Slurry walls have been widely used for more than 25 years to control the migration of contaminants in the subsurface. In the USA, vertical barriers are mostly constructed of soil-bentonite using the slurry trench method of construction. In this method, sodium bentonite is mixed with water to form a viscous slurry that is pumped into a trench during excavation to maintain the trench stability. The stable trench is then backfilled with a mixture of soil and slurry having a consistency of high slump concrete. These barriers have been designed primarily for low permeability, generally less than 10&minus / 9 m/s. Some investigations have pointed toward improved performance using admixtures that would provide low permeability. In this study, Soma thermal power plant fly ash, granulated blast furnace slag, lime, and steel slag are used as admixture to improve the performance of slurry walls. Permeability, compressive strength, slump, compressibility properties of the mixtures were found and checked for the minimum requirements. According to the findings of this study, granulated blast furnace slag (GGBS), fly ash and steel slag can be used at certain percentages and curing periods as additive in cement-bentonite barrier wall construction. Permeability of specimens having fly ash decreases by increasing fly ash content. Mixtures having 50 % of GGBS type I with 5 % of lime and 9% bentonite content gave acceptable results in 28 days of curing time. Specimens including 50 % of GGBS type II with 5 % of lime and 9% bentonite content gave the higher permeability value in 28 days of curing time with respect to GGBS type I. In addition, most of the mixtures prepared by steel slag gave the acceptable permeability values in 28 days of curing period. Unconfined compressive strength of all mixtures increase by increasing curing time. Cc, Cr, Cv, kcon values were found from consolidation test results. Permeability values found from consolidation tests are 10 times to 100 times higher than flexible wall k results for the same effective stress of 150 kPa. Generally, mv values are decreasing with increasing curing time. As mv decreases, D increases.

