O aproveitamento de fibras de origem vegetal, como reforço de matrizes inorgânicas frágeis à base de cimento, é uma alternativa que tem despertado interesse ao redor do mundo pelas suas vantagens a nível econômico, social e ambiental. Porém, seu uso apresenta limitações em relação à baixa durabilidade apresentada por este material de reforço nos compósitos, refletida na perda de resistência das fibras celulósicas degradadas pelo ambiente alcalino da matriz e na instabilidade dimensional-volumétrica. Como alternativa para esse problema, pesquisas têm mostrado que é possível implementar mecanismos que modifiquem certas propriedades das fibras celulósicas antes de serem incorporadas como reforço na matriz cimentícia. Dentro desse contexto, este estudo aplicou e avaliou o efeito do tratamento de hornificação, que consta de quatro ciclos de secagem e umedecimento, sobre polpas celulósicas de eucalipto e pinus branqueadas e não branqueadas, como processo para otimizar as suas características e permitir uma maior durabilidade e desempenho dos compósitos de cimento reforçado. Foram determinadas e analisadas as características químicas, físico-mecânicas, morfológicas e microestruturais das polpas antes e após o processo de hornificação. Posteriormente, em uma segunda etapa do trabalho, foram produzidos compósitos cimentícios reforçados com polpas tratadas e não tratadas e realizada a avaliação de suas propriedades termo-físico-mecânicas, microestruturais e de durabilidade após cura térmica e 200 ciclos de envelhecimento acelerado. Os resultados indicam que o tratamento de hornificação nas fibras provocou a redução dos teores de retenção de água, não gerou diminuição significativa na viscosidade ou índice de cristalinidade e foram observadas mudanças morfológicas em relação ao colapso da fibra e maior rugosidade da sua superfície. Em relação ao desempenho das propriedades físicas dos compósitos com cura térmica ou após envelhecimento acelerado não foi identificada influência significativa das fibras de reforço tratadas, quando comparadas com não tratadas. Considerando as propriedades mecânicas, foram observadas melhorias na energia especifica de compósitos submetidos à cura térmica com fibras tratadas, destacando-se as polpas de eucalipto não branqueado tratadas como a fibra de reforço, com os melhores valores de energia especifica e módulo de ruptura. Após o ensaio de envelhecimento acelerado foi observado uma queda nas propriedades mecânicas de interesse dos compósitos para todos os tipos de fibras tratadas e não tratadas, indicando uma deterioração das polpas e perda da capacidade de reforço ao longo do tempo. Os resultados de condutividade térmica indicam que o fibrocimento com fibras hornificadas apresenta um desempenho térmico que favorece sua aplicação em coberturas de instalações zootécnicas. / The use of vegetable fibers as reinforcement of cement based inorganic matrices, is an alternative that has attracted attention around the world for its economic, social and environmental benefits. However, their use has limitations with respect to low-term reinforcement capacity in composites, reflected in the strength loss of cellulosic fibers which are degraded by the alkaline environment of the matrix and the volumetric-dimensional instability. As an alternative to this problem, several researches have showed that it is possible to implement mechanisms that modify certain properties of cellulosic fibers before their incorporation as cement matrix reinforcement. In this context, this study applied and evaluated the effect of the treatment of hornification, which consists of four drying and wetting cycles on bleached and unbleached eucalyptus and pine pulps, as a process to optimize their characteristics and allow a greater durability and performance of the reinforced cement composites. Chemical, physical-mechanical, morphological and microstructural characteristics of the pulp were determined and analyzed before and after hornification process. Later, in a second stage, cement composites reinforced with treated and untreated pulp were produced and the evaluation of its thermo-physical and mechanical properties, microstructural and durability after thermal curing and 200 cycles of accelerate aging ware assessed. The results indicate that the treatment of hornification on the fibers induced reduction of water retention values, did not cause significant decrease in viscosity or crystallinity index and morphological changes were observed regarding to the collapse of the fiber and its surface roughness increased. In relation to the physical properties of the composites with thermal curing or after accelerated aging not significant influence of treated reinforcing fibers was identified, when compared with untreated. Considering the mechanical properties improvements in specific energy was observed determined for composites subjected to thermal curing with treated fibers, highlighting the treated unbleached eucalyptus as reinforcing fiber, with the best specific energy and modulus of rupture values. After the accelerated aging a decrease in the mechanical properties of the composites was observed for all types of treated and untreated fibers indicating a deterioration of pulp and a loss of its capacity of reinforcement over time. The results of thermal conductivity indicated that the fibercements with hornificated fibers have a thermal performance that would favor its application in livestock roofing facilities.

