Development of a Portable Rheometer for Fresh Portland Cement Concrete RESEARCH REPORT ICAR –105-3F Sponsored by the Aggregates Foundation for Technology, Research and Education Technical Report Documentation Page 1. Report No. 2. Government Accession No. 3. Recipient's Catalog No. ICAR 105-3F 4. Title and Subtitle 5. Report Date August 2004 DEVELOPMENT OF A PORTABLE RHEOMETER FOR FRESH 6. Performing Organization Code PORTLAND CEMENT CONCRETE 7. Author(s) 8. Performing Organization Report No. Eric P. Koehler and David W. Fowler Research Report ICAR 105-3F 9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) International Center for Aggregates Research The University of Texas at Austin 11. Contract or Grant No. ECJ 5.200 Project No. ICAR-105 Austin, Texas 78712-1076 12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered Aggregates Foundation for Technology, Research, and Education Research Report 1415 Elliot Place NW September 2002-August 2004 Washington, D. C. 20007 14. Sponsoring Agency Code 15. Supplementary Notes 16. Abstract: The purpose of this research was to identify an effective field test method for measuring the workability of concrete in general and of high-microfines concrete in particular. The workability of fresh concrete has traditionally been measured with the slump test, which provides an inadequate indication of workability. For certain concrete mixtures—such as that containing fiber reinforcement, ground granulated blast furnace slag, or high contents of aggregate microfines—the slump test can provide inaccurate and misleading results. The need for a better test method for workability is well established within the concrete industry. Based on a literature search in which 61 existing workability test methods were identified and on feedback from government, industry, and academia, criteria for an improved workability test device were developed. It was determined that the best approach to measuring workability would be to develop a new portable rheometer. The ICAR rheometer—a low-cost, fully portable test device for concrete—was developed and tested. A first generation prototype was built using off-the-shelf components. The ICAR rheometer is approximately the size of a drill and can be operated by hand or positioned above a standard container. It is capable of measuring a flow curve or performing a stress growth test and is appropriate for nearly the full range of concrete workability ranging from a slump of approximately 2 inches to self-consolidating concrete. Experimental testing on a wide range of concrete mixtures indicated that the ICAR rheometer was able to detect changes in workability and rheology successfully. As a dynamic test that adds energy to concrete, it is well suited for measuring high-microfines concrete and other highly thixotropic concrete mixtures. Field testing confirmed the portability of the ICAR rheometer. The low cost and portable form factor of the ICAR rheometer can make the routine measurement of concrete rheology in the field an economically viable solution to characterizing concrete workability. 17. Key Words 18. Distribution Statement ICAR rheometer, fiber reinforcement, ground granulated blast No restrictions. furnance slag, aggregates, slump test, concrete workability, high microfines 19. Security Classif.(of this report) 20. Security Classif.(of this page) 21. No. of Pages 22. Price Unclassified Unclassified 306 Form DOT F 1700.7 (8-72) Reproduction of completed page authorized DEVELOPMENT OF A PORTABLE RHEOMETER FOR FRESH PORTLAND CEMENT CONCRETE Eric P. Koehler The University of Texas at Austin Austin, TX and David W. Fowler The University of Texas at Austin Austin, TX ICAR Report 105-3F ICAR 105: Measuring the Workability of High Fines Concrete Sponsored by: International Center for Aggregates Research The University of Texas at Austin Aggregates Foundation for Technology, Research and Education (AFTRE) August 2004 ACKNOWLEDGEMENTS The research described in this report was conducted at the International Center for Aggregates Research at The University of Texas at Austin. The authors gratefully acknowledge the funding provided by the Aggregates Foundation for Technology, Research, and Education. The authors also wish to thank the following companies for contributing materials used in the research (in alphabetical order): Aggregate Industries, Boral Material Technologies, Capitol Aggregates, Edward C. Levy Company, Grace Construction Products, Holcim (US), Sika Corporation, and Vulcan Materials Company. The BTRHEOM rheometer used in the research was on loan from the Federal Highway Administration. The authors acknowledge the helpful input from the participants of the concrete workability workshop in May 2003 and Degussa Admixtures for assisting in facilitating the workshop. The authors thank the National Institute of Standards and Technology for organizing the field testing where the ICAR rheometer was used. Finally, the authors gratefully acknowledge the assistance of Chiara Ferraris of the National Institute of Standards and Technology in serving as a consultant to the research project. ii ABSTRACT The purpose of this research was to identify an effective field test method for measuring the workability of concrete in general and of high-microfines concrete in particular. The workability of fresh concrete has traditionally been measured with the slump test, which provides an inadequate indication of workability. For certain concrete mixtures—such as those containing fiber reinforcement, ground granulated blast furnace slag, or high contents of aggregate microfines—the slump test can provide inaccurate and misleading results. The need for a better test method for workability is well established within the concrete industry. Based on a literature search in which 61 existing workability test methods were identified and on feedback from government, industry, and academia, criteria for an improved workability test device were developed. It was determined that the best approach to measuring workability would be to develop a new portable rheometer. The ICAR rheometer—a low-cost, fully portable test device for concrete—was developed and tested. A first generation prototype was built using off-the-shelf components. The ICAR rheometer is approximately the size of a drill and can be operated by hand or positioned above a standard container. It is capable of measuring a flow curve or performing a stress growth test and is appropriate for nearly the full range of concrete workability ranging from a slump of approximately 2 inches to self-consolidating concrete. Experimental testing on a wide range of concrete mixtures indicated that the ICAR rheometer was able to detect changes in workability and rheology successfully. As a dynamic test that adds energy to concrete, it is well suited for measuring high-microfines concrete and other highly thixotropic concrete mixtures. Field testing confirmed the portability of the ICAR rheometer. The low iii cost and portable form factor of the ICAR rheometer can make the routine measurement of concrete rheology in the field an economically viable solution to characterizing concrete workability. iv TABLE OF CONTENTS LIST OF TABLES .................................................................................................xi LIST OF FIGURES..............................................................................................xiv CHAPTER 1: INTRODUCTION ........................................................................... 1 1.1 Research Background............................................................................ 1 1.2 Historical Perspective............................................................................ 4 1.3 Research Objectives .............................................................................. 8 1.4 Project Scope......................................................................................... 9 CHAPTER 2: FLUID RHEOLOGY..................................................................... 11 2.1 Introduction ......................................................................................... 11 2.2 Properties of Fluids ............................................................................. 11 2.2.1 Definition of a Liquid................................................................. 12 2.2.2 Constitutive Equations for Fluid Flow....................................... 14 2.2.3 Thixotropy and Anti-Thixotropy................................................ 17 2.2.4 Dilatancy .................................................................................... 18 2.2.5 Viscosity..................................................................................... 18 2.2.5.1 Definition .................................................................... 18 2.2.5.2 Origin of Viscosity in Fluid Suspensions.................... 21 2.2.6 Yield Stress ................................................................................ 23 2.3 Measurement of Rheology ..................................................................... 25 2.3.1 Capillary Tube Viscometers....................................................... 25 2.3.1.1 Description .................................................................. 25 2.3.1.2 Derivation of Equations for Capillary Tube Viscometers....................................................................... 26 2.3.2 Rotational Rheometers ............................................................... 29 2.3.2.1 Description