Made available in DSpace on 2014-06-11T19:28:57Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-07-07Bitstream added on 2014-06-13T18:35:10Z : No. of bitstreams: 1 barca_dc_me_sjc.pdf: 4808947 bytes, checksum: 238892d410325de1d23eb76694cb9763 (MD5) / Este estudo avaliou a influência da espessura da cerâmica, do tempo e tipo de fotopolimerização do cimento resinoso na resistência da união entre uma cerâmica vítrea e a dentina coronária humana. A hipótese é a de que o tipo e o tempo de fotopolimerização do agente cimentante e a espessura da cerâmica influenciem na resistência de união entre cimento e dentina. Foram selecionados cento e doze dentes molares humanos hígidos que foram incluídos em resina acrílica e tiveram a superfície oclusal cortadas em máquina Labcut, expondo a dentina planificada. Dois grupos foram tiveram a dentina condicionada com ácido fosfórico 37% lavada e aplicado adesivo (Excite, Ivoclar) fotopolimerizando por 20s. No grupo controle (n=16), utilizou-se cimento auto-adesivo. Foram confeccionados cento e doze blocos (6 x 6 mm) de cerâmica feldspática (Vita PM9) com três espessuras: 1, 2 e 3 mm que tiveram a superfície de cimentação tratad a com ácido fluorídrico 10%, lavada, seca e silanizada. Os blocos cerâmicos foram cimentados, de acordo com o grupo experimental: Variolink II (Ivoclar Vivadent); e fotopolimerizados com LED por 40 ou 80 segundos de fotopolimerização ou cimento Multilink II (no grupo controle). Assim, formaram-se sete grupos (n=16). Os espécimes foram armazenados em água destilada (37°C) por 24 horas e seccionados em dois eixos, X e Y, para a obtenção dos espécimes. Cada grupo (N=16) foi subdividido em 2 (n=8) onde um grupo foi termociclado e o outro submetido ao ensaio de microtração 24 horas após a cimentação. Esse palito (cerâmica/dente) foi fixado no dispositivo de microtração Erios, levado à máquina de ensaio universal e testado com velocidade de 1 mm/min. Os valores médios obtidos (MPa) foram à análise de Variáveis ANOVA 3- fatores, teste de Dunnett e ao teste de Tukey (5%). A resistência adesiva foi significantemente influenciada pelos fatores... / This study evaluated the influence of the thickness of the ceramic, time and type of light curing resin cement on bond strength between a ceramic and glass human dentin. The hypothesis is that the type and time of curing luting agent and the thickness of the ceramic bearing on the bond strength between cement and dentin. We selected one hundred and twelve healthy human molar teeth were embedded in acrylic resin and were cut in the occlusal surface Labcut machine, exposing the dentin. Two groups have had to dentin conditioned with 37% phosphoric acid washed applied adhesive (Excite, Ivoclar) light cured for 20s. In the control group (n = 16), we used self-adhesive cement. We made one hundred and twelve blocks (6 x 6 mm) ceramic feldspathic (Vita PM9) with three thicknesses: 1, 2 and 3 mm that had cement surface treated with hydrofluoric acid 10%, washed, dried, and silanized. The ceramic blocks were cemented according to the experimental group: Variolink II (Ivoclar Vivadent) and cured with LED for 40 or 80 seconds of curing cement Multilink or II (control group). Thus, they formed seven groups (N = 16). The specimens were stored in distilled water (37 ° C) for 24 hours and sectioned in two axes, X and Y, to obtain the specimens. Each group (N = 16) was subdivided into two (n = 8) where a group was thermocycled and another test by microtensile 24 hours after cementation. This toothpick (ceramic / tooth) was mounted in microtensile Erios, led to a universal testing machine and tested at a speed of 1 mm / min. The average values (MPa) were the ANOVA analysis of three variables - factors, Dunnett test and Tukey test (5%). The bond strength was significantly influenced by light irradiation time, thickness of the ceramic thermal cycling

Submitted by MONICA IRMA APARECIDA VALDECI DE SOUZA null (cristina_monicas@hotmail.com) on 2016-05-16T23:39:27Z No. of bitstreams: 1 tese correção biblio 5.pdf: 1814748 bytes, checksum: 1bfe9a56010305cbe2ef946d8d005ec9 (MD5) / Approved for entry into archive by Ana Paula Grisoto (grisotoana@reitoria.unesp.br) on 2016-05-17T20:04:08Z (GMT) No. of bitstreams: 1 souza_miav_me_arafo.pdf: 1814748 bytes, checksum: 1bfe9a56010305cbe2ef946d8d005ec9 (MD5) / Made available in DSpace on 2016-05-17T20:04:08Z (GMT). No. of bitstreams: 1 souza_miav_me_arafo.pdf: 1814748 bytes, checksum: 1bfe9a56010305cbe2ef946d8d005ec9 (MD5) Previous issue date: 2016-03-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O