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Alkali-Silica Reactivity: an Overview of Research

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SHRP-C-342 Alkali-Silica Reactivity: An Overview of Research Richard Helmuth Construction Technology Laboratories, Inc. With contributions by: David Stark Construction Technology Laboratories, Inc. Sidney Diamond Purdue University Micheline Moranville-Regourd Ecole Normale Superieure de Cachan Strategic Highway Research Program National Research Council Washington, DC 1993 Publication No. SHRP-C-342 ISBN 0-30cL05602-0 Contract C-202 Product No. 2010 Program Manager: Don M. Harriott Project Maxtager: Inam Jawed Program AIea Secretary: Carina Hreib Copyeditor: Katharyn L. Bine Brosseau May 1993 key words: additives aggregate alkali-silica reaction cracking expansion portland cement concrete standards Strategic Highway Research Program 2101 Consti!ution Avenue N.W. Washington, DC 20418 (202) 334-3774 The publicat:Lon of this report does not necessarily indicate approval or endorsement by the National Academy of Sciences, the United States Government, or the American Association of State Highway and Transportation Officials or its member states of the findings, opinions, conclusions, or recommendations either inferred or specifically expressed herein. ©1993 National Academy of Sciences 1.5M/NAP/593 Acknowledgments The research described herein was supported by the Strategic Highway Research Program (SHRP). SHRP is a unit of the National Research Council that was authorized by section 128 of the Surface Transportation and Uniform Relocation Assistance Act of 1987. This document has been written as a product of Strategic Highway Research Program (SHRP) Contract SHRP-87-C-202, "Eliminating or Minimizing Alkali-Silica Reactivity." The prime contractor for this project is Construction Technology Laboratories, with Purdue University, and Ecole Normale Superieure de Cachan, as subcontractors. Fundamental studies were initiated in Task A. 1 in 1988. Dr. Diamond assembled a data base of 1460 references to published and other reports. Each of the authors reviewed selected works. Dr. Helmuth critically reviewed the literature on mechanisms, supplemented by other important information, and prepared Part I, Mechanisms of Damage to Concrete by Alkali- Silica Reactivity, which was reviewed by David Stark, Sidney Diamond and Micheline Moranville-Regourd. This summary is the context in which important deficiencies in our knowledge of all aspects of alkali-silica reactivity have been identified in Part II, Gaps in our Knowledge of Alkali-Silica Reactions in Concrete. Sections 1, 6, 7, 8 and 9 of Part II were prepared by Richard Helmuth, sections 2 and 3 by David Stark, sections 4 and 5 by Sidney Diamond, and sections 9 and 10 by Micheline Moranville-Regourd. All sections were edited by Stark and Helmuth. ..o 111 Contents °°* Acknowledgments ................................................ nl List of Figures ................................................... vii List of Tables ................................................... ix Abstract ........................................................ 1 Executive Summary ................................................ 3 I Mechanisms of Damage to Concrete by Alkali-Silica Reactivity ............. 7 1. Introduction ..................................................... 7 2. Reaction Chemistry ............................................... 11 2.1 Reaction with Alkali Hydroxides ................................ 11 2.2 Reaction with Calcium and Alkali Hydroxides ...................... 13 2.3 Compositions of Products of Alkali-Silica Reactivity ................. 16 3. The Physical Nature of Alkali-Silica Reaction Swelling Gels ................ 23 3.1 Chemical Shrinkage ......................................... 23 3.2 Swelling of Undissolved Silica ................................. 24 3.3 Shrinkage and Swelling of Gels ................................ 25 3.4 Osmotic Swelling Pressures ................................... 26 3.5 Osmotic Cell Tests .......................................... 29 4. Mechanical Effects of Alkali-Silica Reactivity ........................... 33 4.1 Mortar and Concrete Expansion and Cracking ...................... 33 4.1.1 Powers' and Steinour's Hypothesis ......................... 35 4.1.2 Reaction Zone Compositions ............................. 38 4.1.3 Effects of Particle Size and Pozzolans ...................... 40 4.1.4 Effects of Chloride Salt Additions ......................... 43 4.1.5 Aggregate Fracture by Alkali-Silica Reactivity in Concrete ....... 48 V 4.2 The Effect of Pressure on Alkali-Silica Reactivity ................. 49 4.3 Stresses on Expanding Particl,_s ............................. 49 4.4 Restraint of Expansion of Mo,_stMortars ....................... 51 4.5 Restraint of Expansion of Mo:,st Concretes ...................... 