Aquesta tesi conté una recerca amb possibilitat de generar una patent, que afecta a "Magnesitas Navarras S.A" / En la presente tesis doctoral se evalúa el potencial de algunos subproductos de magnesio empleados para la formulación de diferentes materiales de construcción y su utilización en diferentes soluciones constructivas. En este sentido, el uso de subproductos industriales para el desarrollo de materiales de construcción potencia criterios de sostenibilidad y beneficios medioambientales asociados a la reutilización de materiales secundarios y a la disminución de actividades extractivas de recursos naturales. La memoria de la presente tesis doctoral se ha estructurado siguiendo el mismo eje conductor desarrollado en la parte experimental del trabajo. Así, ésta incluye una primera parte en la que se detalla el estado del arte referente a los materiales de construcción, así como las soluciones constructivas propuestas. Estas soluciones son, por un lado, el desarrollo de morteros destinados a la protección pasiva frente al fuego (PPF) y, por otro, la formulación de cementos químicos de fosfato (CBPC) de magnesio como material reparador de estructuras de hormigón. Como primer punto del trabajo experimental se ha estudiado y caracterizado exhaustivamente los diferentes subproductos empleados, tanto físico-química como morfológicamente. Esta caracterización preliminar es de gran importancia en el desarrollo de la investigación, dado que, al tratarse de subproductos industriales, no se conocen de antemano las características y las propiedades que éstos presentan, siendo su conocimiento de vital importancia para la correcta consecución de los objetivos establecidos. En el desarrollo experimental de la primera de las soluciones constructivas propuestas, se ha empleado dos subproductos de magnesio [Low-Grade Magnesium Hydroxide (LG-MH) y Low-Grade Magnesium Carbonate (LG-MC)] en la formulación de morteros PPF, utilizando en este caso el cemento Portland convencional como material aglomerante. Ambos subproductos industriales descomponen térmicamente mediante procesos endotérmicos que cubren un amplio rango de temperaturas, retardando así el tiempo necesario para alcanzar una determinada temperatura. En este caso, se han formulado morteros empleando como áridos distintos porcentajes de ambos subproductos, dando lugar a un material con buenas propiedades térmicas y mecánicas, factible de ser utilizado como un mortero PPF. Sin embargo, su utilización como mortero revoco puede verse limitada por la elevada densidad de los áridos utilizados. En este supuesto, puede mejorarse su aplicabilidad añadiendo a los morteros formulados con subproductos de magnesio un árido ligero, como la vermiculita, sin que ello perjudique al resto de propiedades evaluadas. En la consecución de la segunda solución constructiva propuesta, se evalúa la viabilidad del uso como materia prima de otro subproducto de magnesio [Low-Grade Magnesium Oxide (LG-MgO)], en este caso para el desarrollo de cementos químicos de fosfato (CBPC) de magnesio. A tal efecto, se han determinado las propiedades mecánicas de distintas dosificaciones, así como el efecto de un aditivo retardante del fraguado, el ácido bórico (HB), descrito en la bibliografía como retardante de fraguado que permite mejorar la trabajabilidad de los CBPC. Este estudio se ha realizado empleando una herramienta estadística, el diseño de experimentos (DoE), con la finalidad de obtener modelos matemáticos que justifiquen las interacciones entre los distintos componentes de la mezcla y su efecto sobre las propiedades mecánicas y el tiempo de fraguado. Asimismo, el uso del DoE ha de permitir reducir el número de experimentos y establecer el mejor rango de dosificaciones en función de las características deseadas, dando lugar a una formulación adecuada para su utilización en las soluciones constructivas objeto de estudio. Destacar que el uso de LG-MgO en la formulación de CBPC introduce fases inertes no-reactivas contenidas en el propio subproducto, lo que implica que los CBPC desarrollados puedan considerarse como morteros. A partir de los resultados obtenidos se ha seleccionado un pequeño grupo de formulaciones con porcentajes adecuados para evaluar su potencial empleo en el desarrollo de morteros reparadores de estructuras de hormigón. Con este propósito, se han realizado ensayos de adhesión sobre distintos sustratos (hormigón o terrazo) y se ha determinado algunas propiedades requeridas para su uso en la solución constructiva propuesta. La presente tesis doctoral pretende confirmar la viabilidad tecnológica para los distintos campos de aplicación que se han postulado. Sin embargo, no es un objetivo de este estudio el desarrollar un producto final que pueda ser comercializado, sino demostrar su viabilidad gracias al know-how adquirido durante los años de esta investigación, y sentar así las bases para futuros estudios en el desarrollo de materiales de construcción empleando estos subproductos. / The present thesis is focused in the assessment of some magnesium by-products and their potential reutilization for the formulation of different materials for several construction applications. Therefore, the use of industrial by-products for the development of construction materials highlights the sustainability criteria along with the environmental benefits associated with the reutilization of secondary materials whilst diminishing the extractive activities of natural resources. This thesis has been structured following the same pattern for the experimental work. Thus, the first part details the state of the art in what construction materials concerns as well as some of the construction solutions suggested. These solutions are, on the one hand, included in the development of mortars for passive fire protection (PFP) and, on the other hand, in the formulation of chemical bonded phosphate ceramics (CBPC) as a repairing material for concrete structures. The first part presents an exhaustive chemical, physical and morphological characterization of the by-products used. This preliminary characterization is of great importance in the development of the research because of the industrial origin of these by-products. In the first part of the experimental section, the first of the solutions proposed used two types of magnesium by-products [Low-Grade Magnesium Hydroxide (LG-MH) and Low-Grade Magnesium Carbonate (LG-MC)] in the formulation of PFP mortars, using conventional Portland cement as a binder. Both industrial by-products thermally decompose through endothermic processes in a wide range of temperatures, delaying the time needed to achieve a selected temperature. In this case, the mortars were formulated by using different percentages of both by-products as aggregates, obtaining a material with good thermal and mechanical properties and therefore feasible to be used as a PFP mortar. However, its utilization as a sprayed mortar can be limited because of the high density of the aggregates used. In this sense, the practical applicability can be improved by adding a lightweight aggregate such as vermiculite, without diminishing the rest of the assessed properties. Subsequently, in the second part of the experimental section, the viability of another magnesium by-product [Low-Grade Magnesium Oxide (LG-MgO)] is evaluated. In this case, for the development of chemical bonded phosphate ceramics (CBPC). The assessment was made by determining the mechanical properties of different dosages as well as by measuring the effect of a setting-time retarder additive, boric acid (HB), described in the literature as a good additive for this purpose while improving workability as well. This study has been realized by means of a statistical method, the design of experiments (DoE), with the purpose of obtain mathematical models that justify the interactions between different components in the mix and their effect in the mechanical properties and the setting-time. Moreover, the use of DoE enables the reduction in the number of experiments and establishes the best range of dosages as a function of the desired characteristics, giving an optimized formulation to be used in the construction solutions that are object of study. It has to be emphasize that the use of LG-MgO in the formulation of CBPC introduces inert phases that are contained in the by-product itself and that are non-reactive, which implies that the CBPC obtained could be considered as mortars. From the results obtained, a small group of formulations with different percentages was selected to be studied with respect their potential as repairing mortars in concrete structures. Following this objective, adhesion tests were performed over different substrates (concrete or terrazzo) and some of the properties required for their use were determined. The main objective of this thesis is to confirm the technological viability for the different fields of application postulated. However, it is not the main purpose to develop a final product able to be commercialized but to prove the viability by means of the know-how acquired during the years of this research and setting up the base for future studies in the development of construction materials using these by-products.