objetivo deste estudo foi avaliar a influência da incorporação de nanopartículas de óxido de zinco (NPZnO) nas concentrações de 3, 5 e 7%, sobre propriedades mecânicas e físicas do cimento de ionômero de vidro (CIV) Ketac Molar Easymix. A mistura das NPZnO ao CIV foi realizada pelo método manual e pela calcinação. As propriedades avaliadas foram: análise microestrutural, microdureza Vickers, resistência à compressão, à tração diametral e à flexão. A análise microesturural foi realizada por meio de MEV – FEG, a microdureza com auxilio de um microdurômetro digital (Micromet 2100) e os demais testes em máquina de ensaios mecânicos EMIC. Os dados foram avaliados pelo teste de ANOVA two-way e pelo post-hoc de Tukey, com nível de significância de 5%. Em relação à microestrutura, a calcinação proporcionou melhor distribuição e homogeneização das NPZnO entre as partículas de vidro do CIV. A microdureza, resistência à compressão, à tração diametral e à flexão, após utilização do método da calcinação, apresentaram os melhores resultados. Assim, este estudo indica o método de calcinação quando da mistura de NPZnO ao CIV, uma vez que o mesmo demonstrou ser promissor, diante de todos os testes analisados. / The aim of this study was to evaluate the incorporation of zinc oxide nanoparticles (NPZnO) in concentrations of 3, 5 and 7% on mechanical and physical properties of glass ionomer cement (GIC) Ketac Molar Easymix. The mixture of NPZnO the MIC was conducted by manual method and the calcination. The properties evaluated were: microstructural analysis, Vickers hardness, compressive strength, diametral tensile strength and flexural strength. The microesturural analysis was performed by SEM - FEG, the hardness with the aid of a digital microhardness (Micromet 2100) and other tests EMIC universal testing machine. Data were evaluated by two-way ANOVA test and the post-hoc Tukey, with 5% significance level. Regarding the microstructure, the calcination provided better distribution and mixing of NPZnO between the glass particles of the MIC. The hardness, compressive strength, diametral tensile strength and flexural strength after use of the calcination method, showed the best results. Thus, this study indicates the calcination method when mixing NPZnO the GIC once it has shown promise in front of all the analyzed tests.

Made available in DSpace on 2014-12-17T14:07:13Z (GMT). No. of bitstreams: 1 JoaoBD_DISSERT.pdf: 1988359 bytes, checksum: 0207f1a988edf03be9aba6cc36f1919a (MD5) Previous issue date: 2013-11-29 / The sharp consumption of natural resources by the construction industry has motivated numerous studies concerning the application of waste to replace partially or fully, some materials, such as aggregates, thereby reducing the environmental impact caused by the extraction of sand and crushing process. The application of stone dust from crushing process arising as an aggregate for the production of Portland cement concrete is a viable alternative in view of the high cost of natural sands, in addition to the environmental damage which causes its operation to the environment. The stone dust has reduced cost compared to natural sand because it is produced in the beds of their own quarries, which are usually located close to major urban centers. This study examined the feasibility of using stone dust from the crushing of rock gneisses in the state of Bahia, replacing natural quartz sand. In the development of scientific study was conducted to characterize physical and chemical raw materials applied and molded cylindrical specimens , using as reference values Fck 20, Fck 25 and Fck 30 MPa ( resistance characteristic of the concrete after 28 days) in following compositions stone powder: 10%, 30%, 50 %, 100% and 100% with additive. The specimens were cured and subjected to the tests of compressive strength and water absorption, then the samples were subjected to the tests of X-ray diffraction and scanning electron microscopy. The results obtained showed that the composition with 10% stone powder showed the best results regarding the physical and mechanical tests performed, confirming the reduction in compressive strength and increased water uptake increased as the content of the powder stone in the concrete composition / O acentuado consumo de recursos naturais pela ind?stria da constru??o civil tem motivado in?meros estudos referentes ? aplica??o de res?duos que substituam parcialmente ou totalmente alguns materiais, como os agregados, reduzindo assim o impacto ambiental causado pela extra??o da areia e pelo processo de britagem. A