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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Pastas de cimento branco modificadas com diferentes tipos de látex. / Modified white cement pastes with different types of polymers.

Carbone, Carlos Eduardo 28 September 2012 (has links)
A adição de látex polimérico em argamassas usadas para reparos, argamassas colantes, argamassas técnica decorativas, argamassas de impermeabilização e chapiscos de alto desempenho é prática comum no setor de construção civil, visto que auxiliam seu desempenho no estado endurecido. As modificações do cimento Portland branco com diversos teores (de 5% a 20%) e tipos de látex (etileno vinil acetato, poliacetato de vinil versatato, estireno acrílico e estireno butadieno) resultaram em alterações no estado fresco (cinética de hidratação, cinética de consolidação, teor de ar incorporado) e no estado endurecido (resistência mecânica, elasticidade, absorção de água por capilaridade, permeabilidade ao ar e ao vapor), em muitos casos, proporcionais ao aumento de seus teores. Ao se atingir 20% de adição, em ralação à massa do cimento, houve ganhos expressivos no estado endurecido das pastas, como o aumento da resistência à tração na compressão diametral, e da resistência de aderência, diminuição do módulo elástico e da absorção de água por capilaridade sem comprometer a facilidade à permeabilidade do vapor. Todavia, no estado fresco não apresentaram condições de aplicação devido à excessiva fluidez e diminuição acentuada no processo de consolidação. / Modified Portland cement mortars have been used for repair, stickers, highperformance and finishing of facades is common practice in the construction industry, due his performance in hardened state. Additions of several latex levels (5% to 20%) and types (ethylene vinyl acetate, vinyl poliacetate versatate, styrene acrylic and styrene butadiene) resulted in changes in the fresh state (hydration kinetics, kinetic consolidation, air content) and hardened state (mechanical strength, elasticity, water absorption by capillarity, and steam permeability) and mostly the effects increase with the increase of its levels. When the Latex levels reached 20% in relation of cement were expressive gains in state hardened state, as increased tensile strength in diametral compression, and grip strength, decreased elastic modulus and water absorption by capillarity without compromising ease of vapor permeability. However, in the fresh state did not show application conditions due to the excessive fluidity and strong decrease in the consolidation process.
2

Pastas de cimento branco modificadas com diferentes tipos de látex. / Modified white cement pastes with different types of polymers.

Carlos Eduardo Carbone 28 September 2012 (has links)
A adição de látex polimérico em argamassas usadas para reparos, argamassas colantes, argamassas técnica decorativas, argamassas de impermeabilização e chapiscos de alto desempenho é prática comum no setor de construção civil, visto que auxiliam seu desempenho no estado endurecido. As modificações do cimento Portland branco com diversos teores (de 5% a 20%) e tipos de látex (etileno vinil acetato, poliacetato de vinil versatato, estireno acrílico e estireno butadieno) resultaram em alterações no estado fresco (cinética de hidratação, cinética de consolidação, teor de ar incorporado) e no estado endurecido (resistência mecânica, elasticidade, absorção de água por capilaridade, permeabilidade ao ar e ao vapor), em muitos casos, proporcionais ao aumento de seus teores. Ao se atingir 20% de adição, em ralação à massa do cimento, houve ganhos expressivos no estado endurecido das pastas, como o aumento da resistência à tração na compressão diametral, e da resistência de aderência, diminuição do módulo elástico e da absorção de água por capilaridade sem comprometer a facilidade à permeabilidade do vapor. Todavia, no estado fresco não apresentaram condições de aplicação devido à excessiva fluidez e diminuição acentuada no processo de consolidação. / Modified Portland cement mortars have been used for repair, stickers, highperformance and finishing of facades is common practice in the construction industry, due his performance in hardened state. Additions of several latex levels (5% to 20%) and types (ethylene vinyl acetate, vinyl poliacetate versatate, styrene acrylic and styrene butadiene) resulted in changes in the fresh state (hydration kinetics, kinetic consolidation, air content) and hardened state (mechanical strength, elasticity, water absorption by capillarity, and steam permeability) and mostly the effects increase with the increase of its levels. When the Latex levels reached 20% in relation of cement were expressive gains in state hardened state, as increased tensile strength in diametral compression, and grip strength, decreased elastic modulus and water absorption by capillarity without compromising ease of vapor permeability. However, in the fresh state did not show application conditions due to the excessive fluidity and strong decrease in the consolidation process.
3

Concreto autoadensÃvel com agregados graÃdos reciclados de concreto / Self-compacting Concrete with Recycled Concrete Coarse Aggregate

