A reação álcali-agregado (RAA) é uma reação química complexa envolvendo os álcalis presentes no cimento Portland e minerais silicosos presentes em alguns tipos de agregados reativos. O produto dessa reação expande quando em contato com a água, causando fissuração e deformação, o que afeta a durabilidade e importantes propriedades mecânicas das estruturas de concreto. Entretanto, estruturas que estejam sob tensão de compressão, aplicada por carregamentos ou induzida pela presença de armadura, apresentam expansão reduzida na direção comprimida. Uma das ferramentas que se utiliza para a previsão da vida útil de estruturas afetadas pela RAA é a modelagem numérica da expansão do concreto, possibilitando a previsão e projeto de reparos necessários. Nesse contexto, modelos paramétricos combinam os principais fatores que influenciam a reação (reatividade dos constituintes, porosidade, temperatura, umidade e estado de tensões), possibilitando a determinação da distribuição e da taxa de expansão na estrutura. Nessa pesquisa foi desenvolvido um modelo paramétrico cujo principal interesse foi o estudo das tensões induzidas pela presença de fibras e armadura na expansão do concreto afetado pela RAA. O modelo implementado em elementos finitos tem como parâmetros nodais as posições, uma formulação alternativa ao método dos elementos finitos baseado em deslocamentos; a medida de deformação utilizada é a de Green e a lei constitutiva dos materiais é a de Saint-Venant-Kirchhoff. O material composto é discretizado por meio de uma matriz elástica bi-dimensional reforçado por fibras lineares perfeitamente aderidas à matriz. Comparações entre os resultados obtidos por meio do modelo desenvolvido e resultados de trabalhos experimentais comprovam a aplicabilidade e potencialidade do modelo numérico apresentado. / The alkali-aggregate reaction (AAR) is a complex chemical reaction involving alkalis present in the Portland cement paste and siliceous minerals present in some types of reactive aggregates. The product of this reaction expands in contact with water, causing cracking and deformation that affects durability and important mechanical properties of the concrete structures. However, structures under compressive stress, applied or induced by the presence of rebars, the expansion is reduced in the compressed direction. One of the tools used to predict the service life of structures affected by AAR is the numerical modeling of the concrete expansion, allowing prevision and projecting repairs needed. In this context, parametric models combine the main factors that influence the reaction (reactivity of the constituents, porosity, temperature, humidity and stress state), enabling the determination of distribution and rate of expansion in the structure. In this research was developed a parametric model whose main interest was the study of stresses induced by the presence of fibers and rebars in the expansion of concrete affected by AAR. The model implemented in finite element has as nodal parameters positions, an alternative formulation to the finite element method based on displacement; the deformation measurement used is Green and the material constitutive law is the Saint-Venant-Kirchhoff. The composite material is discretized by a two-dimensional elastic matrix reinforced by perfectly adherent linear fibers. Comparisons between the results obtained from the developed model and results of experimental studies demonstrate the applicability and potential of the numerical model presented.

Submitted by JOSIANE SANTOS DE OLIVEIRA (josianeso) on 2017-06-20T12:30:42Z No. of bitstreams: 1 Moisés Mário Cachepa_.pdf: 3004067 bytes, checksum: 24c7ce290fa414a34e3454c918c0403c (MD5) / Made available in DSpace on 2017-06-20T12:30:42Z (GMT). No. of bitstreams: 1 Moisés Mário Cachepa_.pdf: 3004067 bytes, checksum: 24c7ce290fa414a34e3454c918c0403c (MD5) Previous issue date: 2017-05-22 / CNPQ – Conselho Nacional de Desenvolvimento Científico e Tecnológico / O uso de adições minerais, como as pozolanas, tem sido adotado como adição ou substituição parcial do cimento, fundamentalmente na produção de concretos, com intuito de melhorar algumas das características, tais como redução de calor de hidratação, melhoria da trabalhabilidade, aumento da resistência à compressão, aumento da durabilidade em meios agressivos, redução da emissão de CO2, redução do aparecimento de eflorescência. Um sério problema de durabilidade é a reação álcali-agregado (RAA), que é um fenômeno que em geral se manifestam em estruturas de concreto massa, como barragens. A RAA é entendida como sendo um processo químico que ocorre em concreto, em que alguns constituintes mineralógicos presentes no agregado reagem com íons alcalinos, provenientes de hidróxidos originados na hidratação do cimento que estão dissolvidos na solução dos poros, formando um gel higroscópico expansivo. Este trabalho teve como objetivo avaliar a mitigação da reação álcali-agregado em concreto mediante o emprego de resíduos da cerâmica vermelha (RCV) e metacaulim (MK) como pozolanas. O RCV foi adquirido como resíduo de indústria da produção de blocos cerâmicos, enquanto que o MK é um produto comercializado, sabidamente mitigador da RAA e, geralmente, com elevada atividade pozolânica. Para se alcançar o objetivo, foram analisadas as características físicas, químicas, mineralógicas do RCV e do MK, e determinou-se o índice da atividade pozolânica. Tanto o RCV como o MK apresentaram índice de atividade pozolânica superior a 90%. O agregado utilizado foi classificado como potencialmente reativo por meio de análise de petrografia e do método acelerado de barras de argamassa. Para avaliação da eficiência das adições minerais na mitigação da RAA, empregou-se o método acelerado de barras de argamassa. As pozolanas isoladas e combinadas foram empregadas em teores de substituição de cimento de 20% e 30%. Avaliou-se também resistência à compressão e absorção capilar de água em 48h e 28 dias, submetidos à solução saturada de em Ca(OH)2; e em 28 dias de imersão em solução de NaOH. Com os resultados de expansão, foi possível verificar que todos os materiais e teores propostos promoveram uma mitigação da RAA em relação às amostras confeccionadas somente com cimento, com valores de expansão inferiores a 0,10%. Para os aglomerantes estudados, foi possível verificar que entre as pozolanas, quanto menor o equivalente alcalino, menores são as expansões. No entanto, as misturas somente com MK apresentam valores de equivalente alcalino similares ao cimento e as expansões são significativamente reduzidas. Para uma mesma relação Ca/Si dos aglomerantes, quanto maior for o teor de RCV menor é a expansão. Quando se avalia o teor de alumina dos aglomerantes, percebe-se que aqueles que contém MK apresentam o maior teor, mas, no entanto, não retornam as menores expansões, o que se explica pela sua maior dimensão média equivalente, em relação aos aglomerantes que contém RCV. A menor dimensão das partículas de RCV parecem aumentar o efeito mitigador que o teor de Al possui, pois a superfície de dissolução destas partículas é maior. A comparação dos resultados da resistência à compressão e absorção de água antes de iniciar o ensaio acelerado e após, bem como a comparação com as argamassas aos 28 dias que não sofreram ataques ajudam a enteder o comportamento das pozolanas na mitigação da RAA. / The use of mineral additions through pozzolans, both naturally and artificially, has been adopted by several civil engineering professionals through the partial substitution of cement