aplica??o do p? de pedra oriundo do processo de britagem como agregado para a produ??o de concretos de cimento Portland, ? uma alternativa vi?vel, tendo em vista o alto custo das areias naturais, al?m dos danos ambientais que sua explora??o ocasiona ao meio ambiente. O p? de pedra possui custo reduzido comparado ao da areia natural pelo fato de ser produzido nos canteiros das pr?prias pedreiras, que geralmente ficam localizadas pr?ximas aos grandes centros urbanos. A presente pesquisa analisou a viabilidade da utiliza??o do p? de pedra proveniente da britagem de rochas gnaisses no estado da Bahia, em substitui??o ? areia natural quartzosa. No desenvolvimento deste estudo cient?fico foi realizada a caracteriza??o f?sica e qu?mica das mat?rias-primas aplicadas e moldados corpos de prova cil?ndricos, utilizando-se como refer?ncia os valores de Fck 20, Fck 25 e Fck 30 MPa (Resist?ncia caracter?stica do concreto aos 28 dias) nas seguintes composi??es de p? de pedra:10%, 30%, 50%, 100% e 100% com aditivo. Os corpos de prova foram curados e submetidos aos ensaios de resist?ncia ? compress?o e absor??o de ?gua, em seguida as amostras foram submetidas ? ensaios de difra??o de raios X e microscopia eletr?nica de varredura. A an?lise dos resultados obtidos constatou que a composi??o com 10% de p? de pedra apresentou os melhores resultados referentes aos ensaios f?sicos e mec?nicos realizados, confirmando a redu??o da resist?ncia ? compress?o e o aumento da absor??o de ?gua ? medida que se aumentou o teor do p? de pedra na composi??o do concreto

Made available in DSpace on 2014-12-17T14:48:10Z (GMT). No. of bitstreams: 1 VeruscaKGR_DISSERT.pdf: 1561104 bytes, checksum: 8cf444f0891dd9cd7517204b9dd26c41 (MD5) Previous issue date: 2011-06-21 / This works aims at investigating the effects of adding waste from RCBP-polyester button manufacturing to Portland cement concrete, particularly regarding its consistency and mechanic strength. The RCBP used came from a button factory located in Parnamirim, RN, Brazil. The waste was added to the concrete on different ratios: 5 %, 10 %, 15 % and 20 % of the total cement mass. A sample of concrete without the RCBP was used as reference, 1:1,33:2,45:0,50. For the mechanic strength test four samples were tested with different ages (3, 7 and 28 days old) and mixtures. Furthermore, a Slump Test was also conducted in order to verify the concrete s consistency. A tendency to a reduction in the compression resistance was noticed for all samples. For the samples with 5 % and 10 %, there was also an increase in the traction resistance during inflexion, regarding the reference concrete. In the microstructural analysis, the RBCP was observed to show an irregular and porous surface, thus explaining the consistency decrease / O presente trabalho objetivou avaliar a influ?ncia da incorpora??o do res?duo de corte de bot?o em poli?ster-RCBP sobre a plasticidade e a resist?ncia mec?nica em concreto de cimento Portland. O RCBP utilizado na pesquisa originou-se do material descartado por uma empresa fabricante de bot?o localizada no munic?pio de Parnamirim/RN. Utilizou-se o res?duo, como carga no concreto, nas concentra??es de 0 %, 5 %, 10 %, 15 % e 20 %, em rela??o ? massa do cimento. O tra?o de refer?ncia do concreto utilizado na pesquisa apresenta a propor??o, em massa, de 1:1,33:2,45:0,50 (cimento:areia:brita:?gua/cimento). Nos ensaios de resist?ncia ? compress?o foram testados quatro corpos-de-prova para cada idade (3, 7 e 28 dias) e tra?o, enquanto que para os ensaios de resist?ncia ? tra??o na flex?o foram testados dois corpos-de-prova para cada tra?o. Al?m disso, fez-se o Slump Test, com vistas a verificar a consist?ncia do concreto. Observou-se uma tend?ncia de redu??o da resist?ncia ? compress?o e abatimento para todos os tra?os com incorpora??o do RCBP. Houve um aumento de resist?ncia ? tra??o na flex?o para os tra?os de 5 % e 10 %, em rela??o ao concreto sem incorpora??o do res?duo, superando o sugerido pela NBR 6118/2003 que apresenta uma correla??o entre resist?ncia ? tra??o e ? compress?o. Na an?lise microestrutural, observou-se que o RCBP apresentou uma superf?cie irregular e porosa, podendo ser o motivo do decr?scimo do abatimento

Made available in DSpace on 2014-10-09T12:52:00Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:57:03Z (GMT). No. of bitstreams: 0 / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