As estruturas de concreto, especialmente as pontes de concreto, estão sujeitas a um conjunto de ações que leva ao seu envelhecimento devido aos processos de deterioração, muitas vezes deixando de responder às exigências para as quais foram projetadas. Tal situação, em muitos casos, é agravada pela falta de conhecimento dos processos e mecanismos de degradação assim como o uso de técnicas tradicionais para inspeção de estruturas, estas muitas vezes se mostram limitadas quando são aplicadas isoladamente. Este trabalho mostra uma comparação entre a inspeção visual (usada há décadas) e a aplicação de métodos de ensaios não destrutivos e semi-destrutivos na avaliação da condição estrutural atual de pontes. Enquanto a inspeção visual mostra uma condição qualitativa, os métodos de ensaios não destrutivos são quantitativos e apresentam o potencial de determinar os danos no interior da estrutura que não são visíveis a olho nu. Portanto, visando alertar para o problema da degradação das pontes, busca-se integrar a inspeção visual com a avaliação através do uso de métodos de ensaio. Assim, neste trabalho é feito um estudo de caso da ponte sobre o rio Jaguari. Este estudo visa determinar a condição atual da estrutura através de ensaios não destrutivos e semi-destrutivos, estabelecendo uma correlação entre os resultados destes ensaios e a avaliação da inspeção visual. Dessa forma, procura-se apresentar uma alternativa na avaliação de pontes de concreto. / Concrete structures, particularly concrete bridges, are subjected to a set of actions that leads to aging due to the processes of deterioration, and many times these structures do not respond to the demands for which they have been designed. This situation, in many cases, is exacerbated by lack of knowledge of processes and mechanisms of degradation and by the use of traditional techniques for inspection of structures, these techniques are limited when applied alone. This work shows a comparison between the visual inspection (used for decades) and the application of nondestructive testing methods and semi-destructive on the evaluation of current structural condition of bridges. While visual inspection shows a qualitative condition, the methods of nondestructive testing are quantitative and have the potential to determine the damage inside the structure that are not visible with a simple view. Therefore, in order to draw attention to the problem of deterioration of bridges, we seek to integrate the visual inspection with the assessment through the use of test methods. Thus, in this work a case study of the bridge about the river Jaguari is done. This study aims at determining the current condition of the structure through nondestructive and semi-destructive methods, establishing a correlation between the results of these tests and the evaluation of visual inspection. We seek to present an alternative in the assessment of concrete bridges.

A durabilidade dos edifícios em concreto armado só pode ser alcançada se for atendido um conjunto de requisitos e critérios nas etapas de projeto, execução e manutenção, nas quais os materiais envolvidos precisam ser adequadamente especificados, produzidos e empregados, de acordo com as respectivas rotinas dessas etapas. Assim, o requisito genérico de proteção das armaduras de aço carbono, para a durabilidade de estruturas, é contemplado por vários critérios, desde a etapa de projeto. Esta dissertação trata dos critérios pertinentes à qualidade do concreto e visou contribuir para a evolução de procedimentos para o controle tecnológico de concretos estruturais de cimento Portland, em atmosferas marítimas e urbanas, em clima tropical, com vistas à proteção de armaduras de aço carbono. O programa experimental estudou três lotes diferentes de concretos estruturais, semelhantes quanto a especificações básicas de abatimento: 10 ± 2 cm, de fck 30 MPa e para ambiente classe III da NBR 6118 (2003). O objetivo foi caracterizar e analisar a influência de propriedades físicas do estado fresco sobre o estado endurecido de concretos, dentro da faixa de consistência citada, com ênfase nas propriedades relacionadas ao teor de ar das misturas e suas respectivas resistências à carbonatação e ao ingresso de íons cloreto. A amostragem, os ensaios no estado fresco e a moldagem dos corpos-de-prova foram realizados durante três concretagens conduzidas em duas obras de edifícios de múltiplos andares, na cidade de João Pessoa/PB. As composições e a produção dos lotes ficaram a cargo da central dosadora e fornecedora do concreto em cada obra. O lote inicial serviu para o treinamento da equipe, em campo e laboratório, com amostragem de seis caminhões. Os outros dois lotes, identificados como 1 e 2, foram caracterizados em condições bastante semelhantes, sempre pela mesma equipe, e representados pela amostragem de cinco e seis caminhões, respectivamente. As propriedades medidas no estado fresco foram: abatimento do tronco de cone pela ABNT NBR NM 67 (1998); teor de ar por método pressométrico da ABNT NBR 47 (2002); massa específica pela ABNT NBR 9833 (2008); relação água/materiais secos por analogia à ABNT NBR 9605 (1992); e compactabilidade dos concretos adensado e não adensado, por adaptação da BS EN 12350-4 (2008). Para o estudo das propriedades no estado endurecido, os corpos-de-prova eram cilíndricos, com 10 cm de diâmetro e 20 cm de altura, e foram maturados por dois métodos adaptados do Tipo A da ASTM C 684 (1999). Certas propriedades foram ainda caracterizadas para condições normais de cura da ABNT NBR 5738 (2003). As propriedades estudadas no estado