O refinamento dos poros, associado à reação pozolânica e ao efeito filer, reduz a permeabilidade do concreto com cinza de casca de arroz (CCA), o que pode antecipar a sua degradação em altas temperaturas. A literatura mostra que o concreto reidratado em água pode recuperar substancialmente a sua resistência inicial, porém, os estudos sobre a reidratação ao ar e sobre a influência do modo de resfriamento na reidratação são escassos. A pesquisa desenvolvida teve como principal objetivo avançar na análise experimental de concretos convencional e com CCA em altas temperaturas e na reidratação. Na etapa exploratória se avaliou a influência da temperatura de exposição, da adição mineral, do ambiente de acondicionamento, da taxa de aquecimento e do tempo de exposição na resistência à compressão e módulo de elasticidade. Na etapa principal se avaliou a influência do modo de resfriamento, da adição e da idade de reidratação na resistência residual. Complementarmente se utilizou o ensaio de velocidade de pulso ultrassônico (VPU) para avaliar o grau de microfissuração e correlacionar a VPU com as propriedades mecânicas residuais. Na etapa exploratória concluiu-se que a adição, a temperatura, a taxa de aquecimento e o tempo de exposição influenciaram significativamente os resultados. O concreto com CCA cristalina apresentou pior desempenho em altas temperaturas. O concreto com CCA amorfa apresentou desempenho ligeiramente inferior ao concreto convencional em 200°C, devido ao efeito da poro-pressão. No entanto, ambas as CCA podem ser alternativas viáveis considerando sustentabilidade. Na etapa principal, o resfriamento brusco com água provocou maior redução na resistência devido aos gradientes térmicos, porém, permitiu maior recuperação logo nos primeiros sete dias de reidratação. Apesar da recuperação parcial, a resistência ao fim de 154 dias foi inferior a 40% do valor inicial. Nas análises térmicas e de DRX foi possível observar nos concretos resfriados com água a recristalização dos aluminatos de cálcio, do C-S-H e da portlandita, em maior grau no concreto convencional. Foi possível observar correlações fortes entre as variáveis de resposta na etapa exploratória, porém, o mesmo não ocorreu na etapa principal, devido à fissuração e presença de água nos poros. / The pore refinement, associated with the pozzolanic reaction and the filler effect, reduces the permeability of blended concrete with rice husk ash (RHA), which can anticipate its degradation at high temperatures. The literature shows that concrete rehydrated with water can recover substantially its initial strength, but studies on rehydration in air and on the influence of the cooling method on rehydration are scarce. The main objective of this research was to evaluate the performance at high temperatures and in rehydration of conventional and blended concretes with RHA. In the exploratory stage, the influence of exposure temperature, mineral admixture, conditioning environment, heating rate and exposure time on residual strength and modulus of elasticity of heated concrete was evaluated. In the main stage, the influence of cooling method, mineral admixture and time of rehydration in an unsaturated environment on residual strength of concrete was evaluated. The ultrasonic pulse velocity test (UPV) was used to evaluate the degree of micro cracking of concrete and to correlate the UPV with residual strength and modulus. In the exploratory stage it was concluded that mineral admixture, temperature, heating rate and time of exposure significantly influenced the results. In general, concrete with partially crystalline RHA presented the worst performance at high temperatures. Concrete with amorphous RHA presented worse performance than conventional concrete only at 200°C, due to the pore-pressure effect. Despite these results, RHA can be a viable option considering sustainability and high temperatures performance. In the main stage, the rapid cooling with water caused a greater reduction in strength, due to thermal gradients, however, caused a greater strength recovery in the first seven days of rehydration. Despite this partial recovery, the final strength of both concretes after 154 days of rehydration was less than 40% of the initial value. In water-cooled concretes thermal and XRD analyzes show recrystallization of the calcium aluminates, C-S-H and portlandite, to a greater degree in conventional concrete. In the exploratory stage it was possible to observe strong correlations between the independent variables; however, the same did not occur in the main stage, due to cracking and to the presence of water in the pores.

