Geopolymer cements offer an alternative to, and potential replacement for, ordinary Portland cement (OPC). Geopolymer technology also has the potential to reduce global greenhouse emissions caused by OPC production. There is already a considerable amount of work and research conducted on geopolymers in the past decades, and it is now possible to implement this technology commercially. However, to ensure that geopolymer becomes commercially available and able to be used in the world, further understanding of its ability to provide durable and long lasting materials is required. One main property which is still relatively unexplored compared to other properties is its shrinkage properties. The objective of this thesis is therefore to examine the shrinkage of geopolymers and factors which might influence it. / The factors which influence geopolymer strength were investigated as being the factors which may influence shrinkage. The selection of the activating solution is an important factor in forming the final product of a geopolymer. Activating solution SiO2/Na2O ratio is determined to be an important influence on the shrinkage of geopolymer. SEM images of the samples enable observation of the sample topology and microstructure. An important observation was the existence of a ‘knee point’ which also occurs in OPC shrinkage. The ‘knee point’ is the point where the shrinkage goes from rapid shrinkage to slow shrinkage. From SEMs it is noted that the samples past the knee point are shown to have a smoother topology which means it is more reacted. / Autogenous shrinkage is an important issue for OPC containing a high amount of silica, and is also a key factor in geopolymer shrinkage. Autogenous shrinkage is tested by keeping samples in a sealed environment where water lost to drying is kept to a minimum. It is noted that sealing and bagging the samples reduces the shrinkage considerably. The water to cement ratio, which is an important factor in OPC shrinkage, is also explored for the case of geopolymers. Water content plays an important role in determining early stage shrinkage, and has little to no effect on the later stage shrinkage. The water loss from the samples during drying on exposure to environment is noted and compared. The addition of more water did not necessary means that more water was lost. / Addition of slag is known to be beneficial to geopolymers by giving early structural strength and faster setting time. Commercial geopolymer concrete will also include the use of slag. However, the addition of slag up to a certain extent gives a deleterious affect on shrinkage. / A different type of Class F fly ash source with different composition data was used to see its effect on shrinkage, with only a slight influence observed between the two ashes tested. Fly ash was also ground for different lengths of time before use in geopolymerization, with grinding for less than 12 hours giving higher shrinkage than an unground sample, but shrinkage the decreasing with grinding for 18 or 24 hours. This initial higher shrinkage has been attributed to the mechanism of grinding which resulted in unevenly shaped fly ash particles taking up a larger initial volume resulting in higher shrinkage. The sample grinded for 24 hours showed higher shrinkage due to the particle size to be so fine that agglomerates may have form during mixing which would result in a lower reaction rate which increases the shrinkage. Elevated curing temperatures also reduce geopolymer shrinkage. / Thus, it is clear that the shrinkage of geopolymers is influenced by a wide range of variables, and more notably by a few important variables: activating solution ratio, addition of water, grinding and bagging. The shrinkage of geopolymers can be correlated to the strength to a certain extent. However, the understanding of the shrinkage of geopolymers is still at a very initial phase, and further research is required.