abstract: Early-age cracks in fresh concrete occur mainly due to high rate of surface evaporation and restraint offered by the contracting solid phase. Available test methods that simulate severe drying conditions, however, were not originally designed to focus on evaporation and transport characteristics of the liquid-gas phases in a hydrating cementitious microstructure. Therefore, these tests lack accurate measurement of the drying rate and data interpretation based on the principles of transport properties is limited. A vacuum-based test method capable of simulating early-age cracks in 2-D cement paste is developed which continuously monitors the weight loss and changes to the surface characteristics. 2-D crack evolution is documented using time-lapse photography. Effects of sample size, w/c ratio, initial curing and fiber content are studied. In the subsequent analysis, the cement paste phase is considered as a porous medium and moisture transport is described based on surface mass transfer and internal moisture transport characteristics. Results indicate that drying occurs in two stages: constant drying rate period (stage I), followed by a falling drying rate period (stage II). Vapor diffusion in stage I and unsaturated flow within porous medium in stage II determine the overall rate of evaporation. The mass loss results are analyzed using diffusion-based models. Results show that moisture diffusivity in stage I is higher than its value in stage II by more than one order of magnitude. The drying model is used in conjunction with a shrinkage model to predict the development of capillary pressures. Similar approach is implemented in drying restrained ring specimens to predict 1-D crack width development. An analytical approach relates diffusion, shrinkage, creep, tensile and fracture properties to interpret the experimental data. Evaporation potential is introduced based on the boundary layer concept, mass transfer, and a driving force consisting of the concentration gradient. Effect of wind velocity is reflected on Reynolds number which affects the boundary layer on sample surface. This parameter along with Schmidt and Sherwood numbers are used for prediction of mass transfer coefficient. Concentration gradient is shown to be a strong function of temperature and relative humidity and used to predict the evaporation potential. Results of modeling efforts are compared with a variety of test results reported in the literature. Diffusivity data and results of 1-D and 2-D image analyses indicate significant effects of fibers on controlling early-age cracks. Presented models are capable of predicting evaporation rates and moisture flow through hydrating cement-based materials during early-age drying and shrinkage conditions. / Dissertation/Thesis / Ph.D. Civil and Environmental Engineering 2011

A lixiviação de resíduos industriais e de mineração usualmente resultam em águas residuárias com pH extremamente ácido. Estes contaminantes podem migrar para o solo ou percolar através de barreiras de fundo em aterros de resíduos sólidos, perturbando a estrutura do solo e modificando a sua condutividade hidráulica. A adição de cimento Portland a este tipo de barreira pode ser uma opção para a neutralização do pH, buscando reduzir os impactos da lixiviação ácida nas águas subterrâneas. Embora muitos estudos abordem o comportamento de barreiras compactadas quando submetidas à ação dos mais diversos tipos de contaminantes, poucos tem explorado os aspectos microestruturais dos materiais componentes das barreiras e suas modificações ao longo do processo de percolação do contaminante. Neste contexto, este trabalho propôs a avaliação do comportamento microestrutural e macroestrutural de um solo argiloso residual compactado, com e sem a adição de cimento Portland (0, 1 e 2%), para fins de aplicação em barreiras impermeáveis sumetidas à ação de lixiviados ácidos. Os resultados motraram uma notável redução da condutividade hidráulica com a percolação de uma solução a 2% de ácido sulfúrico, a qual foi acompanhada pela ocorrência de recalques e redução do pH. Com relação à análise do tamanho e distribuição dos poros, pôde-se concluir que tanto a adição de cimento como a variação do peso específico de compactação, aliadas à ocorrência de recalques, contribuíram para a redução dos microporos e a consequente redução da condutividade hidráulica. Com relação às modificações químicas e mineralógicas, o ataque ácido promoveu principalmente a solubilização de Fe2O3 nas camadas superiores das amostras ensaiadas, porém não causou alterações significativas na estrutura dos argilominerais. Pode-se inferir que o peso específico de compactação não influenciou os resultados e que a adição de cimento contribuiu de maneira