O objetivo do trabalho é analisar e compreender os efeitos das características do fibrocimento reforçado com fibras sintéticas na retração por secagem deste compósito. A importância social do fibrocimento como material de construção, justifica a realização do presente trabalho, de modo a expor como acontece a retração por secagem neste compósito, e desta forma auxiliar o meio técnico na mitigação das manifestações patológicas relacionadas à retração e contribuindo para a redução do importante problema da indústria produtora de fibrocimento, que é a fissuração de borda nas telhas onduladas. Para tal buscou-se demostrar o efeito da porosidade e distribuição de tamanho de poros na retração por secagem. Além disso, foram realizados experimentos onde se variou o tipo de cimento utilizado, as quantidades de todas as matérias-primas envolvidas, além da aplicação de tratamentos modificadores da movimentação higroscópica, manipulando diretamente a tensão capilar causadora da retração. Concluiu-se que a porosidade elevada do fibrocimento faz com que a retração por secagem deste compósito seja fortemente influenciada pela porosidade total do mesmo, com correlação direta com a quantidade de mesoporos. Além disso, no estudo de caso realizado concluiu-se que a redução da retração devido à redução da tensão superficial da água do poro, se refletiu em menor fissuração de borda nas telhas onduladas. / The objective is to analyze and comprehend the effects of properties of cement based composite reinforced with synthetic fibers, on drying shrinkage of such composite. The social importance of fiber cement as construction material justifies the execution of the present work, in order to expose how drying shrinkage occurs on this composite and by those means to assist the technical community on mitigating pathological manifestations related to shrinkage, thus contributing for the reduction of an important problem on fiber cement industry, the edge cracking on corrugated sheets. In order to achieve this goal, it was sought to demonstrate the effect of porosity and pore size distribution on drying shrinkage. Moreover, experiments were performed, varying the type of cement used and the quantities of all materials involved, in addition to the application of treatments that modify hygroscopic movement, directly manipulating the capillary tension which causes shrinkage. It was concluded that the elevated porosity of the fiber cement causes drying shrinkage of this composite to be strongly influenced by its total porosity, directly correlated to the quantity of mesopores. Furthermore, in the case study performed it was concluded that shrinkage reduction due to the reduction of pore water surface tension was reflected into minor edge cracking on corrugated sheets.

O objetivo deste estudo foi avaliar o cimento de ionômero de vidro modificado por resina de nanopartículas Ketac&trade;N100, por meio de três metodologias diferentes: resposta tecidual em subcutâneo de camundongos isogênicos, liberação de flúor e tensão de contração de polimerização, in vitro. Foram utilizados 90 camundongos isogênicos da linhagem BALB/c, divididos em 9 grupos (n=10), nos quais foram implantados tubos de polietileno contendo o Ketac&trade; 100, ChemFilR (ionômero de vidro convencional) ou tubo vazio. Nos períodos experimentais de 7, 21 e 63 dias o tubo e o tecido adjacente foram removidos para análise microscópica. Para o ensaio de avaliação da tensão de contração de polimerização, foram utilizados dois bastões de vidro fixados a uma máquina de ensaio universal. Nos bastões foi acoplado um extensômetro para medição da força de contração de polimerização de cinco materiais (Resina Filtek&trade;Z350, CompoglassR F, VitremerMR, Ketac&trade;N100 e ChemFilR), com 10 corpos de prova para cada material. Para o ensaio de liberação de flúor, foram confeccionados 8 corpos de prova de 3 diferentes materiais (Ketac&trade; 100, Vidrion R e Resina Filtek&trade; Z250), colocados individualmente em 1 ml de saliva artificial. O corpo de prova foi trocado a cada dia por 15 dias e a solução obtida utilizada para a leitura do íon fluoreto.Os resultados microscópicos