Orientador: Jorge Luís Akasaki / Banca: Marco Antonio Morais Alcantara / Banca: Geraldo Cechella Isaia / Resumo: Em conseqüência às inúmeras vantagens intrínsecas dos concretos de alto desempenho, sejam relacionadas à performance mecânica ou de durabilidade, se faz constante no cenário mundial a expansão de suas aplicações. Contudo os concretos de alto desempenho apresentam comportamento de ruptura frágil, característica destoante dos demais materiais usualmente empregados na concepção de estruturas, os quais por serem dúcteis propiciam maior capacidade de redistribuição de esforços aos elementos estruturais. Neste enfoque aborda-se a investigação do concreto de alto desempenho com adição de resíduos de borracha de pneu, sendo que, dentre as mais variadas aplicações bem sucedidas dos resíduos de borracha de pneu ressalta-se sua adição em cimentos asfálticos, no intuito do aumento da resistência à temperatura e a esforços mecânicos, e também em concretos convencionais de cimento Portland, visando por exemplo majorar a tenacidade. Com a utilização desses resíduos de borracha de pneu ocorre ainda notável contribuição ao desenvolvimento sustentável e ao meio ambiente, uma vez que em todo o mundo existe uma grande problemática ligada ao acúmulo pneus inservíveis. Assim no intuito de substanciar a performance do concreto de alto desempenho com adição de resíduos de borracha de pneu obtido, cabe destacar alguns números: resistência à compressão superior a 70MPa, aos 28 dias de idade; módulo de elasticidade acima dos 50GPa, aos 91 dias; maior tenacidade em relação ao CAD; sua resistência ao impacto foi superior de 11% a até 26% a do CAD; possui absorção de água por imersão menor que 1%, aos 28 dias; resistência à tração equivalente a até 12,6% da sua resistência à compressão e ainda demonstrou maior resistência à abrasão do que um concreto de alta resistência, com resistência à compressão equivalente. / Abstract: Innumerable advantages of high performance concrete, being related to the mechanics or durability performance, it makes world-wide expansion scene of its application. However, fragile rupture behavior is presented on high performance concrete, different characteristic of usual material used into the structure conception, which being ductile, it propitiates higher redistribution capacity efforts of structural elements. In this way it is approached the high performance concrete inquiry the tire rubber scrap addition, being the most varied successful tire rubber scrap application, standing out its addition in asphalt cements, aiming the resistance increasing to temperature and mechanical strength, and also to conventional Portland cement concrete, reaching better tenacity. The tire rubber scrap using occurs sustainable development and also to the environment, there are a great problematic on idle tire accumulation. Intentioning to substantiate the presentation of high performance concrete with tire rubber scraps addition obtained, some numbers can be highlighted: compressive strength higher than 70MPa, age of 28 days; modulus of elasticity above 50GPa, to 91 days; greater tenacity in relation to the HPC; its impact resistance was superior of 11% up to 26% of the HPC; occurs water absorption for lesser than 1%, to the 28 days; tensile splitting strength equivalent up to 12,6% of its compressive strength and still demonstrated to greater resistance to the abrasion of that a high strength concrete, with the same compressive strength. / Mestre

La surveillance des structures de génie civil, afin d'en estimer l'état de santé, est un enjeu majeur pour les maîtres d'ouvrages. Les systèmes de mesures réparties par fibre optique, composés d'un interrogateur connecté à une fibre optique intégrée dans un câble, permettent de mesurer le profil de déformation avec un pas de mesure centimétrique et une portée kilométrique. Ils sont donc adaptés aux structures présentant de grands linéaires ou de grandes surfaces. Mais, avant tout déploiement industriel, il est nécessaire d'en évaluer leurs performances. Du fait de la déformation par cisaillement du revêtement du câble, le profil de déformation mesuré le long de la fibre optique n'est pas strictement identique à celui du matériau environnant. Une méthode, basée sur la mise en œuvre d'essais et de simulations numériques, a été développée afin de caractériser les mécanismes de transfert d'effort du milieu hôte à la fibre optique à travers le revêtement du câble. Cette méthode a été appliquée pour déterminer la réponse mécanique d'un câble particulier noyé dans le béton. Les performances métrologiques d'un système de mesure donné ont été évaluées sur la base d'une analyse d'essais « du laboratoire au terrain ». Cette étude a permis de quantifier les différentes composantes d'incertitude et d'estimer les performances du système de mesure complet. Enfin, le câble, noyé dans le béton, ne peut être remplacé. La connaissance de l'impact du vieillissement sur la réponse mécanique du câble est donc primordiale. Une étude spécifique est menée dont le but est d'estimer la durabilité du câble face aux sollicitations chimique, thermique et mécanique correspondant à une application donnée / Structural Health Monitoring is a key factor in life-cycle management of civil structures. Truly distributed fiber optic sensors, composed by an optoelectronic device paired with an optical fiber in a cable, provide strain profiles over several kilometers with a centimeter resolution. They are thus able to provide relevant information on large structures. However, a preliminary performance assessment is required prior to any industrial application. Due to shear deformation of the cable's protective coating, strain measurements provided by the measuring system may differ from actual strains in the embedding medium. A methodology, based on mechanical tests and modelling, was thus developed to determine the relationship between measured/actual strains. It was applied to determine the mechanical response of a specific cable embedded in concrete. Performance assessment method was applied to a specific measuring system. Tests were carried out under laboratory conditions on the fiber optic cable, out of the concrete medium in a first stage, and then embedded in concrete structures. It enabled to evaluate its components and standard uncertainties. The cable could not be replaced after being embedded in concrete. It is necessary to evaluate the ageing effects on its mechanical properties to use it for a long term period. A specific study was carried out to determine the cable durability under chemical, thermal and mechanical solicitations

Cette étude concerne le comportement de mortiers constitués par une matrice résineuse à base d’époxyde désignés dans ce qui suit par mortier de résine, MR.Des études antérieures ont montré que l’ouvrabilité des MR élaborés avec un taux de polymère en masse mp≤12%, afin de baisser leur coût considéré élevé par comparaison à celui des mortiers hydrauliques MH, est médiocre et constitue un frein majeur au développement de ces matériaux dans le domaine de la préfabrication et de la réparation.Un moyen de favoriser le développement des MR consiste, donc, à faciliter leur mise en œuvre. Or le fait de diminuer le taux de polymère afin de diminuer le coût rend la mise en œuvre du mortier encore plus difficile. Par ailleurs l’utilisation de sable recyclé « SR » en substitution au sable naturel « SN »pour répondre à des exigences environnementales en matière d’épuisement de ressources naturelles exacerbe cette difficulté.L’objectif de cette thèse est, donc, de trouver un diluant à incorporer dans les formulations des MR, destinées soit à la préfabrication (2 formulations avec des taux massique de liant à base d’époxyde mp= 9% et 12%) ou à la réparation (mp= 20%). Le but ultime consiste à améliorer leur ouvrabilité tout en assurant leurs propriétés mécaniques et leur durabilité vis-à-vis de la diffusion des ions chlorure. Une comparaison systématique avec des mortiers hydrauliques, MH, est réalisée.Différents diluants ont été sélectionnés. Leur influence sur le point de gel, sur le temps de réticulation et sur les propriétés mécaniques et physiques des époxydes a fait l’objet d’une étude détaillée. Il en ressort que l’octanoate de méthyle permet de diminuer la viscosité de la résine époxyde sans affecter le point de gel et les cinétiques de durcissement de façon significative. Cependant, il joue un rôle de plastifiant à l’origine de l’augmentation de la ductilité et de la diminution des résistances et des rigidités des époxydes à l’état réticulé. Le taux optimal de diluant (md) à incorporer dans la formulation des mortiers de résine a été estimé à 5%.L’incorporation du diluant, avec md= 5%, dans les MR a amélioré leur ouvrabilité, modifié leur microstructure et leurs propriétés de transfert mais a généré une baisse des résistances mécaniques. En effet une baisse de 31% est observée pour MR-SN formulé avec mp= 20%. La substitution du SN par le SR dans les mortiers de réparation (MR avec mp= 20%) engendre, également, une diminution des propriétés mécaniques et une modification des propriétés rhéologiques. Toutefois, ces résistances mécaniques demeurent nettement plus élevées que celles des mortiers hydrauliques à sable naturel (MH-SN) et recyclé (MH-SR). En compression, le mortier MR-SR fabriqué