endurecido foram: resistência à compressão pela ABNT NBR 5739 (2007); resistência à tração por compressão diametral pela ABNT NBR 7222 (1994); absorção de água por capilaridade pela ABNT NBR 9779 (1995); absorção de água total e índice de vazios pela ABNT NBR 9778 (2005); resistência à carbonatação em câmara com CO2 (5%; UR 65 + 10 %; 23 + 3 °C); e resistência à penetração de cloretos e CO2, por três ciclos de um dia de molhagem e 27 dias de secagem, entre sete e 91 dias. De modo complementar, foram moldados corpos-de-prova específicos de aço e concreto, para medidas de potencial de circuito aberto, com vistas à continuidade de pesquisas sobre envelhecimento acelerado. A maioria das propriedades foram medidas por duas repetições, constando os resultados individuais em apêndices. A análise inicial dos resultados dos três lotes foi descritiva e resumiu em tabelas o valor médio, desvio padrão, valor máximo, valor mínimo, a amplitude e o coeficiente de variação de cada lote. As propriedades de cada lote também foram comparadas por análise de variância e, ao final, foram correlacionadas de modo conjunto, independentemente do lote de origem. Nesse caso, foram destacadas as melhores correlações entre propriedades, independentemente dos materiais constituintes de cada concreto. Entre as propriedades do estado fresco, destacaram-se as seguintes: a) o abatimento do tronco de cone apresentou correlação forte e inversa (r² = -0,802, para lotes 1 e 2) com resistência à compressão após um dia de cura acelerada em temperatura moderada, em método similar ao Tipo A da ASTM C 684 (1999); b) o teor de ar pelo método pressométrico apresentou correlações de razoáveis a fortes com a resistência à compressão a 28 dias (r² = -0,698, para lotes 1 e 2), com a resistência à tração por compressão diametral por cura acelerada a sete dias (r² = -0,818, para lotes 1 e 2), com a profundidade de carbonatação em câmara de CO2 (r² = 0,699, para lotes 1 e 2) e com a profundidade de penetração de cloretos por três ciclos de imersão e secagem (r² = 0,625, para lotes 1 e 2); c) as medidas de compactabilidade do concreto adensado, ainda que realizadas em condições de campo, apresentaram várias correlações moderadas com outras propriedades do estado fresco e endurecido. No estado endurecido, destacaram-se as seguintes correlações: a) r² da ordem de -0,75 para a resistência à compressão a um dia dos concretos dos lotes 1 e 2, com cura acelerada de 0/24 horas em temperatura moderada, e a profundidade de carbonatação em câmara de CO2 (5%) e a de penetração de cloretos por três ciclos de imersão e secagem, ambas analisadas a 91 dias, tendo os corpos-de-prova recebido cura inicial acelerada de 24/48 h, em temperatura moderada, seguida de imersão normal por até sete dias; b) r² de -0,682 entre a resistência à tração por compressão diametral, com cura acelerada de 24/48h em temperatura moderada seguida de cura normal por até sete dias, e a profundidade de ingresso de íons cloreto, para os três lotes submetidos aos ciclos citados; c) valores de r² entre 0,521 e - 0,561 para as correlações entre a absorção de água por capilaridade, em corpos-de-prova submetidos à cura inicial acelerada em temperatura moderada por 24/48 h e em temperatura normal por até sete dias, e a resistência à carbonatação para os lotes submetidos aos ciclos citados. Assim, esta pesquisa conclui e propõe que, além do teor de ar no estado fresco, as resistências à compressão e à tração por compressão diametral entre um e sete dias, por cura acelerada do Tipo A da ASTM C 684 (1999) ou por duração adaptada da mesma, sejam propriedades que passem a ser avaliadas em concretos, com vistas a melhorar e controlar a sua resistência a agentes agressivos. Nesta pesquisa, a microestrutura nas primeiras idades do concreto mostrou ser mais determinante da rede de conexão de poros e do transporte de agentes agressivos do que a microestrutura em idades mais avançadas de hidratação; e trabalhos futuros devem confirmar esta interpretação. Espera-se que estes resultados possam estimular novas práticas de qualificação de concretos em estudos de dosagem ou no ato do recebimento de concretos pré-misturados, especialmente em ambientes mais agressivos às armaduras, com vistas à futura evolução de procedimentos da ABNT NBR 12655 (2006). / Durability of reinforced concrete buildings can only be achieved if a set of requirements and criteria is met in the design, execution and maintenance phases, in which the materials must be properly specified, manufactured and employed, according to the respective procedures of these phases. Therefore, the general requirement of protection of carbon steel reinforcements, for structural durability, is contemplated by several criteria as early as the design phase. This thesis addresses the relevant criteria concerning concrete quality and its objective was to contribute to the evolution of technological control procedures for Portland cement structural concretes, in urban and maritime atmospheres in tropical climate, aiming at the protection of carbon steel reinforcements. The experimental program studied three different batches of structural concrete that were similar in terms of slump test basic specifications: 10 ± 2 cm, fck = 30 MPa and class III of ABNT NBR 6118 (2003) environmental classification. The goal was to characterize and analyze the influence of physical properties of fresh concrete on hardened concrete, within the previously mentioned consistency range, with emphasis on those properties related to air content of the mixtures and their respective carbonation and chloride