evidenciaram que a inflamação presente na abertura dos tubos, aos 7 dias, sofreu uma diminuição em área e espessura até os 63 dias, nos 2 materiais e no grupo controle. Comparando a área da reação inflamatória o Ketac&trade;N100 foi diferente estatisticamente do ChemFilR, nos períodos de 7 e 21 dias (p>0,05), com uma área menor para o Ketac&trade;N100. A espessura da reação inflamatória nos períodos de 7 e 21 dias apresentou valores semelhantes entre o Ketac&trade;N100 e ChemFilR (p>0,05). Aos 63 dias, os valores foram estatisticamente diferentes, com um pequeno aumento de espessura para o Ketac&trade;N100. Os valores de tensão de contração de polimerização obtidos seguiram a seguinte ordem crescente: ChemFilR < VitremerMR < Ketac&trade;N100 < CompoglassR F ~ Filtek&trade;Z350 (p>0,05). Quando comparados dois a dois, o ionômero modificado por resina de nanopartículas Ketac&trade;N100 se aproximou mais dos valores da resina Filtek&trade; Z350 (p>0,05) do que do ionômero de vidro convencional ChemFilR (p<0,05). A sua liberação de flúor ocorreu mais significativamente nos dois primeiros dias, com valores médios 33% menores em comparação ao Vidrion R. Concluímos que o ionômero resinoso nanoparticulado Ketac&trade;N100 é um material que induz uma resposta inflamatória tecidual satisfatória em subcutâneo de camundongos isogênicos. Sua contração de polimerização foi menor do que de a resina Filtek&trade; Z350 e a liberação de flúor foi um terço menor do que a dos ionômeros convencionais. / The aim of this study was to evaluate the resin modified nano ionomer Ketac&trade;N100, by three different methodologies: tissue response in of isogenic mice subcutaneous, fluoride release and shrinkage stress of polymerization in vitro. We used 90 isogenic mice (BALB / c), divided into 9 groups (n = 10), which were implanted with polyethylene tubes containing Ketac&trade; 100, ChemFilR (Ionomer conventional) or empty tube. In the experimental periods of 7, 21 and 63 days the tube and the surrounding tissue were removed for microscopic analysis. To evaluating the stress of contraction of polymerization, we used two glass rods attached to a universal testing machine. In the rods was attached to an extensometer to obtain the measure of the polymerization shrinkage strength of five materials (resin Filtek&trade;Z350, CompoglassR F, VitremerMR F, Ketac&trade; 100 and ChemFilR), with 10 specimens for each material. In the fluoride release test, 8 specimens of 3 different materials (Ketac&trade; 100, Vidrion R and Resin Filtek&trade; Z250) placed individually in 1 ml of artificial saliva. The specimens were changed each day for 15 days and we use this solution used for reading the fluoride ion. The microscopic results showed that the inflammation in the opening of the tubes at 7 days decreased in area and thickness up to 63 days in 2 materials and the control group. Comparing the inflammatory reaction area, Ketac&trade;N100 was statistically different from ChemFilR, in periods of 7 and 21 days (p> 0.05), with a smaller area for Ketac&trade;N100. The inflammatory reaction in the periods of 7 and 21 days showed similar values between the Ketac&trade;N100 and ChemFilR (p> 0.05). At 63 days, the values were statistically different, with a small increase in thickness to Ketac&trade;N100. The values of polymerization shrinkage strength obtained after polymerization followed this ascending order: ChemFilR < VitremerMR F < Ketac&trade; 100 < CompoglassR F ~ Filtek&trade;Z350 (p> 0.05). When compared two by two, the resin modified nano ionomer Ketac&trade;N100 approached most of the values of resin Filtek&trade; Z350(p> 0.05) than the conventional glass Ionomer ChemFilR (p <0.05). The fluoride release occurred more significantly in the first two days, with average 33% lower compared with Vidrion R. We conclude that the resin modified nano ionomer Ketac&trade;N100 is a material that induces an satisfactory inflammatory response in subcutaneous tissue of isogenic mice. Its polymerization shrinkage strength was lower than the resin Filtek&trade; Z350 and fluoride release was a third lower than the conventional glass ionomer.