This degree project is about sustainable low-cost housing in Ethiopia with a focus on CSSB-technology, which is one method of constructing houses. The project allowed me to visit Ethiopia during seven weeks in 2010, to observe, gather information and to perform tests regarding the specific subject. It is a sub-project to a larger research project initiated in 2002 at Halmstad University in an attempt to introduce low-cost housing technologies for the Kambaata Region in Ethiopia. The aim of the research project has been to develop and test new, sustainable, low-cost building technologies intended for the population, with regard to local traditions, needs and affordability. / Sustainable Low-Cost Housing for the Kambaata region in Ethiopia

Civil engineers are at times required to stabilize sulfate bearing clay soils with calcium based stabilizers. Deleterious heaving in these stabilized soils may result over time. This dissertation addresses critical questions regarding the consequences of treating sulfate laden soils with calcium-based stabilizers. The use of a differential scanning calorimeter was introduced in this research as a tool to quantify the amount of ettringite formed in stabilized soils. The first part of this dissertation provides a case history analysis of the expansion history compared to the ettringite growth history of three controlled low strength mixtures containing fly ash with relatively high sulfate contents. Ettringite growth and measurable volume changes were monitored simultaneously for mixtures subjected to different environmental conditions. The observations verified the role of water in causing expansion when ettringite mineral is present. Sorption of water by the ettringite molecule was found to be a part of the reason for expansion. The second part of this dissertation evaluates the existence of threshold sulfate levels in soils as well as the role of soil mineralogy in defining the sensitivity of soils to sulfate-induced damage. A differential scanning calorimeter and thermodynamics based phase diagram approach are used to evaluate the role of soil minerals. The observations substantiated the difference in sensitivity of soils to ettringite formation, and also verified the existence of a threshold level of soluble sulfates in soils that can trigger substantial ettringite growth. The third part of this dissertation identifies alternative, probable mechanisms of swelling when sulfate laden soils are stabilized with lime. The swelling distress observed in stabilized soils is found to be due to one or a combination of three separate mechanisms: (1) volumetric expansion during ettringite formation, (2) water movement triggered by a high osmotic suction caused by sulfate salts, and (3) the ability of the ettringite mineral to absorb water and contribute to the swelling process.