Dans le cadre du stockage des déchets radioactifs en couches géologiques profondes (argilite du Callovo-Oxfordien), des bétons à faible alcalinité et à faible chaleur d'hydratation référencés "bas pH " ont été élaborés. L'utilisation de ces types de béton permet de limiter la dégradation des propriétés confinantes du matériau argileux type bentonite. Deux bétons bas pH à base de liants ternaires ont étudiés : un composé de ciment, fumée de silice et cendres volantes (TCV) et l'autre composé de ciment, fumée de silice et laitier moulu de haut fourneau (TL). L'objectif de l'étude est d'analyser le comportement de ces matériaux pour s'assurer : d'une mise en œuvre correcte à l'échelle industrielle, d'une bonne tenue chimique et mécanique dans le temps et d'un confinement performant. Le programme expérimental comprend la caractérisation physico-chimique et mécanique de ces matériaux à forte teneur en additions et est couplé à de la modélisation dans le but, in fine, de disposer d'outils permettant de prédire leur comportement au sein de l'ouvrage. Les résultats montrent qu'un cobroyage des constituants du liant permet d'améliorer la réactivité du liant et de s'assurer d'une bonne robustesse des formules de béton. La condition essentielle de l'obtention d'un pH de leur solution interstitielle de 11 est assurée dès 28 jours. Les bétons peuvent être considérés à faible chaleur d'hydratation du fait des échauffements rencontrés à court terme. A long terme, de hautes performances mécaniques, de faibles coefficients de perméabilité et de diffusion sont obtenus sur ces matériaux. Les modélisations de l'hydratation, de l'évolution de propriétés mécaniques, de l'endommagement, des déformations différées et des transferts hydriques ont été abordées. Le modèle d'hydratation utilisé a été adapté aux liants ternaires en prenant en compte les phénomènes de nucléation des additions sur l'hydratation du ciment. Pour les autres modèles, l'acquisition des mesures expérimentales a permis de fournir les données d'entrée pour leur utilisation et de vérifier leur validité sur des liants fortement dilués. Tous ces travaux permettent au final d'envisager sereinement la modélisation et la prédiction du comportement des structures réalisées en béton bas pH. / In the context of the radioactive wastes disposal in deep geological repository of clay, low-alkalinity and low heat of hydration concretes referenced "low pH " were designed. The degradation of the properties of the clay can be limited by using these types of concrete. Two types of low pH binder were chosen for this research: the first one is comprised of cement, silica fume and fly ash (TCV) and the other one is comprised of cement, silica fume and slag (TL). The objective of this research is to comprehend the behavior of these concrete in order to ensure the well-placing of the fresh concrete at an industrial scale and good mechanical performances, chemical stability and confining properties. The experimental program focuses on a physico-chemical and mechanical characterization of these recent materials with high pozzolanic addition content. The experimental data are then modeled for the purpose of having a tool that, in the end, is able to predict the behavior of the low pH concretes within the structure. The results show that grinding altogether the three constituents improves the reactivity of the binder and allows a good reproducibility of the low pH design. The most important criterion which is a pH of the interstitial solution below 11 is met at 28 days. The heat measurements at early age show that the low pH concretes are low heat of hydration concretes as well. In the long run, high mechanical performances, low permeabilities and diffusivities were obtained on these materials. The modeling of the hydration, evolution of mechanical properties, damage, creep and hydric transfers is also covered in this thesis. The model of hydration was adjusted to match the hydration of ternary binders by taking into account the effects of the additions such as the heterogeneous nucleation, on the hydration of the cement. As for the other models, the experimental results were used as data input to validate the models on binders with high replacement rates. Ultimately, this work allows us to contemplate serenely the modeling and the prediction of the behavior of structure made of low pH concretes.