Made available in DSpace on 2014-08-20T14:30:15Z (GMT). No. of bitstreams: 1 Dissertacao_Fernanda_Barbosa_Leal.pdf: 806160 bytes, checksum: 37717162c453100433c520a8c9d199ef (MD5) Previous issue date: 2012-12-19 / The aim of this study was synthesize, characterize and photopolymerize an alternative monomers for use in dentistry. Three siloxane-oxirane monomers were synthesized and the products conversion was followed by Fourier-transform infrared spectroscopy. The products obtained were characterized by 1H and 13C NMR and evaluated for viscosity and refractive index. The polymerization was evaluated by formulating of two experimental photoinitiation systems wich varied for the presence of 1,2 ethanediol. A ternary system with camphorquinone (CQ), ethyl 4-dimethylaminobenzoate (EDAB) and diphenyliodonium hexafluorphosphate (DPI) was used as control. The degree of conversion was accessed by FTIR and DSC-PCA. The NMR confirmed the synthesis success with 75, 87 and 55% yield for the monomers synthesized. Moreover, the presence of 1,2 ethanediol increase the degree conversion of the siloxane-oxirane monomers. This study showed simple and effective way to synthesize siloxane-oxirane monomers with a high potential for application in dental materials / O objetivo deste estudo foi sintetizar, caracterizar e fotopolimerizar monômeros alternativos para aplicação em Odontologia. Três monômeros siloxano-oxiranos foram sintetizados e a conversão de produtos foi acompanhada por espectroscopia de infravermelho por transformada de Fourier. Os produtos obtidos foram caracterizados por 1H e 13C RMN e avaliados quanto à viscosidade e índice de refração. Para investigar a polimerização, dois sistemas experimentais de fotoiniciação foram formulados, variando quanto à presença de 1,2 etanodiol. Um sistema ternário composto por canforoquinona (CQ), 4-dimetilaminobenzoato (EDAB) e difeniliodonio hexafluorfostato (DPI) foi utilizado como controle. O grau de conversão foi obtido por FTIR e DSC-PCA. As análises de RMN confirmaram a obtenção dos produtos com 75, 87 e 55% de rendimento. Além disso, a presença de 1,2 etanodiol aumentou o grau de conversão dos monômeros siloxano-oxiranos. Este estudo demonstrou um método simples e eficaz para sintetizar monômeros siloxano-oxiranos com grande potencial para aplicação em materiais dentários

Abstract : Wastepaper sludge ash (WSA) is generated by a cogeneration station by burning wastepaper sludge. It mainly consists of amorphous aluminosilicate phase, anhydrite, gehlenite, calcite, lime, C2S, C3A, quartz, anorthite, traces of mayenite. Because of its free lime content (~10%), WSA suspension has a high pH (13). Previous researchers have found that the WSA composition has poor robustness and the variations lead to some unsoundness for Portland cement (PC) blended WSA concrete. This thesis focused on the use of WSA in different types of concrete mixes to avoid the deleterious effect of the expansion due to the WSA hydration. As a result, WSA were used in making alkali-activated materials (AAMs) as a precursor source and as a potential activator in consideration of its amorphous content and the high alkaline nature. Moreover, the autogenous shrinkage behavior of PC concrete at low w/b ratio was used in order to compensate the expansion effect due to WSA. The concrete properties as well as the volume change were investigated for the modified WSA blended concrete. The reaction mechanism and microstructure of newly formed binder were evaluated by X-ray diffraction (XRD), calorimetry, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). When WSA was used as precursor, the results showed incompatible reaction between WSA and alkaline solution. The mixtures were not workable and provided very low compressive strength no matter what kinds of chemical activators were used. This was due to the metallic aluminum in WSA, which releases abundant hydrogen gas when WSA reacts with strong alkaline solution. Besides, the results of this thesis showed that WSA can activate the glassy phase contained in slag, glass powder (GP) and class F fly ash (FFA) with an optimum blended ratio of 50:50. The WSA/slag (mass ratio of 50:50) mortar (w/b of 0.47) attained 46 MPa at 28 days without heat curing assistance. A significant fast setting was noticed for the WSA-activated binder due to the C3A phase, free lime and metallic aluminum contained in the WSA. Adding 5% of gypsum can delay the fast setting, but this greatly increased the potential risk of intern sulfate attack. The XRD, TGA and calorimetry analyses demonstrated the formation of ettringite, C-S-H, portlandite, hydrogarnet and calcium carboaluminate in the hydrated binder. The mechanical performance of different binder was closely related to the microstructure of corresponding binder which was proved by the SEM observation. The hydrated WSA/slag and WSA/FFA binder formed a C-A-S-H type of gel with lower Ca/Si ratio (0.47~1.6). A hybrid gel (i.e. C-N-A-S-H) was observed for the WSA/GP binder with a very low Ca/Si ratio (0.26) and Na/Si ratio (0.03). The SEM/EDX analyses displayed the formation of expansive gel (ettringite and