ion penetration resistances. Sampling, fresh concrete tests and specimen molding were conducted during three cast-in-place concretes in two construction sites of multi-storey buildings in the city of João Pessoa, state of Paraíba, in Brazil. The batch plant supplying the concrete for each construction site was responsible for batch composition and production. The initial batch was used to train the team, in the field and laboratory, with a sample of six trucks. The other two batches, identified as 1 and 2, were characterized under very similar conditions, always by the same team, and the samples consisted of five and six trucks, respectively. The properties measured in fresh concrete were: slump test according to Brazilian norm ABNT NBR NM 67 (1998); air content by the pressure method of ABNT NBR 47 (2002); bulk density according to ABNT NBR 9833 (2008); water/dry material ratio by analogy with ABNT NBR 9605 (1992); and compactability of compacted and non-compacted concretes, by adaptation of BS EN 12350-4 (2008). In order to study the properties of hardened concrete, the specimens were cylindrical, measuring 10 cm in diameter and 20 cm in height, and were matured by using two methods adapted from Type A of ASTM C 684 (1999). Some properties were also characterized for normal curing conditions according to ABNT NBR 5738 (2003). The properties studied in hardened concrete were: compressive strength according to ABNT NBR 5739 (2007); splitting tensile strength as per ABNT NBR 7222 (1994); capillary water absorption according to ABNT NBR 9779 (1995); water absorption by immersion and void ratio following ABNT NBR 9778 (2005); carbonation resistance in CO2 chamber (5%; 65 + 10 % RH; 23 + 3 °C); and chloride and CO2 penetration resistance, using three one-day wet and 27-day dry cycles, between seven and 91 days. As a complement, specific steel and concrete specimens were molded to measure open circuit potential, aiming at the continuity of researches on accelerated ageing. Most properties were measured twice and the individual results are presented in appendices. Preliminary analysis of results from the three batches was descriptive and summarized in tables the mean value, standard deviation, maximum value, minimum value, amplitude and coefficient of variation for each batch. The properties of each batch were also compared using analysis of variance and, at the end, were correlated as a whole, regardless of the batch of origin. In this case, the best correlations among properties were highlighted, regardless of the materials used in each concrete. Among the properties of fresh concrete, the following are noteworthy: a) the slump test presented strong and inverse correlation (r² = -0.802, for batches 1 and 2) with compressive strength after one day of accelerated curing at moderate temperature, using a method similar to Type A of ASTM C 684 (1999); b) air content in the pressure method presented reasonable to strong correlations with compressive strength at 28 days (r² = -0.698, for batches 1 and 2), with splitting tensile strength with accelerated curing at seven days (r² = - 0.818, for batches 1 and 2), with carbonation depth in CO2 chamber (r² = 0.699, for batches 1 and 2) and with chloride penetration depth after three immersion-drying cycles (r² = 0.625, for batches 1 and 2); c) compactability measurements of compacted concrete, despite being taken in field conditions, presented several moderate correlations with other properties of fresh and hardened concrete. In hardened concrete, the following correlations should be highlighted: a) r² was -0.75 for compressive strength at one day of the concretes from batches 1 and 2, with 0/24- hour accelerated curing at moderate temperature, and carbonation depth in CO2 chamber (5%) and chloride penetration depth after three immersion-drying cycles, both analyzed at 91 days, after the specimens underwent 24/48-hour initial accelerated curing at moderate temperature, followed by normal immersion for up to seven days; b) r² was -0.682 between splitting tensile strength, with 24/48-hour accelerated curing at moderate temperature followed by normal curing for up to seven days, and chloride ion penetration depth, for the three batches submitted to the aforementioned cycles; c) r² values between 0.521 and - 0.561 for the correlations between capillary water absorption, in specimens submitted to initial accelerated curing at moderate temperature for 24/48h and at normal temperature for up to seven days, and carbonation resistance for the batches submitted to the aforementioned cycles. Therefore, this research concludes and proposes that, besides air content in fresh concrete, compressive strength and splitting tensile strength between one and seven days, using accelerated curing of Type A of ASTM C 684 (1999) or for a duration adapted from that norm, are properties that should be evaluated in concrete, with the purpose of improving and controlling resistance to aggressive agents. In this research, the microstructure of the early ages of concrete proved to be more determinant of the pore structure connection and of the transport of aggressive agents than the microstructure at later ages of hydration; and future studies should confirm this interpretation. It is expected that these results will encourage new practices for the qualification of concrete in mixture proportion studies or when ready mixed concrete is received at construction sites, especially in environments that are more aggressive to reinforcements, with a view to developing future procedures of ABNT NBR 12655 (2006).

