AN INVESTIGATION OF GEOPOLYMERS FOR USE IN HIGH TEMPERATURE APPLICATIONS A THESIS SUBMITTED TO THE FACULTY OF THE UNIVERSITY OF MINNESOTA BY CASEY SUNDBERG IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE DR. MARY CHRISTIANSEN, DR. ANDREA SCHOKKER, DR. BRIAN HINDERLITER, AUGUST 2018 © 2017 Casey Sundberg Table of Contents List of Tables .................................................................................................................... vii List of Figures ..................................................................................................................... x Chapter 1: Introduction ....................................................................................................... 1 1.1 Motivation ................................................................................................................. 1 1.2 Project Goals ............................................................................................................. 4 1.3 Organization .............................................................................................................. 7 Chapter 2: Literature Review .............................................................................................. 8 2.1 Nuclear Power Plants .............................................................................................. 10 2.1.1 Mechanisms of a core meltdown ...................................................................... 12 2.1.2 Challenges in cooling a core meltdown ............................................................ 14 2.2 Ordinary Portland Cement ...................................................................................... 16 2.2.1 Cement chemist notation .................................................................................. 17 2.2.2 Portland cement production .............................................................................. 17 2.2.3 Portland cement hydration ................................................................................ 18 2.3 Effect of Elevated Temperature on Ordinary Portland Cement .............................. 21 2.4 Geopolymer Cement ............................................................................................... 24 2.4.1 Geopolymerization ........................................................................................... 26 2.5 Geopolymer Stoichiometry for High Temperature Applications ............................ 28 i 2.5.1 Effect of precursor material on thermal performance ...................................... 28 2.5.1.1 Fly ash ........................................................................................................ 29 2.5.1.2 Metakaolin ................................................................................................. 31 2.5.1.3 Ground glass .............................................................................................. 33 2.5.2 Effect of activator solution and stoichiometry on thermal performance .......... 35 2.5.2.1 Activator types ........................................................................................... 35 2.5.2.2 Molar concentration ................................................................................... 36 2.5.2.3 Activator/precursor ratio ............................................................................ 36 2.5.2.4 Water/solids (w/s) ratio .............................................................................. 37 2.5.2.5 Silica/alumina (SiO/Al O) ratio ............................................................. 37 2.5.2.6 Sodium/alumina (Na O/Al O) ratio ........................................................ 38 2.5.2.7 Alumina content ......................................................................................... 39 2.6 Thermal Conductivity of Geopolymer Cement ....................................................... 40 2.6.1 Effects of thermal conductivity on materials under thermal loading ............... 40 2.6.2 Effect of aggregate material on thermal conductivity ...................................... 43 2.7 Effect of Elevated Temperatures on Geopolymer Cement ..................................... 44 2.7.1 Thermal loading conditions .............................................................................. 47 Chapter 3: Materials and Experimental Methods ............................................................. 48 3.1 Material Selection and Characterization ................................................................. 48 ii 3.1.1 Fly ash............................................................................................................... 48 3.1.2 Metakaolin ........................................................................................................ 49 3.1.3 Ground Waste Glass ......................................................................................... 51 3.1.4 Activator solution ............................................................................................. 53 3.1.5 Fine aggregate ................................................................................................... 55 3.1.6 Coarse aggregate ............................................................................................... 55 3.2 Mixture Design and Development .......................................................................... 55 3.2.1 Stoichiometry.................................................................................................... 56 3.2.2 Mixture proportioning and water content ......................................................... 57 3.2.3 Mixing procedure ............................................................................................. 58 3.2.4 Fresh properties ................................................................................................ 59 3.2.5 Mortar cube and cylinder preparation .............................................................. 60 3.2.6 Curing ............................................................................................................... 61 3.3 High Temperature Durability Testing ..................................................................... 61 3.3.1 Phase 1 thermal durability testing .................................................................... 63 3.3.2 Phase 2 thermal durability and hardness testing ............................................... 64 3.4 Thermal Transport Properties.................................................................................. 66 3.4.1 Thermal conductivity testing ............................................................................ 68 3.4.2 Molten metal testing ......................................................................................... 69 iii Chapter 4: Results and Discussion .................................................................................... 71 4.1 Mixture Design ........................................................................................................ 71 4.1.1 Mixture naming convention.............................................................................. 71 4.1.2 Stoichiometric ratios ......................................................................................... 72 4.1.2.1 Sodium equivalent/alumina (Na O(eq)/Al O) ratio ............................... 73 4.1.2.2 Water/solids (w/s) ratio .............................................................................. 73 4.1.2.3 Activator/precursor ratio ............................................................................ 74 4.1.2.4 Silica/alumina (SiO/Al O) ratio ............................................................ 74 4.1.3 Fly ash-based mixtures ..................................................................................... 75 4.1.3.1 Baseline fly ash-based mixture .................................................................. 75 4.1.3.2 Variations of the baseline fly ash-based mixture ....................................... 76 4.1.4 Ground glass-based mixtures............................................................................ 79 4.1.4.1 Baseline ground glass-based mixture......................................................... 79 4.1.4.2 Variations of the baseline ground glass-based mixture ............................. 80 4.2 Phase 1 Compressive Strengths .............................................................................. 83 4.2.1 Phase 1 fly ash-based geopolymer compressive strengths ............................... 83 4.2.2 Phase 1 ground glass-based geopolymer compressive strengths...................... 85 4.2.3 Discussion of Phase 1 geopolymer compressive strengths .............................. 86 4.3 Phase 1 Thermal Durability Testing ....................................................................... 94 iv 4.3.1 Phase 1 thermal durability testing at 600°C ..................................................... 94 4.3.2 Phase 1 thermal durability testing at 1100°C ................................................... 95 4.3.3 Discussion of Phase 1 high temperature durability tests ................................ 103 4.3.3.1 Fly ash-based geopolymer high temperature durability tests .................. 104 4.3.3.2 Ground glass-based geopolymer high temperature durability tests ......... 105 4.3.3.3 Mixtures selected for further study in Phase 2 ......................................... 107 4.4 Phase 2 High Temperature Thermal Durability Tests ........................................... 107 4.4.1 Impulse