thaumasite) in the gypsum added WSA/slag concrete. The gradual emission of hydrogen gas due to the reaction of WSA with alkaline environment significantly increased the porosity and degraded the microstructure of hydrated matrix after the setting. In the last phase of this research WSA-PC blended binder was tailored to form a high autogenous shrinkage concrete in order to compensate the initial expansion. Different binders were proportioned with PC, WSA, silica fume or slag. The microstructure and mechanical properties of concrete can be improved by decreasing w/b ratios and by incorporating silica fume or slag. The 28-day compressive strength of WSA-blended concrete was above 22 MPa and reached 45 MPa when silica fume was added. The PC concrete incorporating silica fume or slag tended to develop higher autogenous shrinkage at low w/b ratios, and thus the ternary binder with the addition of WSA inhibited the long term shrinkage due to the initial expansion property to WSA. In the restrained shrinkage test, the concrete ring incorporating the ternary binder (PC/WSA/slag) revealed negligible potential to cracking up to 96 days as a result of the offset effect by WSA expansion. The WSA blended regular concrete could be produced for potential applications with reduced expansion, good mechanical property and lower permeability. / Résumé : Les cendres de boues de désencrage (CBD) sont générées par une centrale de cogénération par combustion boues de désencrage. Ils se composent principalement de phase amorphe d'aluminosilicate, anhydrite, gehlenite, calcite, chaux, C2S, C3A, quartz, anorthite, des traces de mayénite. En raison de leur teneur en chaux libre (~ 10%), CBD ont un pH élevé (13). Les chercheurs précédents ont montré que la composition des CDB a une mauvaise robustesse et les variations conduisent à une certaine inconsistance pour le béton avec un mélange de ciment Portland (CP) et des CBD. Cette thèse a porté sur l'utilisation des CBD dans différents types de mélanges de béton pour éviter l'effet délétère de l'expansion due à l'hydratation des CBD. Par conséquent, les CBD ont été utilisées dans la fabrication des matériaux à activation alcaline (MAA), en tant que source précurseur et comme activateur potentiel en tenant compte de sa teneur en matière amorphe et la nature très alcaline des CBD. De plus, le retrait endogène du béton avec CP à faible rapport E/L a été utilisé afin de compenser l'effet d'expansion en raison des CBD. Les propriétés du béton ainsi que le changement de volume ont été étudiés pour le béton mélangé avec des CBD modifiés. Le mécanisme réactionnel et la microstructure du liant nouvellement formé a été évaluée par la diffraction aux rayons X diffraction (DRX), calorimétrie, l'analyse thermogravimétrique (ATG), microscopie électronique à balayage (MEB) et spectroscopie à dispersion d'énergie aux rayons X (DEX). Quand les CBD ont été utilisés comme précurseur, les résultats ont montré des réactions incompatibles entre CBD et une solution alcaline. Les mélanges ne sont pas maniables et donnent de très faibles résistances en compression, peu importe le type d'activateurs chimiques utilisés. Cela est dû à l'aluminium métallique dans les CBD, qui permet de libérer de l'hydrogène gazeux en abondance quand les CBD réagissent avec une solution alcaline forte. D'ailleurs, les résultats de ces recherches ont montré que les CBD peuvent activer la phase amorphe contenue dans le laitier, poudre de verre (PV) et les cendres volantes de classe F (CVF) avec un rapport de mélange optimal de 50:50. Un mortier avec un rapport massique 50:50 de CBD et de laitier (E/L de 0,47) atteint 46 MPa à 28 jours sans l’aide d’un murissement à chaud. Une prise rapide significative a été notée pour le liant CBD activé en raison de la phase C3A, chaux libre et l’aluminium métallique impliqué dans les CBD. L’ajout de 5% de gypse peut retarder la prise rapide, mais augmente grandement le risque potentiel de l’attaque au sulfate interne. Le DRX, ATG et l’analyse calorimétrique ont démontré la formation d'ettringite, C-S-H, la portlandite, hydrogrenat et carboaluminate de calcium dans le liant hydraté. Les différentes performances mécaniques du liant ont été étroitement liées à la microstructure correspondante qui a été prouvée par le MEB. Les liants hydratés CBD/laitier et CBD/CVF ont formé un type de gel C-A-S-H avec un faible rapport Ca/Si (0,47 ~ 1,6). On a observé un gel hybride (à savoir C-N-A-S-H) pour le liant CBD/PV avec un des très faibles rapports Ca/Si (0,26) et Na/Si (0,03). Les analyses MEB/DRX ont montré une formation de gel expansive (d’ettringite et de thaumasite) dans le gypse ajouté au béton avec les CBD et le laitier. L'émission progressive de l'hydrogène gazeux en raison de la réaction des CBD dans un environnement alcaline a augmenté la porosité et la dégradation de la microstructure de matrice hydratée après la prise. Dans la dernière phase de cette recherche, le liant avec un mélange de CBD et de CP a été développé pour former un retrait autogène élevé, afin de compenser l'expansion initiale. Différents liants ont été préparés avec le CP, CBD, la fumée de silice