primarily in the production of concrete slabs, with the aim of improving some of the characteristics such as: Reduction of the heat of hydration, improvement of the workability, increase of the resistance to compressive strength, increase of the durability in aggressive environments, reduction of the emission of CO2, reduction of the appearance of efflorescence and reduction of the expansions due to the alkali-aggregate reactions. One of the pathologies that greatly affects mass concrete structures such as dams is the alkali-aggregate reaction, which is understood to be a chemical process occurring in concrete, in which some mineralogical constituents present in the aggregate react with hydroxides from the cement that are dissolved In the solution of the pores forming an expansive hygroscopic gel. The elaboration of this work, on the one hand, was motivated by the fact that one of the main dams in Africa located in Mozambique, shows signs of expansion according to several authors and, on the other hand, as a way of evaluating the Pozolan potential of RCV and MK. This work aimed to evaluate the mitigation of the alkali-aggregate reaction in concrete through the use of residues of red ceramics and metakaolin as pozzolans. The RCV was purchased as a waste from the production of ceramic blocks, while the MK was from a commercial product. In order to reach the objective, the RCV and MK underwent an investigation taking into account physical, chemical, mineralogical characteristics and the determination of the index of the pozzolanic activity. Both RCV and MK had pozzolanic activity index higher than the 90% established by NBR 12653 (2014). The aggregate used was classified as potentially reactive through analyzes of petrography, DRX, FRX and accelerated method of mortar bars. For the evaluation of RAA, samples were prepared and analyzes of aggregate reactivity and mineral additions efficiency were performed using the accelerated method of mortar bars, compressive strength and water capillary absorption in a substitution of 20% and 30% of cement by RCV, MK and RCV + MK, in the following curing ages: 48h, 28 days in Ca (OH) 2 and 28 days of immersion in NaOH solution. By the expansion results, it was possible to verify that all materials and cement substitution contents by pozzolans proposed had a reduction of less than 0.10% recommended by ASTM C1567 (2013), classified as insufficient to cause deleterious reactions due to potential Pozolânico of the MK and RCV. It was possible to verify that the higher the alkaline equivalent, the larger the expansions, the smaller the Ca / Si ratio, the smaller the expansions, the higher the alumina content, the smaller the expansions, the smaller the average equivalent size Of the particles, the smaller the expansions, and the larger the total porosity, the larger the expansions. The results of the compressive strength and water absorption showed that the mixtures submitted to the accelerated test presented worse performance in relation to the cured mixtures in Ca (OH) 2 due to the microstructure of the mortars, creating internal microcracks, or because the formed gel permeable to water penetration.

Les normes plus restrictives visent à réduire les émissions de polluants, en particulier le CO2, favorisant l'usage des biocarburants. Cependant, le biodiesel contient des éléments inorganiques (Na, K, Ca et P) qui réduisent la durabilité des systèmes de post-traitement. Dans ce travail sont évalués les performances des catalyseurs d'oxydation diesel (DOCs, catalyseur de référence PtPd/CeZrO2/La-Al2O3). Les résultats de caractérisation ont montré l’influence de ces impuretés sur les propriétés physico-chimiques et catalytiques. Bien que la structure cristalline du catalyseur de référence ne change pas après l'incorporation des impuretés, la surface spécifique diminue. La capacité redox a diminué lorsque les impuretés Na, K et Ca sont présents du à leur faible électronégativité, ce qui augmente l'interaction avec l'oxygène. Cette interaction semble être responsable de l’augmentation de la vitesse de réaction de C3H6. Les résultats NO-TPD ont montré que la forte basicité ces impuretés entraînait une plus forte adsorption du NO. Par DRIFT il a été aussi montré que l’adsorption des intermédiaires du NO, associée au champ électrostatique créé par ces cations, empêche l'oxydation de NO. L'adsorption de CO a été favorisée, améliorant la conversion du CO. La formation de phosphate de cérium observée pourrait stabiliser l'état d'oxydation de Ce3+ (vérifié par XPS), en diminuant l'oxydation de NO due au blocage des sites catalytiques. Néanmoins, les co-oxydations de CO et de C3H6 ont été améliorées en évitant l'auto-empoisonnement. Après vieillissement hydrothermal, l'effet des impuretés a été masqué par le frittage de Pt/Pd, ce qui diminue les performances catalytiques / The more restrictive regulations to reduce pollutants emissions, especially CO2, promote the use of biofuels. However, biodiesel contains inorganic elements (Na, K, Ca and P) that reduce the durability of the after-treatment catalysts. This work aims to evaluate the performance of Diesel Oxidation Catalysts (DOCs, PtPd/CeZrO2/La-Al2O3 reference catalyst). The characterization results have shown that the above-mentioned impurities affect the physico-chemical, redox, surface and catalytic properties. Although the catalyst crystalline structure of reference catalyst did not change after impurities incorporation, the specific surface area decreased. The redox ability was also decreased when Na, K and Ca impurities are present due to their low electronegativity, which increased the oxygen interaction. This high interaction seems to be responsible of the enhanced C3H6 reaction rate. NO-TPD results evidenced that the high basicity of Na, K and Ca impurities resulted in an increase of NO adsorption strength. Accordingly, DRIFT results showed the presence of NO intermediates adsorption associated to the electrostatic field created by these cations, hindering NO oxidation. CO adsorption was also promoted, enhancing CO reaction rate. The formation of cerium phosphate was also observed, which could stabilize the Ce3+ oxidation state (checked by XPS), decreasing NO oxidation due to the blockage of catalytic sites. Nevertheless, CO and C3H6 co-oxidations were enhanced by avoiding self-poisoning. After catalyst hydrothermal aging, the effect of impurities was masked by the sintering of Pt/Pd active sites, which decreases the DOC catalytic performances