La nécessité de construire de manière durable, rationnelle et écologique incite à l’innovation et la recherche d’alternatives, telles que la géopolymérisation et l’activation alcaline, qui suscitent un intérêt croissant. Dans ce sens, ces technologies permettent de valorise rdes matières premières à plus faible impact environnemental pour le développement d’une nouvelle famille de matériaux. Cependant, ces mécanismes réactionnels sont complexes et il est encore nécessaire de lever plusieurs verrous avant leur implémentation : la confusion entre les deux processus, l’absence d’approches de formulation rationnelles, la méconnaissance de certaines vulnérabilités, etc. La thèse s’intègre dans cette dynamique et a pour objectif une meilleure connaissance des géopolymères et des matériaux alcali-activés. Le cadre de travail est le développement de coulis d’injection. Un programme expérimental basé sur une sélection de compositions est établi afin de caractériser leurs principales propriétés. Les différences entre les deux processus de structuration sont relevées à travers une étude physico-chimique (DRX, RMN) et liées aux évolutions macroscopiques au jeune âge. Un travail d’optimisation de formulation est mené afin de répondre à des critères d’application et définir les paramètres influençant le comportement rhéologique et mécanique des coulis. Une méthodologie basée sur l’analyse micromécanique et l’homogénéisation multi-échelles a permis d’évaluer le module élastique des matériaux et peut servir de plateforme pour une analyse globale du comportement mécanique. Enfin, une étude de la durabilité est entamée en évaluant la sensibilité au séchage et à la lixiviation en milieu acide. / The need for more durable, rational and ecological constructions encourages innovation and the search for alternatives, such as geopolymerization and alkali-activation, with a growing interest. These technologies allow the use of resources with a lower environmental impact in developing a new class of materials. However, both reaction mechanisms are complex and some issues need further investigation before a proper implementation: the confusion between these processes, the absence of a rational design approach, the lack of knowledge concerning some mechanisms of degradation, etc. The present thesis joins this dynamic and aims at a better understanding of geopolymers and alkali activated materials to design soil injection grouts. An experimental program has been established based on selected mix designs to study their main properties. The differences between both structuration processes were determined through a physicochemical study (XRD, NMR). They were correlated to the macroscopic phenomena observed at early age. An optimization of the mixtures was carried to satisfy the application criteria and define the parameters controlling the rheological and mechanical behavior of the grouts. Using a micromechanical characterization and multiscale homogenization, a methodology has been designed to determine the elastic modulus of the materials.This can be used as a first tool to analyze the global mechanical behavior. Finally, the sensitivity to drying and exposure to acid environments was assessed.

Stricter greenhouse gas emission limits and renewable energy requirements are expected to further increase the worldwide practices of firing biomass and co-firing biomass with coal, which are both considered more sustainable energy sources than coal-only combustion. Reuse options for the by-products of these processes -biomass ash and co-fired fly ash -remain limited. Therefore, this research examines their use as supplementary cementitious materials (SCMs) in concrete and as precursors for alkali-activated geopolymers. Toward their potential use as an SCM, after characterizing these ashes assessing their compliance with ASTM C618 requirements, their impact on early-age hydration kinetics, rheology, setting time and permeability was assessed. Furthermore, the pozzolanic reactivity and the microstructural and hydrated phase development of the cement-ash samples were analyzed. The results show that a wood biomass ash sample was not satisfactory for use as an SCM. On the other hand, the findings demonstrate that co-fired fly ashes can significantly improve the strength and durability properties of concrete compared to ordinary portland cement, in part due to their pozzolanicity. Thus, it is recommended that the ASTM C618 standard be modified to permit co-fired fly ash sources that meet existing requirements and any additional requirements deemed necessary to ensure their satisfactory performance when used in concrete. Toward their potential use in geopolymers, this study characterized the early-age reaction kinetics and rheological behavior of these materials, showing that their exothermic reactivity, plastic viscosity and yield stress are significantly influenced by the activator solution chemistry and other characteristics of the ash. Two co-fired fly ashes were successfully polymerized, with compressive strengths generally highest for ashes activated with solutions with a molar ratio of SiO₂/(Na₂O + K₂O) = 1. The results show that geopolymerization is a viable beneficial reuse for these emerging by-products. Further characterization of these materials by scanning transmission X-ray microscopy analysis revealed the heterogeneity of the aluminosilicate phase composition of the co-fired fly ash geopolymer gel at the nano- to micro-scale.