ou du laitier. La microstructure et les propriétés mécaniques du béton peuvent être améliorées en diminuant les rapports E/L et en incorporant la fumée de silice ou du laitier. La résistance en compression à 28 jours du béton aux CBD était supérieure à 22 MPa et atteint 45MPa lorsqu'on a ajouté de la fumée de silice. Le béton avec du CP incorporant de la fumée de silice ou du laitier ont tendance à développer un retrait endogène plus élevée à de faibles rapports E/L, et donc le liant ternaire avec l'ajout des CBD réduit le retrait à long terme en raison de la propriété d’expansion initiale des CBD. Dans l'essai de retrait empêché, l'anneau en béton incorporant le liant ternaire (CP/CBD/laitier) a révélé un potentiel négligeable à la fissuration jusqu'à 96 jours en raison de l'effet de décalage de l'expansion des CBD. Des liants modifiés avec des CBD peuvent être utilisés dans des mélanges de béton ordinaire pour des applications potentielles avec des expansions réduites, des bonnes propriétés mécaniques et une faible perméabilité.

La conception écologique des structures et le développement durable jouent un rôle important dans l'industrie de la construction. Les matériaux écologiques de construction tels que le béton de terre, contenant une proportion de divers composants écologiques, sont de grande importace aujourd'hui. L'objectif de la production de ce béton est de réduire la consommation de ciment et donc la production de CO2, de fournir des solutions pour éviter l’épuisement des ressources naturelles comme les granulats et de réduire la consommation d'énergie dans le processus de production.Ces dernières années, de nombreux efforts ont été réalisés dans le domaine de la construction pour remplacer le béton traditionnel par des matériaux alternatifs tels que le béton contenant une forte proportion de divers composants écologiques appelés « vert » en maintenant des propriétés acceptables pour l'application souhaitée. Par exemple, les constructions réalisées à partir de la terre crue sont intéressantes considérant leurs meilleures propriétés thermiques et acoustiques par rapport à un béton ordinaire. Cependant, des recherches additionnelles sont nécessaires pour mieux comprendre leurs propriétés mécaniques et leur durabilité.Cette étude vise à optimiser la composition d’un nouveau béton écologique constitué de sols locaux. Plusieurs mélanges composés de différentes proportions de sols argileux, de sols sableux et de faible quantité de ciment, de chaux et de fibres de chanvre ont été testés. La minéralogie et la composition chimique du sol argileux ont été étudiées par analyse des résultats obtenus par diffraction des rayons X (XRD) et par Microscopie à balayage électronique (ESEM) associée à la spectrométrie dispersive énergétique des rayons X (EDS). Le compactage des mélanges de béton de terre a été réalisé par vibration, comme dans le cas d’un béton ordinaire, pour obtenir l'ouvrabilité requise sur les chantiers de construction. Des essais de compression ont été effectués sur des éprouvettes d’âges différents et conservées dans différentes conditions de cure. La technique non destructive des ultrasons a été utilisée pour suivre le durcissement du béton de terre en fonction des conditions de cure. Les propriétés de transfert de ce béton ont été aussi étudiées en réalisant des essais de perméabilité, de porosité à l’eau, de porosimétrie à mercure et des essais d'absorption d'eau. La carbonatation de ce béton a été également évaluée. La durabilité du béton de terre a été examinée en suivant les déformations différées et plus particulièrement le retrait endogène et de dessiccation ainsi que le fluage en flexion. / The ecological design of structures and the sustainable development is nowadays of high importance in the construction industry. Thus, alternative building materials such as soil concrete containing a proportion of various ecological components are of high importance nowadays. The aim of producing ecological concrete is to reduce the consumption of cement and thus the CO2 production, to provide alternatives to the impoverishment of resources and to reduce the energy consumption in the production process.In recent years, many changes have been observed in the construction methods with the aim to replace traditional concrete by alternative construction materials such as concrete containing a high proportion of various ecological component called "green" while maintaining acceptable properties for the desired application. For instance, constructions made of cost effective raw soils are of real interest since the thermal and acoustic properties are more important than that of ordinary concrete. However, more researchs are needed in order to have a better understanding of their mechanical properties and their durability.This study aims to optimize the composition of a new ecological concrete constituted of upgraded excavated soil. Several soil concrete mixtures, composed of different proportions of clayey soil, sandy soil and small quantities of cement, lime and hemp fibers have been tested. The mineralogy and chemical composition of clayey soil was studied by X-ray