Nanostructure and Engineering Properties of 1.4 nm Tobermorite, Jennite and Other Layered Calcium Silicate Hydrates Pouya Pourbeik Thesis submitted to the Faculty of Graduate and Postdoctoral Studies in partial fulfillment of the requirements for the Doctorate in Philosophy degree in Civil Engineering Department of Civil Engineering Faculty of Engineering University of Ottawa © Pouya Pourbeik, Ottawa, Canada, 2015 Abstract The nature of the calcium-silicate-hydrate phase in hydrated Portland cement has been the subject of considerable debate for decades. Various nanostructural models have been proposed including those constructed from colloidal-based particulate systems and those formulated on the basis of layered calcium-silicate-hydrates. These are examined in detail in the literature review section of the thesis. Relatively recent composition-based models have been proposed by Taylor and Richardson-Groves. These models contain structural elements comprised of 1.4 nm tobermorite and jennite. Details are also provided in the literature review. There is however a paucity of data on the engineering properties of pure calcium- silicate-hydrate phases and virtually none on the mechanical performance of 1.4 nm tobermorite and jennite. The global objective of this thesis was to examine the compatibility of the composition-based models with the engineering behaviour of the pure tobermorite and jennite phases. Pure phases of a variety of layered calcium-silicate-hydrates were synthesized and novel techniques developed to determine their engineering characteristics in a variety of test environments. The silicate phases investigated included high temperature silicates e.g. gyrolite as these layered structures are known to be cross-linked. Investigation of the role of ‘structural’ water in layered silicates was also a part of these studies. The thesis is based on a series of twelve refereed journal papers by the candidate (eight are published or accepted and four have been submitted for publication). The research is reported in four parts with each part comprised of three papers. Each part provides insight into the nanostructure of C-S-H in hydrated cement. The arguments developed evolve from an assessment of various factors including aging and the state of water in the layered silicates. The first part of the thesis focuses on the development and application of dynamic mechanical thermo-analysis methods that are sensitive to phase changes and are useful for assessing the compatibility of engineering behaviour with model composition based on 1.4 nm tobermorite and jennite. The second part represents a study of volume stability and mechanical property- porosity relationships for the pure silicate phases that are germane to these studies. The third part focuses on prolonged aging and role of structural water in cement paste hydrated for 45 years. The fourth and final part attempts to address the role of layer structure e.g. cross- linking of silicate sheets on engineering behaviour. The non-uniqueness of modulus of ii elasticity with respect to equilibrium moisture content is demonstrated. Structurally related irreversible effects that are dependent on drying history are rationalized. A summary chapter is provided wherein the evidence for a composition-based model with tobermorite and jennite structural units is rationalized in terms of the experimental evidence provided in this study and suggestions for future research are discussed. iii To my beloved parents and brother iv Acknowledgements I would like to first express my sincere appreciation to my supervisor, Dr. James J. Beaudoin (Researcher Emeritus at the National Research Council, Canada (NRC) and Adjunct Professor at the University of Ottawa) for his continuous support. The completion of this thesis would not have been possible without his encouragement, constant support, invaluable suggestions, and continuous assistance throughout this research program. I am grateful I had the opportunity to work with him. A big thank you goes to Dr. Rouhollah (Aali) Alizadeh (CEO at Giatec Scientific) for his willingness to share his experiences regarding the application of engineering techniques and nanotechnology in the study of cement-based materials. My deep gratitude goes to Dr. Laila Raki for her guidance in PhD Research project. She introduced me to different aspects of chemistry and its application in studying cement-based materials and for her insightful comments and suggestions on various parts of my research. I thank my kind colleagues for their support: Mses. Rahil Khoshnazar and Dan-Tam Nguyen. Considerable thanks go to Mr. Gordon Chan as well for his invaluable help with lab equipments at National Research Council Canada. (NRC) The experimental work of this thesis was conducted at the National Research Council of Canada including the laboratories at the Institute for Research in Construction, Steacie Institute for Molecular Sciences and Institute for Chemical Process and Environmental Technology. I would also like to acknowledge the financial support provided through an NSERC discovery grant on “Nanostructural tailoring of cement systems for sustainability”. I was also partially supported by assistantships at the University of Ottawa. A special thank you to my examination committee members Drs. Arezki Tagnit-Hamou, Pouria Ghods, Beatriz Martin-Pérez, and Mamadou Fall for their suggestions on the current work. This doctoral research also benefited from scientific discussions with researchers at NRC: Drs. Jon Makar, Taijiro Sato, Patrick Grattan-Bellew, Jean-Francois Masson and Pierre-Claver Nkinamubanzi. I am truly thankful to Messrs. Jim Margeson, Ken Trischuk, Dave Edwards, Bruce Baldock, Omran Madani and Peter Collins, and Mses. Ana Delgado, Sladana Bundalo-Perc and Helen Yew for their training on various experimental methods and equipment. I thank my friends for all their support and encouragement. v Finally, special appreciation goes to my beloved parents and brother, Pedram, for their endless support, encouragement, and understanding during this long journey. vi Contents Abstract .................................................................................................................................. ii Acknowledgements ................................................................................................................ v Chapter 1 Introduction .......................................................................................................................... 1 1.1 Statement of Global Objectives .................................................................................. 1 1.2 Historical Background ................................................................................................ 2 1.3 Program Description ................................................................................................... 2 References .............................................................................................................................. 3 Chapter 2 Pure Calcium-Silicate-Hydrates Phases Investigated- General Description .................. 4 References .............................................................................................................................. 9 Chapter 3 Calcium-Silicate-Hydrate Phases in Cement-Based Materials ..................................... 10 3.1 The Portland cement-water reaction ......................................................................... 10 3.2 Relation of C-S-H with more ordered phases ...................................................... 11 3.3 Characteristics of C-S-H ...................................................................................... 13 3.3.1C/S ratio ...................................................................................................... 13 3.3.2 State of water in C-S-H ............................................................................. 14 3.4 Silicate polymerization.............................................................................................. 15 References ............................................................................................................................ 17 Chapter 4 Physico - chemical and Compositional Models of Cement Paste and C-S-H Nanostructure ..................................................................................................................... 22 4.1 Introduction ............................................................................................................... 22 vii 4.2 Powers and Brownyard (P-B) Model ........................................................................ 22 4.3 Feldman-Sereda (F-S) Model .................................................................................... 23 4.3.1 Cement paste mass and length-change sorption isotherms ………...……….... 27 4.3.2 Mechanical property isotherms ......................................................................... 31 4.3.3 Helium inflow methods ..................................................................................... 33 4.3.4 C-S-H (I) - a nanostructural model for the removal of water from cement paste ............................................................................................................................................. 36 4.3.5 Stress relaxation of C-S-H ................................................................................. 40 4.3.6 Colloidal-based model (P-B) and layered silicate model (F-S) – a polemic ..... 44 4.4 Model of Daimon