avec mp=20% présente une résistance supérieure de 44% par rapport à celle du MH-SN et de 53% par rapport à celle du MH-SR.La résistance des mortiers à la diffusion des ions chlorure a été appréhendée par un essai de migration en régime transitoire (Non Steady State Migration) et le coefficient de diffusion apparent Dnssm a été calculé pour 10 formulations de mortiers : 1 MH-SR, 1 MH-SN, 2 MR-SR et 6 MR-SN. Il en ressort que les bétons de résine ont une résistance à la diffusion des ions chlorure nettement plus élevée que celle des mortiers hydrauliques. Les coefficients Dnssm des mortiers MH-SN et MH-SR sont respectivement 100 et 200 fois plus élevés que celui du MR-SN (mp= 20%).Le mortier MR-SN destiné à la réparation (avec mp= 20% et md=5%) est caractérisé par une très bonne ouvrabilité et des résistances mécaniques et à la diffusion des ions chlorure les plus élevées. On montre que son adhérence à un support constitué d’un MH-SN dépend de l’état de surface du support (lisse sec, lisse saturé, rugueux sec et rugueux saturé). Le mortier de réparation n’adhère pas aux supports à surface saturée en eau alors qu’une bonne adhérence est observée pour les surfaces sèches. Cette adhérence est meilleure lorsque la surface est lisse. / This study concerns the behavior of mortars constituted by epoxy-based resinous matrix and sand designated in what follows by resin mortar, RM.Previous studies have shown that the workability of RM made with a polymer rate by weight mp≤12% in order to reduce their cost which is considered high compared to that of hydraulic mortars HM, is poor and is a major obstacle to the development of these materials in the area of prefabrication and repair. However decreasing the polymer content to reduce the cost makes the mortar implementation even more difficult. Furthermore the use of recycled sand "RS" to substitute natural sand "NS" to answer environmental requirements regarding natural resource depletion exacerbates this difficulty.The objective of this work is, therefore, to find a thinner to incorporate into RM formulations, intended either to prefabrication (2 formulations with mass rate of epoxy based binder mp= 9% and 12%) or repair (mp = 20%). The ultimate goal is to improve their workability while maintaining their mechanical properties and their sustainability to chloride ion diffusion. A systematic comparison with hydraulic mortars, HM, is performed.Various thinners were selected. Their influence on the gel point, on the time of crosslinking and mechanical and physical properties of the epoxy resin has been the subject of detailed study. It shows that methyl octanoate reduces the viscosity of the epoxy resin without affecting significantly the gel point and curing kinetics.However, it acts as a plasticizer which represents the origin of the increased ductility and reduced resistance and rigidity of the epoxy resin in the cured state.The optimal rate of the thinner (md) to be incorporated in the formulation of resin mortar was estimated at 5%.The incorporation of thinner, with md=5% in the RM improved their workability, changed their microstructure and their transfer properties but generated lower mechanical strength. Indeed a decrease of 31% was observed for RM-NS formulated with mp=20%. The substitution of NS by the RS in repair mortars (RM with mp=20%), leads also, to decreased mechanical properties and modified rheological ones.However, these strengths remain significantly higher than those of hydraulic natural sand (HM-NS)and recycled (HM-RS) mortars. In compression, the RM-RS mortar manufactured with mp=20% has a higher resistance by 44% compared to the HM-NS and 53% compared to that of HM-RS.The resistance of mortars to chloride ions diffusion was apprehended by non Steady state migration test and apparent diffusion coefficient "Dnssm" was calculated for 10 mortar formulations: 1 HM-RS, 1 HM-NS, 2 RM-RS and 6 RM-NS. It follows that the resin concrete has a resistance to chloride ions diffusion considerably higher than that of hydraulic mortars. The "Dnssm" coefficients of HM-NS and HM-RS mortars are respectively 100 and 200 times higher than that of RM-NS (mp= 20%).The RM-NS mortar intended for repair (with mp=20% and md=5%) is characterized by very good workability and the highest mechanical strength and resistance to chloride ions diffusion. We show that adhesion to a support consisting of a HM-NS depends on the surface condition of the support (smooth dry , smooth saturated, rough dry and rough saturated). The repair mortar does not adhere to the surface saturated on water while a good adhesion was observed for dry surfaces. This adhesion is better when the surface is smooth.