L’estimation des déformations différées, en particulier dans le cas des Béton à Hautes Performances (BHP) destinés aux ouvrages d’art, est primordiale pour prédire les flèches, les redistributions des contraintes dans les structures hyperstatiques et les pertes de précontrainte dans des éléments en béton précontraint. L’expérience montre néanmoins une dispersion certaine des valeurs de déformations instantanées et différées mesurées et des écarts non négligeables avec les valeurs calculées selon les règlements de dimensionnement.L’objectif de ce travail de thèse est de s’intéresser à un paramètre non pris en compte dans les règlements qui pourrait être à l’origine des imprécisions de leurs prédictions : le gravillon. Le programme expérimental s’articulera autour d’une étude comparative des comportements mécaniques instantanés et différés sans charge, retrait, et sous charge, fluage, de six BHP de même formulation de base (rapport E/L, volume de pâte), se différenciant principalement par le type de gravillon. A partir de cette base de données complétée par des analyses mécaniques et physico-chimiques sur les granulats, des paramètres influents liés au type de gravillon incorporé ont été détectés. Des comparaisons avec les estimations des modèles actuels tels que l'Eurocode 2 ont également été réalisées et ont montré des différences notables avec les valeurs expérimentales.Des analyses microstructurales ont été menées afin d'identifier l'état de la microstructure et du réseau poreux des matériaux, plus particulièrement à l'interface pâte-granulat (Interfacial Transition Zone ITZ). L'étude de l’ensemble des résultats a permis d’établir des corrélations entre le comportement mécanique et les analyses microstructurales. Une synthèse des données récoltées durant ce travail de recherche montre que le gravillon a une influence non négligeable sur les comportements mécaniques instantané et différé à travers différents paramètres de degré d'influence variable / The prediction of the time-dependent deformations, particularly in the case of high performance concrete (HPC) envisioned for bridges is essential for predicting the deflections, the stress distribution in statically indeterminate structures and the loss of pre-stressing force in elements of pre-stressed concrete. However, the experience shows a certain dispersion of values of instantaneous and delayed deformations measured and some significant differences with the values calculated using the building codes.The objective of the present thesis work focuses on the coarse aggregate parameter which is not taken into account in building codes, which could causes the inaccuracies of their predictions. The experimental program includes a comparative study of the mechanical behaviours (instantaneous and delayed), shrinkage, creep, of six HPC with the same basic formulation (water cement ratio, volume of paste), differing principally in the type of coarse aggregate. From this database and thanks to the mechanical and physicochemical analyses of the aggregates, some influent parameters related to the type of the coarse aggregate were detected. The comparisons with estimations of standard models such as Eurocode 2 were also performed and showed significant differences with the experimental values.Micro-structural analyses were carried out in order to identify the state of the microstructure and the porosity of materials, more particularly at the interface between the cement paste and the coarse aggregate (Interfacial Transition Zones ITZ). The study of the results made it possible to establish correlations between the mechanical behaviour and the micro-structural analyses. A synthesis of the data collected during this research work shows that the coarse aggregate has a considerable influence on the mechanical behaviours (instantaneous and delayed) through various parameters from variable degree of influence

O refinamento dos poros, associado à reação pozolânica e ao efeito filer, reduz a permeabilidade do concreto com cinza de casca de arroz (CCA), o que pode antecipar a sua degradação em altas temperaturas. A literatura mostra que o concreto reidratado em água pode recuperar substancialmente a sua resistência inicial, porém, os estudos sobre a reidratação ao ar e sobre a influência do modo de resfriamento na reidratação são escassos. A pesquisa desenvolvida teve como principal objetivo avançar na análise experimental de concretos convencional e com CCA em altas temperaturas e na reidratação. Na etapa exploratória se avaliou a influência da temperatura de exposição, da adição mineral, do ambiente de acondicionamento, da taxa de