In calcium aluminate cement (CAC) systems the hydration process is different than portland cement (PC) systems. The hydration products of CAC are subjected to conversion depending on temperature, moisture, water-cement ratio, cement content, etc. Consequently, strength of CAC system can be seriously reduced. However, presence of other inorganic binders or additives may alter the hydration process and improve various properties of CAC based composites. The objective of this study is to investigate the temperature effect on the behaviour of CAC based composite binders. Throughout this research, several combinations of CAC-PC, CAC-gypsum, CAC-lime, CAC-ground granulated blast furnace slag (CAC-GGBFS) were studied. These CAC based composite binders were subjected to seven different curing regimes and their strength developments were investigated up to 210 days. In addition, the mechanism of strength development was examined by XRD analyses performed at 28 and 210 days. Finally, some empirical relationships between strength-time-curing temperatures were formulated. Experimental results revealed that the increase in ambient temperature resulted in an increase in the rate of conversion, thereby causing drastic strength reduction, particularly in pure CAC mix. It has been observed that inclusion of small amount of PC, lime, and gypsum in CAC did not induce conversion-free CAC binary systems, rather they resulted in faster conversion by enabling rapid formation of stable C3AH6 instead of metastable, high strength inducing CAH10 and C2AH8. On the other hand, in CAC-GGBFS mixes, the formation of stable straetlingite (C2ASH8) instead of calcium aluminate hydrates hindered the conversion reactions. Therefore, CAC-GGBFS mixes, where GGBFS ratio was over 40%, did not exhibit strength loss due to conversion reactions that occurred in pure CAC systems.

The measurement and monitoring of the elastic properties of cement-based materials is very important for assessing their quality, integrity and performance. Due to the nonhomogeneous and time-dependent characteristics of these materials, it is difficult to observe the developments in elastic properties with traditional destructive methods. The aim of this thesis is to determine and monitor elastic properties of mortar specimens made with different cements by using resonant frequency and ultrasonic pulse velocity test methods, and to obtain relationships between these elastic properties. For this purpose, eight different cement mortar mixtures were prepared with different constituent CEM I cements. Dynamic elastic moduli, static elastic moduli, dynamic Poisson&rsquo / s ratio and strength of these mixtures were observed for different ages. The relationships between these elastic properties are determined and the results obtained from two different nondestructive test methods are compared. Although nondestructive tests made it possible to obtain elastic properties of mortar mixtures, the results revealed that it is very difficult to develop a single relationship between different elastic properties of mortars with varying mixture proportions. This situation is mainly due to the anisotropy and nonlinear behavior of the mortar and the difficulty of describing the actual behavior of mortar by formulations defined for perfectly elastic materials.

Fluid migration behind the cased holes is an important problem for oil and gas industry both considering short terms and long terms after cementing operation. For many reasons like high formation pressures, high shrinkage rate of cement slurry while setting, lack of mechanical seal, channeling due to cement slurry setting profile, hydrocarbon migration may occur and lead expensive recompletion operations and sometimes abandonment. Solutions to this problem vary including high density-low fluid loss cement slurry or right angle cement setting profile. During this study, the effect of &ldquo / free water&rdquo / which is the basic quality property of API G class cement, on fluid migration potential has been tested for different samples and in combination with different physical conditions. For this study API G class cements have been used. In order to justify the quality of each cement sample standard API G class quality tests were conducted. Moreover, as a main instrument &ldquo / Static Gel Strength Analyzer&rdquo / is used to measure the static gel strength of cement slurry and how long it takes to complete transition time. Bolu cement, Nuh cement, and Mix G cement samples were tested according to their free fluid values which are %2.5, %5, %3.12 respectively, and it is found that the Bolu cement with lowest free fluid content has the lowest potential for fluid migration. As a conclusion, fluid migration through behind the cased hole is a major threat for the life of the well. Appropriate cement slurry system may easily defeat this threat and lead cost saving well plans. Key words: Fluid migration, fluid loss, transition time, channeling, right angle, API G class cement, free water, high formation pressure