A presente dissertação trata da implementação e otimização de um sistema de detecção condutométrica sem contato capacitivamente acoplada (C4D) para Eletroforese Capilar (CE). O sistema é caracterizado pela compactação do sistema de detecção, versatilidade e flexibilidade de instalação em diferentes equipamentos comerciais de eletroforese capilar e home made. Desde a década de 80, a eletroforese capilar vem se consolidando como uma das técnicas de separação mais relevantes. Normalmente, os instrumentos comerciais são disponibilizados com detectores ópticos e detectores eletroquímicos. A C4D é utilizada em eletroforese capilar posicionando-se dois eletrodos tubulares envoltos ao capilar. A aplicação de sinais de alta frequência entre os eletrodos permite monitorar variações de condutividade da solução dentro do capilar. Assim, a resposta do detector depende de diversos fatores como mobilidade do analito, do co-íon do eletrólito, da frequência e amplitude do sinal aplicado entre os eletrodos e da geometria dos mesmos. A ausência de componentes móveis torna o presente detector compacto (6,5 cm3) e robusto. O presente C4D é constituído de um oscilador local funcionando a 1,1 MHz, um circuito capaz de converter corrente em tensão, retificar e filtrar os sinais analógcos, além de apresentar um conversor de sinais analógicos em digitais (Conversor A/D) de alta resolução (21 bits efetivos). Outra vantagem é a possibilidade de determinar o diâmetro interno do capilar através da leitura do conversor A/D quando se faz passar um fluxo de ar e, posteriormente água através do capilar. A diferença de leitura de conversor A/D pode ser convertida em diâmetro interno mediante uma curva de calibração. Em uma aplicação típica, os limites de detecção baseado no critério 3s (sem filtragem inicial) foi de 0,6, 0,4, 0,3, 0,5, 0,6 e 0,8 µmol L-1 para K+, Ba2+, Ca2+, Na+, Mg2+ e Li+, respectivamente, é comparável a outras implementações de alta qualidade de um detector condutométrico sem contato capacitivamente acoplado. / This dissertation deals with the implementation and optimization of a Capacitively Coupled Contactless Conductivity Detector (C4D) applied to capillary electrophoresis (CE). The system is characterized by compaction of the detection system, installation flexibility and versatility in different commercial capillary electrophoresis equipment and home-made. Since the 80s, capillary electrophoresis has been consolidated as one of the most important separation techniques. Typically, commercial instruments are available to optical detectors and electrochemical detectors. The C4D is used in capillary electrophoresis positioning two electrodes encased in tubular capillary. The application of high frequency signals between the electrodes allows monitoring changes in conductivity of the solution within the capillary. Thus, the detector response depends on several factors such as mobility of the analyte, the co-ion electrolyte, the frequency and amplitude of the signal applied between the electrodes and the geometry of the same. The absence of moving parts makes this compact detector (6.5 cm3) and robust. This C4D is composed of a local oscillator, working at 1.1 MHz, a circuit capable of converting current into voltage, rectify and filter the analogs signals, besides presenting a high-resolution analog-to-digital converter (ADC) (21 bits effective). Another advantage is the possibility of determining the internal diameter of the capillary by reading the ADC when it is passed a stream of air and then water through the capillary. A readings different ADC can be converted into inner diameter through a curve a calibration curve. In a typical application, the detection limits based on the 3s criterion (without baseline filtering) was 0.6, 0.4, 0.3, 0.5, 0.6 and 0.8 µmol L-1 for K+, Ba2 +, Ca2 +, Na+, Mg2+ and Li+, respectively, is comparable to other high-quality implementations of a capacitively coupled contactless conductivity detector.

[pt] O fenômeno de dessorção iônica a partir da incidência de pulsos de radiação laser ultravioleta sobre superfícies em vácuo foi estudada. A dessorção de três tipos diferentes de sólidos foi analisada: insulina, carbono (amorfo e grafite) e policristais de haletos alcalinos. Os processos fundamentais da interação da radiação laser com sólido e o vapor formado, assim como a evolução do plasma gerado, foram descritos satisfatoriamente através de um modelo térmico e da simulação de espectros de têmpo-de-vôo para os primeiros instante da expansão ao vácuo. Um novo método foi proposto para determinar as velocidades iniciais e o início da expansão livre em função da intensidade do laser para LDI (Laser Desorption Ionization) e MALDI (Matrix Assisted Laser Desorption Ionization). Embora o estudo da expansão do plasma gerado não tenha sido tratada dinamicamente pela sua complexidade, a análise utilizando varias combinações do sólido irradiado permitiram concluir que a dessorção induzida por laser pode ser caracterizada por dois processos fundamentais: i) a atomização seguida de recombinação dos constituintes do alvo formando aglomerados e ii) a emissão de aglomerados pré-formados do material. As estruturas geométricas mais estáveis das espécies detectadas foram caracterizadas utilizando a Teoria do Funcional da Densidade (DFT) e classificadas taxonomicamente em função de sua energia (método D-plot); determinou-se a influência da estabilidade dessas estruturas nas abundâncias relativas no espectro de massa. / [en] Ion desorption induced by ultraviolet laser radiation pulses was studied in surfaces in vacuum. The ion desorption from three different solids was analyzed: insulin, carbon (amorphous and graphite) and polycrystals of alkali halides. The main processes involved in the laser-solid and laser-vapor interactions, as well as in the plasma evolution, were well described by a thermal model and by the simulation of the time-of-flight spectra for the first moments of the plasma expansion to vacuum. A new method to determine the initial velocity and the beginning of the free expansion regime as a function of the laser intensity was proposed for LDI (Laser Desorption Ionization) and MALDI (Matrix Assisted Laser Desorption Ionization). Considering the complexity of the dynamical treatment of the expansion of the laser-generated plasma, an analysis by using several combinations of irradiated solids was performed. It was established that the desorption process is characterized by two main mechanisms: i) the atomization followed by recombination of the target elements in clusters and ii) the emission of preformed clusters of the target material. The most stable geometric structures of the measured species were characterized using Density Functional Theory (DFT) and classified taxonomically as a function of their internal total energy (D-plot method); the influence of the structure`s stability on the relative mass abundances was also determined. / [fr] Le phénomène de la désorption ionique induite par des pulses laser ultraviolets dans la surface de solides est étudié. Trois types différents de solides ont été analysés: insuline, carbone (amorphe, graphite et CO condensé) et halogénures alcalins polycristallins (CsI, KI, KBr). La dynamique des ions secondaires émis est analysée par la comparaison des résultats de modélisation avec leur distributions de vitesse mesurées. Un modèle thermique est proposé pour décrire l´interaction entre la radiation laser avec une pellicule de CsI polycristallin et aussi avec la plume émise dans ce processus. Dans le cadre de ce modèle, une nouvelle méthode est utilisée pour caractériser le régime de collision dans lê plasma, soit dans le cas du LDI (Laser Desorption Ionization), fait sur le CsI, soit dans le cas du MALDI (Matrix Assisted Laser Desorption Ionization), fait sur l´insuline dissoute dans une solution solide d´ ACHC. Il est rappelé que le ions CsI émis peuvent être reconstitués après une atomisation complète de la cible mais ceux des de l´insuline difficilement le peuvent. Pour mieux comprendre l´émission des agrégats ioniques Cn + et des halogénures alcalins, leurs structures moléculaires ont été étudiées théoriquement par DFT (Density Functional Theory). L´énergie totale de chaque isomère a été calculée et transformée dans une nouvelle quantité nommée déviation énergétique (D). Le graphique D-plot, oú D est présenté en fonction du nombre de monomères, n, s´est montré très utile pour classer les agrégats en familles et pour estimer leur stabilité, laquelle est liée vraisemblablement à ses abondances de désorption.