aquecimento e do tempo de exposição na resistência à compressão e módulo de elasticidade. Na etapa principal se avaliou a influência do modo de resfriamento, da adição e da idade de reidratação na resistência residual. Complementarmente se utilizou o ensaio de velocidade de pulso ultrassônico (VPU) para avaliar o grau de microfissuração e correlacionar a VPU com as propriedades mecânicas residuais. Na etapa exploratória concluiu-se que a adição, a temperatura, a taxa de aquecimento e o tempo de exposição influenciaram significativamente os resultados. O concreto com CCA cristalina apresentou pior desempenho em altas temperaturas. O concreto com CCA amorfa apresentou desempenho ligeiramente inferior ao concreto convencional em 200°C, devido ao efeito da poro-pressão. No entanto, ambas as CCA podem ser alternativas viáveis considerando sustentabilidade. Na etapa principal, o resfriamento brusco com água provocou maior redução na resistência devido aos gradientes térmicos, porém, permitiu maior recuperação logo nos primeiros sete dias de reidratação. Apesar da recuperação parcial, a resistência ao fim de 154 dias foi inferior a 40% do valor inicial. Nas análises térmicas e de DRX foi possível observar nos concretos resfriados com água a recristalização dos aluminatos de cálcio, do C-S-H e da portlandita, em maior grau no concreto convencional. Foi possível observar correlações fortes entre as variáveis de resposta na etapa exploratória, porém, o mesmo não ocorreu na etapa principal, devido à fissuração e presença de água nos poros. / The pore refinement, associated with the pozzolanic reaction and the filler effect, reduces the permeability of blended concrete with rice husk ash (RHA), which can anticipate its degradation at high temperatures. The literature shows that concrete rehydrated with water can recover substantially its initial strength, but studies on rehydration in air and on the influence of the cooling method on rehydration are scarce. The main objective of this research was to evaluate the performance at high temperatures and in rehydration of conventional and blended concretes with RHA. In the exploratory stage, the influence of exposure temperature, mineral admixture, conditioning environment, heating rate and exposure time on residual strength and modulus of elasticity of heated concrete was evaluated. In the main stage, the influence of cooling method, mineral admixture and time of rehydration in an unsaturated environment on residual strength of concrete was evaluated. The ultrasonic pulse velocity test (UPV) was used to evaluate the degree of micro cracking of concrete and to correlate the UPV with residual strength and modulus. In the exploratory stage it was concluded that mineral admixture, temperature, heating rate and time of exposure significantly influenced the results. In general, concrete with partially crystalline RHA presented the worst performance at high temperatures. Concrete with amorphous RHA presented worse performance than conventional concrete only at 200°C, due to the pore-pressure effect. Despite these results, RHA can be a viable option considering sustainability and high temperatures performance. In the main stage, the rapid cooling with water caused a greater reduction in strength, due to thermal gradients, however, caused a greater strength recovery in the first seven days of rehydration. Despite this partial recovery, the final strength of both concretes after 154 days of rehydration was less than 40% of the initial value. In water-cooled concretes thermal and XRD analyzes show recrystallization of the calcium aluminates, C-S-H and portlandite, to a greater degree in conventional concrete. In the exploratory stage it was possible to observe strong correlations between the independent variables; however, the same did not occur in the main stage, due to cracking and to the presence of water in the pores.

Made available in DSpace on 2016-06-02T19:58:04Z (GMT). No. of bitstreams: 1 4074.pdf: 4697966 bytes, checksum: 64813ff9b248b32e10837a5c1be8190a (MD5) Previous issue date: 2011-12-16 / Universidade Federal de Minas Gerais / Brazil is the main sugarcane world-producer and it is the leader in all segments (sugarcane, sugar and alcohol). The waste consisting of sugarcane bagasse is produced at the end of grinding process and it is used to generate energy through burning in boilers. At the end of burning, the ashes of bagasse are often thrown into environment improperly. In this context, the Construction Industry is a sector in which the incorporation of a couple of wastes is propitious, whereas applications of construction materials