V E R E S E A R C H P R O G R A M S CRP STAFF FOR NCHRP RESEARCH REPORT 847 Christopher J. Hedges, Director, Cooperative Research Programs Lori L. Sundstrom, Deputy Director, Cooperative Research Programs Edward T. Harrigan, Senior Program Officer Anthony P. Avery, Senior Program Assistant Eileen P. Delaney, Director of Publications Doug English, Editor NCHRP PROjECT 09-56 PANEL Field of Materials and Construction—Area of Bituminous Materials Kim A. Willoughby, Washington State DOT, Olympia, WA (Chair) Timothy L. Ramirez, Pennsylvania DOT, Harrisburg, PA Mark J. Brum, Massachusetts DOT, Boston, MA Michael S. Buchanan, Oldcastle Materials Company, Birmingham, AL Nathan D. Maack, Michigan DOT, Lansing, MI Charles W. Paugh, Engineering & Software Consultants, Inc., Chantilly, VA Gregory A. Sholar, Florida DOT, Gainesville, FL Brett Stanton, Superior Bowen, Kansas City, MO Dean C. Weitzel, Carson City, NV Matthew Corrigan, FHWA Liaison

F O R E W O R D This report presents a proposed practice in AASHTO standard format for installa- tion, operation, and maintenance of ignition furnaces. The report will be of immediate inter- est to materials engineers in state highway agencies and the asphalt pavement construction industry. AASHTO T 308, “Determining the Asphalt Binder Content of Hot Mix Asphalt (HMA) by the Ignition Method,” requires determination of asphalt and aggregate correction factors for asphalt mix designs for each ignition furnace used to test a design. In some cases, where there are numerous asphalt mix designs or numerous ignition furnaces testing a particular mix design, correction factors may be shared between ignition furnaces, though this practice is not strictly permitted by AASHTO T 308 without supporting evidence. There is a lack of knowledge of (1) how ignition furnace installation, operation, and mainte- nance influence correction factors; (2) consequences of sharing correction factors between units/ mixes; and (3) ways to minimize differences that arise between ignition furnaces. Moreover, there is a lack of a statistically valid verification procedure to identify causes for non-comparing, statistically different, or biased test results from ignition furnaces. A verification procedure may promote consistency in test results and assist in dispute resolution. The objectives of this research were to (1) determine the significant influences that affect the variability of asphalt and aggregate correction factors for ignition furnaces; (2) develop guidelines for the installation, operation, and maintenance of ignition furnaces to minimize the variability in correction factors between furnaces; and (3) develop and document a statis- tically valid correction factor verification procedure to identify and troubleshoot causes for non-comparing, statistically different, or biased results of AASHTO T 308. The research was performed by the National Center for Asphalt Technology (NCAT), Auburn, Alabama, with the support of Advanced Materials Services, LLC, Auburn, Alabama. The research was conducted in three parts: (1) a study of the sensitivity of asphalt and aggregate correction factors to variation in experimental factors such as furnace type, test temperature, asphalt content, and sample mass; (2) a round-robin study to identify cor- rection factor outliers and determine the contributory cause(s); and (3) troubleshooting by NCAT of outliers from the round-robin study. The research found that the primary factors affecting asphalt and aggregate correction factors determined by AASHTO T 308 are furnace type and test temperature. Conducting the test at 800°F appears to substantially reduce the magnitude and standard deviation of the correction factors for asphalt mixtures that do not contain lime. Sharing correc- tion factors among different ignition furnaces appears acceptable for low correction factor aggregates (0.1% or less) but is problematic for aggregates with correction factors of 1.0% By Edward T. Harrigan Staff Officer Transportation Research Board

or greater. The current precision estimates in AASHTO T 308 appear applicable only to mixtures with low correction factor aggregates. The key product of this research is a Proposed Standard Practice for Installation, Opera- tion, and Maintenance of Ignition Furnaces (Appendix I). The NCHRP project panel, after careful review of the experimental results with the research team, concluded that develop- ment of a verification procedure to identify causes for non-comparing, statistically differ- ent, or biased test results from ignition furnaces was premature. Further research is planned to conduct an interlaboratory study of AASHTO T 308 in accordance with ASTM E691 as a basis for development of a robust, definitive verification procedure. This research will also address the effect of reclaimed asphalt pavement and recycled asphalt shingle content on determination of asphalt mixture correction factors. This report fully documents the research and includes nine appendixes: Appendix A: State DOT and Contractor Survey Appendix B: Summary of State Test Methods Compared with AASHTO T 308 Appendix C: Sensitivity Experiment Matrices and Asphalt Content Test Results Appendix D: Instructions to Round-Robin Participants and Data Report Appendix E: Round-Robin Test Results Appendix F: Round-Robin Test Results Analyses Tables per ASTM E691 Appendix G: Checklist for Troubleshooting Laboratory Visits Appendix H: Comparison of Burning Profiles for Laboratory 23 Appendix I: Proposed Standard Practice for Installation, Operation, and Maintenance of Ignition Furnaces with Commentary

C O N T E N T S 1 Chapter 1 Introduction 1 1.1 Objective 1 1.2 Scope 2 Chapter 2 Literature Review 2 2.1 Background 4 2.2 Types of Ignition Furnaces 5 2.3 Ignition Furnace Studies 16 2.4 RAP and RAS Asphalt Content Determination Using Ignition Furnace 17 2.5 Summary of Findings from the Literature Review 18 Chapter 3 Survey of State DOT and Industry Practice Regarding the Use of Ignition Furnaces 18 3.1 Introduction 25 3.2 Summary of Survey of State DOT and Industry Practice 27 Chapter 4 Experimental Plan Description 27 4.1 Sensitivity Study at the NCAT Lab 31 4.2 Round-Robin Study at Various Labs 33 4.3 Troubleshooting Correction Factors That Differ Significantly from Other Correction Factors in Round-Robin Study 34 Chapter 5 Results and Analysis of the Experiments 34 5.1 Sensitivity Experiments 48 5.2 Round-Robin Study 58 5.3 Troubleshooting Outliers from Round-Robin Study 65 Chapter 6 Summary of Findings 65 6.1 Sensitivity Study at NCAT Lab 66 6.2 Round-Robin Study 69 Chapter 7 Conclusions and Recommendations 70 References A-1 Appendix A State DOT and Contractor Survey B-1 Appendix B Summary of State Test Methods Compared with AASHTO T 308 C-1 Appendix C Sensitivity Experiment Matrices and Asphalt Content Test Results D-1 Appendix D Instructions to Round-Robin Participants and Data Report

E-1 Appendix E Round-Robin Test Results F-1 Appendix F Round-Robin Test Results Analyses Tables per ASTM E691 G-1 Appendix G Checklist for Troubleshooting Laboratory Visits H-1 Appendix H Comparison of Burning Profiles for Laboratory 23 I-1 Appendix I Proposed Standard Practice for Installation, Operation, and Maintenance of Ignition Furnaces with Commentary