Pavement markings are vital for safely navigating roadways. The nighttime visibility of pavement markings is enhanced by addition of retroreflective glass beads, most of which are made from recycled glass. Concern has been raised over the presence of heavy metals in glass beads used in pavement markings and their effect on human and environmental health. Based upon the potential risk associated with the presence of arsenic and lead in the glass beads, two Bills are currently being considered before the 112th Congress of the United States of America seeking to set a maximum permissible limit for the amount of arsenic and lead in glass beads used within pavement marking systems on domestic roadways. This study was designed to support legislative decision making by providing data necessary for risk assessment. The experiments carried out provide: an analysis of glass bead metal content and extractability; an evaluation of the relationship between arsenic content of the glass beads and their retroreflective performance; an evaluation of analytical methods used to measure the total bead metal content; and an analysis of samples of glass bead and soil mixture from a glass bead storage site used to determine site-specific metal concentrations in the soil media. Mean arsenic content, measured using the Pacific Northwest National Laboratory's KOH fusion digestion, in all the glass beads examined ranged from 11 ppm to 82 ppm, while mean lead content, measured using KOH fusion digestion, ranged from below quantification limit to 199 ppm. Total metal content measurements indicated a high amount of variability in the glass bead samples; most likely associated with the use of recycled glass feed during manufacturing. The relationship between the retroreflective performance and the arsenic content of the glass beads was analyzed and a weak but positive correlation was observed between the two factors. However, a more detailed study is required to evaluate the relationship between arsenic content and retroreflectivity. Different methods to evaluate the total metal content in glass beads were compared; it is recommended that any analytical method may be used, as long as the standard reference material is reproduced within the range of concentration expected in the glass beads. In the analysis of the field site samples of soil containing glass beads obtained from a glass bead storage and transfer facility, the mass content of beads in the soil varied from a mean of 19% to 78% depending on the location within the facility. However, a detailed analysis with larger number of samples must be performed to evaluate the effect of glass beads on the total arsenic content of the soil.

The aim of the thesis has been to evaluate and understand the effect of caustic alkali solution of varying composition on the behaviour of expansive soil containing mixed layered minerals. Mixed layered minerals are formed of two or more kinds of inter grown layers, not physical mixtures. Illite - smectite is the most abundant and wide spread of the mixed layered clay minerals in sedimentary rocks and soils and also more common than either discrete illite or smectite. In geotechnical engineering much attention has not been paid to the behaviour of soils containing mixed layered minerals. Much less is known about the behaviour of these soils in polluted environment. Mixed layered minerals are more susceptible to environmental changes as the structural linkages between the layer minerals are weak compared to normal layered phyllosilicates. One important pollutant that can have considerable effect on the behaviour of soils is the caustic alkali contamination released from various industries. Recent studies have shown that the behaviour of even stable minerals is affected by alkali contamination. However, the effect of caustic alkali contamination on the behaviour of soils containing mixed layered minerals is not known and has been chosen for detailed study. Also to understand the mechanism of their interaction with alkali, it is necessary to study the effect of alkali solutions on the constituent clay minerals viz., montmorillonite and illite under similar conditions. To elucidate the mechanism of soil alkali interaction limited tests were conducted with simple electrolyte solution, as the alkali solution also acts as electrolyte apart from being alkaline. To confirm the mechanism of interaction, tests are also conducted on these soils with industrial spent liquor containing high caustic alkali and suspended alumina obtained from an alumina extraction plant treating bauxite with high alkali solutions at high temperatures. The results obtained in the laboratory are compared with the soil samples contaminated with leaking industrial Bayer's liquid in the field. Studies are also conducted to suggest remedial measures to control the adverse effects of alkali solutions on soil containing mixed layer minerals. The content of the thesis is broadly divide into 8 Chapters - viz., Introduction, Background and overview, Experimental program and procedures, Behaviour of soils containing mixed layer mineral illite - smectite (BCSI), Behaviour of montmorillonite and illite, Influence of Bayer's liquor and study on the field contaminated soils, Measures to control the influence of alkali contamination on BCSI and Summary and conclusions. The broad outline of these chapters is given in Chapter 1. A review of literature on the behaviour of soils containing different types of clay minerals with emphasis on mixed layer minerals has been presented in Chapter 2. The influence of different inorganic contaminants on the properties of soils in terms of their physical and chemical characteristics as well as their concentration has been summarized. The importance of changes in surface characteristics of soil particles and the changes in the thickness of diffuse double layer in altering the property of soils at low concentration of contaminants and changes in the mineralogy with high concentrated contaminants such as acids and alkalis has been highlighted. This forms the background information necessary to bring out the scope of the study. Four soils having different mineralogy have been used in this study. These soils are, black cotton soil containing predominantly mixed layer mineral illite - smectite mineral called rectorite, illite, montmorillonite (common smectite) and black cotton soil containing predominantly montmorillonite. The properties of the soils used are described in Chapter 3. Caustic alkali solutions of 1N, 4N concentration prepared in the laboratory and industrial alkali-spent liquor are used as contaminants. The spent Bayer's liquor had about 4N alkali concentration and 10% alumina in suspension. To simulate the effect of suspended alumina, two more caustic alkali solutions of 1N and 4N solutions containing 10% alumina by weight of solutions are also prepared. To isolate the effect of electrolyte solutions from that of alkali solution, two electrolyte solutions of 1N and 4N sodium chloride solutions are also used. Test procedures for conducting various tests such as pH, water adsorption characteristics, X-ray diffraction studies, SEM studies, thermal characteristics and geotechnical properties such as Atterberg limits, Oedometer tests and Shear Strength are given in this chapter. The test procedures are modified, wherever necessary, to bring out the effect of contaminants, particularly the effect of duration of interaction on the properties of soils. The source and properties of black cotton soil are presented in Chapter 4. Detailed x-diffraction studies have confirmed the presence of inter layered illite-smectite mineral viz., rectorite, which is uncommon in Indian expansive soils, and is classified as CH (Clay of high compressibility) as per ASTM soil classification. Effect of alkali and salt solutions of 1N