properties are considered. This research is justified by the need of assess the possibility of use of sugarcane bagasse ash in construction products, especially given its large volume. Used like raw material, the waste would no longer be the primary cause of problems related to public health and the environment. The goal of this research was to analyze the sugarcane bagasse ash (SBA) as a substitute for fine aggregate in concretes and mortars directed to the production of artifacts for the urban infrastructure. The SBA samples were collected in sugar and alcohol mills in the state of São Paulo and, then, they were characterized by physical and chemical tests. The SBA was used in cement mortars with 0%, 10%, 20%, 30%, 50% and 100% substitution levels. After the mechanical tests, the 30% and 50% levels of SBA were chosen for the study and production of concretes, which were evaluated through dosage studies, mechanical and durability tests, and economical and environment studies for SBA like a substitution of sand. The artifact chosen for analysis was a concrete curb (dimensions 1,00 x 0,15 x 0,30 m) that was used for drainage and pavement of pathways. Regarding the results obtained, the concrete produced with the SBA and cement CP II E 32 (Group C) had the best mechanical results compared to their respective reference series. Regarding durability, it is possible to say that the use of ash as a partial replacement of sand does not affect the service life of concrete artifacts. It can be also concluded that despite the use of the SBA did not diminish significantly the final value of m3 of concrete, the gain in relation to mechanical performance was higher. On the analysis of the artifact, it can be concluded that the guides produced in this research had sufficient mechanical strength to be demolded, transported and stored before use in the same way that guides conventional precast pavement. / O Brasil é o maior produtor mundial no complexo sucroalcooleiro e exerce a liderança em todos os segmentos (cana-de-açúcar, açúcar e álcool). O resíduo constituído pelo bagaço da cana é gerado ao final do processo de moagem e é utilizado para a geração de energia por meio da queima em caldeiras. Ao final da queima, geralmente, as cinzas residuais do bagaço são lançadas no meio ambiente de forma inadequada. Nesse contexto, a indústria da Construção Civil é um setor no qual a incorporação dos vários tipos de resíduos apresenta-se como favorável, desde que consideradas as propriedades de aplicação dos materiais de construção. O interesse na realização desta pesquisa justificou-se pela necessidade de se avaliar a possibilidade do emprego da cinza do bagaço da cana-de-açúcar (CBC) em produtos para a construção, notadamente pelo grande volume de geração. Utilizados como matériaprima, tais resíduos deixariam de ser causa primária de problemas ligados à saúde pública e ao meio ambiente. Como objetivo principal, esta pesquisa analisou a CBC como substituto do agregado miúdo em concretos e argamassas direcionados à produção de artefatos para a infraestrutura urbana. As amostras de CBC foram coletadas em usinas do estado de São Paulo e, caracterizadas por meio de ensaios físicos e químicos. A CBC foi utilizada em argamassas de cimento nos teores de 0%, 10%, 20%, 30%, 50% e 100% de substituição. Após as análises mecânicas, os teores de 30% e 50% de CBC foram escolhidos para o estudo e produção dos concretos, que foram avaliados por meio de estudos de dosagem e de ensaios mecânicos e de durabilidade, além de estudos econômicos e ambientais do uso da CBC em substituição à areia. O artefato escolhido para análise foi a guia de concreto (dimensões 1,00 x 0,15 x 0,30 m) utilizada na drenagem e na pavimentação de vias. Em relação aos resultados obtidos, os concretos produzidos com a CBC e com o cimento CP II E 32 obtiveram os melhores resultados mecânicos em comparação com a série de referência. Em relação à durabilidade, pode-se afirmar que o uso da CBC como substituto parcial da areia não afetará a vida útil dos artefatos de concreto. Conclui-se, também, que apesar do uso da CBC não ter diminuído significativamente o valor final do m3 do concreto, o ganho em relação ao desempenho mecânico foi maior. Pode-se concluir que as guias de pavimentação produzidas obtiveram resistência mecânica suficiente para serem desmoldadas, transportadas e acondicionadas antes do uso, da mesma forma que as guias pré-moldadas convencionais. '

Made available in DSpace on 2014-10-09T12:52:10Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:01:02Z (GMT). No. of bitstreams: 0 / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

