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Hardened properties of self-compacting concrete - A statistical approach

ALMEIDA FILHO, F. M.; BARRAGAN, B. E.; CASAS, J. R.; DEBS, A. L. H. C. El
Fonte: ELSEVIER SCI LTD Publicador: ELSEVIER SCI LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
96.76%
This work presents a statistical study on the variability of the mechanical properties of hardened self-compacting concrete, including the compressive strength, splitting tensile strength and modulus of elasticity. The comparison of the experimental results with those derived from several codes and recommendations allows evaluating if the hardened behaviour of self-compacting concrete can be appropriately predicted by the existing formulations. The variables analyzed include the maximum size aggregate, paste and gravel content. Results from the analyzed self-compacting concretes presented variability measures in the same range than the expected for conventional vibrated concrete, with all the results within a confidence level of 95%. From several formulations for conventional concrete considered in this study, it was observed that a safe estimation of the modulus of elasticity can be obtained from the value of compressive strength; with lower strength self-compacting concretes presenting higher safety margins. However, most codes overestimate the material tensile strength. (C) 2010 Elsevier Ltd. All rights reserved.; Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq); Spanish Ministry of Science and Technology; Spanish Ministry of Education and Science[MAT2003-5530]; Spanish Ministry of Education and Science[PSS 11-2005]

Contribuição ao estudo da aderência entre barras de aço e concretos auto-adensáveis ; Contribution to the study of the bond between steel bars and self-compacting concrete

Almeida Filho, Fernando Menezes de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 18/08/2006 PT
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A busca por novos materiais estruturais visa a melhoria da qualidade e desempenho das estruturas, impulsionando o desenvolvimento científico e tecnológico. O concreto auto-adensável surgiu da necessidade de se dispensar o difícil e oneroso trabalho de vibração do concreto, sendo definido como um material capaz de fluir dentro de uma fôrma, passando pelas armaduras e preenchendo a mesma, sem o uso de equipamentos de vibração. Esta pesquisa caracteriza-se como um estudo teórico-experimental da aderência aço-concreto, utilizando concreto do tipo auto-adensável, mediante ensaios monotônicos de flexão em vigas e de arrancamento seguindo o modelo padrão do Rilem-Ceb-Fip (1973). O estudo considerou como parâmetros fundamentais o tipo de concreto (auto-adensável e convencional), a resistência à compressão do concreto e os diâmetros das barras. Ainda, realizou-se um estudo com relação à variabilidade do concreto auto-adensável nos estados fresco e endurecido, constatando que este possui pequena variação. De posse dos resultados, buscou-se verificar a previsão das formulações empregadas na literatura e pelos principais códigos internacionais. De acordo com os resultados, o comportamento dos modelos de viga e de arrancamento para ambos os concretos foi similar...

Dosagem do concreto auto-adensável: produção de pré-fabricados.; Self-compacting concrete mix design: precast production.

Alencar, Ricardo dos Santos Arnaldo de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 28/04/2008 PT
Relevância na Pesquisa
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Aborda-se, neste trabalho, a tecnologia do concreto auto-adensavel CAA aplicada a producao de pre-fabricados. Destaca-se a contribuicao feita ao Metodo IBRACON, largamente utilizado no pais para a dosagem do concreto comum, a partir de uma nova metodologia de dosagem proposta para o CAA, que considera duas inovacoes principais. A primeira foi o conceito de correcao da coesao do concreto fresco por substituicao de finos pozolanicos ou nao pozolanicos correspondentes, de maior area especifica, de modo que formulacoes mais pobres em cimento exigem maior teor de substituicao quando comparadas com composicoes mais ricas, para manter as mesmas caracteristicas de trabalhabilidade. Com isso, foi possivel acrescentar um 4° quadrante de correlacao dos parametros envolvidos na mistura ao Diagrama de Dosagem do metodo original. A segunda inovacao foi incorporar alguns ensaios de trabalhabilidade especificos. Para tanto, realizou-se uma analise critica dos principais testes disponiveis, apresentando suas vantagens e limitacoes, correlacionando com os parametros reologicos fundamentais, bem como com uma aplicacao pratica, validando-os para a qualificacao do CAA para a producao. Dessa forma, foram estudados tracos com dois niveis de auto-adensabilidade...

