Zugl.: Erlangen, Nürnberg, Univ., Diss., 2007

Zugl.: Erlangen-Nürnberg, Universiẗat, Diss., 2007.

L’objectif de cette thèse est la caractérisation de la porosité de la pâte de ciment partiellement saturée par des ondes ultrasonores. Les corrélations entre les vitesses ultrasonores et la porosité ont été étudiées en se basant à la fois sur les résultats expérimentaux et la modélisation micromécanique. Des mesures expérimentales de vitesses ultrasonores longitudinales et transversales en fonction du rapport eau/ciment et à différents états de saturation ont été réalisées sur la pâte de ciment avec et sans entraîneur d’air. En modélisation micromécanique, les effets de saturation ont été modélisés en supposant que la structure poreuse est formée d’inclusions ellipsoïdales de facteur de forme variable selon le rapport E/C. Afin d’estimer les modules homogénéisés élastique de la pâte de ciment et de pâte de ciment à entraîneur d’air différents modèles micromécaniques ont été étudiés. Les résultats de la modélisation micromécanique ainsi que les résultats expérimentaux ont montré que les vitesses des ondes longitudinales et transversales de la pâte de ciment à l’état sec sont inférieures à ceux de l’état saturé. Cet effet est tout aussi important pour l’ensemble des rapports E/C. Le modèle de Mori-Tanaka a donné la meilleure estimation des résultats expérimentaux mesurés sur la pâte de ciment. Alors que le modèle auto-cohérent a donné la meilleure estimation des propriétés mécaniques et ultrasonores de la pâte de ciment avec entraîneur d’air.Les résultats de ce travail devraient constituer le fondement d’un processus d’inversion et d’amélioration de la détermination de la porosité de la pâte de ciment par les ultrasons en tant que méthodes non destructives / The objective of this work is the characterization of unsaturated cement paste porosity through the use of ultrasonics. The correlation between ultrasonic velocity and porosity in cement paste material is studied based on both micromechanical modelling and experiments.Experimental measurements of ultrasonic longitudinal and transverse velocities as a function of water to cement ratio and under different saturation states were performed on cement paste with and without air-entrained adjuvant. In the micromechanical modeling, the effects of saturation were modeled by approximating the porous structure as a penny shaped ellipsoidal inclusions of aspect ratio varying with the W/C ratio. Several different micromechanical models for estimating the homogenized elastic moduli of cement paste and air-entrained cement paste were studied.The micromecanical modelling has shown that the longitudinal and transverse wave velocities of the dry cement paste are lower than those of the water saturated cement paste. This effect is equally prominent for all the cement paste W/C ratios. The model of Mori-Tanaka was found to give the best fit with the experimental results for the cement paste modeling. While, the self-consistent model gave the best estimate of the mechanical and ultrasonic air-entrained cement paste properties when compared to the laboratory experimental results.The findings of this work should be most appropriate as a foundation for an inversion process and improved cementitious material porosity determination by nondestructive methods

Made available in DSpace on 2014-06-11T19:27:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-04-12Bitstream added on 2014-06-13T20:27:39Z : No. of bitstreams: 1 bertolucci_fs_me_ilha.pdf: 2860301 bytes, checksum: 3f3004f9d02861054ffe5fb10b1b2e7d (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A indústria estruturas de concretos pré-moldados possui como grande preocupação a ligação entre seus elementos, tendo em vista que a mesma exerce grande influência no comportamento da estrutura, sendo responsável pela transmissão e redistribuição dos esforços na estrutura. A grande diferença entre estruturas pré-moldadas e estruturas de concreto moldadas “in loco” em relação ao seu comportamento estrutural está na ligação entre seus elementos. As ligações apresentam certa deformação quando solicitadas, recebendo na literatura técnica a denominação de ligações semi-rígidas. Dessa forma, buscou-se estudar todos os grautes existentes no mercado e desenvolver um compósito cimentício de fácil preparo e de baixo custo, do tipo calda de cimento e argamassa, que apresentasse características mecânicas similares aos grautes. Foram desenvolvidas duas caldas de cimento e uma argamassa, as quais foram submetidas juntamente com os grautes selecionados a ensaios específicos de propriedades adesão e