O refinamento dos poros, associado à reação pozolânica e ao efeito filer, reduz a permeabilidade do concreto com cinza de casca de arroz (CCA), o que pode antecipar a sua degradação em altas temperaturas. A literatura mostra que o concreto reidratado em água pode recuperar substancialmente a sua resistência inicial, porém, os estudos sobre a reidratação ao ar e sobre a influência do modo de resfriamento na reidratação são escassos. A pesquisa desenvolvida teve como principal objetivo avançar na análise experimental de concretos convencional e com CCA em altas temperaturas e na reidratação. Na etapa exploratória se avaliou a influência da temperatura de exposição, da adição mineral, do ambiente de acondicionamento, da taxa de aquecimento e do tempo de exposição na resistência à compressão e módulo de elasticidade. Na etapa principal se avaliou a influência do modo de resfriamento, da adição e da idade de reidratação na resistência residual. Complementarmente se utilizou o ensaio de velocidade de pulso ultrassônico (VPU) para avaliar o grau de microfissuração e correlacionar a VPU com as propriedades mecânicas residuais. Na etapa exploratória concluiu-se que a adição, a temperatura, a taxa de aquecimento e o tempo de exposição influenciaram significativamente os resultados. O concreto com CCA cristalina apresentou pior desempenho em altas temperaturas. O concreto com CCA amorfa apresentou desempenho ligeiramente inferior ao concreto convencional em 200°C, devido ao efeito da poro-pressão. No entanto, ambas as CCA podem ser alternativas viáveis considerando sustentabilidade. Na etapa principal, o resfriamento brusco com água provocou maior redução na resistência devido aos gradientes térmicos, porém, permitiu maior recuperação logo nos primeiros sete dias de reidratação. Apesar da recuperação parcial, a resistência ao fim de 154 dias foi inferior a 40% do valor inicial. Nas análises térmicas e de DRX foi possível observar nos concretos resfriados com água a recristalização dos aluminatos de cálcio, do C-S-H e da portlandita, em maior grau no concreto convencional. Foi possível observar correlações fortes entre as variáveis de resposta na etapa exploratória, porém, o mesmo não ocorreu na etapa principal, devido à fissuração e presença de água nos poros. / The pore refinement, associated with the pozzolanic reaction and the filler effect, reduces the permeability of blended concrete with rice husk ash (RHA), which can anticipate its degradation at high temperatures. The literature shows that concrete rehydrated with water can recover substantially its initial strength, but studies on rehydration in air and on the influence of the cooling method on rehydration are scarce. The main objective of this research was to evaluate the performance at high temperatures and in rehydration of conventional and blended concretes with RHA. In the exploratory stage, the influence of exposure temperature, mineral admixture, conditioning environment, heating rate and exposure time on residual strength and modulus of elasticity of heated concrete was evaluated. In the main stage, the influence of cooling method, mineral admixture and time of rehydration in an unsaturated environment on residual strength of concrete was evaluated. The ultrasonic pulse velocity test (UPV) was used to evaluate the degree of micro cracking of concrete and to correlate the UPV with residual strength and modulus. In the exploratory stage it was concluded that mineral admixture, temperature, heating rate and time of exposure significantly influenced the results. In general, concrete with partially crystalline RHA presented the worst performance at high temperatures. Concrete with amorphous RHA presented worse performance than conventional concrete only at 200°C, due to the pore-pressure effect. Despite these results, RHA can be a viable option considering sustainability and high temperatures performance. In the main stage, the rapid cooling with water caused a greater reduction in strength, due to thermal gradients, however, caused a greater strength recovery in the first seven days of rehydration. Despite this partial recovery, the final strength of both concretes after 154 days of rehydration was less than 40% of the initial value. In water-cooled concretes thermal and XRD analyzes show recrystallization of the calcium aluminates, C-S-H and portlandite, to a greater degree in conventional concrete. In the exploratory stage it was possible to observe strong correlations between the independent variables; however, the same did not occur in the main stage, due to cracking and to the presence of water in the pores.