and 4N concentration on all physico chemical and geotechnical properties are studied in this chapter. As it is known that presence of certain elements such as aluminium influence the soil alkali interaction, the effect of suspended alumina along with alkali solution has also been investigated. The effect of contaminating fluids such as 1N NaOH, 4N NaOH with and without alumina, 1N NaCl and 4N NaCl on the geotechnical properties of the soil has been studied. Mineralogical changes were observed by XRD and thermal studies in the soil treated with 4N NaOH solution and 4N NaOH + 10% alumina. The interlayer potassium of illite is released and potassium hydroxide is formed in soil treated with 4N NaOH. Swelling compounds such as sodium aluminium silicate hydroxide hydrate (SASH) has formed due to attack of 4N NaOH + 10% alumina on silica rather than on rectorite. Thus the studies clearly bring out that the rectorite present in the soil is dissociated only in the presence of strong alkali solutions of concentration of about 4N. The liquid limit of soil decreased with increase in the electrolyte concentration in the case of NaCl solutions. With 1N NaOH, the liquid limit of soil increased due to increase in the thickness of diffuse double layer due to increased pH. However, Proctor's maximum dry density increased and optimum moisture content decreased with 1N NaOH. With increase in the concentration of alkali solution to 4N, the rectorite dissociates into constituent minerals with the formation potassium hydroxide. The liquid limit of soil decreased probably due to the dominating influence of electrolyte nature of hydroxide solution over the effect of increased negative charge on clay particles due increase in the pH on the constituent minerals. Proctor's maximum dry density decreased and optimum moisture content increased with 4N NaOH. Sediment volume and oedometer free swell at seating/nominal surcharge load of 6.25 kPa of soil increased in 1N and 4N caustic alkali solutions, though by different mechanisms. The increase with 1N solution is essentially due to increased negative charges on clay mineral surface. However, the increase in swelling with 4N solution is associated with the dissociation of rectorite mineral and occurs in two distinct phases unlike in the case of 1N solution. While the first phase can be attributed to the effect of alkaline nature of the solution after reduction in its concentration due to reaction with rectorite and the consequent reduction in its electrolyte nature. The second phase is due to the swelling of the separated constituent minerals in the presence of excess of alkali and occurs after much delay. Consolidation behaviour of rectorite in 1N and 4N alkali solutions has been studied in two ways: 1). Loading without waiting for the second stage of swelling to occur, as in standard consolidation procedure and 2). Loading after completion of second stage of swelling which is occurring after considerable delay as explained earlier. Normally one would initiate loading after equilibrium is reached at the end of first stage of swelling and second stage of swelling is not suspected. As there is no second stage of swelling with 1N solutions, these two types of consolidation tests produced the same results. Abnormal rebound is observed during unloading with 4N solution in which loading cycle is initiated without waiting for second stage of swelling to complete. It is interesting to note that while the liquid limit of soil decreased with increase in the concentration of alkali solution, the swelling increased. The testing procedure and period of interaction as well as the concentration of alkali solution during the test in these two tests are different. The effects of alkali solution are more severe in case of liquid limit because of thorough mixing and consequent effective reaction during testing. Similarly, the volume changes in soil that has already reacted with 4N alkali solution when exposed to further to alkali contamination are considerably less compared to uncontaminated soil exposed to fresh contamination. The shear strength of soil treated with 4N-alkali solution has increased particularly after long period of interaction. This indicates that the soil after mineralogical changes posses good strength. Chapter 5 presents the effect of alkali and salt solutions on the physico chemical and geotechnical properties of component minerals of mixed layered illite/smectite. For this study, commercially obtained montmorillonite (bentonite), naturally occurring black soil containing montmorillonite and commercially pure illite are used. It was observed that montmorillonite alkali reactions would not produce significant mineralogical changes where as illite is dissociated into smectite with the formation of potassium silicate by the interaction of released potassium with soluble silica. This confirms that the ultimate products of rectorite with alkali solutions would be smectite and compounds of potassium. In the absence of mineralogical alterations the liquid limit of montmorillonite decreases due to suppression of diffuse double layer thickness due to dominating influence of alkali solutions on this highly active clay. However a small increase in liquid limit is observed in illite with alkali solutions. Thus the net effect of alkali on rectorite is to decrease the liquid limit with increase in alkali concentration. While the free swell and oedometer swelling of montmorillonite generally decreases with increase in the alkali concentration, they increase in illite. However, in both the minerals the swelling occurs only in one phase. Thus the second phase of swelling that has been observed in rectorite can be attributed to delayed swelling of montmorillonite that has been released by the attack of alkali on rectorite. The behaviour of black soil containing mixed layer mineral contaminated in the field and laboratory by leaking Bayer's spent liquor in an alumina extraction plant has been studied in Chapter 6. The Atterberg limits of the samples treated with liquor are reduced and sediment volume increased. Similarly the swelling at seating load in consolidation test is higher in sample compacted with water and inundated with liquor. X-ray diffraction studies showed that the mineralogical changes are similar to those occurred with 4N caustic alkali solution. The mineralogical and micro structural changes in the soil samples that are contaminated by leaked spent liquor in the field are relatively more marked. Also the behavior of highly montmorillonite clay, bentonite, has been studied contaminated with liquor in the laboratory. The study on the effect of high concentrated alkali solutions on montmorillonite can be useful to study the effect of interaction on the dissociated montmorillonite. These studies are helpful to suggest some possible remedial measures to control the adverse effect of alkali on soils. Possible Remedial schemes that can be adopted before and after contamination of the soil to control the adverse effect of alkali solutions on the black cotton soil containing mixed layered mineral are listed and their effectiveness examined in Chapter 7. The suggested remedial measures include flushing with water to dilute the effect of alkali, neutralisation with dilute hydrochloric acid, stabilisation of soil with lime and calcium chloride and use of impervious membrane to separate the foundation soil from alkali solution. The effectiveness of different measures as well as the method of their application has been described. Efforts are made to understand the mechanism of remedial action. Consolidation tests conducted on soil contaminated with 4N alkali solution and inundated with water showed increased swelling due to dilution of the alkali concentration. Though the swelling of contaminated soil can be controlled by passing dilute hydrochloric acid (1N), the method is not advocated as it can lead to ground water contamination. Mixing the soil with solutions containing up to 5% by weight of calcium compound in water could not prevent the alkali induced heave in the long run when inundated with 4N alkali solution. This was due to dissolution of silica by the strong alkali solutions and formation of swelling compounds such as sodium aluminium silicate hydroxide hydrate (SASH). The formation of sodium aluminates occurred only when the alkali solution contained alumina or soil contained calcium compounds. There are no significant variations in the effects of calcium chloride or calcium hydroxide on contaminated soil. Replacing the foundation soil with soil thoroughly contaminated with 4N alkali solutions and controlling the migration of contaminants into the foundation soil using high-density polyethylene (HDPE) geosynthetic membranes can be an effective measure to control the heaving in alkali contaminated foundation soil containing interstratified illite – smectite. Summary and the major conclusions of the thesis are presented in Chapter 8.