Estudo da influência do teor de argamassa no desempenho de concretos auto-adensáveis; Influence of mortar content on the performance of self-compacting concrete

Manuel, Paulo Jorge Miguel
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
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O concreto auto-adensável (CAA), que representa um dos mais significativos avanços na tecnologia de concreto, foi desenvolvido no Japão em 1988 com o intuito de se obter estruturas de concreto duráveis. É um concreto que dispensa o processo convencional de vibração ou adensamento por ter a capacidade de fluir e preencher os espaços da fôrma apenas através de seu peso próprio. Desde então, várias pesquisas têm sido realizadas e esse tipo de concreto já vem sendo aplicado na prática há algum tempo em alguns países, principalmente por grandes empresas de construção no Japão e na Suécia. Pesquisas para se estabelecerem métodos racionais de dosagem para CAA bem como métodos de ensaios no estado fresco têm sido desenvolvidas, visando fazer do CAA um concreto de aplicação comum. Contudo, ainda não se conhece bem este material e o que se nota é que a maioria dos CAA apresentados em trabalhos científicos é obtida com altos teores de argamassa, além da grande dispersão desses teores. Neste trabalho foi estudada a influência do teor de argamassa sobre as características de concretos auto-adensáveis, tanto no estado fresco como no estado endurecido, produzidos a partir de diferentes teores de argamassa (55, 60...

Análise teórico-experimental da deformação instantânea e lenta de vigas de concretos auto-adensáveis; Analysis of the behavior in terms of immediate and long-term deflections of beams made from self-compacting concrete

Simonetti, Camila
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
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A consolidação das técnicas de dosagem e fabricação de concretos auto-adensáveis com reduzida relação a/c pode ser considerada como um dos desenvolvimentos mais impactantes da nova tecnologia do concreto. No Brasil a utilização deste tipo de concreto, apesar de estar aumentando consideravelmente, ainda é relativamente modesta. Projeta-se, todavia, uma considerável expansão nos próximos anos, em função das vantagens que este material oferece. Por isso, várias instituições têm buscado aprofundar o conhecimento sobre o concreto auto-adensável (CAA), através de estudos e pesquisas sobre o comportamento e características desse novo material. Visando colaborar para um melhor conhecimento sobre as propriedades de concretos autoadensáveis no estado endurecido, foi efetuado um estudo sobre o comportamento, em termos de deformação instantânea e lenta, de vigas fabricadas com CAA. O programa experimental compreendeu a análise de seis vigas de concreto armado dimensionadas segundo as exigências da NBR 6118/2003.Para fabricação das mesmas foi utilizado um concreto convencional, com teor de argamassa de 55%, que serviu como referência, e dois concretos auto-adensáveis, com teores de argamassa de 55% (similar ao do convencional) e 60% (típico de concretos auto-adensáveis). As vigas permaneceram em carga durante aproximadamente cinco meses...

Modelling the influence of age of steel fibre reinforced self-compacting concrete on its compressive behaviour

Cunha, Vitor M. C. F.; Barros, Joaquim A. O.; Sena-Cruz, José
Fonte: Springer Netherlands Publicador: Springer Netherlands
Tipo: Artigo de Revista Científica
Publicado em //2008 ENG
Relevância na Pesquisa
96.59%
Steel fibre reinforced self-compacting concrete (SFRSCC) can combine the benefits of self-consolidating concrete technology with those derived from adding steel fibres to quasi-brittle cement based materials. In a recent applied research project joining pre-casting industry, private and public research institutions, a method was developed to design cost-competitive SFRSCC of rheological and mechanical properties required for the prefabrication of SFRSCC fac¸ade panels. To assure safe demoulding process of the panels, the influence of the concrete age on the compression behaviour of the SFRSCC should be known. For this purpose, series of tests with specimens of 12 h to 28 days were tested in order to analyze the age influence on the compressive strength, strain at peak stress, Young’s modulus, and compressive volumetric fracture energy. The experimental program was divided in two groups of test series, one with SFRSCC of a volumetric fibre percentage of 0.38% and the other with 0.57%. To apply the obtained data in the design and numerical analysis framework, the influence of the age on these SFRSCC properties was modelled. This work describes the carried out experimental program, presents and analyzes the obtained results...