Made available in DSpace on 2014-10-09T12:52:10Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:01:02Z (GMT). No. of bitstreams: 0 / O presente trabalho estuda a viabilidade de utilização da escória de alumínio, que é um rejeito da indústria recicladora de alumínio, atualmente sem valor agregado, como elemento integrante na fabricação de argila expandida. A argila expandida é produzida a partir de argilas que produzam expansão piroplástica, que são utilizadas como agregado leve na fabricação de concreto estrutural e também como artigo decorativo em jardins. Inicialmente foram feitas análises dos materiais de partida, como difração de raios X, microscopia eletrônica de varredura, fluorescência de raios X, análise granulométrica, análise termogravimétrica e análise térmica diferencial da argila. Foram feitas incorporações do rejeito junto à massa de argila, na proporção de 5%, 10%, 15% e 20% em massa. As formulações estudadas foram analisadas quanto à expansão linear, variação de massa, massa específica aparente e absorção de água. Foram feitos também ensaios de lixiviação e solubilização. Os principais resultados obtidos mostraram que é viável o uso da escória de alumínio até aproximadamente 5% em massa, para a produção da argila expandida, com características aceitáveis e dentro das normas vigentes. Palavraschave: reciclagem, escória de alumínio, argila expandida, agregado leve. / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2016-11-11T11:09:07Z No. of bitstreams: 0 / Made available in DSpace on 2016-11-11T11:09:07Z (GMT). No. of bitstreams: 0 / Este trabalho apresenta uma análise da viabilidade econômica e ambiental do processo de reciclagem de Resíduos de Construção Civil em um município. Utilizou-se como base o Município de Guarulhos onde foi efetuado um levantamento das quantidades de resíduos de construção civil produzidos, seu gerenciamento e o processo de reciclagem e reutilização dos agregados reciclados produzidos. O Município de Guarulhos implantou o primeiro Ponto de Entrega Voluntária (PEV) de resíduos em 2003 e, de forma ininterrupta, vem aumentando a disponibilidade desses pontos a população, possuindo 17 pontos em 2014. Inicialmente planejados para receber apenas resíduos provenientes de construção civil, tornaram-se pontos onde a população destina inúmeros resíduos sólidos não orgânicos. A empresa de pública responsável por obras na cidade, PROGUARU, possuiu uma Usina de Reciclagem de Resíduos de Construção Civil (URE) que produz agregados reciclados para uso em manutenções e pavimentação, além de fornecer material para utilização na Fábrica de Pré-Moldados da Prefeitura, fechando um ciclo de captação, processamento e reutilização dos Resíduos de Construção Civil no município. Foram desenvolvidos dois modelos que incluem no cálculo econômico do processo de reciclagem de Resíduos de Construção Civil de um município, a economia obtida com a diminuição do descarte irregular e com a substituição de agregados naturais pelos agregados reciclados produzidos pela PROGUARU. No período de 2003 a 2014, os Pontos de Entrega Voluntária receberam 296.210,11 . 10³ kg de resíduos totais, e enviou 214.910, 57 . 10³ kg de Resíduos de Construção Civil para a URE. O lucro anual do sistema incluindo o custo dos terrenos (PEV e URE) foi de R$ 3,50 por habitante, e desprezando o valor dos terrenos foi de R$ 5,02 por habitante. O trabalho de pesquisa comprova a viabilidade econômica da reciclagem, além dos ganhos ambientais pela diminuição dos descartes irregulares e economia de recursos naturais. / Tese (Doutorado em Tecnologia Nuclear) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Estimating the delayed strains in concrete, namely creep and shrinkage is very important to asses the condition of the structure. Time dependent deformations in concrete, both creep and shrinkage, play a critical role in prestressed concrete structures, such as bridge girders, nuclear containment vessels, etc. These strains result in lossess, through release of prestress, and thereby influence the safety of these structures. Recognizing the role of free and bound moisture movement is the primary ingredient responsible for the development of both creep and shrinkage stains as well as the degradation of concrete under high temperature, the present study has also examined the effects of high temperature on concrete degradation, experimentally and also analytically in the same modelling framework. Fire in concretes deteriorates mechanical properties of the material and lead to col-lapse under loads. Two types of spalling occur in concrete when exposed to high temperature, namely explosive and thermal spalling. Explosive spalling occurs once the hydrostatic stress (developed due to pore pressure) exceeds the tensile strength of the concrete. Where as thermal spalling of concrete happens due to degradation of material properties (elastic modulus, compressive and tensile strength) when exposed to high temperature due to decomposition of chemical bonds that release the bound water. The present study comprises of an experimental and analytical program to assess the levels of creep and shrinkage in different concrete under various loads and environmental conditions. Deformations due to high temperature in di erent concretes forms another component of the present study. Total