aderência. Dentre as principais conclusões obtidas podem ser ressaltadas que a grande parte dos grautes possui problemas de fluidez dificultando o preenchimento total das ligações e sua aplicação. Em relação à aderência as duas caldas de cimento e a argamassa apresentaram comportamento semelhante indicando que há uma boa condição de aderência e, os grautes, devido à sua grande diferença de composição, tiveram comportamentos distintos / One of the concerns of the precast concrete industry is the connection among their different types of elements, in order that they strongly influence the behavior of the structural group, being responsible for the transmission and redistribution of the efforts in the structure. Among the differences between precast structures and concrete structures shaped “in loco” we have the concern about the structural behavior of the link between its elements. The links have shown some deformation when tested, receiving in the technical literature the name of semi-rigid connections. For that the concrete’s precast structure has the behavior of a monolithic structure it’s necessary the solidarization of the connection which is made by filling the vertical and horizontal niches with the aid of the grout. In this paper, we aimed to study some grouts of the Brazilian market and, at the same time, develop a cimentitius composite of easy prepare and low cost, of the cement paste and mortar types, with similar mechanical characteristics to industrialized grouts to be used in the filling of the precast structures. It was rheologically and mechanically created and evaluated two kinds of cement grout and one mortar composition that were submitted along with the selected grouts to an evaluation of their rheological behavior, and to specific tests of their mechanical properties of adhesion and bond. This study let us conclude that the cement paste and mortar developed showed a similar rheological behavior to the Herschel-Bulkley, besides to a good condition of bond and a good behavior in the structure link when compared to some industrialized grouts. Not all the evaluated grouts showed appropriate behaviors for joints’ filling

The aim of the project is to utilise fly ash (PFA), a waste material/industrial byproduct, with metakaolin (MK), as a partial replacement for Portland cement (PC) in mortar and paste. The influence of various compositions of MK-PFA-PC blends on the resistance to the action of sulphate and synthetic seawater solutions, setting time and heat of hydration will be examined. MK is calcinated clay and is a relatively new pozzolanic material. Although it is a very effective pozzolan it is also very expensive. Using FA, which is a much less expensive material, as a PC replacement material, is problematic, as there is slow and low early strength development whereas MK enhances early strength development. Combining these materials in ternary blends should therefore produce a high performance material at an acceptable cost for use as a pozzolan. However the properties and performance of such a material still need to be fully established. The results of the research show, for the initial and final setting time of binary MK-PC pastes there is a substantial increase at 5% MK and then decreases at 10 and 15% MK before increasing again at 20% MK replacement level. However, with PFA there are different trends to those observed when using MK alone. The initial and final setting time of binary PFA-PC pastes shows a slight increase at 10% PFA and then systematically increases with increase in PFA content up to 40% PFA. Evaluation of sample preparation for porosimetry found that, overall, the compression tested samples show a lower proportion of 'fine pores' (volume (%) 0.05) jam than the cored and cut paste disks. It is deducted that this is due to the widespread microcracking during failure of the cubes under compressive loading thus modifying the pore structure present in the compressive tested samples. In strength development of mortar there is very little advantage in using MK over binary PFA-PC mortar blends when exposed to sulphate solution for up to 2 years. The strength behaviour in seawater is however quite different from that observed in mortar exposed to sulphate solution. As the MK replacement levels increase relative to the PFA levels the resistance to seawater attack improves significantly. In mortar exposed to sulphate solution the durability is greatly improved at high replacement levels in both binary and ternary blends. The durability of mortar exposed to seawater is greatly improved at 30 and 40% total replacement in ternary blended mortars.