A madeira quando usada em contato direto com o solo, é atacada por agentes biológicos, principalmente fungos apodrecedores e cupins subterrâneos. Uma maneira de ampliar as possibilidades de utilização das espécies de baixa durabilidade natural, como as do gênero Pinus, é através do tratamento químico preservante. No entanto, faltam informações disponíveis que indiquem a durabilidade destas madeiras em serviço. A fim de se determinar a durabilidade da madeira do gênero Pinus tratada com preservantes, a Escola Superior de Agricultura "Luiz de Queiroz" e o Instituto Florestal do Estado de São Paulo instalaram, em 1980, campos de apodrecimento segundo método de ensaio sugerido pelo IUFRO (International Union of Forestry Research Organizations). As espécies utilizadas no ensaio foram o Pinus elliottii Engl. var. elliottii, o Pinus caribaea Mor. var. hondurensis, B & G., o Pinus oocarpa Shied e o Pinus kesiya Royle ex Gordon; tratadas com os preservantes CCA tipos A, B e C, CCB e pentaclorofenol, em cinco níveis de retenção. Em continuidade ao projeto, foi inspecionado o campo instalado na Estação Experimental de Mogi-Guaçu, visando avaliar o estado de sanidade do material. A análise dos resultados obtidos até o momento, 21 anos de exposição demonstrou que não houve diferença no comportamento entre espécies. Os índices de comportamento mais altos (maior expectativa de durabilidade) correspondem aos tratamentos com CCA tipos A, B e C em retenções acima de 7,5 kg/m3. Mesmo para os tratamentos que apresentaram os menores índices de comportamento (CCA tipo C com retenções de 5,0 kg/m 3 e CCB com 5,9 kg/m 3 ), é prevista uma durabilidade de 30 anos em serviço. / When used in ground contact, wood is deteriorated by biological agents, as root fungi and subterranean termites. A way to increase the use of wood species of low natural durability, as the Pinus lumber, is the preservative treatment. However, there is a lack of information indicating the durability of treated wood. In order to determine the durability of preservative treated Pinus lumber, the Escola Superior de Agricultura "Luiz de Queiroz" and the Instituto Florestal do Estado de São Paulo installed, in 1980, fields tests according to the IUFRO (International Union of Forestry Research Organizations). The species under test were Pinus elliottii Engl. var. elliottii, Pinus caribaea Mor. var. hondurensis, B & G., Pinus oocarpa Shied and Pinus kesiya Royle ex Gordon; treated with the preservatives CCA types A, B and C, CCB and pentachlorophenol, in five retention levels. In continuity to the project, the material installed in the test site of Experimental Station of Mogi-Guaçu was inspected, to evaluate the degree of attack. The analysis of results obtained till now, after 21 years of exposure, demonstrated that there are no differences in durability related with species. The highest performance index (longer durability expectation) correspond to treatments with CCA types A, B and C in retentions above 7,5 kg/m3. Even for the treatments that presented lowest performance index (CCA type C with retention of 5,0 kg/m 3 and CCB with 5,9 kg/m 3 ), the durability expectation is 30 years in service.

Le traitement thermique du bois est une industrie qui se développe depuis une dizaine d'années, mais est freinée par l'absence de certifications. Le bois traité thermiquement est un matériau nouveau dont les propriétés mécaniques et de durabilité sont modifiées grâce aux réactions chimiques des biopolymères avec l'apport de chaleur. Cette étude vise à trouver des indicateurs non destructifs permettant d'apporter des garanties sur les performances des bois chauffés. La caractérisation de plusieurs essences chauffées chez Bois Durables de Bourgogne permet d'abord d'apprécier l'influence du traitement thermique sur des échantillons variés avec de petites éprouvettes sans défaut. Cette première campagne montre une amélioration prononcée de la durabilité permettant des usages en classe d'emploi 4, et des variations de propriétés mécaniques qui dépendent des sollicitations étudiées. Les propriétés apparaissant comme les plus importantes à estimer en vue d'une certification sont celles de la résistance en flexion et de la perte de masse due au traitement thermique, directement reliée à la durabilité grâce aux travaux du LERMAB. A ce stade, l'analyse vibratoire apparaît comme un bon indicateur de l'intensité de traitement. Dans un second temps, l'essence de frêne est étudiée à quatre intensités de traitement entre 170 et 228 °C sur des éprouvettes en dimensions d'emploi. Cette deuxième campagne permet de confirmer que l'analyse vibratoire est un bon indicateur pour la perte de masse, mais ne permet pas cette fois d'estimer la résistance en flexion. La composition élémentaire du bois mis en évidence comme indicateur par d'autres travaux ne semble pas utilisable dans un contexte industriel. En revanche, l'aire sous la courbe de traitement est une mesure globale et disponible qui est bien corrélée avec les valeurs moyennes de résistances en flexion et de pertes de masse. / The heat treatment of wood has been a growing industry in the last decade, but its development is curbed by the lack of certifications. Heat-treated wood is a new material whose mechanical properties and durability are modified by heat transfer and chemical reactions of biopolymers. This study aims at finding non-destructive indicators that can guarantee heat-treated wood quality. The characterization of several species heated by Bois Durables de Bourgogne first enables to assess the influence of heat treatment on various samples using small specimens free from defects. This first approach shows a marked improvement of durability ensuring uses in hazard class 4, and variations of mechanical properties depending on studied reaction. Properties that appear as the most relevant in terms of certifications are bending strength and mass loss due to heat treatment. The latter is directly linked to durability owing to studies previously led by LERMAB. At this stage vibration analysis seems to be a proper way to estimate treatment intensity. In a second part ash wood is studied under four treatment intensity, between 170 and 228 °C on large specimens. This second approach confirms that vibration analysis is an appropriate indicator to estimate mass loss, but does not predict bending strength. Wood elemental composition which has been already highlighted as an indicator by other studies is not suitable for an industrial application. On the other hand the area under the treatment chart is a global measurement which is easily available and well correlated with mean values of bending strength and mass loss.