six concrete mixes has been studied to investigate and asses the extent of creep and shrinkage taking place in the concretes under different environmental conditions, load level and age at loading. In total six mixes, three that are self compacted concrete mixes (35MPa, 55MPa and SCC70MPa), a high volume y ash concrete mix ( 45 MPa) and two normal concrete mixes (35 MPa and 45 MPa) have been considered in this study. To study the high temperature effects, the same mixes considered in the creep and shrinkage study and in addition a heavy density concrete mix (25 MPa) is used. A normal concrete having a 28 day uniaxial compressive strength of 45 MPa after proper curing, referred to as M45 concrete, was one of the six mixes. Likewise a heavy density concrete designated as H25, corresponding to a 28 day uniaxial compressive strength of 25 MPa was another mix that was studied and was made using iron ore aggregate and iron ore sand. A concrete having high volume y ash replacing cement designated as F45 offered a 28 day strength of 45MPa. Three self-compacting concretes with uniaxial compressive strengths of 35, 55 and 70 MPa were designated as SCC35 SCC55 and SCC70, respectively is studied for creep, shrinkage and high temperature effects. F45 concrete shows lower creep strain when compared to normal M45 concrete, under similar casting, curing and testing condtions. This is due to increase in stiffness of y ash based concretes with time. Where as in shrinkage it is observed that a little higher strain takes place in F45 at initial ages than in M45 concrete mix for the same conditions. But in the later age, F45 concrete shows a decreasing rate of shrinkage strain. This is because, water to cement ratio of y ash concrete is higher than the M45 concrete. The SCC35 concrete shows higher creep and shrinkage than M35 concrete even though both the concretes have the same water cement ratio. This difference comes from the aggregate cement ratio (a/c). The lower the aggregate cement ratio, the higher the creep and shrinkage. M35 concrete has a higher aggregate cement ratio than the SCC35. Concretes exposed to higher temperature and lower humidity shows higher creep and shrinkage due to its higher rate of drying. An analytical model has been developed to simulate the drying phenomena in concrete based on poromechanics. The hydration effects of blended cements is considered while developing the model. This models prediction of degree of hydration, temperature and relative humidity is used to model creep and shrinkage in concrete. To model creep and shrinkage, micro prestress solidi cation theory is implemented and validated with the present experimental results. The model is able to predict the drying phenomena of concrete realistically. Further, a benchmark problem reported in the literature is solved through this model and validated through a comparison with the experimental results (beam detection due to creep and shrinkage). Under high temperature tests, H25 concrete shows better resistance for all the ranges of temperatures. This may be because of the hematite aggregate having a high melting point and strong interfacial transition zone (ITZ) properties between aggregate and cement mortar. The SCC70 shows poor performance against explosive spalling at both the ages (28 and 365 days) due to its lower permeability when exposed to high temperature. The intensity of explosive spalling is higher in SCC70 concrete tested at 28 days than at 365 days of age. This is because of variation in moisture content. SCC70 concrete failed due to explosive spalling at temperature of 398oC when tested at 28 days and failed at 575oC when tested at 365 days. This indicates the amount of moisture content in the concrete plays an important role while causing explosive spalling. F45 concrete shows a poor resistance against temperature beyond 500oC in its residual properties. SCC55 contains cement and y ash and shows higher residual properties when compared to normal vibrated M45 mix under similar high temperature conditions. Two geopolymers pastes prepared with y ash and metakaolin as a complete cement replacement were studied for passive re protection capability. The study shows MF70 mix (containing 70% y ash and 30% metakaolin) gives better resistance against heating than MF50 mix (50% each of metakaolin and y ash). Hence y ash geopolmer is a choice of material for passive re protection. An analytical model has been developed based on poromechanics to simulate high temperature e ects in concrete. Two type of spalling is considered while modelling the high temperature e ects of concrete, namely explosive and thermal spalling. Explosive spalling is estimated based on the hydro static stress (Biotech efficient times the pore pressure). If the hydrostatic stress increases beyond the tensile strength of concrete then explosive spalling occurs. Where as the thermal spalling is estimated based on the stresses developed due to applied mechanical and thermal loading. To validate this model, two benchmark problems from the literature have been solved and validated with the reported results. This model is able to predict pore pressure and temperatures gradients accurately, and this in turn helps to predict explosive and thermal spalling realistically in concrete under elevated temperature conditions.