Tensile behavior of steel fiber reinforced self-compacting concrete

Cunha, Vitor M. C. F.; Barros, Joaquim A. O.; Sena-Cruz, José
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Parte de Livro
Publicado em //2010 ENG
Relevância na Pesquisa
96.59%
In the present work the tensile behavior of a self-compacting concrete reinforced with two hooked ends steel fiber contents was assessed performing stable displacement control tension tests. Based on the stressdisplacement curves obtained, the stress-crack width relationships were derived, as well as the energy dissipated up to distinct crack width limits and residual strengths. The number of effective fibers bridging the fracture surface was determined and was compared with the theoretical number of fibers, as well as with the stress at crack initiation, residual stresses and energy dissipation parameters. In general, a linear trend between the number of effective fibers and both the stress and energy dissipation parameters was obtained. A numerical model supported on the finite element method was developed. In this model, the fiber reinforced concrete is assumed as a two phase material: plain concrete and fibers randomly distributed. The plain concrete phase was modeled with 3D solid finite elements, while the fiber phase was modeled with discrete embedded elements. The adopted interface behavior for the discrete elements was obtained from single fiber pullout tests. The numerical simulation of the uniaxial tension tests showed a good agreement with the experimental results. Thus...

Pullout behavior of steel fibres in self-compacting concrete

Cunha, Vitor M. C. F.; Barros, Joaquim A. O.; Sena-Cruz, José
Fonte: ASCE Publicador: ASCE
Tipo: Artigo de Revista Científica
Publicado em /01/2010 ENG
Relevância na Pesquisa
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In steel fiber reinforced composites materials, fiber and matrix are bonded together through a weak interface. The study of this interfacial behavior is important for understanding the mechanical behavior of such composites. Moreover, with the outcome of new composites materials with improved mechanical properties and advanced cement matrices, such in the case of steel fiber reinforced self-compacting concrete, the study of the fiber/matrix interface assumes a new interest. In the present work, experimental results of both straight and hooked end steel fibers pullout tests on a self-compacting concrete medium are presented and discussed. Emphasis is given to the accurate acquirement of the pullout load versus endslip relationship. The influence of fiber embedded length and orientation on the fiber pullout behavior is studied. Additionally, the separate assessment of the distinct bond mechanisms is performed, by isolating the adherence bond from the mechanical bond provided by the hook. Finally, analytical bond-slip relationships are obtained by back-analysis procedure with an interfacial cohesive model.

Steel fiber reinforced self-compacting concrete : experimental research and numerical simulation

Pereira, E. N. B.; Barros, Joaquim A. O.; Camões, Aires
Fonte: ASCE Publicador: ASCE
Tipo: Artigo de Revista Científica
Publicado em /08/2008 ENG
Relevância na Pesquisa
96.78%
Over the last few decades, the astonishing developments of super plasticizers technology allowed great achievements on the conception of concrete mixes exhibiting self-compacting ability. Since the eighties, some methodologies have been proposed to achieve self-compacting requirements in fresh concrete mixes, based on the evaluation of the flowing properties of these mixes. There still persist, however, some doubts about the most appropriate strategy to define the optimum composition of a self-compacting concrete (SCC) mix, based on a required performance. The behavior of SCC as a structural material can be improved if adequate steel fiber reinforcement is added to SCC mix composition. In fact, the fiber reinforcement mechanisms can convert the brittle behavior of this cement based material into a pseudo-ductile behavior up to a crack width that is acceptable under the structural design point-of-view. Fiber addition, however, increases the complexity of the mix design process, due to the strong perturbation effect that steel fibers cause on fresh concrete flow. In the present work, a mix design method is proposed to develop cost effective and high performance Steel Fiber Reinforced Self-Compacting Concrete (SFRSCC). The material properties of the developed SFRSCC are assessed as well as its potentiality as a structural material...