This thesis investigates the stability of coal pillars under realistic conditions of varying weak floor thickness with and without the use of paste backfill. Weak floor strata underlying coal seams are common in the Illinois Basin. They consist mainly of underclay, which is a gray, argillaceous rock that usually occurs immediately beneath beds of coal. Underclay thickness may vary from less than a foot to twenty feet at different locations in the basin (Grim and Allen, 1938). Locally, underclay thickness may vary gradationally over a distance of two pillars. Even though weak floor thickness is not consistent (Gadde, 2009), most research to date has focused on parametric studies with a fixed underclay thickness and formulated coal pillar designs on the basis of the maximum underclay thickness measured in the field. Therefore, it is necessary to investigate more realistic field conditions and quantify the influence of a gradated weak floor thickness using additional parametric studies. This research is primarily numerical modeling incorporating various constitutive models and using some calibration. Therefore, the two dimensional plane strain finite difference model in FLAC 3D is employed to carry out parametric studies on gradated weak floor conditions. Underclay exhibits Mohr Coulomb elastic plastic behavior; hence, the Mohr Coulomb constitutive model is used for the behavior of overburden, coal, and floor. Well-calibrated numerical models can assist in understanding load and failure processes provided that coal, overburden, and weak floor are modeled with sufficient realism. The theoretical approach considers a friction angle of 0° to calculate the load bearing capacity of the weak floor for design of pillars with long-term stability, even if the weak floor has a non-zero friction angle. The stiffness of the weak floor increases with an increase in friction angle (Gadde, 2009; Kostecki and Spearing, 2015). As stiffness increases, a point can be reached where floor bearing capacity exceeds coal pillar strength and coal pillar strength becomes the governing factor. For this scenario, the Mohr Coulomb strain softening model is more realistic in estimating loads carried by coal pillars in the post-failure stage. The three-dimensional Mohr Coulomb strain softening model in FLAC 3D is employed to study qualitatively the floor response in strain softening coal behavior conditions. Maintaining stable coal pillar responses has been a challenge for the coal mining industry due to attempts to increase the primary extraction ratio. Presently, the best available solution seems to be backfilling when considering short-term pillar stability (i.e., less than the long-term factor of safety) with increased extraction ratio. There are various types of mine backfill that have benefits to the mining industry depending on the application, but paste backfill produced from total mill tailings containing no free water is the best option for post-mining ground control in room-and-pillar mines as it prevents weakening of the floor and will not contaminate the ground water. The influence of paste backfill on floor bearing capacity and coal pillar response is studied with numerical modeling using the same constitutive models already identified. Finally, an economic analysis is carried out to look at cost implications of a proposed system with backfill.

Os efeitos terapêuticos dos sais de lítio são comprovados no tratamento de pacientes com depressão, certos tipos de câncer e transtornos bipolares de humor. A dosagem de lítio deve ser cuidadosamente controlada em cada paciente já que excessos na dosagem podem conduzir a danos irreversíveis no sistema nervoso e nos rins. Sendo assim é interessante produzir métodos de baixo custo, simples e rápidos que permitam o monitoramento desse íon. Portanto no presente trabalho foi estudado o desempenho potenciométrico de um eletrodo compósito de pasta de carbono modificado com óxido de manganês tipo espinélio dopado com cobalto (III). O eletrodo de pasta de carbono modificado foi preparado pela mistura de 55% (m/m) de pó de grafite, 20% (m/m) de aglutinante (óleo mineral) e 25% (m/m) de óxido de manganês dopado com cobalto (III) (Li1,05Co0,02Mn1,98O4.). O desempenho eletroquímico do eletrodo foi estudado através de voltametria cíclica (etapa de ativação) e cronopotenciometria (i=0) (etapas de estabilização e adição de padrão). Na caracterização eletroquímica do eletrodo estudou-se a melhor concentração de íons lítio para ativação do sensor, bem como a melhor velocidade de varredura, tempo de estabilização, pH, intervalo linear de resposta, limite de detecção e possíveis íons interferentes. Encontrou-se um limite de detecção de 3,98 x 10-6 mol L-1, intervalo linear de resposta de 1,82 x 10-4 mol L-1 a 1,62 x 10-3 mol L-1, pouca interferência dos íons estudados (Na+, K+, Rb+, Cs+, Mg+2, Ca+2 e Ba+2) sendo a interferência proporcional ao raio iônico dos íons interferentes e sensibilidade de 97,90 mV dec-1. Esse valor de sensibilidade classifica o eletrodo estudado como tendo resposta supernerstiniana o que pode ser