Mineral and chemical admixtures are used today in almost all concrete mixtures to improve concrete fresh and hardened properties, and to enhance concrete durability. In this study, four mineral and four chemical admixtures were investigated: namely, metakaolin (MK), silica fume (SF), Class F fly ash (FA), blast-furnace slag (BFS), two high-range water reducers (SP), water reducer/retarder (WRD), and air-entrainer (AEA). The objective of this study is to assess the effects of commonly used mineral and chemical admixtures on the durability of the cementitious system. Two durability issues were addressed in this study: the potential of the cementitious system to generate heat, and sulfate durability. The properties studied here included heat of hydration (HOH) measurements using isothermal calorimetry, setting properties, compressive strength, and expansion on exposure to a sodium sulfate solution. X-ray diffraction was used to characterize the as-received materials and explain failure trends. The findings of this study indicate that silica fume inclusion sustains superior durability in comparison to the other mineral admixtures considered here. Replacement levels as low as 10% outperformed the other admixtures studied. Fly ash showed improvement in the workability of the mixes, but had the lowest compressive strength results and might pose challenges when the rate of strength gain is critical. However, Class F fly ash mixtures showed better performance than unblended mixtures when exposed to a sulfate source. Metakaolin mixes showed higher heat evolution among all the mixtures studied here. This can potentially lead to durability concerns, especially when temperature rise is a design concern. Blast-furnace slag also improved the workability of the mixes and the later compressive strength, but had mixed performances when examined for sulfate durability.

This thesis contributes to the debate on what makes peace durable by developing an analytical tool that, based on the current research status on what makes peace agreements last, intends to evaluate peace agreements on their capacity to maintain peace. The research was done through a qualitative desk study, using the Colombian peace agreement which was signed in 2016. The agreement, as it is finally negotiated, is according to the analytical framework estimated to have a reasonably good chance to being durable.

Ce travail de recherches se situe dans le cadre de l’ANR VBD2012-ECO-construction par le Recyclage du Béton (ECOREB). Il vise à lever certains verrous scientifiques afin de rendre possible l’utilisation des granulats issus de la démolition/déconstruction pour élaborer de nouveaux bétons pour le bâtiment. L’ANR ECOREB est en relation avec le PN RECYBETON. Les deux projets interagissent fortement.Cette étude a pour objectif d’évaluer la durabilité des bétons recyclés vis-à-vis du gel/dégel modéré sans sels de déverglaçage. Les bétons ont été élaborés en faisant varier : le taux d’incorporation des granulats recyclés (GR) l’état de saturation des gravillons tout en maintenant la même classe de consistance S4 et la classe de résistance de type C35/45. Un agent entraîneur d’air a été introduit afin d’obtenir des bétons conformes à l’EN 206-1 avec deux teneurs en air occlus 4% et 6%.Dans un premier temps, les propriétés physiques et mécaniques des granulats recyclés (GR) ont été étudiées et comparées à celles des granulats naturels (GN). Les GR manifestent une capacité d’absorption d’eau dix fois supérieure à celle des GN, une résistance mécanique deux fois inférieure et une résistance au gel deux fois inférieure. Cependant ils sont classés non gélifs de catégorie Fdéclaré.. Les faibles propriétés des GR comparées à celles des GN s’expliquent par la présence de l’ancienne pâte de ciment qui entoure les grains originaux et qui est caractérisée par une forte porosité et par un fort réseau de fissures connecté créé lors du concassage du béton parent.Les propriétés physiques (porosité et coefficient d’absorption d’eau) de transfert (conductivité thermique, résistivité électrique et perméabilité) et mécaniques sont fortement impactées par l’incorporation des granulats recyclés de part l’augmentation de la porosité capillaire essentiellement et du réseau des fissures présentes dans les gravillons recyclés. Les relations établies entre les propriétés mécaniques et les propriétés physiques et de transfert ont été établies. L’applicabilité des Euro codes égalementLes formulations avec un taux d’air occlus de 4% sont de classe C30/37 pour tous les taux d’incorporations alors qu’une diminution notable des résistances mécaniques à la compression est observée pour un taux d’air occlus de 6% : le béton de référence devient de classe C16/20. L’incorporation des GR affecte la résistance au gel/dégel des bétons. En utilisant les indicateurs préconisés par la norme NFP 424, le béton sans agent entraineur d’air atteint les critères recommandés au 75ème cycle lorsqu’il est élaboré avec 100% de GR et au 125ème cycle quand seuls les GN sont utilisés. L’entraineur d’air améliore la tenue au gel des bétons. Nous remarquons que les bétons C35/45 30R-30R (30% en volume d’incorporation) avec 4% d’air entrainé présentent le comportement ressemblant à celui du béton référence et respecte les critères de la résistance préconisé par la norme NF P 18-424 et l’EN 206-1.Ce travail a permis également de mettre en place