Atualmente, sabe-se que nenhum material estrutural é eternamente durável devido à ação dos agentes ambientais sobre seus componentes. No caso das estruturas de concreto armado, iniciou-se, a partir da década de 70, uma crescente preocupação com a sua deterioração e durabilidade. As soluções mais estudadas geralmente seguem a linha de melhorar as propriedades do concreto para o aumento da durabilidade da estrutura, que se trata, sem dúvida, de uma das possíveis soluções para o problema. Contudo, este trabalho aborda o aumento da durabilidade de outra forma, ou seja, tratando a superfície do concreto com o objetivo de impedir ou desacelerar o processo de corrosão. A forma de ação, neste caso, é a restrição da penetração de agentes agressivos, água e/ou oxigênio através da rede de poros capilares do concreto, componentes imprescindíveis para o desenvolvimento da corrosão. Este tipo de sistema de proteção consiste em uma barreira que funciona como um cobrimento de concreto de alta qualidade, fundamental para a proteção do aço embebido no concreto. Este trabalho apresenta uma metodologia de estudo da eficiência de produtos destinados à proteção superficial para estruturas de concreto armado submetidas ao ataque por cloretos. Além disso, no trabalho é apresentada uma comparação entre três categorias de produtos de proteção superficial: hidrofugantes de superfície, formadores de película e bloqueadores de poros. Outra contribuição é a comprovação da eficácia da aplicação de proteção de superfície sobre estruturas já contaminadas por cloretos. / Currently, it is known that no structural material is ever-lasting due to environment action on its components. In the 1970s, there was an increasing concern with deterioration and durability of reinforced concrete structures. The solutions studied generally aim to improve the concrete properties to increase the durability of the structure. Undoubtedly, this is one of the possible solutions for the problem. However, this work approaches the increase in the durability in another way, treating the surface of the concrete with the aim of inhibiting or decelerating the corrosion process. The action form, in this case, is to restrict the penetration of aggressive agents, water and/or oxygen (essential components for the development of corrosion process) through the pores of the concrete. This type of protection system consists of a barrier that functions as a concrete cover of high quality, important for the protection of the steel reinforcement inside the concrete. This work presents a methodology to study the efficiency of surface treatment used to protect reinforced concrete structures exposed to marine environment. Moreover, in this work, the efficacy of three groups of surface treatments were compared. These groups are: coatings and sealers (physical barrier); pore liners (water repellent) and pore blockers. Another contribution of this work is the evidence of the effectiveness of surface protection applied on structures contaminated with chlorides.

