PORE STRUCTURE AND PORE SOLUTION IN ALKALI ACTIVATED FLY ASH GEOPOLYMER CONCRETE AND ITS EFFECT ON ASR OF AGGREGATES WITH WIDE SILICATE CONTENTS A Thesis Submitted to the Graduate Faculty of the North Dakota State University of Agriculture and Applied Science By Shree Raj Paudel In Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE Major Department: Civil and Environmental Engineering April 2019 Fargo, North Dakota North Dakota State University Graduate School Title PORE STRUCTURE AND PORE SOLUTION IN ALKALI ACTIVATED FLY ASH GEOPOLYMER CONCRETE AND ITS EFFECT ON ASR OF AGGREGATES WITH WIDE SILICATE CONTENTS By Shree Raj Paudel The Supervisory Committee certifies that this disquisition complies with North Dakota State University’s regulations and meets the accepted standards for the degree of MASTER OF SCIENCE SUPERVISORY COMMITTEE: Mijia Yang, PhD, PE Chair Zhibin Lin, PhD, PE Ravi Yellavajjala, PhD Long Jiang, PhD Approved: 04/15/2019 David R. Steward, PhD, PE Date Department Chair ABSTRACT Alkali silica reaction (ASR) is detrimental to concrete. It is a time-dependent phenomenon, which can lead to strength loss, cracking, volume expansion, and premature failure of concrete structures. In essence, it is a particular chemical reaction involving alkali hydroxides and reactive form of silica present within the concrete mix. Geopolymer is a type of alkaline activated binder synthesized through polycondensation reaction of geopolymeric precursor and alkali polysilicates. In this thesis, three types of reactive aggregates with different chemical compositions were used. Systematic laboratory experiments and microstructural analysis were carried out for the geopolymer concrete and the OPC concrete made with the same aggregates. The result suggests that the extent of ASR reaction due to the presence of three reactive aggregates in geopolymer concrete is substantially lower than that in OPC based concrete, which is explained by the pore solution change and verified through their microstructural variations and FTIR images. iii ACKNOWLEDGEMENTS I would like to express my earnest appreciation to many individuals who provided their invaluable guidance and support throughout this study. First of all, my deep gratitude goes to my advisor, Dr. Mijia Yang for his continued attention, helpful guidance, and endless support during my MS study. I consider myself fortunate to have a supportive advisor like him. Besides my advisor, I would like to thank the rest of my thesis committee: Dr. Zhibin Lin, Dr. Ravi Yellavajjala, and Dr. Long Jiang for their reviews and insightful advice with this research project. I am particularly indebted to American Engineering Testing Inc. for their support and assistant in obtaining different types of aggregates for this study. I would like to convey my appreciation to Scott Payne and Jayma Moore for their help in conducting microstructural analysis at electron microscopy lab, NDSU. I would like to thank Chunju Gu from coating and polymeric materials department for providing help on several lab works during this study. I would like to take a moment and thank Jan Lofberg and all the Civil and Environmental Engineering department for their direct and indirect help, encouragement and professional instructions throughout my research. Finally, I would like to take this opportunity to thank my beautiful parents, my sister, my brother, all my friends, colleagues and all the faculty at North Dakota State University. iv TABLE OF CONTENTS ABSTRACT ................................................................................................................................... iii ACKNOWLEDGEMENTS ........................................................................................................... iv LIST OF TABLES ......................................................................................................................... ix LIST OF FIGURES ........................................................................................................................ x CHAPTER 1. INTRODUCTION ................................................................................................... 1 1.1. Background .......................................................................................................................... 1 1.2. Objectives ............................................................................................................................. 3 1.3. Scope of work ....................................................................................................................... 3 1.4. Research methodology layout .............................................................................................. 4 CHAPTER 2. LITERATURE REVIEW ........................................................................................ 6 2.1. Introduction .......................................................................................................................... 6 2.2. Background .......................................................................................................................... 6 2.3. Geopolymer concrete ........................................................................................................... 7 2.3.1. Introduction ................................................................................................................... 7 2.3.2. Constituents of geopolymer concrete ............................................................................ 8 2.3.3. Geopolymerization ...................................................................................................... 13 2.4. Alkali aggregate reaction ................................................................................................... 16 2.4.1. Alkali carbonate reaction (ACR) ................................................................................. 16 2.4.2 Alkali silica reaction ..................................................................................................... 17 2.5. ASR in Fly ash based concrete ........................................................................................... 23 2.6. Microstructure analysis of ASR affected geopolymer concrete......................................... 24 2.6.1. Scanning electron microscopy (SEM) ......................................................................... 24 2.6.2. Fourier transform infrared spectroscopy (FTIR) ......................................................... 25 2.6.3. Micro computed tomography (Micro-CT) .................................................................. 26 v 2.7. Summary ............................................................................................................................ 27 CHAPTER 3. MATERIALS AND METHODOLOGY ............................................................... 28 3.1. Introduction ........................................................................................................................ 28 3.2. Material used ...................................................................................................................... 29 3.2.1. Fly ash.......................................................................................................................... 29 3.2.2. Ordinary Portland cement ............................................................................................ 31 3.2.3. Aggregates ................................................................................................................... 32 3.2.4. Alkaline activator solution ........................................................................................... 36 3.2.5. Water ........................................................................................................................... 37 3.3. Mix design .......................................................................................................................... 37 3.3.1. Cementitious material, sand, and coarse aggregate ratio............................................. 37 3.3.2. Water-binder ratio ........................................................................................................ 38 3.3.3. Preparation of alkaline solution ................................................................................... 39 3.4. Effect of different types of aggregates on expansion of geopolymer/OPC concrete ......... 40 3.4.1. Sample preparation ...................................................................................................... 40 3.4.2. Expansion measurement .............................................................................................. 43 3.5. Effect of different types of aggregates on pore solution chemistry of geopolymer/OPC concrete .............................................................................................................................. 44 3.5.1. Sample preparation ...................................................................................................... 44 3.5.2. Pore solution extraction ............................................................................................... 46 3.5.3. pH measurement .......................................................................................................... 47 3.6. Effects of different types of aggregate on ASR of GPC and OPC at microstructure ........ 48 3.6.1. SEM/EDS ...................................................................................................................