Durability of steel fiber reinforced self-compacting concrete

Frazão, Cristina M. V.; Camões, Aires; Barros, Joaquim A. O.; Gonçalves, Delfina
Fonte: CI-Premier Pte Ltd Publicador: CI-Premier Pte Ltd
Tipo: Conferência ou Objeto de Conferência
Publicado em //2013 ENG
Relevância na Pesquisa
96.68%
Publicado em "Proceedings of the 5th International Conference on The Concrete Future", ISBN 978-981-07-6067-0; For conventional concrete without steel fibers, although still an aspect under discussion, there are some commonly used durability indicators. However, for steel fiber reinforced self-compacting concrete (SFRSCC) literature is sparse and the aspects of durability, particularly corrosion resistance, still deserve deeper research, mainly the corrosion of the fibers, since its influence on the appearance and on the serviceability limit states of a SFRSCC structure can be a concern. Therefore, in the ambit of an ongoing research project dealing with the development of SFRSCC sandwich panels, durability tests were executed to compare the performance of SFRSCC and self-compacting concrete (SCC) specimens. Nine different tests were performed, applied to SFRSCC and SCC in order to characterize their mechanical properties (elasticity modulus, compressive strength and flexural behaviour) and to evaluate its durability indicators normally used for plain concrete, namely: water absorption by immersion and by capillarity, permeability to air, electrical resistivity, chloride diffusion by migration under nonsteady state and carbonation. The results for the different concretes and curing times up to 28 days are presented and analyzed.

Experimental analysis of reinforced concrete columns strengthened with Self-Compacting concrete

Omar,M. Y. M.; Gomes,R. B.; Reis,A. P. A.
Fonte: IBRACON - Instituto Brasileiro do Concreto Publicador: IBRACON - Instituto Brasileiro do Concreto
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2010 EN
Relevância na Pesquisa
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This paper presents the results of reinforced concrete columns strengthened by addition of a self-compacting concrete overlay at the compressed and at the tensioned face of the member, with and without addition of longitudinal steel bars. Eight columns were submit- ted to loading with an initial eccentricity of 60 mm . These columns had 120 mm x 250 mm of rectangular cross section, 2000 mm in length and four longitudinal reinforcement steel bars with 10 mm in diameter. Reference columns P1 and P2 were tested to failure without any type of rehabilitation. Columns P3 to P8 were loaded to a predefined load (close to the initial yield point of tension reinforce- ment), then unloaded and strengthened for a subsequent test until failure. Results showed that the method of rehabilitation used was effective, increasing the loading capacity of the strengthened pieces by 2 to 5 times the ultimate load of the reference column.

Numerical approach of the bond stress behavior of steel bars embedded in self-compacting concrete and in ordinary concrete using beam models

Almeida Filho,F.M.; El Debs,M. K.; El Debs,A.L.H.C.
Fonte: IBRACON - Instituto Brasileiro do Concreto Publicador: IBRACON - Instituto Brasileiro do Concreto
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2013 EN
Relevância na Pesquisa
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The present study evaluates the bond behavior between steel bars and concrete by means of a numerical analysis based on Finite Element Method. Results of a previously conducted experimental program on reinforced concrete beams subjected to monotonic loading are also presented. Two concrete types, self-compacting concrete and ordinary concrete, were considered in the study. Non-linear constitutive relations were used to represent concrete and steel in the proposed numerical model, aiming to reproduce the bond behavior observed in the tests. Experimental analysis showed similar results for the bond resistances of self-compacting and ordinary concrete, with self-compacting concrete presenting a better performance in some cases. The results given by the numerical modeling showed a good agreement with the tests for both types of concrete, especially in the pre-peak branch of the load vs. slip and load vs. displacement curves. As a consequence, the proposed numerical model could be used to estimate a reliable development length, allowing a possible reduction of the structure costs.

Avaliação das propriedades de durabilidade do concreto auto-adensável obtido com resíduo de corte de mármore e granito.; Evaluation of the durability properties of the self compacting concrete with marble and granite cutting waste.