discreta para reduzir o impacto da percolação ácida, na medida em que produziu compostos de Ca e S nas camadas de meio e inferior das amostras, reduziu os microporos e retardou a solubilização de Fe2O3, a qual ocorreu principalmente nas camadas superiores das amostras ensaiadas. / The leaching of industrial and mining solid wastes usually result in wastewaters with extremely acidic pH, which might percolate into the ground or through bottom compacted barriers of landfills, disturbing soil structure and increasing hydraulic conductivity. The addition of Portland cement to containment barriers can be an option for pH neutralization, seeking to reduce the impact of acidic leachate to the groundwater. Although many studies have addressed the behavior of compacted barriers subjected to the action of several types of contaminants, a few have explored the microstructural aspects of barriers component materials and their modifications along the contaminant percolation process. In this context, this work proposed the evaluation of microstructural and macrostructural behavior of a compacted residual clayey soil, with and without the addition of Portland cement (0, 1, and 2%), for purposes of application in containment bottom submitted to acidic leachate percolation. The results showed a noticeable reduction in the compacted soil hydraulic conductivity during the percolation of a 2% sulfuric acid solution, which was accompanied by settlements and pH reduction. Regarding the determination of the size and distribution of pores, it can be concluded that both the addition of cement and the variation of specific weights, coupled with the occurrence of settlements, contributed to the reduction of micropores, which consequently resulted in hydraulic conductivity reduction. Concerning the chemical and mineralogical changes, the acidic attack mainly promoted the solubilization of Fe2O3 in the upper layers of the specimens tested but caused no significant modification in clay minerals structure. It can be inferred that the specific gravity did not influence the results and that the cement addition contributed discretely to reduce the acidic percolation impact, as it produced compounds of Ca and S in the middle and lower layers, reduced micropores, and slowly delayed Fe2O3 solubilization, which occurred mainly in the upper layers of the specimens tested.

Os cimentos de fosfato de cálcio (CFCs) formam uma pasta viscosa após a mistura de uma fase sólida (sal de fosfato de cálcio) com uma fase líquida (água ou uma solução aquosa). Esta pasta endurece, dando lugar a um precipitado que contenha um ou mais fosfatos de cálcio, que graças à sua formação à temperatura corporal evita uma resposta imunológica negativa do organismo. Embora uma das caraterísticas mais importantes dos cimentos de -TCP seja sua reabsorbilidade pelo organismo, a taxa de reabsorção In Vivo pode ser lenta devido à ausência de macroporos abertos. No presente trabalho foram obtidas estruturas macroporosas com presença de interconexões a partir da mistura de cimento de -TCP com uma fase líquida espumada. A fase líquida foi constituída de diferentes concentrações de hidrogenofosfato de sódio e um surfactante (Lutensol ON 110 ou Lauril Sulfato de Sódio), sendo espumada por agitação manual num sistema composto por 2 seringas conectadas por uma válvula de PVC. Após, foi acrescentado o pó de cimento, o qual foi misturado com a espuma no mesmo sistema. Verificou-se que as soluções com Lutensol apresentaram maior espumabilidade (218 – 400%) que as soluções com Lauril (63 – 209%). A difração de raios X evidenciou a transformação de -TCP em Hidroxiapatita deficiente em cálcio em todas as amostras após a imersão em solução de Ringer. As amostras preparadas com Lutensol apresentaram macroporos abertos com diâmetros maiores a 100m. Além disso foi observado que a macroestrutura final e o tamanho dos macroporos dos cimentos espumados varia em função das concentrações de fosfato e surfactante, além da proporção L/P. Por outro lado, a resistência a compressão das amostras macroporosas diminuiu com o aumento da porosidade total. Finalmente, foi observada a formação de uma camada continua de apatita sobre a superfície dos cimentos após imersão em SBF durante 21 dias. Este estudo sugere que as amostras de cimento de fosfato de cálcio espumadas com Lutensol possuem potencial para uso como arcabouços (scaffolds) para crescimento de tecidos. / Calcium phosphate cements (CPCs) form a viscous paste after mixing a solid phase (a calcium phosphate salt) with a liquid phase (water or an aqueous solution). This