d’autre indicateurs performantielles pour estimer la résistance au gel/dégel des bétons à granulats recyclés. / Development in many sectors has negative environmental effects. In construction sector, there are millions of tonnes of construction and demolition waste (CDW) every year. This CDW has a significant damage on the environment and may endanger its sustainability. To find a conceivable solution for CDW and to preserve the natural resources, particularly the non-renewable ones, worldwide researches on recycled aggregates have been increased in order to investigate their revalorization possibilities in concretes.As many developed countries, France also has introduced legislations and strategies to reduce the environmental effects of CDW. Corresponding to problem of CDW, there are two national project called PN-RECYBETON and ANR VBD2012-ECOREB that deal with how to provide concretes for building field using aggregates provided from CDW.This work aims to determine the durability of recycled aggregate concrete by freeze/thaw cycles. Four types of concrete were prepared by varying the replacement ratio of natural aggregates (NA) by recycled one (RA). The volumetric substitutions rates are respectively 0%, 33%, 55% and 100%, while the concretes mix design were adjusted in order to achieve the same consistency class of S4. Furthermore, we also studied the durability of these concretes varying the air content through an air entraining agent.After characterization of physical and mechanical properties of NA and RA, we found that the water absorption capacity of RA is 10 times greater than that of NA due to a low density. Moreover, the RA presents poor mechanical résistance by LA, MDE and freezing action.These poor performances of RA can be explained by the existence of pores and crack in old cement paste that provided during production process. The microstructure of RA was analyzed by SEM.Regarding to the influence of RA in mix design, with total substitution the density of hardened decrease 17% while the porosity become two times greater than those of natural concrete.In addition, the mechanical properties of studied concretes mix design decreases through the incorporation of RA. Regarding to the transfer properties, the gas permeability of the concrete 100% substitution is 2 times higher than that of reference one. On the other hand, the electric resistivity decreases with increasing of RA content.The Air-Entraining agent has a significant effect on the compressive and the splitting tensile strengths. It is observed that with 6% of air content the mentioned mechanical properties decrease drastically (a diminution higher than 50%). The increase of RAC content in the mixtures decreases their freezing/thawing resistance.The introduction of Air-Entraining agent improves the freezing/thawing resistance of concrete. The air-entrained concrete with 50% and 100% of RA present the poor performance than that of reference concrete via the studied durability indicators. Moreover, the air-entrained concrete C35/45 30R-30R with 4% and 6% of air content show the similar performance as air-entrained control concrete.

Les travaux de cette thèse ont porté sur la caractérisation multi-échelle du polyéthylène(PE) en vue d'évaluer l'impact du vieillissement thermo-oxydatif. Cette étude a apporté un premier élément de réponse quant à l'efficacité de quelques méthodes de dosage des hydroperoxydes. Les résultats obtenus ont révélé une différence des concentrations en hydroperoxydes titrées par iodométrie par rapport à celles titrées par SO2 et MDSC lors de la deuxième période c'est-à-dire lors de la décomposition des hydroperoxydes. Cette différence semble directement reliée à l'apparition de double liaison. Les méthodes de dosage par SO2 et MDSC semblent être plus fiables. A l'échelle macromoléculaire, la chute de la masse molaire en poids Mw jusqu'à une valeur asymptotique de deux traduit des phénomènes de coupures de chaînes liés. A l'échelle microstructurale, l'augmentation de Xc est liée aux phénomènes de recuit et de chimicristallisation responsables de la formation et de l'épaississement des lamelles secondaires respectivement. Lors de la seconde période, l'augmentation de Mw liée à la diminution de Xc est due à la réticulation qui est confirmée par l'apparition des doubles liaisons et l'observation d'un gel lors de la dissolution du PEhd. Ces phénomènes de réticulation ont lieu au sein de la phase amorphe mais également à l'interphase avec la phase cristalline / The work of this thesis focused on the multi-scale characterization of polyethylene (PE) to assess the impact of thermo-oxidative aging. This study provided a first answer about the effectiveness of some hydroperoxides titration. The results revealed a difference in hydroperoxides concentrations titrated by iodometry compared to SO2 and MDSC in the second period that correpond to the decomposition of hydroperoxides. This difference appears to be linked to the occurrence of double bond. Titration methods with SO2 and MDSC seem to be more reliable. On the macromolecular scale, the decrease of the molecular weight Mw up to an asymptotic value of two is related to the chain scission process. On the microstructural scale, the increase of Xc is linked to the annealing and the chimicristallisation process which are responsible of the formation and the thickening of secondary lamellae. During the second period, the increase of Mw is related to the decrease of Xc due to crosslinking, which is confirmed by the occurrence of the double bonds and the observation of a gel during the dissolution of HDPE. These crosslinking phenomenon takes place in the amorphous phase but also in the transition region