atribuído à coexistência de sítios de troca iônica e sítios redox no processo de inserção/extração dos íons lítio na matriz do óxido de manganês. A substituição parcial dos íons Mn pelos íons Co provoca uma diminuição no parâmetro de célula unitária do óxido, o que melhora a estabilidade da estrutura durante o processo de inserção/extração de íons lítio fornecendo maior sensibilidade e propiciando maior seletividade. / The therapeutic effects of lithium salts have been proved useful, as an example given, in the treatment of patients who presents depressive behavior, bipolar disorder and certain types of cancer. The lithium dosage for each patient has to be carefully controlled because an excessive dose can produce irreversible damages to the nervous system and the kidneys. Therefore is interesting produce low cost, simple and quick methods to allow the monitoring of this ion. Hence in this work, the performance of a composite potentiometric carbon paste electrode modified with spinel type manganese oxide doped with cobalt (III) (Li1,05Co0,02Mn1,98O4) was studied. The modified carbon paste electrode was prepared by mixing 55% (w / w) of graphite powder, 20% (w / w) binder (mineral oil) and 25% (m / m) manganese oxide doped with Cobalt (III). The potentiometric performance of the electrode was studied by cyclic voltammetry (activation step) and potentiometry - zero current (stabilization and standard addition steps). The electrochemical characterization of the electrode consisted of the studies of the optimal concentration of lithium ions for activation of the sensor, as well as the best scan rate, stabilization time, pH, linear response range, detection limit and possible interfering ions. In pH = 10, the better one chosen for this study, it was found a detection limit of 3.98 x 10-6 mol L-1, a linear response range from 1.82 x 10-4 mol L-1 to 1.62 x 10-3 mol L-1, low interference from the studied ions (Na+, K+, Rb+, Cs+, Mg+2, Ca+2 e Ba+2), which is proportional to their ionic radius and sensitivity of 97,90 mV dec-1. This high sensitivity value can be attributed to the coexistence of ion exchange sites and redox sites in the insertion / extraction of lithium ions in the manganese oxide matrix process. The best working pH was around 10, as opposed to working with similar materials found in the literature. This can be explained by the substitution of manganese for cobalt (III) in the structure of the spinel type manganese oxide. This substitution causes a decrease in the unit cell parameter of the oxide, which improves the stability of the structure during the process of insertion / extraction of lithium ions and resistance to change in alkaline solutions.

Made available in DSpace on 2014-06-11T19:24:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-28Bitstream added on 2014-06-13T19:11:13Z : No. of bitstreams: 1 carmo_el_me_botfca.pdf: 2012226 bytes, checksum: c0e57a99caa15f8b1e1b00a6be28edb0 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Objetivou-se avaliar o crescimento, a produção e composição físicoquímica de raízes e amidos de mandioquinha-salsa e suas potencialidades. Foram avaliados nove clones BGH (4560, 5741, 5744, 5746, 5747, 6414, 6513, 6525 e 7609) e a cultivar Amarela de Senador Amaral, os quais foram cultivados na Fazenda Experimental São Manuel- SP, safra de 2009. O delineamento experimental utilizado no plantio foi de blocos casualizados com três repetições. Foram avaliados o crescimento vegetativo durante o cultivo, produção total, comercial, por classe e calibre das raízes e as características físico-químicas das raízes: umidade, amido, cinzas, proteína bruta, matéria-graxa, açúcares, fibra bruta, pH, acidez e cor e caracterização do amido quanto ao teor de amilose, propriedades térmicas e de pasta. Os materiais que destacaram foram BGH 6414, maior crescimento vegetativo; ‘Amarela de Senador Amaral’ e BGH 5741, menores quantidades de raízes por planta; e BGH 6414, menor produção total, comercial, nas classes e calibres. Na caracterização da coloração das raízes, BGH 6513 e BGH 4560 apresentaram menores valores de luminosidade, BGH 6414 e BGH 5744 maiores valores para croma a* e BGH 5746, BGH 6513 e BGH 5744 os menores valores para o croma b*. A cultivar Amarela de Senador Amaral apresentou pH mais alto e a maior quantidade de acidez foi observada no clone BGH 6525. Os clones que apresentaram maiores teores de umidade foram BGH 7609 e BGH 6414. Os clones BGH 5744, BGH 7609, BGH 6414 e BGH 5741 apresentaram menores teores de cinzas e na avaliação de matéria graxa BGH 6525, BGH 5741 e BGH 5744 apresentaram os maiores teores. O clone BGH 7609 apresentou maior teor de fibras, açúcares totais, menor teor de amido, maiores temperaturas de gelatinização e menor temperatura de pico nos amidos retrogradados, além de apresentar a maior porcentagem de amidos retrogradados... / The objective was to evaluate the growth, yield and physico-chemical composition of starches from roots and peruvian carrot and its capabilities. We evaluated nine clones BGH (4560, 5741, 5744, 5746, 5747, 6414, 6513, 6525 and 7609) and cultivar