Precise measurements of both absolute frequencies and small frequency differences of atomic energy levels have played an important role in the development of physics. For example, high precision measurements of absolute frequencies of the 2S½ → 2P ½ transition (D1 line) of alkali atoms form an important link in the measurement of the fine structure constant, α. Similarly, precise interferometric measurements of the local gravitational acceleration (g) rely on the knowledge of the absolute frequencies of the 2S½ → 2P 3/2 transition (D2line) in alkali atoms. Difference frequency measurements of hyperfine structure and isotope shifts of atomic energy levels provide valuable information about the structure of the nucleus, which in turn helps in fine tuning the atomic wave functions used in theoretical calculations. The work reported in this thesis starts with the development and refinement of high precision measurement of absolute frequencies using a ring-cavity resonator. The measurement technique is relatively simple and cost-effective, but the accuracy is comparable to that achieved with the frequency comb technique (10¯11) when the accuracy is limited by the natural linewidth of the transition being measured. The technique combines the advantages of using tunable diode lasers to access atomic transitions with the fact that the absolute frequency of the D2 line in87Rb is known with an accuracy of 6 kHz. A frequency-stabilized diode laser locked to this line is used as a frequency reference, along with a ring-cavity resonator whose length is locked to the reference laser. For a given cavity length, an unknown laser locked to an atomic transition has a small frequency offset from the nearest cavity resonance. We use an acousto-optic modulator (AOM) to compensate for this frequency offset. The measured offset is combined with the cavity mode number to obtain a precise value for the frequency of The unknown laser. We have used this technique for absolute frequency measurements Of the D lines in133Cs and 6,7Li, and the 398.8nm line in Yb. We have also developed a technique to measure the ‘difference frequency’ of atomic energy levels using a single diode laser and an AOM. In this technique, the laser is first locked to a given hyperfine transition. The laser frequency is then shifted using the AOM to another hyperfine transition and the AOM frequency is locked to this difference. Thus the AOM frequency directly gives a measurement of the hyperfine interval. Applying this AOM technique we have measured the hyperfine interval of the D1 lines of all alkali atoms with high precision. We have further developed a technique of coheren-tcontrol spectroscopy (CCS) using co-propagating control and probe beam that is useful for highresolution spectroscopy. In this technique, the probe beam is locked to a transition and its absorption signal is monitored while the control beam is scanned through neighbouring transition. As the control comes into resonance with another transition, the probe absorption is reduced and the signal shows a Doppler free dip. This technique allows us to resolve transitions that are otherwise swamped by crossover resonances in conventional saturated absorption spectroscopy (SAS). We have applied this technique to measure hyperfine intervals in the D2 line of several alkali atoms. Thus, we were able to do high-precision measurements of both absolute and difference frequency of atomic transitions. The precision of the absolute frequency measurement is finally limited by the accuracy of 6 kHz with which the reference frequency is known. The nearby two photon transition in Rb, i.e. the 5S1/2→5D3/2 transition at 778 nm, is known with an accuracy of 1 kHz. In future, we hope to improve the accuracy of our technique using this transition as the reference. This thesis is organized as follows: In Chapter1,we give a brief introduction to our work.. We review the importance of frequency measurements and precision spectroscopy, followed by a comparison of the frequency comb and our ring cavity technique. In Chapter2, we describe measurements of the absolute frequency of the D lines of 133Cs using the ring cavity. We give a detailed discussion of the technique, the Possible sources of errors, and ways to check for the errors. The measurement of the absolute frequency of the D lines of Cs allows a direct comparison to frequency comb measurements, and thus acts as a good check on our technique. In Chapter 3, we describe the absolute frequency and isotope shift measurements in the 398.8 nm line in Yb. We probed this line by frequency doubling the output of a tunable Ti:Sapphire laser. We obtained< 60 kHz precision in our measurements and were able to resolve several discrepancies in previous measurements on this line. In Chapter 4, we describe the measurement of hyperfine structure in the D1 lines of alkali atoms. We used conventional saturated-absorption spectroscopy in a vapor cell to probe different hyperfine transitions and then used our AOM technique to measure the hyperfine interval with high precision. In Chapter 5 we discuss our measurements of hyperfine structure in the D2 lines of several alkali atoms. In the case of 23Na and 39K, the closely-spaced hyperfine transitions are not completely resolved in conventional saturatedabsorption spectroscopy due to the presence of cross over resonances. We have used coherent control spectroscopy to obtain crossover-free spectra and then measured the hyperfine intervals using an AOM. This technique was also used for high resolution spectroscopy in the D2 line of 133Cs. Finally, we describe our measurements of hyperfine structure in the D2 line of Rb using normal saturated absorption spectroscopy. Chapter 6, describes the relative and absolute frequency measurements in the D lines of6,7 Li at 670nm. High-precision measurements in lithium are of special interest because theoretical calculations of atomic properties in this simple three electron system are fairly advanced. Lithium spectroscopy poses an experimental challenge and we describe our efforts in doing highresolution spectroscopy on this system. Chapter 7 describes the hyperfine spectroscopy on the1P 1 state of 173Yb. Measurement of hyperfine structure in 173Yb has a problem because two of the hyperfine transitions overlap with the transition in 172Yb. In our earlier work (described in chapter 4), we had solved this problem by using multipeak fitting to the partially resolved spectrum. Here, we directly resolve the hyperfine transitions by using transverse laser cooling to selectively deflect the 173Yb isotope. In Chapter 8 , we give a broad conclusion to the work reported in this thesis and suggest future avenues of research to continue the work commenced here.