paste hardens, forming a precipitate with one or more calcium phosphates, which thanks to their formation at body temperature prevent a negative immune response. Even though one of the most important characteristics of -TCP cements is their resorbability in the body, their In Vivo resorption rate is low due to the lack of open macropores. In the present work, macroporous interconnected structures were obtained by mixing the -TCP cement with a foamed liquid phase. The liquid phase was composed of different concentrations of sodium hydrogenphosphate and a surfactant (Lutensol ON 110 or Sodium Lauril Sulfate), and it was foamed by manual agitation in a system of two syringes connected by a PVC valve. The cement powder was then added to the system and mixed with the foam likewise. Solutions with Lutensol showed better foamability (218 - 400%) than solutions with Lauril (63 - 209%). X-ray diffraction showed the transformation of -TCP into Calcium Deficient Hydroxyapatite in every sample after immersion in Ringer’s solution. Samples prepared with Lutensol showed open macropores with diameters greater than 100m. It was found that final macrostructure and size of macropores in the foamed cements vary according to phosphate and surfactant concentrations, as well as to the L/P ratio. It was also found that compressive strength of the macroporous samples decreased with the increase of the total porosity. Finally, a continuous apatite layer was observed on the surface of the cements after immersion in SBF for 21 days. This study suggests that the calcium phosphate cement samples foamed with Lutensol have potential to be applied as scaffolds for bone tissue regeneration.

La sorption et les réactions redox des radionucléides (RN) sont des processus critiqués pour une évaluation de la sécurité des dépôts de déchets nucléaires. Dans les dépôts géologiques, ces procédés peuvent se produire dans (i) une couche de corrosion (acier), (ii) un béton armé, par exemple, sur le ciment hydraté et (iii) l'argilite, sur la pyrite et les argiles ou le granit. Les produits de corrosion de l'acier et la pyrite agissent comme des tampons de réduction locaux, contrôlant le potentiel redox (Eh) et donc le comportement de sorption des RN sensibles au rédox. En revanche, la sorption de RN n'impliquant pas de processus redox peut se produire sur des argiles, des oxydes de fer et des produits d'hydratation de ciment et impliquent souvent des processus d'adsorption de surface, d'échange d'ions ou de co-précipitations. Dans cette thèse de doctorat, des phases d'AFm cimentaires mineures, mais hautement réactives (acides gras AFm-Cl2 ou AFm-SO4, appartenant aux LDH CaAl) ont été utilisées pour adsorber MoO42- et SeO32- à diverses charges de surface. Une combinaison de la modélisation de l'équilibre chimique PHREEQC et des techniques de rayons X à base de synchrotron (par exemple, XRD, PDF et XAFS résolus dans le temps) révèle que les sites de sorption multiples, y compris deux types de sites de bord, des sites d'échange d'ions intercalaires et une précipitation de phase riche en Ca, sont des processus actifs dans la rétention des RN sur les phases AFm. Une relation linéaire permet de lier l'espacement basal AFm et le rayon d'anion intercalé hydraté. L'adsorption macroscopique MoO42 a été évaluée sur le ciment hydraté renforcé d'acier et de ses composants individuels (p. Ex. Fe0, CSH, ettringite, phase AFm, portlandite, gypse, pyrite, mackinawite) à pH 13,5 et le signal EXAFS ne pouvait être obtenu que pour Mo sorbed sur les phases AFm et les produits d'oxydation Fe0, en montrant qu'ils sont les absorbants les plus efficaces. La co-sorption de U et Mo sur le ciment-ciment hydraté renforcé par Fe0 a également été étudiée par cartographie micro-sonde, montrant que U doit être immobilisé instantanément par des matériaux de ciment tandis que Mo est préférentiellement sorbé sur des produits de réaction de Fe. La valeur Eh prédominant dans le béton est difficile à déterminer. Ici, les RN sensibles à la réduction rénale (par exemple, UVI, SeIV, MoVI et SbV) sont utilisées comme sondes, pour mesurer les valeurs Eh in-situ, en calculant l'équation de Nernst de la manière suivante. La concentration des espèces réduites a été mesurée en fonction de la concentration totale de RN précipitée par réduction et de la spéciation parmi ces espèces réduites, tel qu'obtenu par l'analyse LCF des données XANES. La concentration de l'espèce oxydée unique a été prise égale à la concentration chimique aqueuse totale, car toutes les espèces réduites identifiées sont extrêmement