Custo e durabilidade ainda são os maiores impeditivos para a entrada das células a combustível no mercado de dispositivos usados para produção de eletricidade. Assim, o objetivo deste trabalho foi avaliar a durabilidade dos conjuntos eletrodo-membrana-eletrodo (MEAs) produzidos no IPEN pelo método de impressão à tela para uso em células a combustível do tipo PEM. Para tanto, foi necessário desenvolver um protocolo adequado de teste de durabilidade de longa duração, visando obter estimativas da taxa de queda do potencial elétrico da célula a combustível ao longo do tempo e, assim, fazer inferência a respeito do tempo de vida deste dispositivo. Os MEAs testados durante este estudo foram preparados pelo método de impressão à tela com catalisador de Pt/C comercial e membrana Nafion® 115. O aprimoramento do protocolo de teste de durabilidade de longa duração se deu pela escolha dos procedimentos a serem executados e pelo ajuste de alguns parâmetros de operação da célula a combustível, tais como temperatura da célula, fluxo de H2 e fluxo de O2. Para a análise dos dados obtidos com os testes, foram aplicados métodos estatísticos de ajuste de modelos e curvas de polarização. Além disso, amostras da camada catalítica de um dos MEAs utilizados nos testes de durabilidade de longa duração foram analisadas por meio de microscopia eletrônica de transmissão (MET) para serem comparadas com amostras da camada catalítica de um MEA de controle. Para se avaliar o desempenho global da célula a combustível do tipo PEM em operações de longa duração, um dos grandes desafios foi fazer a separação entre as componentes de perda de desempenho que são reversíveis das irreversíveis. As estimativas obtidas para a taxa de queda do potencial elétrico da célula a combustível ao longo do tempo variaram num intervalo de 108,19 a 318,15 μV.h-1. Estes resultados podem ser considerados satisfatórios quando comparados com valores apresentados na literatura. Finalmente, as imagens obtidas por MET mostraram uma tendência de aumento no tamanho médio das partículas Pt em decorrência do tempo de operação dos MEAs, mas que não implicou numa queda significativa do desempenho das células a combustível do tipo PEM testadas. / Cost and durability still represent the major barriers to the entry of proton exchange membrane fuel cells (PEMFCs) in the market. Thus, the objective of this work was to assess the durability of membrane-electrode assemblies (MEAs) produced at IPEN through the sieve printing method to be used in PEMFCs. For this purpose, an adequate long-term test protocol was developed aiming to obtain estimates of the voltage decay rate and lifetime of the PEMFCs. In the preparation of the MEAs through the sieve printing method commercial Pt/C catalyst and Nafion® 115 membranes were used. In the development of the long-term test protocol some procedures were defined and the fuel cell operational parameters were adjusted, such as cell temperature, H2 and O2 flows. In the analysis of the data obtained from the tests, statistical methods and polarization curves were applied. Samples of the catalyst layer from a MEA used in a long-term test were compared with samples from a control MEA using a Transmission Electron Microscopy (TEM). To evaluate the overall performance of the PEMFCs in long-term operations, a major challenge was to make the separation between the components of performance loss that are reversible from the ones that are irreversible. The estimates for the voltage decay rate ranged from 110 to 318 μV.h-1. These results can be taken as satisfactory when compared with values reported in the literature. Finally, there was an increase in the average size of Pt particles in the catalyst of the long-term tested MEA, as observed in the micrographs. However, this increase did not lead to a significant performance loss of the PEMFCs.

Submitted by Erika Demachki (erikademachki@gmail.com) on 2014-09-24T21:42:24Z No. of bitstreams: 2 COUTO, T.A. - RAA Estudo do fenômeno em rochas silicosas 2008.pdf: 9649591 bytes, checksum: 0ecde13fd55a962ac1bc6a8f43f44415 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2014-09-25T10:37:27Z (GMT) No. of bitstreams: 2 COUTO, T.A. - RAA Estudo do fenômeno em rochas silicosas 2008.pdf: 9649591 bytes, checksum: 0ecde13fd55a962ac1bc6a8f43f44415 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2014-09-25T10:37:27Z (GMT). No. of bitstreams: 2 COUTO, T.A. - RAA Estudo do fenômeno em rochas silicosas 2008.pdf: 9649591 bytes, checksum: 0ecde13fd55a962ac1bc6a8f43f44415 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2008-08-29 / The symposium on Alkali-Aggregate Reaction (AAR) held in Goiânia in 1997 led to a greater dissemination of this deleterious reaction in Brazil, motivating engineers to find solutions for the problem. Recently, in Brazil, this occurrence has occurred in several building foundations in the Recife metropolitan area besides hydraulic powers plants, as can be seen in some publications from the last AAR Symposium in 2006. This study presents an investigation of