Sub-surface soil pollution by various processes with high concentration of contaminants can significantly alter geotechnical properties of soils causing unexpected failures of structures founded on them. The changes can occur due to alteration in soil water interaction processes and/or by intense chemical interactions leading to mineralogical and microstructural changes. Behaviour of soil upon contamination with alkali pollutant is one of the major concerns faced by the geotechnical researchers in recent years. In the present study an attempt has been made to understand the role of mineralogical and morphological changes on the volume change (swelling and compressibility) behaviour of soils by prolonged interaction with caustic alkali pollutant. Based on the results it has been proposed to develop remedial measures to nullify and/or control the detrimental effects. A comprehensive experimental program has been planned to achieve these objectives. The experimental investigations carried out and results obtained are presented in eight chapters as follows. The broad outline of thesis is given in Chapter 1. A detailed review of literature on the type of phyllosilicate minerals present in various soils is presented in Chapter 2 with a view to select most common soils for the study. Various sources of contaminants and their effect on the properties of soils have been summarised. Present understanding on the mechanisms leading to changes in the soil properties has been elucidated. The occurrence of alkali contamination has been reviewed in this chapter which enabled to select the ranges of alkali concentration for the study. Based on the review of various methods employed to improve the soil behaviour, the use of salt solutions such as potassium chloride (KCl) and magnesium chloride (MgClB2B) and pozzolanic fly ash has been considered to counteract the alkali effects. Based on this detailed survey, the scope of the present investigation has been elaborated at the end of the chapter. Chapter 3 presents different materials used and various methods adapted in the current study. Three soils having different mineralogy have been used in this study to bring out the effect of alkali solutions on their volume change behaviour. While two soils were classified as CH, the third one was of CL. The CH soils used in this study are called Black Cotton Soils in India. One soil contained predominantly mixed layer illite-smectite mineral (BCS I) and the other contained predominantly montmorillonite mineral (BCS M). The locally available CL soil used is referred as red earth (RE) whose predominant mineral is kaolinite. Alkali solutions of concentration ranging from 1N to 4N are prepared using sodium hydroxide pellets (NaOH). Slat solutions viz. potassium chloride and magnesium chloride and pozzolanic fly ash obtained from Neyveli thermal power plant (NFA) are used as additives. Procedures to determine the geotechnical properties of the soils such as Atterberg limits, specific gravity, grain size distribution and compaction characteristics are given in this chapter. Procedures for identifying the mineral and microstructure of the soils such as X-ray diffraction (XRD) and scanning electron microscopy (SEM) are also presented in this chapter. Standard oedometer tests with fixed ring apparatus were performed to study the volume change behaviour of soils under various conditions. Volume change behaviour of soils in the presence of alkali solutions is presented in Chapter 4. In order to assess the effect of alkali solution on the volume change behaviour of soils it is necessary to study their behaviour in water. Relatively very high swell was observed in BCS M, whereas the swell in RE and BCS I soil specimens was very low and moderate respectively. Adsorption of water to form diffuse double layer near the negative surface of clay mineral particles leads to swelling in soils. The thickness of the double layer depends on the cation exchange capacity of soil. Higher cation exchange capacity leads to development of higher thickness of double layer thereby inducing swell. The higher is the swell the higher would be the compression. The effect of different concentrations (1N, 2N and 4N) of alkali solutions on volume change behaviour of three types of soil is presented in this chapter. All the three soils studied, irrespective of their mineralogical composition, exhibited high swell when contaminated with alkali solution compared to water. However, the extent and nature of swell varied both with the type of mineral present in the soil and concentration of sodium hydroxide solution. The swell in BCS I increases with increase in the concentration of the alkali solution. In 1N alkali solution the high swell occurred is due to the breaking up of interstratified mineral into constituent minerals initiated by the leaching of potassium from soil due to high pH. In 2N and 4N alkali solutions, the observed high swell occurs in two stages: the first stage of swelling is due to breaking up of interstratified mineral into constituent minerals initiated by the leaching of potassium from soil due to high pH, and the second stage of swelling is due to the formation of new minerals (Zeolite P in case of 2N NaOH and Sodalite in case of 4N NaOH). The nature of swell is influenced by the formation of minerals depending on the concentration of alkali solution. Thus the studies clearly indicate that the swelling is due to the release of potassium from soil at higher pH and due to mineralogical changes depending upon the concentration of alkali solution. Confirmative tests were conducted to support the release of potassium during first stage of swelling and mineralogical alteration after second stage of swelling. The high swell in BCS M becomes higher in 1N alkali solution. The increased swell in the soil with 1N alkali solution is due to increase in the ion exchange capacity of soil at higher pH. The swell which is very high with 1N alkali solution decreases with 2N alkali solution. With increase in concentration of alkali solution to 2N, the increase in the negative charges due to alkalinity becomes less and the swell decreases due to dominant influence of electrolyte effect. With increase in the concentration of alkali solution to 4N, both these influences become less and the amount of swell remains the same. Significant increase in the amount of swell is observed with alkali solution even in non-swelling red earth. The nature of swell as well as the formation of minerals is not altered by the change in the concentration of alkali solution. At any concentrations of alkali solution the observed swell is noticed in two stages – very small first stage of swell due