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Multiscale Engineering Response of Alkali Activated Aluminosilicate Binders

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Multiscale Engineering Response of Alkali Activated Aluminosilicate Binders Multiscale Engineering Response of Alkali Activated Aluminosilicate Binders by Akash Dakhane A Dissertation Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy Approved November 2016 by the Graduate Supervisory Committee: Narayanan Neithalath, Chair Subramaniam Rajan Barzin Mobasher Robert Marzke Sumanta Das ARIZONA STATE UNIVERSITY December 2016 ABSTRACT Sustainable materials and methods have achieved a pivotal role in the research plethora of the new age due to global warming. Cement production is responsible in contributing to 5% of global CO2 emissions. Complete replacement of cement by alkaline activation of aluminosilicate waste materials such as slag and fly ash is a major advancement towards reducing the adverse impacts of cement production. Comprehensive research has been done, to understand the optimized composition and hydration products. The focus of this dissertation is to understand the multiscale behavior ranging from early age properties, fundamental material structure, fracture and crack resistance properties, durability responses and alternative activation methods to existing process. The utilization of these materials has relied primarily on the dual benefits of reduced presence in landfills and cost. These have also proven to yield a higher service life as opposed to conventional ordinary portland cement (OPC) concrete due to an enhanced microstructure. The use of such materials however has not been readily acceptable due to detrimental early age behavior. The influence of design factors is studied to understand the reaction mechanism. Silicon polymerization at the molecular level is studied to understand the aluminosilicate interactions which are responsible for prevention of any leaching of ions. A comparative study between fly ash and slag binders is carried out to evaluate the stable states of sodium, aluminum and silicon in both these binders, since the likelihood of the sodium ions leaching out is high. i Compressive and flexural strength have been reported in previous literature, but the impact of crack resistance was unevaluated from an approach of characterizing the fracture process zone. Alternative routes of activation are explored with an intent to reduce the high alkalinity by use of neutral salts such as sodium sulfate. High volume OPC replacement by both class C and F fly ash is performed to evaluate the differences in hydration phase formation responsible for its pore refinement and strength. Spectroscopic studies have also allowed to study the fundamental material structure. Durability studies are also performed on these samples to understand the probability external sulfate attacks as opposed to OPC mixes. ii DEDICATION I dedicate this to Mummy, Papa and Akshay. Without their love, understanding and support this incredible journey would not have been possible. iii ACKNOWLEDGMENTS I would like to express my sincere gratitude to my advisor and committee chair, Dr. Narayanan Neithalath, for his undivided attention, guidance, encouragement and motivation throughout my research. I would like to extend my regards to my committee members: Dr. Subramaniam D. Rajan, Dr. Barzin Mobasher, Dr. Robert Marzke, and Dr. Sumanta Das for serving in my committee and their guidance in my study. I want to thank Dr. Kirk Vance for teaching and supporting in the beginning of my research work. I greatly appreciate the assistance provided by lab support team and engineering technical services comprising of Peter Goguen, Jeff Long and Kenneth Witczak for all of their assistance during my active years of research. I would like to acknowledge all my colleagues Kirk, Sumanta, Vikram, Ben, Matthew, Pu, Aashay, Sateesh and my friends for their help. iv TABLE OF CONTENTS Page LIST OF TABLES ............................................................................................................ xvi LIST OF FIGURES ........................................................................................................ xviii CHAPTER 1 INTRODUCTION ................................................................................................... 1 1.1 General ................................................................................................................. 1 1.2 Impact of Manufacture/Utilization of OPC.......................................................... 1 1.3 Use of Supplementary Cementitious Materials (SCM)........................................ 2 1.4 Alternative Methods for Sustainable Binder Development ................................. 3 1.5 Motivation for Present Research .......................................................................... 3 1.6 Objectives and Significance of the Research ....................................................... 4 1.7 Organization of Dissertation ................................................................................ 6 2 LITERATURE REVIEW ........................................................................................ 9 2.1 General ................................................................................................................. 9 2.2 Need for OPC-free Binders .................................................................................. 9 2.3 Alternative Binder Systems................................................................................ 10 2.3.1 Geopolymers ............................................................................................... 10 2.3.2 Activated Glassy Cements .......................................................................... 11 v CHAPTER Page 2.3.3 Hydraulic Fly Ash Cements ........................................................................ 11 2.3.4 Activated Slag Cements .............................................................................. 12 2.3.5 Calcium Aluminate Cements ...................................................................... 12 2.3.6 Calcium Sulfoaluminate Cements............................................................... 13 2.3.7 Magnesia Cements ...................................................................................... 14 2.3.8 CO2 Cured Cement...................................................................................... 15 2.4 History and Application of Alkali Activated Binders ........................................ 16 2.5 Activator media and its properties ..................................................................... 18 2.5.1 Alkali Hydroxides ....................................................................................... 18 2.5.2 Alkali Silicates ............................................................................................ 18 2.5.3 Alkali Sulfates............................................................................................. 20 2.5.4 Calcium Oxide ............................................................................................ 21 2.6 Alkali Activation of Class F Fly Ash Binders.................................................... 24 2.6.1 Constituent Materials .................................................................................. 24 2.6.2 Material Structure and Reaction Mechanism.............................................. 24 2.6.3 Alkali activation of Fly Ash........................................................................ 27 2.6.4 Fundamental Structure of N-A-S-H gel ...................................................... 28 2.6.5 Limitations of Alkali Activated Fly Ash Binders ....................................... 29 vi CHAPTER Page 2.7 Alkali Activation of Glass Granulated Blast Furnace Slag (GGBFS) ............... 30 2.7.1 Reaction Mechanism................................................................................... 30 2.7.2 Hydration of Slag ........................................................................................ 33 2.7.3 Fundamental Structure of C-A-S-H gel ...................................................... 34 2.7.4 Limitations of Alkali Activated Slag .......................................................... 35 2.8 Alkali Activation of OPC-Fly Ash Blended Binders via Neutral Salts ............. 36 2.8.1 Need for Neutral Salt Activation ................................................................ 36 2.8.2 Reaction Mechanism................................................................................... 36 2.8.3 Hydration Product Phases and Composition............................................... 37 2.8.4 Durability Concerns .................................................................................... 37 2.9 Alkali Activated Binder Synthesis ..................................................................... 39 2.9.1 Mixing Procedure........................................................................................ 39 2.9.2 Curing Conditions ....................................................................................... 40 2.10 Summary of Testing Methodology and Properties of Alkali Activated Binders ........................................................................................................................ 41 2.10.1 Fresh Paste Properties ............................................................................... 41 2.10.2 Mechanical Properties ............................................................................... 44 2.10.3 Reaction products and Microstructure Characterization ........................... 45 vii CHAPTER Page 2.10.4 Durability Properties ................................................................................
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