Amarela de Senador Amaral, which were cultivated at the Experimental Farm São Manuel-SP, the 2009 harvest. The experiment was planted in a randomized block design with three replications. We evaluated the vegetative growth during cultivation, total production, trade, by class and size of roots and the physicochemical characteristics of the roots for moisture, starch, ash, protein, raw grease, sugar, crude fiber, pH, acidity and color and characterization of starch and amylose content, thermal properties and paste. The materials that were highlighted BGH 6414, increased vegetative growth, 'Amarela de Senador Amaral' and BGH 5741, lower amounts of roots per plant, and BGH 6414, lower overall production, commercial classes and sizes. In characterizing the coloration of the roots, BGH 6513 and BGH 4560 had lower levels of brightness, BGH 6414 and BGH 5744 higher values for chroma and a* BGH 5746, BGH 6513 and BGH 5744 the lowest values in the chrome b*. The cultivar Amarela de Senador Amaral presented higher pH and higher amount of acidity was observed in clones BGH 6525. The clones that showed higher levels of humidity were BGH 7609 and BGH 6414. Clones BGH 5744, BGH 7609, BGH 6414 and BGH 5741 had lower levels of ash and fatty matter in the evaluation of BGH 6525, BGH 5741 and BGH 5744 showed the highest levels. BGH Clone 7609 showed a higher fiber content, total sugar, less starch, higher temperatures and lower gelatinization peak temperature in starch downgraded, besides presenting the highest percentage of retrograded starch. Differ significantly higher than BGH 4560 and 'Amarela de Senador Amaral in crude protein and BGH 5746, BGH 6513... (Complete abstract click electronic access below)

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Orientador: Mônica Pinto Barbosa / Coorientador: Marcelo de Araújo Ferreira / Banca: Antonio Anderson da Silva Segantini / Banca: José Celso da Cunha / Resumo: A indústria estruturas de concretos pré-moldados possui como grande preocupação a ligação entre seus elementos, tendo em vista que a mesma exerce grande influência no comportamento da estrutura, sendo responsável pela transmissão e redistribuição dos esforços na estrutura. A grande diferença entre estruturas pré-moldadas e estruturas de concreto moldadas "in loco" em relação ao seu comportamento estrutural está na ligação entre seus elementos. As ligações apresentam certa deformação quando solicitadas, recebendo na literatura técnica a denominação de ligações semi-rígidas. Dessa forma, buscou-se estudar todos os grautes existentes no mercado e desenvolver um compósito cimentício de fácil preparo e de baixo custo, do tipo calda de cimento e argamassa, que apresentasse características mecânicas similares aos grautes. Foram desenvolvidas duas caldas de cimento e uma argamassa, as quais foram submetidas juntamente com os grautes selecionados a ensaios específicos de propriedades adesão e aderência. Dentre as principais conclusões obtidas podem ser ressaltadas que a grande parte dos grautes possui problemas de fluidez dificultando o preenchimento total das ligações e sua aplicação. Em relação à aderência as duas caldas de cimento e a argamassa apresentaram comportamento semelhante indicando que há uma boa condição de aderência e, os grautes, devido à sua grande diferença de composição, tiveram comportamentos distintos / Abstract: One of the concerns of the precast concrete industry is the connection among their different types of elements, in order that they strongly influence the behavior of the structural group, being responsible for the transmission and redistribution of the efforts in the structure. Among the differences between precast structures and concrete structures shaped "in loco" we have the concern about the structural behavior of the link between its elements. The links have shown some deformation when tested, receiving in the technical literature the name of semi-rigid connections. For that the concrete's precast structure has the behavior of a monolithic structure it's necessary the solidarization of the connection which is made by filling the vertical and horizontal niches with the aid of the grout. In this paper, we aimed to study some grouts of the Brazilian market and, at the same time, develop a cimentitius composite of easy prepare and low cost, of the cement paste and mortar types, with similar mechanical characteristics to industrialized grouts to be used in the filling of the precast structures. It was rheologically and mechanically created and evaluated two kinds of cement grout and one mortar composition that were submitted along with the selected grouts to an evaluation of their rheological behavior, and to specific tests of their mechanical properties of adhesion and bond. This study let us conclude that the cement paste and mortar developed showed a similar rheological behavior to the Herschel-Bulkley, besides to a good condition of bond and a good behavior in the structure link when compared to some industrialized grouts. Not all the evaluated grouts showed appropriate behaviors for joints' filling / Mestre