several aggregates commercially used in the State of Goiás, Brazil, in order to determine their potential reactivity. In addition, their behavior were compared to the ones from aggregates from several Brazilian classic cases such as Furnas HPP (MG), Moxotó HPP (AL/BA), Pedro Beicht Dam (SP/MG) and Jaguara HPP (SP), beyond aggregates used in civil works of Pernambuco and also a highly reactive basalt from Paraná. The experimental program tested twenty-two rock samples with varied lithology and two local types of cements that had the same clinker (cement A and B). The research uses petrographic analyses, accelerated mortar bar test (NBR 15577), chemical test method (NBR 9774) and accelerated concrete prisms test (based on NBR 15577), to assess the reactivity of the rocks. The results indicate that aggregates show varied expansivity and reactivity among them and sometimes one specific aggregate present different behavior by comparing the results form the test methods performed. This study also discusses the possibility of preventing deleterious expansion from tested aggregates by using the correct type of cement. / Desde 1997, quando as reações expansivas do tipo álcali-agregado ganharam uma maior difusão no âmbito nacional com o primeiro Simpósio sobre Reação Álcali- Agregado (RAA), foi observado um envolvimento mais expressivo de diversos profissionais da área na busca de soluções para este problema. Atualmente, no Brasil, esta manifestação patológica que até então, de uma maneira geral, era exclusiva de obras hidráulicas, já vem sendo observada em estruturas residenciais e comerciais dentro de grandes centros, como os casos relatados da região metropolitana de Recife durante o segundo Simpósio sobre RAA em 2006. No estado de Goiás esta preocupação não foi diferente e, em virtude disto, este trabalho tem por objetivo apresentar a investigação da potencialidade reativa de agregados deste estado comparando com o comportamento de agregados procedentes de algumas obras que representam casos clássicos brasileiros com a UHE Furnas (MG), UHE Moxotó (AL/BA), Barragem de Pedro Beicht (SP) e UHE Jaguara (SP), além de agregados utilizados em obras civis de Pernambuco e um basalto altamente reativo do Paraná. Foram, portanto, selecionados vinte e dois agregados com litologias variadas para este trabalho. A utilização da técnica de petrografia e do método acelerado em barras de argamassa (NBR 15577) foram objeto de estudo da pesquisa, incluindo a análise dos agregados por meio do método químico (NBR 9774) e pelo método dos prismas de concreto (NBR 15577), adaptado na versão acelerada. Foram empregados dois tipos de cimento de mesmo clínquer (cimento A e B) procedentes do estado de Goiás. Os resultados indicaram potencialidades reativas variadas entre os agregados e comportamentos distintos entre alguns métodos de ensaio para o mesmo agregado, bem como a viabilidade do combate da RAA, dependendo do cimento empregado.

O objetivo desse trabalho foi investigar as relações entre a durabilidade e as diversas configurações dos componentes de uma célula a combustível do tipo PEM por meio de Testes de Durabilidade de Longa Duração. Foram comparados três tipos de geometria de fluxo, duas espessuras de membranas poliméricas e dois níveis de cargas de platina. Em diversos aspectos, a geometria de canais de fluxo do tipo serpentina se mostrou superior aos demais. Em relação às membranas, as do tipo Nafion 212 se mostraram bastante frágeis e suscetíveis ao crossover de H2, apesar de fornecerem maior potência elétrica que as membranas Nafion 115, as quais exibiram maior durabilidade. No que diz respeito à carga de platina nos eletrodos, verificou-se que os eletrodos preparados com 0,1 mg Pt cm-2 perderam, proporcionalmente, mais área eletroquimicamente ativa que aqueles preparados com 0,4 mg Pt cm-2, mas, ao mesmo tempo, apresentaram as menores taxas de perdas irreversíveis de desempenho. As análises por diversas técnicas eletroquímicas indicaram que os aumentos das resistências ôhmicas e de transporte de massas são os fatores que mais contribuem para as perdas irreversíveis de desempenho, enquanto que o aumento da resistência de transporte de cargas devido ao encharcamento dos eletrodos é o principal responsável pelas perdas reversíveis de desempenho. A proporção de ionômero na camada catalítica foi investigada e verificou-se que, apesar de facilitar para que ocorram perdas reversíveis de desempenho, a maior proporção de ionômero na camada catalítica contribuiu em mitigar a degradação do MEA. Por fim, observou-se que a qualidade do contato entre os eletrodos e a membrana tem grande contribuição na durabilidade das células a combustível do tipo PEM. / The aim of this work was to investigate the relations between durability and the several Proton Exchange Membrane Fuel Cell (PEMFC) setups via long-term durability tests. Comparisons were made with three types of flow field designs, two polymeric membranes thicknesses and two platinum loadings. In many aspects, the serpentine flow field design has presented better