La zone d'enrobage des aciers des structures en béton armé est soumise au cours de la vie de l'ouvrage à l'action de divers agents agressifs (ions chlorure, dioxyde de carbone, etc.) qui sont susceptibles d'entraîner la corrosion des armatures. Dans le cadre de la maintenance de l'ouvrage, une réparation du béton dégradé est généralement imposée afin d'assurer l'intégrité et la sécurité de la structure, et d'en allonger la pérennité. Cette étude s'attache à explorer les transferts hydriques qui limitent l'efficacité de la réparation au cours de l'hydratation du mortier de réparation. L'évolution microstructural et les profils hydriques sont obtenus par des techniques non-destructives comme l'imagerie résonance magnétique (IRM) et la gamma-densimétrie (GD) depuis très jeune âge à 28 jours. La durabilité du béton réparé est concernée. L'effet du séchage est évité dans cette étude. Le mortier isolé d'une même formulation est préparé pour la comparaison du comportement d'hydratation avec le mortier de réparation. Des diverses techniques classiques aident de compléter les résultats obtenus par IRM et GD. Donc le système de réparation est désigné. Les transferts hydriques à l'interface sont visualisés pendant la réparation (0 - 28 jours), afin de permettre une exploration en profondeur sur les mécanismes des couplages physico-chimiques. La réparation plus efficace donc est déterminée par cette méthodologie, en étudiant divers matériaux de réparation, divers états de support (saturé ou séché) et divers conditions environnementaux, etc. De plus, après la réparation (1 - 2 mois), la porosité totale est mesurée par GD ou la porosimétrie par l'intrusion de mercure (PIM). La distribution poreuse est aussi examinée par PIM selon la hauteur du système de réparation. Les indicateurs de durabilité (Cl- et CO2) après la réparation (> 2 mois) présentent l'empêchement de pénétration des ions chlorures et un effet non-évident pour la pénétration du dioxyde de carbone. L'évolution est suivie au fur et à mesure pendant la pénétration, afin d'explorer l'efficacité de la réparation qui s'adresse à une vie de service prolongée. Cette méthodologie pourra être appliquée aussi sur des autres systèmes, où il existe des transferts hydriques. Par exemple, une couche de protection en Béton Fibré à Ultra-haute Performance (BFUHP) sur le béton ordinaire. En conclusion, cette méthodologie en combinant des techniques non-destructifs et destructifs, est un outil d'étudier le système de réparation par un moyen systématique et quantitatif. C'est intéressant de comparer des divers cas. L'efficacité de réparation est étudiée afin d'assurer une durabilité à long terme / The coating area of steel reinforced concrete structures is subjected during service life time to various aggressive agents (carbon dioxide, chloride ions, etc.), which causes corrosion of steel rebars. Concerning the maintenance, repair works of degraded concrete cover are generally imposed to ensure its integrity and structural safety, and to extend long-term durability. This research aims in exploring moisture transfers which limit the efficiency of repair work during mortar hydration. Microstructure evolution and water profiles are obtained by non-destructive techniques such as Magnetic Resonance Imaging (MRI) and Gamma-Ray Attenuation (GRA) since casting until 28 days. The durability of repaired concrete is involved after the repair procedure. The effect of drying is avoided in this research. Sealed mortar of the same formula is prepared to compare its hydration performance with the repair mortar. Various conventional techniques help to supplement the results obtained by MRI and GRA. The configuration of designed repair systems is shown. Moisture transfers at the interface between the repair mortar and the old concrete are investigated during the repair procedure (0 - 28 days), which allows exploring the mechanisms of physico-chemical couplings. Efficient repair work can be determined for various repair materials, various substrates (initially-saturated or initially-dried), various environmental conditions, etc. Furthermore, total porosity is measured by GRA or by Mercury Intrusion Porosimetry (MIP) after the repair procedure (1 - 2 months). Pore size distribution (PSD) is also investigated by MIP at different positions within the repair systems. Durability indicators (Cl- and CO2) after the repair procedure (> 2 months) present a prevention of chloride penetration and a non-evident influence on carbonation. Evolution is followed during penetration, in order to explore repair efficiency during prolonged service life time. This methodology could also be applied on various systems where exist moisture transfers. For example, a protective layer of Ultra High Performance Fiber-Reinforced Concrete (UHPFRC) on conventional concrete. In conclusion, this methodology is a tool to investigate the repair systems in a systematic and quantitative way, by combining non-destructive and destructive techniques. It is interesting to compare aforementioned systems. Repair efficiency is investigated in order to ensure a long-term durability