Kelvya Maria de Vasconcelos Moreira 06 June 2012 (has links)
CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / O Concreto AutoadensÃvel (CAA) possui propriedades intrÃnsecas que o distingue do atual concreto convencional. SÃo fatores como capacidade de autoadensamento, grande quantidade de finos e uso obrigatÃrio de aditivo superplastificante que tornam o CAA um material de elevado desempenho, favorÃvel para a durabilidade, sendo considerado uma evoluÃÃo na tecnologia do concreto e propenso a se tornar o concreto convencional do futuro. Por outro lado, o resÃduo originÃrio da prÃpria indÃstria da construÃÃo civil tem despertado sÃrias preocupaÃÃes para a comunidade, pois se trata de um resÃduo de difÃcil descarte e gerado em volumes cada vez mais crescentes, dado o crescimento econÃmico do PaÃs com consequente aumento do poder aquisitivo da populaÃÃo. Sob esta Ãtica, analisou-se o potencial de produÃÃo do CAA com substituiÃÃo do agregado graÃdo natural (AGN) por agregados reciclados oriundos da reciclagem de concreto, chamado de agregado graÃdo reciclado (AGR), nas porcentagens de 0%, 10%, 20% e 30%. Sabendo que o agregado reciclado, em geral, possui caracterÃsticas distintas do agregado natural, a metodologia empregada iniciou com o tratamento do AGR e caracterizaÃÃo fÃsica de todos os agregados (convencionais e reciclados). Efetuou-se, entÃo, o estudo de dosagem para as relaÃÃes a/c de 0,35, 0,45 e 0,55. ApÃs, estudaram-se um total de 12 traÃos de CAA para avaliaÃÃo de suas propriedades no estado fresco e no estado endurecido. Os ensaios no estado endurecido foram: resistÃncia à compressÃo axial aos 28 e 56 dias, mÃdulo de elasticidade aos 56 dias, absorÃÃo de Ãgua por imersÃo aos 28 dias, Ãndice de vazios aos 28 dias, massa especÃfica real aos 28 dias e profundidade de carbonataÃÃo natural aos 200 dias. Procedeu-se ao tratamento estatÃstico dos resultados pela anÃlise de variÃncia (ANOVA) com posterior modelagem matemÃtica e ANOVA do modelo proposto. Ao final, concluiu-se que o alto teor de aditivo superplastificante resultante do estudo de dosagem da relaÃÃo a/c mais baixa pode ter influenciado para a obtenÃÃo de concretos mais trabalhÃveis e menos suscetÃveis à incorporaÃÃo de um agregado mais poroso do que o agregado natural. TambÃm se concluiu que as propriedades dos CAA manufaturados foram afetadas mais significativamente pela relaÃÃo a/c, indicando a possibilidade de substituiÃÃo de maiores teores de AGN por AGR. / The self-compacting concrete (SCC) has intrinsic properties that distinguish it known current conventional concrete. It is factors like self-compacting capacity, high amount of fines and mandatory use of superplasticizer that make the SCC a material of high performance, favorable to the durability and is considered an evolution in concrete technology and prone to become the future conventional concrete. On the other hand, the residue originated in the construction industry itself has aroused serious concern to the community, because it is a residue difficult to discard. It is generated in ever-increasing volumes due to economic growth in the country with con sequent increase in power population's purchasing. From this perspective, we analyzed the production of SCC with replacement of natural coarse aggregate (NCA) for recycled aggregates from concrete recycling, called recycled coarse aggregate (RCA), in the percentages of 0%, 10%, 20% and 30%. Knowing that recycled aggregate, in general, has distinct characteristics of natural aggregate, the methodology started with the treatment of RCA and physical characterization of all aggregates (conventional and recycled). Then, it was done the dosage study with the w/c ratio of 0.35, 0.45 and 0.55. After, we studied a total of 12 mixtures of SCC to evaluate its properties in fresh and hardened state. The tests in the hardened state were: compressive strength at 28 and 56 days, modulus of elasticity at 56 days, water absorption by immersion at 28 days, content of voids at 28 days, specific gravity at 28 days and the depth of natural carbonation at 200 days. We proceeded to statistical processing of results by analysis of v ariance (ANOVA) followed by mathematical modeling and model‟s ANOVA. Finally, it was concluded that the high content of superplasticizer results from the dosage study of lower w/c ratio can be influenced to achieve concretes more workable and less sensitiv e to the incorporation of an aggregate more porous than the natural aggregate. It was also found that the properties of the SCC manufactured were affected more significantly by the w/c ratio, indicating the possibility of substitution of higher levels of NCA by RCA
4