diffraction (XRD) analysis, and by Environmental Scanning Electron Microscopy (ESEM) coupled with the X-Ray Energy Dispersive Spectrometry (EDS). The casting of the concrete mixtures has been realized by vibration, as ordinary concrete, to obtain the required workability on construction sites.Compressive tests have been carried out on samples at different curing time and conditions. The ultrasonic non-destructive technique has been used for monitoring the hardening of soil concrete in function of the curing conditions. As soil concrete presents important volumetric change that can cause the infiltration of water and impact their durability, an experimental investigation on autogenous and drying shrinkage is reported. Water porosity and water absorption tests have been also carried out to evaluate the transfer property of the porous material. The carbonation of this concrete was also evaluated. The durability of the soil concrete was examined by following the deferred deformations and more particularly the endogenous shrinkage and desiccation as well as the flexural creep.

[pt] O petróleo é uma mistura complexa de hidrocarbonetos e pode conter em sua composição parafinas que, quando submetidas a baixas temperaturas, podem precipitar e gelificar, apresentando uma Tensão Limite de Escoamento. O estudo do comportamento do petróleo nesta condição é importante para a indústria porque, uma vez que o petróleo esteja gelificado, o reinício do escoamento pode demandar a adição de energia ao sistema, cujo dimensionamento para operação com altas pressões envolve custos elevados. Os valores de pressão de reinício de escoamento do petróleo gelificado encontrados no campo são frequentemente menores em relação aos valores calculados. O presente trabalho simulou o processo de reinício de escoamento através de uma bancada experimental que reproduz o resfriamento estático sofrido pelo petróleo parafínico em um duto submarino. Além disso, são apresentados dois métodos para cálculo da contração que resulta do resfriamentoe gelificação dos óleos parafínicos, objetivando verificar se existe uma relação entre a contração do fluido e a diferença entre a Tensão Limite de Escoamento e a tensão efetiva para iniciar o seu escoamento. O primeiro método proposto é o método da Pipeta, que consiste na utilização de uma pipeta, acoplada a um recipiente com controle de temperatura, para medição do volume de líquido. O segundo método proposto é o da célula PVT, que consiste na utilização de um sistema fechado de volume conhecido em que a medição da variação do volume de líquido é estimada pela variação do volume do gás à baixa pressão com a adoção da hipótese de gás ideal. Foram utilizados fluidos sintéticos, visando representar o petróleo parafínico, com diferentes concentrações de parafina, óleo mineral e querosene. A determinação da Tensão Limite de Escoamento foi feita a partir de testes de Creep. Os resultados mostraram que a contração do fluido é uma grandeza de difícil medição, com um alto grau de incerteza, mas que é possível estimar ordem de grandeza dessa contração para os fluidos estudados. / [en] Petroleum, as it is a complex mixture of hydrocarbons, may contain paraffinic compounds which, when subjected to low temperatures, can deposit and gel. The study of the behavior of petroleum in this condition is very important for the industry because, once the waxy crude oil gels, the restart process may demand extra energy addition to the system, whose dimensioning is expensive for high operation required pressures. Restart pressure values of the gelled oil found from laboratory tests often show a significant difference from the real values found in the field. In order to compare the yield stress and the effective stress, the present work simulated the flow restarting process through an experimental rig to reproduce the static cooling applied to a pipeline with waxy crude oil. In addition, two methods are presented for calculating the thermal shrinkage formed during the cooling and gelation of the waxy crude oils, in order to verify if there is a relationship between the shrinkage and the difference between the yield stress and the effective stress to start flowing. The first method proposed is the Pipette method, which consists of the use of a pipette, coupled to a container with temperature control, to measure the volume of liquid. The second method proposed is the PVT cell method, which consists of the use of a closed system of known volume in which the measurement of the liquid volume variation is estimated by the variation of the gas volume at low pressure with the adoption of the Ideal gas hypothesis. The fluids selected for the studies to represent paraffinic oil were laboratory-synthesized fluids with different concentrations of paraffin, mineral oil and kerosene, and they were characterized rheologically by stress ramp and creep tests for the determination of the yields stress. The results showed that thermal shrinkage is a difficult quantity to measure, which gives it a high degree of uncertainty, but it is possible to estimate the magnitude order of the thermal shrinkage for the fluids studied.