results than the others. Regarding the membranes, Nafion 212 has shown to be very fragile and susceptible to H2 crossover, although it provides more electrical power than the Nafion 115 membrane which exhibited better durability. Concerning the platinum loading, the electrodes prepared with 0.1 mg Pt cm-2 have lost proportionally more electrochemical surface area than the ones prepared with 0.4 mg Pt cm-2 but at the same time, the electrodes with the lowest platinum load presented lower irreversible performance loss rate. The analyses made by several electrochemical techniques have indicated that the raise of the ohmic and mass transport resistances are the factors that most contribute to the irreversible performance loss, meanwhile the charge transport resistance due to the electrodes flooding is the main responsible for the reversible performance loss. The proportion of ionomer in the catalytic layer was studied and it was possible to infer that the highest ionomer proportion contributes to mitigate the MEA degradation, although it facilitates the reversible performance loss occurrence. Finally, it was observed that the contact quality of the electrodes and the membrane has remarkable influence on the PEMFCs durability.

O tema desta pesquisa consiste no desenvolvimento das técnicas de aplicação da madeira de reflorestamento como base na construção habitacional de interesse social. Considera-se suas potencialidades para a realização de uma arquitetura que seja socialmente justa, tecnicamente viável, e acessível economicamente através de uma sistemática por autoconstrução. A pesquisa apresenta, de maneira geral, o estudo e sistematização de tecnologias construtivas em madeira, aplicadas na região sul do país, em especial na cidade de Florianópolis/SC. Buscam-se, portanto, indicadores de desempenho no processo de produção da habitação, para contribuir no aperfeiçoamento dos sistemas construtivos, do ponto de vista da durabilidade, e também na proposição de novas alternativas. / The subject of this research consists of the development of the techniques of application of the reforestation wood as base in the social housing. Considering its potentialities for the accomplishment of an architecture that is socially joust, technical viable, and accessible economically through a systematics for self-building. The research intends to present, in a general way, the study and systematization of constructive technologies in wood, applied in the south region it country, in special in the city of Florianópolis/SC. Searching pointers of performance in the process of production of the habitation, to contribute in the perfectioning of the constructive systems, it point of view of the durability, and also in the proposal of new alternatives.

Pasta de cimento é um material comum em repositórios para rejeitos radioativos, atuando como material estrutural e de imobilização. Sua utilização como material de preenchimento em um repositório tipo poço tubular profundo para fontes seladas, no entanto, requer um maior tempo de vida útil do material. O conhecimento de seu comportamento em longo prazo é necessário para garantir a segurança da instalação em milhares de anos. O presente trabalho avaliou as alterações na pasta de cimento induzidas por fatores de degradação, como ataque de agentes agressivos, alta temperatura e presença de campo de radiação. Corpos de prova (cps) de pasta de cimento foram submetidos a ensaios acelerados de degradação e os efeitos deletérios foram avaliados por meio de ensaios de resistência mecânica, variação dimensional, lixiviação/penetração de íons, DRX, TGA e MEV. Observou-se que a hidratação dos cps foi beneficiada pela imersão (em água destilada ou em solução salina) e alta temperatura, resultando em uma resistência maior. O armazenamento à seco prejudicou a hidratação, mantendo a resistência mais baixa. O tempo de imersão e a irradiação não foram capazes de alterar a mineralogia e a resistência da pasta de cimento. / Cement paste is widely used in repositories for radioactive wastes, acting as structural and immobilization material. However, its use as backfill material in boreholes for sealed sources requires a longer service life of this material. The assessment of the cement paste behavior in long term is needed to improve the confidence that the material will perform as required during the service life of the facility. This research evaluated the changes in cement paste induced by degradation parameters. Portland cement paste specimens (cps) were submitted to accelerated degradation tests and the damage effects was evaluated by mechanical strength, variation of sample mass and volume, leaching/penetration of ions, XRD, TGA and SEM. It was observed that cps hydration was benefited by immersion (in distilled water or salt solution) and high temperatures, resulting in a higher strength. Dry storage, however, influenced the hydration process and maintained strength lower. Time of treatment and irradiation were not able to alter mineralogy and durability of cement paste.