Geopolymers are a relatively new class of material that has many broad applications, including use as a substitute for Ordinary Portland Cement (OPC), use in soil stabilisation, fire resistant panels, refractory cements, and inorganic adhesives. The synthetic alkali aluminosilicate structure of geopolymer results in a highly versatile material that can be synthesised en masse, cost competitively and from a wide varietyof aluminosilicate bearing raw materials. / Despite the commercial promise and technical viability of the technology, the fundamental understanding of the chemical structure and characteristics of geopolymeric materials, and to some degree the academic rigor of some aspects of the science related to geopolymers, leave a lot to be desired. In particular, the understanding of the effects of Si/Al ratio and alkali cation type on the molecular structure of the binder, and how these relate to the microstructure and mechanical and thermal properties are poorly understood. / The thesis explores the structure and characteristics of a systematic multi-dimensional matrix of geopolymers derived from metakaolin, a relatively pure aluminosilicate source. The thesis addresses the determination of the core molecular structure of geopolymers by solid-state NMR spectroscopy, and how this is altered by the nominal Si/Al ratio and alkali cation type. The chemical ordering is observed to reduce with Si/Al ratio and with inclusion of potassium over sodium. Most significantly, the presence of Al-O-Al linkages is identified for the first time in specimens with Si/Al ratios close to unity, by the application of 17O NMR techniques on geopolymers. The role of molecular structure and gel chemistry of geopolymers is elucidated, and links are drawn to understand the development of the microstructure and physical properties of the material. The thermal evolution of geopolymeric gels derived from metakaolin is investigated in terms of physical and structural development when exposed to temperatures up to 1000°C. The response of geopolymers to heating is characterised into four regions regardless of the extent of shrinkage or crystallisation. Several critical material performance relationships exist that are related to both the microstructure and chemical composition. / The thesis presents an updated structural model of geopolymers to include new insights obtained from application of solid-state NMR techniques and thermal analysis. The improvements in structural understanding described in the thesis have the potential to affect all aspects of geopolymer science.

abstract: Alkali-activated aluminosilicates, commonly known as "geopolymers", are being increasingly studied as a potential replacement for Portland cement. These binders use an alkaline activator, typically alkali silicates, alkali hydroxides or a combination of both along with a silica-and-alumina rich material, such as fly ash or slag, to form a final product with properties comparable to or better than those of ordinary Portland cement. The kinetics of alkali activation is highly dependent on the chemical composition of the binder material and the activator concentration. The influence of binder composition (slag, fly ash or both), different levels of alkalinity, expressed using the ratios of Na2O-to-binders (n) and activator SiO2-to-Na2O ratios (Ms), on the early age behavior in sodium silicate solution (waterglass) activated fly ash-slag blended systems is discussed in this thesis. Optimal binder composition and the n values are selected based on the setting times. Higher activator alkalinity (n value) is required when the amount of slag in the fly ash-slag blended mixtures is reduced. Isothermal calorimetry is performed to evaluate the early age hydration process and to understand the reaction kinetics of the alkali activated systems. The differences in the calorimetric signatures between waterglass activated slag and fly ash-slag blends facilitate an understanding of the impact of the binder composition on the reaction rates. Kinetic modeling is used to quantify the differences in reaction kinetics using the Exponential as well as the Knudsen method. The influence of temperature on the reaction kinetics of activated slag and fly ash-slag blends based on the hydration parameters are discussed. Very high compressive strengths can be obtained both at early ages as well as later ages (more than 70 MPa) with waterglass activated slag mortars. Compressive strength decreases with the increase in the fly ash content. A qualitative evidence of leaching is presented through the electrical conductivity changes in the saturating solution. The impact of leaching and the strength loss is found to be generally higher for the mixtures made using a higher activator Ms and a higher n value. Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) is used to obtain information about the reaction products. / Dissertation/Thesis / M.S. Civil Engineering 2012