La modélisation de la fissuration du béton armé à l'aide de la méthode des éléments finis nécessite de prendre en compte, outre l'endommagement du béton, trois phénomènes : la spécificité de la liaison acier-béton, l’autocontrainte due au retrait, et l'effet d'échelle probabiliste dû à l'hétérogénéité du béton. Cette recherche s'appuie sur une campagne expérimentale pour obtenir le comportement de la liaison et les caractéristiques des fissures sur des éléments de structures. La technique de corrélation d'images numériques a été utilisée pour observer l'espacement et l'ouverture des fissures.La liaison acier-béton est considérée dans la modélisation à l'aide d'éléments d'interface élasto-plastiques basés sur les résultats expérimentaux des tests de pull-out. Les effets du retrait sont pris en compte via un cadre poro-mécanique. Enfin, l'effet d'échelle probabiliste est intégré dans la modélisation via une méthode de champs aléatoires, puis de maillon faible. La modélisation est appliquée à l'élément de structure en béton armé étudié en laboratoire ce qui permet de quantifier l'importance relative de la liaison acier-béton, des contraintes induites par le retrait empêché, et de l'hétérogénéité du matériau. / The modelling of cracking of reinforced concrete using the finite element method requires taking into account, in addition to the concrete damage, three phenomena: the specificity of the steel-concrete bond, the self-stress due to shrinkage, and the probabilistic scale effect due to the heterogeneity of concrete. This research is based on an experimental campaign to obtain the behaviour of the bond and the characteristics of the cracks on structural elements. The technique of digital image correlation was used to observe the spacing and opening of the cracks.The steel-concrete bond is considered in modelling using elastoplastic interface elements based on the experimental results of the pull-out tests. The effects of shrinkage are taken into account via a poro-mechanical framework. Finally, the probabilistic scale effect is integrated into the modelling via a random field method and then a weakest link one. Modelling is applied to the reinforced concrete structural element studied in the laboratory, which makes it possible to quantify the relative importance on cracking of the steel-concrete bond, the stresses induced by shrinkage, and the tensile strength heterogeneity of the material.

abstract: There has been a renewed interest to understand the degradation mechanism of concrete under radiation as many nuclear reactors are reaching their expiration date. Much of the information on the degradation mechanism of concrete under radiation comes from the experiments, which are carried out on very small specimens. With the advent of finite element analysis, a numerical predictive tool is desired that can predict the extent of damage in the nuclear concrete structure. A mesoscale micro-structural framework is proposed in Multiphysics Object-Oriented Simulation Environment (MOOSE) finite element framework which represents the first step in this direction. As part of the framework, a coupled creep damage algorithm was developed and implemented in MOOSE. The algorithm considers creep through rheological models, while damage evolves exponentially as a function of elastic strain and creep strain. A characteristic length is introduced in the formulation such that the energy release rate associated with each element remains the same to avoid vanishing energy dissipation with mesh refinement. A creep damage parameter quantifies the effect of creep strain on the damage that was calibrated using three-point bending experiments with varying rates of loading. The creep damage model was also validated with restrained ring shrinkage tests on cementitious materials containing compliant/stiff inclusions subjected to variable drying conditions. The simulation approach explicitly considers: (i) moisture diffusion driven differential shrinkage along the depth of the specimen (ii) viscoelastic response of aging cementitious materials (iii) isotropic damage model with Rankine′s failure initiation criterion, and (iv) random distribution of tensile strengths of individual finite elements. The model was finally validated with experimental results on neutron-irradiated concrete. The simulation approach considers: (i) coupled hygro-thermal model to predict the temperature and humidity profile inside the specimen (ii) radiation-induced volumetric expansion of aggregates (RIVE) (iii) thermal, shrinkage and creep effects based on the temperature and humidity profile and (iv) isotropic damage model with Rankine’s criterion to determine failure initiation. / Dissertation/Thesis / Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2020