Barros, Pedro Gustavo dos Santos
Fonte: Universidade Federal de Alagoas; BR; Estruturas; Programa de Pós-Graduação em Engenharia Civil; UFAL Publicador: Universidade Federal de Alagoas; BR; Estruturas; Programa de Pós-Graduação em Engenharia Civil; UFAL
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
96.67%
The self-compacting concrete (SCC) is a special concrete with excellent fluidity in the fresh state that dispenses the use of equipments of vibration for its compacting, furthermore ensures a resistance to blocking when released into elements with high rate reinforcement, decrease of transverse cross section and complex forms. The SCC mixes use a superplasticizer admixture and additions type filler and/or viscosity modifying, moreover lower volume and lower maximum size of the coarse aggregates. The use of mineral additions from industrial waste as a component of concrete, especially the so-called special concrete, has grown in several countries. In the SCC the use of waste as addition type filler is highly receptive, like the "mud" generated in the processing of blocks of marble and granite. The Residue of Court of Marble and Granite (RCMG) is generated on a large scale in many parts of Brazil, which led the Universidade Federal de Alagoas through its researchers to develop various experimental works using RCMG as addition type filler. They pointed out that the use of RCMG improved the performance of the concrete in the states fresh and hardened, however, demonstrated the need for a broader study of the durability of the CAA using the residue. In this way...

Avaliação do comportamento de vigas de concreto auto-adensável reforçado com fibras de aço.; Evaluation of the behavior of self-compacting concrete beams reinforced with steel fibers.

Barros, Alexandre Rodrigues de
Fonte: Universidade Federal de Alagoas; BR; Estruturas; Programa de Pós-Graduação em Engenharia Civil; UFAL Publicador: Universidade Federal de Alagoas; BR; Estruturas; Programa de Pós-Graduação em Engenharia Civil; UFAL
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
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The self-compacting concrete (SCC) has been characterized as a great evolution in the concrete technology, being able to fill all empty spaces of the formwork and selfcompacting only by action of its own weight. If steel fibers are added to SCC, without prejudice its properties in the fresh state, new advantages and possibilities of applications will provide concretes more efficient. In this context, a SCC with addition of industrial waste is used, and steel fibers with l/d ratio equal to 50 are incorporated, in a volume fraction of 1%, in order to assess the behavior of reinforced self-compacting concrete beams, with and without the addition of steel fibers, subject to normal and tangential stresses, and compare them with the behavior of conventional reinforced concrete beams. For that, were made reinforced concrete beams of dimensions (12,5 x 23,5 x 132) cm, which were tested by four-point bending, to the 28 days of age. To compare the results, were produced conventional concretes of different compositions, with and without steel fibers. The tests results in the fresh state shown that was possible the obtaining of concrete with self-compacting properties, even with the addition of steel fibers, from a mix already existent of SCC. The addition of the steel fibers to the SCC promoted slight gain in the load capacity of the beam...

Contribuição ao estudo da aderência de barras de aço em concreto autoadensável reforçado com fibras metálicas; Contribution to the study of adhesion of steel bar in self compacting concrete reinforced with fibers

Tojal, Thaise Lima
Fonte: Universidade Federal de Alagoas; BR; Estruturas; Programa de Pós-Graduação em Engenharia Civil; UFAL Publicador: Universidade Federal de Alagoas; BR; Estruturas; Programa de Pós-Graduação em Engenharia Civil; UFAL
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
96.84%
One of the conditions of existence assigned to the concrete as a building material is the adhesion between the concrete and steel. This adhesion has been the subject of several research studies that give rise to models that mathematically describe the behavior of adhesion; present testing techniques and in analysis of the influence of different factors that affect the concrete-steel adhesion. With the technological advancement of the concrete there were some special concrete compositions which contain chemical additives and minerals, and fiber, as is the case of self compacting concrete and concrete reinforced with fibers. These special concretes have shown different behavior compared to conventional concrete, contributing to an improved system of steel-concrete adhesion. Thus, this study used the pullout test of a steel bar of a massive concrete, following the standard model of RILEM-CEB-FIP (1973) known as Pull Out Test (Steel Reinforced Bond Test) were used conventional concrete, self compacting concrete and self compacting concrete with the addition of 1% steel fibers and steel bars used were 10mm and 16mm od diameter. The analyses were based on curves that describe the behavior of the loss of adhesion between the concrete and steel...