abstract: The alkali activation of aluminosilicate materials as binder systems derived from industrial byproducts have been extensively studied due to the advantages they offer in terms enhanced material properties, while increasing sustainability by the reuse of industrial waste and byproducts and reducing the adverse impacts of OPC production. Fly ash and ground granulated blast furnace slag are commonly used for their content of soluble silica and aluminate species that can undergo dissolution, polymerization with the alkali, condensation on particle surfaces and solidification. The following topics are the focus of this thesis: (i) the use of microwave assisted thermal processing, in addition to heat-curing as a means of alkali activation and (ii) the relative effects of alkali cations (K or Na) in the activator (powder activators) on the mechanical properties and chemical structure of these systems. Unsuitable curing conditions instigate carbonation, which in turn lowers the pH of the system causing significant reductions in the rate of fly ash activation and mechanical strength development. This study explores the effects of sealing the samples during the curing process, which effectively traps the free water in the system, and allows for increased aluminosilicate activation. The use of microwave-curing in lieu of thermal-curing is also studied in order to reduce energy consumption and for its ability to provide fast volumetric heating. Potassium-based powder activators dry blended into the slag binder system is shown to be effective in obtaining very high compressive strengths under moist curing conditions (greater than 70 MPa), whereas sodium-based powder activation is much weaker (around 25 MPa). Compressive strength decreases when fly ash is introduced into the system. Isothermal calorimetry is used to evaluate the early hydration process, and to understand the reaction kinetics of the alkali powder activated systems. A qualitative evidence of the alkali-hydroxide concentration of the paste pore solution through the use of electrical conductivity measurements is also presented, with the results indicating the ion concentration of alkali is more prevalent in the pore solution of potassium-based systems. The use of advanced spectroscopic and thermal analysis techniques to distinguish the influence of studied parameters is also discussed. / Dissertation/Thesis / M.S. Engineering 2013

V této závěrečné práci bylo popsáno časné reologické chování alkalicky aktivované strusky, anorganického materiálu, který vzniká aktivací mleté granulované vysokopecní strusky alkalickým roztokem. Vliv typu aktivačního roztoku (hydroxidů, křemičitanů a uhličitanů) a jeho koncentrace na časné reologické parametry byl zkoumán pomocí amplitudových oscilačních měření. Bylo pozorováno, že typ aktivátoru je hlavním faktorem ovlivňujícím reologické chování alkalicky aktivované strusky. Dále bylo pozorováno, že aktivátory na bázi draslíku vedou ke slabší struktuře (nižší mez kluzu, mez toku a nižší hodnoty viskoelastických modulů) oproti použití aktivátorů na bázi sodíku. To lze vysvětlit rozdíly ve velikosti alkalických iontů. Na rozdíl od ostatních aktivátorů křemičitany způsobovaly zvýšení ztrátového faktoru, přičemž vykazovaly spíše kapalné chování. Z výsledků vyplynulo, že většina aktivátorů má tzv. kritickou hodnotu koncentrace, po jejímž dosažení mají reologické vlastnosti vzorků tendenci se měnit s rostoucí koncentrací. Získané výsledky korelovaly s výstupy zeta potenciálu.

Evaluation of physical and chemical properties of geopolymer composites based on alkali aktivated metakaoline and silicate oxide.

This thesis deals with preparation of geopolymeric binders for inhibition of toxic elements, especially arsenic. It studies influence of content progress of different phases in prepared binders on leachability of As during the setting. The aim of this study is to determine the type of inhibition or the cause of leachability of As in prepared binders respectively. Fly ash from high-temperature coal combustion, slag, cement kiln dust and sodium hydroxide solution were used for experimental works. FT-IR, TG-DTA, XRD analyses after different hydration times were used. The leachates were analyzed by ICP-MS. Calorimetric measurements of tested mixtures fresh pastes were implemented to learn about setting process. Hardened binder specimens were tested for bending and compressive strength.

Portland cement-based products are the most commonly used building materials. However, it is well known that the production of OPC not only consumes a significant amount of natural resources and energy but also releases high quantity of carbon dioxide (CO2) to the atmosphere. Purpose of this work is to develop new cementitious material similar to Portland cement-based concrete, which is convenient in terms of energy and is environmental-friendly at once. This work presents preparation, composition and properties of inorganic aluminosilicate polymer, called geopolymer, synthesized from blast furnace slag and fly ash, activated by sodium hydroxide and cement kiln dust. Study of the microstructure was based on SEM-EDX-WDX, TG-DTA-EGA and XRD analysis.