This present study benchmarked the chloride resistance of concretes mixes at the limit state of BS 8500-1:2006 using the newly published CEN TS12390-11. Of the three allowed methodologies, the immersion test was carried out. At least two water-cement ratios were produced for each mix design to enable normalisation of the results. The performance of concrete was compared on the basis of equal compressive strength, i.e. 40 and 50 N/mm2 and an equal water-cement ratio of 0.45. In addition to the CEN TS 12390-11:2010, rapid test methods NT Build 492 and a steady-state migration test UNE 83987:2009 were also conducted. Selected concretes were also tested for cyclic wetting in artificial sea water and evolution of chloride diffusion over the test period. The ageing factor of concrete mixes, which describes the development of diffusion coefficient (D) from the unsteady to steady-state determined from this research was compared with those reported in The Concrete Society Technical Report 61. Test specimens for highway exposure were also produced for future research work. CEN has just agreed and published (at the time of the writing of this thesis) a test methodology for chloride resistance as a technical standard (CEN, 2010). The test method underpins the equivalent durability performance approach. Therefore, the use of this test was investigated in terms of evolution of the chloride diffusion, and effect of cyclic wetting and drying in artificial seawater exposure. As the test method is slow, (3 months to complete), other rapid test methods were also studied on the same specimens. The results from these tests were compared to look for the possibility of having a faster test methodology for chloride durability. Overall, the results showed that concrete mixes at the limiting value of BS 8500-1:2006 have a wide range of performance between 0.3 × 10-12 m2/s and 20 × 10-12 m2/s regardless of the test methods. Ranking of concrete according to performance shows that this changes with age. This is the same for all test methods although the rate of change is different between different test methods. However, the ranking of concrete at equal compressive strength and equal water-cement ratio follows the general order of (from best to worst) ggbs> fly ash> silica fume> limestone> CEM I. It was also postulated that there is a limit to the benefit of reducing water-cement ratio to improve durability. This is because of at very low water cement ratio, concrete may develop autogenous cracking that is detrimental to the porosity. Using the CEN TS 12390-11:2010 it was found that CEM I, fly ash and silica fume mixes follows the same ageing factor proposed by Concrete Society Technical Report 61 although ggbs shows a different ageing factor. The improvement of ggbs quality was attributed to this change. It was also found that 90 days test duration was optimum as a shorter period risks giving a non stable diffusion rate whilst longer than 90 days shows insignificant change in Dnss values. Exposure of selected concrete specimens to cyclic wetting and drying in artificial seawater elevated to 1 M NaCl equivalent shows reduced chloride diffusion. However, the mechanism controlling this is not clear. The thesis showed that some of the limiting value requirement for BS 8500-1:2006 does not meet the durability requirements for chloride resistance. There are some concrete mixes recommended that performs poorly in testing. The research reported also provides further understanding of the new CEN TS 12390-11:2010 in terms comparative ranking of cements up to the point of comparative performance between other tests methods. Validation of the ageing factor for chloride durability is also provided as well as the need for updates in the age factor values due to changes in the nature of cements.