52 4.6 Triaxial Restraint of Expansion of Moist Concrete ................. 52 4.7 Stresses in Moist Mortars and Concretes ....................... 55 5. Environmental Effects ........................................ 57 5.1 Moisture Conditions in Field Concretes ........................ 57 5.2 Effects of Drying and Creep ............................... 59 5.3 Effects of Salt Solutions ................................. 61 6. Concluding Discussion ........................................ 67 Appendix A. Effect of Fly Ash on Hydroxyl Ion Concentrations ............. 71 Appendix B. Compositions of Alkali-Silica Reaction Gels ................. 73 References ............................................... 75 H Gaps in Our Knowledge of Alkali-Silica Reactions in Concrete 1. Introduction .............................................. 81 2. Rapid and Reliable Test Methods to Identify Potentially Reactive Aggregates in Concrete ................................ 83 3. Moisture Conditions of Concrete in Highway Structures .................. 85 4. Effects of Salts and Direct Participation of Chloride Ions in Alkali-Silica Reactivity ...................................... 87 5. Role of Sulfate Reactions Accompanying Expansion Caused by Reactivity ............................................... 91 6. Measurement of Aggregate Reactivities Unimpeded by External Diffusion Processes ................................... 93 7. Effects of Restraint of Expansion on Reaction Kinetics ................... 95 8. Mechanisms by Which Pozzolans Inhibit Expansion ..................... 97 9. Pozzolan and Mineral Admixture Test Methods and Specifications to Prevent Deleterious Alkali-Silica Reactivity ....................... 99 10. Inhibiting Expansion Due to Reactivity by Chemical Agents ............... 103 vi List of Figures Figure 2.2.1 Calculated Reduction of Hydroxyl Ion Concentration Caused by Reaction of 15% Fly Ash Blends with Different Alkali (cement + fly ash) Contents .................... 17 Figure 2.2.2 Calculated Reduction of Hydroxyl Ion Concentration Caused by Reaction of Fly Ash in Blends with 0.67 % Sodium Oxide equivalent Portland Cement with Fly Ashes of Different Alkali contents ..................... 17 Figure 2.3.1 Calcium Oxide and Alkali Contents of Alkali-Silica Reaction Gels ......................................... 21 Figure 2.3.2 Composition of Alkali-Silica Reaction Gels Considered as a Two Component Mixture ...................... 21 Figure 3.3.1 Partial and Apparent Specific Volumes of Sodium Silicate Gels .................................... 27 Figure 3.5.1 Effect of Calcium Hydroxide on Observed Height Differentials in Osmotic Cell Tests ........................... 31 Figure 4.1.1. Powers and Steinour's Model for Reactions with Opal Particles ........................................ 36 Figure 4.1.2 Scanning Electron Microscope-Energy Dispersive X-Ray Microanalysis of Opal-Cement Paste Reaction Zones After 8 Months Moist Curing .......................... 39 Figure 4.3.1 Stresses on Particles of Radius R and in Paste at Particle Surface Caused by Paste Shrinkage, or Particle Expansion, Calculated for 0.05 % Expansion and Selected Properties .................................. 50 Figure 4.6.1 Expansion of Concrete Prisms Stored over Water In Sealed Containers at 100°F (38°C) ......................... 53 vii Figure 4.6.2 Pressure Developed Due to Alkali-Silica Reactivity in Triaxially Confined Concretes Stored at 100°F (38°C) ........................................ 54 Figure 5.1.1. Relative Humidity in Concrete Pavement Located in Hot Desert Area ..................................... 58 Figure 5.1.2 Relative Humidity in Concrete Pavements Located in Different Climatic Regions .............................. 58 Figure 5.1.3 Relative Humidity in Column of Bridge Located in Hot Desert Area in California ............................ 59 Figure 5.2.1 Model for Alkali-Silica Reactivity Cracking in Concrete Pavements ........................................... 62 ..o VUl List of Tables Table 2.3.1 Semi-Quantitative Analyses (in mass percent) of Alkali-Silica Reaction Products ............................ 19 Table 3.3.1 Water Sorption by Alkali Silicate Clear Gels ..................... 25 Table 3.3.2 Sodium Silicate Gel Volume Data ............................ 26 Table 3.4.1 Calculated Osmotic Pressures for Sodium Hydroxide Solutions at 77°F (25°C) ................................. 28 Table 4.1.1 Scanning Electron Microscope-Energy Dispersive X-Ray Analyses of Interfacial Reaction Zones and Opal .................. 40 Table 4.1.2 Expansions of Mortar Bars Made with Akase Opal and Mineral Admixtures .................................. 42 Table 4.1.3 Pore Solution Data for Mortar Cylinders Made With and Without 30 % Fly Ash and Additions of Sodium Chloride and
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