Stereocomplex poly(methyl methacrylate) (PMMA) fibers for the purpose of reinforcing PMMA materials were developed. These kinds of composites are known as "self-reinforced" composites. We were successful in producing stereocomplex PMMA fibers with three different methods - wet spinning, gel spinning and electrospinning. Gel spinning and electrospinning produced the most crystalline fibers. Steroecomplex PMMA fibers were further shown to be resistant to high temperature and also to hot monomer solvent during bulk polymerization. We further describe our efforts in characterization, replication and mimicry of structural color features of butterflies and beetles. We have developed a simple method of characterizing the bidirectional reflectance distribution function of microscopic objects such as butterfly wing scales. We used this method to characterize nanometer sized structural color features resulting from the replication of butterfly Morpho rhetenor, mimickry of butterfly Papilio palinurus and also the native structural color features of iridescent beetle Chrysina gloriosa, which were shown to be cholesteric focal conic defects lined on the surface.

Masonry is a layered composite consisting of mortar and the masonry unit. Perfect bond between the masonry unit and the mortar is essential for the masonry to perform as one single entity in order to resist the stresses due to various loading conditions. Nature of stresses developed in the masonry unit and the mortar and the failure pattern of masonry subjected to compression greatly depends upon the relative stiffness of the masonry unit and the mortar. The thesis is focused on (a) some issues pertaining to masonry unit – mortar bond strength and its influence on masonry compressive strength, and (b) developing a finite element (FE) model to predict the compressive strength of masonry. Importance of masonry bond strength and masonry behaviour is highlighted in chapter 1. Characteristics of masonry units and mortars used in the investigations are presented in Chapter 2. Two types of soil-cement blocks with widely varying strength and elastic properties and cement-lime mortars of two different proportions were used in the investigations. Results of stress-strain relationships and other characteristics were determined for the blocks as well as for mortars. Block-mortar combinations were selected to have block modulus to mortar modulus ratio of <1.0, ~1.0 and >1.0. Different artificial methods of enhancing the shear bond strength of masonry couplets have been discussed in chapter 3. Shear bond strength of the masonry couplets was determined through a modified direct shear box test apparatus. Without altering the block and mortar properties, bond strength values for three block-mortar combinations were generated through experiments. Effect of pre-compression on shear bond strength has also been examined for certain block-mortar combinations. Considering five different bond strength values and three block-mortar combinations, compressive strength and stress-strain characteristics of masonry was obtained through the tests on masonry prisms. A detailed discussion on influence of shear bond strength on masonry compressive strength is presented. Major conclusions of the investigation are: (a) without altering the block and mortar characteristics shear bond strength can be enhanced considerably through the manipulation of surface texture and surface coatings, (b) masonry compressive strength increases linearly as the shear bond strength increases only for the combination of masonry unit modulus less than that of mortar modulus, (c) masonry compressive strength is not sensitive to bond strength variation when the modulus of masonry unit is larger than that of the mortar. Chapter 4 is dedicated to the development of a 3D FE model to predict the masonry compressive strength. Literature review of empirical methods/formulae and some failure theories developed to predict masonry strength are presented. Existing FE models for masonry dealing with both macro and micro modelling approaches are reviewed. The proposed FE model considers (a) 3D non-linear analysis combined with a failure theory, (b) uses multi-linear stress-strain relationships to model the non-linear stress-strain behaviour of masonry materials, (c) adopting Willam-Warnke’s five parameter failure theory developed for modelling the tri-axial behaviour of concrete, and (d) application of orthotropic constitutive equations based on smeared crack approach. The predicted values of masonry compressive strength are compared with experimental values as well as those predicted from other failure theories. The thesis ends with a summary of conclusions in chapter 5.

Thesis (M.S.)--Mississippi State University. Department of Civil Engineering. / Title from title screen. Includes bibliographical references.