La terre est le premier matériau de construction par les hommes, disponible et peu consommateur d’énergie. Aujourd’hui encore, environ 30 % des habitants de la planète vit dans des habitats en terre, et pour les pays en développement, ce pourcentage s’élève à 50 % de la population rurale. De plus, les matériaux à base de terre permettent un meilleur équilibre et contrôle du climat thermique et acoustique intérieur par rapport aux matériaux usuels de construction. Cependant, la majorité des constructions en terre ne répondent pas aux exigences actuelles en termes de contraintes mécaniques, thermiques ou architecturales. Afin de répondre à ces exigences, un travail tant au niveau scientifique qu’au niveau des praticiens est à accomplir dans ce domaine.L’objectif de cette étude est de déterminer l’influence des propriétés des matériaux utilisés sur le comportement mécanique et hygrothermique de composites terre-fibres végétales. Pour cela, différents types de sols et de fibre végétales (paille de lin, paille de blé) ont été utilisés. Ensuite, les performances mécaniques (compression, flexion) et hygrothermiques (sorption/désorption, perméabilité à la vapeur d’eau, conductivité thermique) ont été déterminées pour différents composites terre-fibres végétales. Les résultats montrent que l’utilisation de paille de lin permet d’obtenir des performances mécaniques supérieures à celles obtenues pour la paille de blé. Cependant, il est à noter que l’introduction de fibres aux sols diminue les performances mécaniques due à la diminution de la densité du matériau. Aucune influence claire de la longueur des fibres sur les performances mécanique n’a été constatée. L’étude du comportement hygrothermique a permis de montrer que le comportement à la sorption/désorption du matériau terre-fibres végétales peut être approximer à partir des résultats obtenus pour les matériaux de base. De plus, il a été démontré que l’évolution de la conductivité thermique du matériau terre-fibres végétales au cours du séchage est reliée au comportement au retrait. / Soil is the first construction material used by man, widely available and low energy consuming. Indeed, about 30% of the current world population lives in earthen structures and, in developing countries, this rate rise to 50%, mostly rural. Moreover, earth-based materials allow an improved balance and control of thermal and acoustic indoor climate compared to industrial construction materials. However, most of earthen structures do not reach current requirements in terms of mechanical, thermal or architectural. To respond to these requirements, a work at scientific and craftsman levels is necessary.The objective of this study is to determine the influence of materials’ properties on the mechanical and hygrothermal behaviour of earth-fiber composites. In order to do this, different types of soil and plant fiber (flax straw, wheat straw) were used. Then, mechanical (compression, bending) and hygrothermal performances (sorption / desorption, water vapor permeability, thermal conductivity) were determined for different soil-fiber composites. Results show that the use of flax straw provides better mechanical performances than use of wheat straw. However, it should be noted that fibers addition to soil decreases mechanical performance due to the decrease of material density. No clear influence of fiber length on mechanical performance was found. The study of hygrothermal behaviour has shown that the sorption / desorption behaviour of earth-fiber material can be approximated from the results obtained from basic materials. In addition, it has been shown that the thermal conductivity evolution of earth-fiber material during drying is related to the shrinkage behaviour.

Determination of rheological phenomenon is very difficult, because there are many unknown inputs parameters, e.g. concrete age, the size of elements, relative humidity of the surrounding environment, cement hydration rate, temperature influence, type of strain and treatment. This Ph.D. thesis deals with the effective cross-section thickness and its effect on the behaviour of concrete constructions that is how the rheological phenomena change in time as a result of the application or removal of insulation layer from the concrete surface. Long-term experimental measurements of specimens and real bridge constructions were performed. The data collected from these measurements were described, evaluated and mathematical modifications for the standards Model Code 2010 and Model B4 (B3) have been proposed. Using these new computational formulas is possible to take into consideration the changes in the effective cross-section thickness and therefore make the computational models for concrete structures more accurate.