insolubles. Les valeurs Eh déterminées expérimentalement obtenues de cette façon étaient remarquablement fermées pour toutes les RN avec des valeurs centrées de -368 à -524 mV pour l'eau de pore de ciment (CPW) équilibrée avec Fe0 et des valeurs de -346 à -509 mV pour CPW équilibrées avec des produits de corrosion Fe - couples d'oxydes (magnetite / hématite ou magnetite / goethite) à pH ~ 13,5. Ni la valeur Eh calculée pour ces couples ni pour Fe0 / Fe (OH)2 correspond à ces données. Au lieu de cela, le potentiel redox semble être contrôlé par le couple Fe (OH)3 / Fe (OH)2 prédominant au début de la corrosion Fe0. Enfin, dans le domaine de l'argile ou du granit, plusieurs facteurs peuvent affecter de manière critique l'Eh imposé par la minérale mine de pyrite, à savoir les impuretés élémentaires dans le réseau de pyrite et les fractures résultant du broyage et de la présence de Fe3+et S2- à la surface de la pyrite. Les impuretés des éléments et la présence de S2- sur la surface de la pyrite ont largement accéléré la réduction des U (VI). / Sorption and redox reactions of radionuclides (RNs) are critical processes for a nuclear waste disposal repository safety assessment. In geological repositories, these process may occur in (i) canister (steel) corrosion layer, (ii) reinforced concrete, e.g. on hydrated cement and (iii) argillite, e.g. on pyrite and clays or granite. Both steel corrosion products and pyrite act as local reducing buffers, controlling the redox potential (Eh) and thus the sorption behavior of redox-sensitive RNs. In contrast, sorption of RNs not involving redox processes may occur on clays, iron oxides and cement hydration products, and often involve surface adsorption, ion exchange, or co-precipitations processes. In this PhD thesis, minor but highly reactive cementitious AFm phases (AFm-Cl2 or AFm-SO4 solids, belonging to CaAl LDHs) were employed to adsorb MoO42- and SeO32- at various surface loadings. A combination of PHREEQC chemical equilibrium modelling and synchrotron-based X-ray techniques (e.g., in-situ time-resolved XRD, PDF, and XAFS) reveals that multiple sorption sites, including two types of edge sites, interlayer ion exchange sites, and a Ca-rich phase precipitation, are active processes in the RNs retention on AFm phases. A linear relationship is shown to link AFm basal spacing and hydrated intercalated anion radius. MoO42- macroscopic adsorption was evaluated on steel-reinforced hydrated cement and its individual components (e.g., Fe0, C-S-H, ettringite, AFm phase, portlandite, gypsum, pyrite, mackinawite) at pH 13.5, and EXAFS signal could only be obtained for Mo sorbed on AFm phases and Fe0 oxidation products, showing they are the most effective absorbents. Co-sorption of U and Mo on Fe0-reinforced hydrated cement-core has also been investigated by micro-probe mapping, showing U to be instantly immobilized by cement materials while Mo is preferentially sorbed on Fe reaction products.The Eh value prevailing in concrete is hard to be determined. Here, redox-sensitive RNs (e.g., UVI, SeIV, MoVI, and SbV) are employed as probes, to measure in-situ Eh values, by computing the Nernst equation in the following way. Reduced species concentration were measured based on the total concentration of reductively precipitated RN and on speciation among these reduced species as obtained by LCF analysis of XANES data. The single oxidized species concentration was taken equal to the total aqueous chemical concentration, as all identified reduced species are extremely insoluble. The experimentally determined Eh values obtained that way were remarkably closed for all RNs with centered values of -368 to -524 mV for cement pore water (CPW) equilibrated with Fe0 and values of -346 to -509 mV for CPW equilibrated with corrosion products Fe-oxides couples (magnetite/hematite or magnetite/goethite) at pH ~13.5. Neither the Eh value computed for these couples or for Fe0/Fe(OH)2 match these data. Instead, the redox potential appear to be controlled by the Fe(OH)3/Fe(OH)2 couple predominating at the beginning of Fe0 corrosion. Finally, within clay or granite far field, several factors may critically affect the Eh imposed by pyrite minor mineral, namely element impurities in pyrite lattice and fractures resulting from grinding and presence of Fe3+ and S2- at the pyrite surface. Element impurities and presence of S2- on the pyrite surface were shown to largely speed up U(VI) reduction. The experimental results obtained above could provide fundamental data for the safety assessment of nuclear waste disposal.