Optimisation des caractéristiques rhéologiques, mécaniques et thermiques des bétons à base de granulats recyclés avec différents couples ciment/adjuvant / Optimization of rheological, mechanical and thermal characteristics of concrete with recycled aggregates with different couple cement / adjuvant

Tahar, Zine-el-abidine 08 November 2016 (has links)
Devant le besoin croissant de ressources en matériaux de construction ainsi que les exigences en terme de préservation de l’environnement dans une vision de développement durable, il est devenu nécessaire d'étudier toutes les possibilités de réutilisation et de valorisation des déchets et des sous-produits industriels, notamment dans le domaine de la construction et des travaux publics.Les mortiers et bétons confectionnés à partir de granulats recyclés ont fait l’objet de nombreuses études. Toutefois, aucune règle générale n’a encore été dégagée pour quantifier l’influence de telles substitutions sur leurs propriétés rhéologiques et mécaniques. L’élargissement de l’utilisation des bétons comportant des granulats recyclés, dont les propriétés physico-chimiques sont différentes des bétons à base de granulats naturels, est inévitablement cautionné par une maitrise accrue, d’une part, de leurs propriétés mécaniques et d’autre part, de leur mise en œuvre.L’objectif de ce travail est de quantifier l’influence de la nature et du dosage des gravillons et du sable recyclé sur les propriétés rhéologiques et mécaniques.Pour y parvenir, une campagne d’essais a été menée sur des bétons confectionnés avec différents taux de substitutions (sur le sable et les granulats) et avec différents couples ciments/adjuvants. En ce qui concerne les propriétés rhéologiques, les paramètres mesurés sont les suivants : le seuil de cisaillement, la viscosité plastique, l’ouvrabilité, la teneur en air et la masse volumique. De plus, afin de suivre l’évolution de ces propriétés dans le temps les essais ont été réalisés à différents âges (à la sortie du malaxeur, 30 minutes, 60 minutes et 90 minutes après la fin du malaxage). En ce qui concerne les propriétés mécaniques, des essais de compressions ont été effectués à 1 jour, 7 jours et 28 jours. Les propriétés des bétons ainsi confectionnés ont été comparées à un béton témoin.Les résultats montrent que les propriétés des bétons et des MBE (Mortier de Béton Equivalent) à base de granulats recyclés dépendent du couple ciment/adjuvant et du dosage de substitution en granulats recyclés. Cela signifie qu'il existe effectivement une influence du granulat recyclé sur la compatibilité (équilibre physico-chimique) du couple ciment/adjuvant. Cette influence est plus remarquable sur le sable que sur les gravillons. Les résultats montrent aussi que pour des bétons à base de granulats recyclés, plus le pourcentage de substitution est élevé et plus le seuil de cisaillement et la viscosité plastique augmentent, la résistance à la compression, quant à elle, diminue.Mots clés : béton, gravillons recyclés, sable recyclé, rhéologie, maniabilité. / With the growing need of building material resources and requirements in terms of environmental protection in a vision of sustainable development, it has become necessary to explore all possibilities for the reuse and recycling of and industrial waste products, especially in the field of construction and public works.Mortars and concrete made from recycled aggregates were the subject of numerous studies. However, no general rule has been identified to quantify the influence of such substitutions on their rheological and mechanical properties. Expanding the use of concrete containing recycled aggregates whose physicochemical properties are different from concrete with natural aggregates, is inevitably backed by increased mastery, on the one hand, of their mechanical properties, and secondly their implementation.The objective of this work is to quantify the influence of the nature and dosage of recycled gravel and sand on the rheological and mechanical properties.To do so, a test campaign was conducted on concrete made with different percentages of substitutions (on the sand and aggregates) and with different combination cements / admixtures. Regarding the rheological properties, the measured parameters are: shear threshold, plastic viscosity, workability, air content and density. Furthermore, in order to follow the evolution of these quantities in the time the tests were carried out at different ages (at the outlet of the mixer, 30 minutes, 60 minutes and 90 minutes after the end of mixing). Regarding the mechanical properties, compression tests were performed at 1 day, 7 days and 28 days. The properties of these concretes were compared to a control concrete.The results show that the properties of recycled concrete aggregates and ECM (Equivalent Concrete Mortar) depend on the couple cement / admixture and the level of substitution on recycled aggregates. This means that there is indeed an influence of recycled aggregate on the compatibility (phisico-chemical equilibrium) of the couple cement / admixture. This influence is most notable on the sand than on gravel. The results also show that for concrete based on recycled aggregate, the higher the percentage of substitution increases, the higher the yield stress and plastic viscosity and the lower the resistance to compression.Keywords: concrete, recycled aggregates, recycled sand, rheology, workability.

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