to lower ion exchange capacity and considerable second stage of swell due to the formation of new mineral (Sodalite) with any concentration of alkali solution. It has been observed that the normal hyperbolic swell – compression relationship does not apply for the alkali contaminated soils. The higher swell does not result in higher compression, as the swollen soil remains fairly incompressible. Analysis of the results and detailed studies on micro-structure and mineralogy of soils bring out mechanism of alkali effects. Comparing the swell behaviour of soils with alkali solutions brings out the relative importance of various mechanisms proposed for induced heave. The effect of salt solutions used viz., potassium chloride and magnesium chloride to restrict the influence of alkali solution on the volume change behaviour of BCS I is presented in Chapter 5. These salts react with alkali solution to form partly soluble potassium hydroxide (KOH) and sparingly soluble magnesium hydroxide (Mg(OH)B2B) respectively. Presence of ionic potassium can bring out potassium linkages, by bridging potassium ion between the unit layers of expansive minerals reducing the swell. Magnesium ions can restrict swell, by replacing the monovalent exchangeable ions present in soil and/or by formation of magnesium hydroxide which is a weak cementing agent. The effect of potassium hydroxide on the volume change behaviour of soil has been studied and the results clearly indicate that fixation of potassium is facilitated by high pH of KOH solution. Addition of potassium chloride has partially controlled the alkali induced heave in soil. Of the two stages of swelling observed in soil in the presence of 4N alkali solution, only the first phase of swelling is reduced which may be due to electrolyte effect and/or due to fixation of potassium. The second phase of swelling that occurs in soil due to mineralogical changes can not be controlled with the use of potassium chloride. Addition of magnesium chloride salt solution also reduced the effect of alkali solution mostly due to suppression of thickness of diffuse double layer that develops near clay surface. The nature of reduction in the swell of alkali solution during the two stages by magnesium chloride is similar to that of potassium chloride. The partial reduction in swell of soil in the presence of salt solutions leads to reduction in the compressibility of soil. Detailed data and analysis, presented in this chapter, bring out the role of microstructure and mineralogy on soil behaviour. The abnormal volume changes due to mineralogical changes affected by high concentration of sodium hydroxide could not be controlled with salt solutions, attempts are made to utilize fly ash to control the alkali induced heave. The pozzolanic compounds produced by hydration of compounds presented and/or produced by lime silica reactions can bind the soil particles controlling the swelling. The results on the effectiveness of fly ash on BCS I soil are presented in Chapter 6. The physical and chemical properties of fly ash along with the mineralogical composition and the microstructure of the fly ash are also presented in this chapter. Before studying the effect of fly ash to control the volume change behaviour of soils in presence of alkali solutions, the effect of alkali solutions on the volume change behaviour of fly ash itself has been studied. The results showed no noticeable changes in swell and compressibility of fly ash, encouraging its use for controlling the alkali induced swell. The ability of different percentages (10%, 20% and 50%) of fly ash to control alkali induced volume changes in soil with varying concentrations of alkali solutions, viz., 1N, 2N and 4N has been studied. The results indicate that the addition of fly ash effectively reduces alkali induced swell in BCS I. The effectiveness of fly ash increases with increase in its content. The reduction in swelling of soil is partially due to replacement of soil with fly ash and mainly due to cementation of soil particles by pozzolanic compounds produced. More than 25% of fly ash is generally required to significantly reduce the swell in alkali solutions. The reduction in swell with addition of fly ash also leads to lower compressibility of soil. The role of microstructure and mineralogy in controlling the volume change behaviour are also presented in this chapter. The effectiveness of fly ash in controlling the volume changes in RE and BCS M due to alkali solutions are studied in Chapter 7. The addition of fly ash completely eliminates the swelling in both the soils. The reduction in swelling up on addition of fly ash is essentially due to efficient binding of particles by pozzolanic reaction compounds. Addition of even 10% of fly ash is sufficient in completely arresting the swelling of RE and BCS M by alkali solution. Detailed data and analysis of the results to bring out the role of microstructure and mineralogy on the behaviour of soils are presented. It is clear that relatively higher amounts of fly ash is required to control the alkali induced heave in BCS I than in other soils at higher concentrations of alkali solution. The major conclusions from the study are presented in Chapter 8. The thesis demonstrates that alkali contamination alters mineralogy and morphology of soils affecting the volume change behaviour significantly. The study also brings out that fly ash can control the undesirable swell that occurs in most types of soils by cementing the soil particles to resist swelling. Though the amount of fly ash required to control the alkali induced heave varies, 25% of fly ash is often sufficient.

From the Proceedings of the 1973 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - May 4-5, 1973, Tucson, Arizona / Measurements of penetrability and hydraulic conductivity in calcareous soils treated with a dilute sulfuric acid solution showed a severe decrease in conductivity with increasing concentrations over 1000 ppm. A slight decrease in penetrability was observed. Carbon dioxide evolution appeared to be responsible for flow reduction and temporary cessation at 10,000 ppm and 20,000 ppm. In sodic soils penetrability and conductivity increased markedly with sulfuric acid concentrations between 1,000 and 10,000 ppm. For a neutral soil, penetrability decreased with increasing sulfuric acid concentrations, and the stable conductivity for 500 to 5,000 ppm was higher than for water alone. The findings suggest that disposal of sulfuric acid concentrations greater than 1,000 ppm will result in plugging by carbon dioxide. In sodic soils the possibility exists of using sulfuric acid solutions for reclaiming salt and sodium-affected soils.