Orientador: Rebeca Di Nicoló / Banca: Maria Beatriz Duarte Galvão / Banca: Maria Naira Pereira Friggi / Banca: Maria Amélia Máximo de Araujo / Banca: Silvio Issáo Myaki / Resumo: O objetivo deste estudo foi avaliar a microdureza de cimentos de ionômero de vidro (CIV): Vidrion R (V) .- SS White; Fuji IX (F) . GC Corp; Magic Glass ART (MG) - Vigodent; Maxxion R (MR) - FGM e ChemFlex (CF) - Dentsply, na presença ou ausência de proteção superficial, em diferentes períodos de armazenamento. Para cada CIV foram confeccionados 36 corpos-de-prova (3 mm altura X 3 mm diâmetro), divididos em 3 grupos em função da proteção superficial (sem proteção, verniz do Fuji IX ou esmalte para unha). Os espécimes foram armazenados em água destilada por 24 h, 7 e 30 dias e os testes de microdureza foram realizados nestes tempos. Os dados obtidos foram submetidos ao teste de ANOVA para medidas repetidas e teste de Tukey ('alfa'=5%), e revelaram que os valores médios de microdureza, no geral, em ordem decrescente dos CIV foram: F > CF = MR > MG > V; que a proteção superficial foi significante para o MR em 24 h sem proteção (64,2'mais ou menos'3,6a), proteção com verniz (59,6'mais ou menos'3,4b) e com esmalte (62,7'mais ou menos'2,8ab); para o F, em 7 dias, sem proteção (97,8'mais ou menos'3,7ab), proteção com verniz (95,9'mais ou menos'3,2b) e com esmalte (100,8'mais ou menos'3,4a) e em 30 dias para o F sem proteção (98,8'mais ou menos'2,6b), proteção com verniz (103,3'mais ou menos'4,4a) e com esmalte (101'mais ou menos'4,1ab) e V sem proteção (46'mais ou menos'1,3b), proteção com verniz (49,6'mais ou menos'1,7ab) com esmalte (51,1'mais ou menos'2,6a) e o aumento do tempo de armazenamento proporcionou um aumento da microdureza. Concluiu-se que os diferentes CIV, tipo de proteção e tempo de armazenamento, podem alterar os valores de microdureza...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The aim of this study was to evaluate the microhardness of glass ionomer cement (GIC): Vidrion R (V) - SS White; Fuji IX (F) - GC Corp.; Magic Glass ART (MG) - Vigodent; Maxxion R (MR) - FGM and ChemFlex (CF) - Dentsply, with or without surface protection in different storage time. Thirty six specimens for each GIC (3 mm diameter X 3 mm height) were made and these specimens were divided into three groups, according to the surface protection (without protection, varnish protection of the Fuji IX or protection with nail varnish). The samples were stored in distilled water for 24 h, 7 and 30 days and the microhardness test was carried out using a microhardner in those times. The data were submitted to repeated measures analysis of variance test and Tukey test ('alfa' =0.05) and showed that mean microhardness values, in general, of the GIC followed the decrescent order: F > CF = MR > MG > V; the surface protection was significant for MR in 24 h without protection (64.2'mais ou menos'3.6a), protection with varnish (59.6'mais ou menos'3.4b) and nail varnish (62.7'mais ou menos'2.8ab); for F in 7 days without protection (97.8'mais ou menos'3.7ab), protection with varnish (95.9'mais ou menos'3.2b) and nail varnish (100.8'mais ou menos'3.4a); for F in 30 days without protection (98.8'mais ou menos'2.6b), protection with varnish (103.3'mais ou menos'4.4a) and nail varnish (101'mais ou menos'4.1ab) and for V in 30 days without protection (46'mais ou menos'1.3b), protection with varnish (49.6'mais ou menos'1.7ab) and nail varnish (51.1'mais ou menos'2.6a) and surface microhardness generally increased with time. It was concluded that different trade mark, surface protection and storage times can influence microhardness of GIC. / Doutor