INFLUÊNCIA DE ADIÇÕES MINERAIS POZOLÂNICAS E DE FINOS DE PEDREIRA NAS PROPRIEDADES MECÂNICAS E NA MICROESTRUTURA DO CONCRETO AUTO-ADENSÁVEL; Influence of the mineral additions and the quarry dust in the mechanical properties and the microstructure of the self-compacting concrete

ARAÚJO, Janaína das Graças
Fonte: Universidade Federal de Goiás; BR; UFG; Mestrado em Engenharia Civil; Engenharias Publicador: Universidade Federal de Goiás; BR; UFG; Mestrado em Engenharia Civil; Engenharias
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
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For the benefits of its properties in fresh state, self-compacting concrete (SCC) demands a high powder content in the composition, nearby 450kg/m³. The quarry dust, resultant material of the coarse aggregate production, can b considered as an economic and sustainable alternative for the development of the SCC. As well as the quarry dust, mineral additions, is used in conventional concretes and can also be used in the self-compacting concrete, with the same kind of benefits. Using the mix design for SCC developed by Tutikian (2004) a study for evaluation of the SCC mechanical properties were done, where natural sand had been partially replaced by quarry micaschist, granite and gneiss - and cement for silica fume, metakaolin and calcined clay pozolan. The test methods for fresh state used was Slump-flow (FURNAS, 2005a), U-Box (FURNAS, 2005b), Entrained air (NM 47, 2002) and Specific gravity (9833, 1997). Cylindrical test specimen 100x200 mm had been molded for tests - compressive strength (NBR 5739, 1994), modulus of elasticity (NBR 8522, 1984), splitting tensile strength (NBR 7222, 1994) and flexural strength (NBR 12142, 1991) -the age of 28 days. Samples using the mixture1: 4,5 had been analyzed by scanning electron microscope (SEM). The results show that it can be possible the use of different additions for the production of high quality SCC. We detach the small variability of the specific gravity...

Análise de ligação entre o substrato de concreto antigo e concreto auto adensável com lançamento subaquático; Analysis of the connection between the substrate of old concrete and self-compacting concrete casting underwater

Mendes, Henry Silvério
Fonte: Universidade Federal de Uberlândia Publicador: Universidade Federal de Uberlândia
Tipo: Dissertação
POR
Relevância na Pesquisa
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O objetivo deste trabalho é apresentar os resultados do estudo da ligação entre um substrato e o concreto auto-adensável com lançamento subaquático simulando a realização de reparos em estruturas de concreto submersas em diversas aplicações. Para tanto foram utilizadas amostras de concreto “antigo” provenientes de estruturas extraídas da Usina Hidrelétrica de Itumbiara no estado de Goiás, que foram considerados substratos, o concreto utilizado no presente trabalho segue os parâmetros de dosagens estabelecidos na pesquisa concluída em 2003 pelo laboratório de Furnas Centrais Elétricas e foi ajustado aos materiais (brita e areia) encontrados na região de Uberlândia do Estado de Minas Gerais. Os resultados obtidos são provenientes de testemunhos das juntas verticais e horizontais dos corpos-de-prova prismáticos concretados com substratos e mantidos submersos e extraídos após um ano, portanto, a hidratação quase completa. As análises relativas ao processo de lançamento do concreto indicam que é totalmente viável sua produção para pequenas aplicações. A visibilidade durante a concretagem foi dificultada pelo aumento de turbidez da água produzida pelo concreto, portanto deve-se diminuir a presença de um fluxo de água direto no concreto. As análises foram por comparação entre os resultados dos testemunhos e dos corpos-de-prova. Foi observado um aumento da resistência em relação direta ao diâmetro do testemunho. Nos testemunhos de 50 mm x 100 mm obteve-se um coeficiente de variação de 9% dando ao concreto uma variabilidade baixa. Os testemunhos compostos de concreto submerso e substrato de concreto (com junta inclinada) obtiveram uma resistência com valor 84% em relação os corpos-de-prova. A resistência à tração por compressão diametral dos testemunhos correspondeu a 54% do valor de referência. Também pode ser verificada a interface entre substrato e concreto após a ruptura. __________________________________________________________________________________________ ABSTRACT; The objective of this paper is to present the results of the connection between a substrate and self-compacting concrete with underwater launch simulating the repairs to concrete structures submerged in various applications. Therefore...

