ALKALI CONTENT OF FLY ASH: MEASURING AND TESTING STRATEGIES FOR COMPLIANCE Final Report April 2015 Sponsored by Iowa Highway Research Board and the Iowa Department of Transportation (IHRB Project TR-628) MaterialsMaterials AnalysisAnalysis aandnd RResearchesearch LaboratoryLaboratory About the MARL and the Office of Biotechnology The Materials Analysis and Research Laboratory (MARL) is a core instrumentation facility supported by the Office of Biotechnology at Iowa State University. The MARL offers chemical and physical characterization of a wide range of materials. The Office of Biotechnology, established in 1984, facilitates and advances programs in research, education, and outreach that contribute to the goals of Iowa State University’s strategic plan in the area of biotechnology. The office oversees the biotechnology programs developed by the 10-member Biotechnology Council and the Office of the Vice President for Research. A major initiative of the office is to establish and support state-of-the-art instrumentation for biotechnology research. Iowa State’s instrumentation facilities for biotechnology research are open to faculty and students from the university, other educational institutions, and to industry scientists. Disclaimer Notice The contents of this report reflect the view of the author, who is responsible for the facts and the accuracy of the information presented herein. Non-Discrimination Statement Iowa State University does not discriminate on the basis of race, color, age, ethnicity, religion, national origin, pregnancy, sexual orientation, gender identity, genetic information, sex, marital status, disability, or status as a U.S. veteran. Inquiries regarding non-discrimination policies may be directed to Robinette Kelley, Director, Office of Equal Opportunity, Title IX /ADA Coordinator, and Affirmative Action Officer, 3350 Beardshear Hall, Ames, Iowa 50011, Tel. 515 294-7612, email [email protected]. Iowa Department of Transportation Statements The preparation of this report was financed in part through funds provided by the Iowa Department of Transportation. The opinions, findings, and conclusions expressed in this publication are those of the authors and not necessarily those of the Iowa Department of Transportation. Technical Report Documentation Page 1. Report No. 2. Government Accession No. 3. Recipient’s Catalog No. IHRB Project TR-628 4. Title and Subtitle 5. Report Date Alkali Content of Fly Ash – Measuring and Testing Strategies for Compliance April 2015 6. Performing Organization Code 7. Author(s) 8. Performing Organization Report No. Scott M. Schlorholtz 9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) Materials Analysis and Research Laboratory Iowa State University 11. Contract or Grant No. Room 68 Town Engineering Building Ames, IA 50010-8664 12. Sponsoring Organization Name and Address 13. Type of Report and Period Covered Iowa Highway Research Board Final Report Iowa Department of Transportation 14. Sponsoring Agency Code 800 Lincoln Way IHRB Project TR-628 Ames, IA 50010 15. Supplementary Notes 16. Abstract Sodium and potassium are the common alkalis present in fly ash. Excessive amounts of fly ash alkalis can cause efflorescence problems in concrete products and raise concern about the effectiveness of the fly ash to mitigate alkali-silica reaction (ASR). The available alkali test, which is commonly used to measure fly ash alkali, takes approximately 35 days for execution and reporting. Hence, in many instances the fly ash has already been incorporated into concrete before the test results are available. This complicates the job of the fly ash marketing agencies and it leads to disputes with fly ash users who often are concerned with accepting projects that contain materials that fail to meet specification limits. The research project consisted of a lab study and a field study. The lab study focused on the available alkali test and how fly ash alkali content impacts common performance tests (mortar-bar expansion tests). Twenty-one fly ash samples were evaluated during the testing. The field study focused on the inspection and testing of selected, well documented pavement sites that contained moderately reactive fine aggregate and high-alkali fly ash. A total of nine pavement sites were evaluated. Two of the sites were control sites that did not contain fly ash. The results of the lab study indicated that the available alkali test is prone to experimental errors that cause poor agreement between testing labs. A strong (linear) relationship was observed between available alkali content and total alkali content of Class C fly ash. This relationship can be used to provide a quicker, more precise method of estimating the available alkali content. The results of the field study failed to link the use of high-alkali fly ash with the occurrence of ASR in the various concrete sites. Petrographic examination of the pavement cores indicated that Wayland sand is an ASR-sensitive aggregate. This was in good agreement with Iowa DOT field service records. It was recommended that preventative measures should be used when this source of sand is used in concrete mixtures. 17. Key Words 18. Distribution Statement available alkali—fly ash — ASR performance — rapid determination No restrictions. 19. Security Classification (of this 20. Security Classification (of this 21. No. of Pages 22. Price report) page) Unclassified. Unclassified. 125 NA Form DOT F 1700.7 (8-72) Reproduction of completed page authorized ALKALI CONTENT OF FLY ASH: MEASURING AND TESTING STRATEGIES FOR COMPLIANCE Final Report April 2015 Principal Investigator Scott Schlorholtz Scientist Author Scott Schlorholtz Sponsored by the Iowa Highway Research Board and the Iowa Department of Transportation (IHRB Project TR-628) A report from The Materials Analysis and Research Laboratory A Core Service Facility for the Office of Biotechnology Iowa State University Room 68 Town Engineering Building Ames, IA 50011-3260 Phone: 515-294-8761 www.marl.iastate.edu TABLE OF CONTENTS ACKNOWLEDGMENTS ............................................................................................................ IX EXECUTIVE SUMMARY .......................................................................................................... XI INTRODUCTION ...........................................................................................................................1 Problem Statement ...............................................................................................................1 Background ..........................................................................................................................1 Objectives ............................................................................................................................2 Research Plan and Scope .....................................................................................................3 LITERATURE REVIEW ................................................................................................................4 Test Methods Available for Fly Ash ....................................................................................4 Summary of the Alkali Tests .............................................................................................15 Specifications for Fly Ash (National) ................................................................................15 Specifications for Fly Ash (Iowa DOT).............................................................................16 Alkali Content – Prescriptive Limits or Performance Limits ............................................16 Future of Coal Power Generation ......................................................................................19 DETAILS - EXPERIMENTAL PROCEDURES ..........................................................................22 Materials ............................................................................................................................22 Chemical Testing Methods ................................................................................................24 Physical Testing Methods ..................................................................................................25 Pavement Core Sites and Project Information ...................................................................26 RESULTS AND DISCUSSION ....................................................................................................28 Materials Properties ...........................................................................................................28 Checking the Iowa DOT Available Alkali Model .............................................................36 Mortar-Bar Expansion Testing ..........................................................................................40 Summary of the Mortar-bar Expansion Tests ....................................................................54 Summary of Field Surveys and Petrographic Studies........................................................55 ADDITIONAL DISCUSSION ......................................................................................................62 SUMMARY AND CONCLUSIONS ............................................................................................70 Conclusions – Field Study .................................................................................................70 Conclusions – Lab Study ...................................................................................................73