Estudos experimentais sobre cisalhamento em vigas de concreto auto adensável variando-se a altura e a taxa de armadura longitudinal; Experimental studies on shear in self compacting concrete beams by varying beam depth and longitudinal reinforcement ratio

Teodoro, Heitor Ventura
Fonte: Universidade Federal de Goiás; Brasil; UFG; Programa de Pós-graduação em Engenharia Civil (EEC); Escola de Engenharia Civil - EEC (RG) Publicador: Universidade Federal de Goiás; Brasil; UFG; Programa de Pós-graduação em Engenharia Civil (EEC); Escola de Engenharia Civil - EEC (RG)
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
96.86%
This study presents the results of an experimental research on shear in self compacting concrete beams. The influence of beam depth and longitudinal reinforcement ratio in beams was evaluated and results compared with similar beams cast with conventional concrete beams. Cracking, deformations in compression strut, vertical displacements, reinforcement deformation and load failure and failure mode were evaluated. Sixteen 1000 mm long beams with a 150 mm cross sectional width were tested. Eight beams were cast with self compacting concrete and eight with conventional concrete. Both were designed for a concrete fck = 25 MPa. The longitudinal reinforcement of each beam was design to ensure shear failure. Each group consisted of eight beams with four beams had a longitudinal reinforcement ratio of 1.3% and beam depths of 20 cm, 25 cm, 30 cm and 35 cm in height, and the other four beams had longitudinal reinforcement ratio of 2,3% with the same beam depths. The beams were instrumented with seven LVDT's, five of which were positioned to read vertical displacements and the other two were glued on the side of the beam for measuring crack width and displacements in the compression strut. Four strain gages used in the beam’s longitudinal and transverse reinforcement. The beams were tested to failure with a concentrated load at midspan. The results showed that all the beams failed by crushing of the concrete compression zone above the shear crack. Overall...

Obtenção do concreto autoadensável utilizando resíduo do beneficiamento do mármore e granito e estudo de propriedades mecânicas; Obtaining of the Self Compacting-Concrete using Residue of the Improvement of the Marble and Granite and Study of Mechanical Properties

Lisbôa, Edvaldo Monteiro
Fonte: Universidade Federal de Alagoas; BR; Estruturas; Programa de Pós-Graduação em Engenharia Civil; UFAL Publicador: Universidade Federal de Alagoas; BR; Estruturas; Programa de Pós-Graduação em Engenharia Civil; UFAL
Tipo: Dissertação Formato: application/pdf
POR
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The Self-Compacting Concrete (SCC) it needs of the high amount of fine in yo ur composition to assist your properties in the fresh state. In the context of the fine materials if show the Residue of the Improvement of the Marble and Granite (RBMG), which was chosen to compose the dosagem of CAA in that research. This was a form of contributing with the technological progress and maintainable development of the concrete. Using Gomes' Methodology (2002) for obtaining of SCC, the study of the paste was developed through the rehearsals in the Cone of Marsh and in the Mini-slump and the study of the mortar using the rehearsals in the Cone of Marsh and in the cone log of the consistence table, all, in the sense of obtaining the percentile great of superplasticizer and an appropriate amount of RBMG in the composition of the mixture. Starting from parameters obtained in the study of the paste and mortar was given segment to a practical application of completion of premolded pieces, without the use of any type of mechanical vibration, with self-compacting mortar. Soon after, through the study of the composition of the granular skeleton it was obtained the great relationship among the small and great aggregate. The study of the concrete was developed using the rehearsals of Slump-flow...

Impact of vibrations on the final characteristics of normal and self-compacting concrete

Juradin,Sandra; Baloević,Goran; Harapin,Alen
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2014 EN
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The quality and durability of normal concrete directly depends on the number and the shape of voids, so, in order to produce durable concrete, it is necessary to reduce the amount of air that is trapped inside the concrete, which is usually done by vibrating the concrete in the mixing stage or the casting stage. Self-compacting concretes are concretes that, in principle, don't require vibrating during casting. Such concretes possess enough compactness and flowability through gravity that during pouring they fill all the space in the formwork. However, it is frequently the case that the ideal self-compacting concrete that is produced in a laboratory cannot be produced on a construction site so such concretes require additional vibrations. The work examines the impact that the introduction of vibrations during mixing and during casting has on the final appearance and the compressive strength of normal and self-compacting concretes. Achieved results confirm that vibrating during the mixing stage can improve the workability of fresh concrete but not its final strength, especially for self-compacting concretes, while vibrating in the casting stage significantly contributes to the final strength of the concrete.