Biblioteca Digital

A study of the bond behaviour between steel reinforcement bars and four different types of surrounding concrete: normal strength concrete (NSC), steel fibber reinforced concrete (SFRC) and two structural lightweight aggregate concretes (SLWAC) is here presented. Five beam-tests according to Standard RILEM (1982) [5] were conducted on specimens under monotonously increased loading. Bond-slip response curves between concretes and reinforcement are obtained and discussed. The results obtained show that standard bond length of 10∅d is not adequate to determine bond characteristics of reinforcement in concretes with grades higher than C 25/30. Bond failure of the NSC beam did not occur but the bar itself failed. Bond failure was observed for NSC beam and for LWAC and SFRC beams when reduced bond length of 5∅d was used. A numerical simulation of the beam tests using the finite element method analysis, using bond-slip model of CEB-FIP Model Code 1990 [1] and real properties of test materials, was also carried out and the results are compared with the experimental values.

The main objective of this study was to evaluate the potential application of a lightweight concrete produced with lightweight coarse aggregate made of the water treatment sludge and sawdust (lightweight composite), by determining the thermal properties and possible environmental impact of future residue of this concrete. Two types of concrete were prepared: concrete produced with the lightweight composite dosed with cement/sand/composite/water in a mass ratio of 1:2.5:0.67:0.6 and conventional concrete dosed with cement/sand/crushed stone/water in a mass ratio of 1:4.8:5.8:0.8. The thermal properties were determined by the hot wire parallel technique. The possible environmental impact was measured using the procedures and guidelines of the Brazilian Association of Technical Standards - ABNT. The concrete produced with the lightweight composite presented a 23% lower thermal conductivity than the conventional concrete. The concrete produced with the lightweight composite presented a set of thermal properties suitable for the application of this concrete in non-structural sealing elements. The concentration of aluminum in the solubilized extract of the concrete produced with the lightweight composite was much lower than the concentration of aluminum in the water treatment sludge...

This paper deals with the effect of silica fume and styrene-butadiene latex (SBR) on the microstructure of the interfacial transition zone (ITZ) between Portland cement paste and aggregates (basalt). Scanning electron microscope (SEM) equipped with energy dispersive X-ray analysis system (EDX) was used to determine the ITZ thickness. In the plain concrete a marked ITZ around the aggregate particles (55 mu m) was observed, while in concretes with silica fume or latex SBR the ITZ was less pronounced (35-40 mu m). However, better results were observed in concretes with silica fume and latex SBR (20-25 mu m). (C) 2008 Elsevier Ltd. All rights reserved.; Research Sponsoring Foundation of Sao Paulo State (Fundacao de Apoio a Pesquisa do Estado de Sao Paulo - FAPESP); Civil Engineering National Laboratory (Laboratorio Nacional de Engenharia Civil - LNEC) in Lisbon, Portugal

Bearing pads are used in precast concrete connections to avoid concentrated stresses in the contact area between the precast elements. In the present research, the bearing pads are Portland cement mortar with styrene-butadiene latex (SB), lightweight aggregate (expanded vermiculite-term) and short fibers (polypropylene, glass and PVA), in order to obtain a material with low modulus of elasticity and high tenacity, compared with normal Portland cement mortar. The objective of this paper is to analyze the influence of surface roughness on the pads and test other types of polypropylene fibers. Tests were carried out to characterize the composite and test on bearing pads. Characterization tests show compressive strength of 41MPa and modulus of elasticity of 12.8GPa. The bearing pads tests present 30% reduction of stiffness in relation to a reference mortar. The bearing pads with roughness on both sides present a reduction up to 30% in stiffness and an increase in accumulated deformation of more than 120%, regarding bearing pads with both sides smooth.

Esta tese aborda a aplicação da tecnologia dos concretos leves de alto desempenho (CLAD) para a produção de elementos construtivos esbeltos pré-fabricados, tais como painéis estruturais e de vedação e peças para cobertura, apresentando um concreto com propriedades especiais em função da utilização conjunta de látex de estireno butadieno (SB), sílica ativa, superplastificante acelerador e agregados leves nacionais, denominado concreto leve de alto desempenho modificado com SB. Desenvolveu-se um amplo programa experimental para a análise dos concretos, tendo como objetivos o estudo dos processos de dosagem e produção, caracterização das propriedades dos concretos nos estados fresco e endurecido, análise da ductilidade de elementos construtivos esbeltos pré-fabricados submetidos à flexão, assim como a obtenção de informações microestruturais sobre a matriz de cimento e a zona de transição entre o agregado e a matriz de cimento. Os resultados do programa experimental demonstraram que os concretos leves de alto desempenho modificados com SB são extremamente adequados à produção de elementos pré-fabricados esbeltos, devido essencialmente à redução da massa específica e ao excelente desempenho das propriedades relacionadas à resistência mecânica e durabilidade. Nos estudos microestruturais...

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...

Nos países em desenvolvimento, como o Brasil, os resíduos gerados nos decantadores e filtros das estações de tratamento de água são geralmente dispostos nos mesmos rios e córregos que suprem água para o tratamento. Outro problema ambiental está relacionado à disposição irregular dos resíduos de madeira. As indústrias de base florestal geram grande quantidade deste resíduo desde a exploração florestal até a manufatura do produto final. Este trabalho avalia a possibilidade de combinar estes dois resíduos e produzir um compósito leve para uso como agregado graúdo em concreto. O lodo seco e moído foi misturado com água e serragem e moldado manualmente na forma de pelotas redondas de 14±02 mm. A relação em massa da serragem, lodo e água foi 1:6:4,5. Depois de seco, os grãos do compósito foram imersos em óleo de linhaça cozido por 1 min. Este tempo foi considerado o menor período de imersão necessário para estabilizar a resistência mecânica, reduzir a absorção de água e evitar a quebra dos grãos durante a preparação e aplicação do concreto. Depois que o óleo foi aplicado, os grãos foram secos à temperatura ambiente. A massa unitária do compósito no estado seco e solto foi 672 kg/m3. A serragem de madeira usada no desenvolvimento e produção do compósito foi do gênero Pinnus. Esta madeira apresentou diâmetro médio dos poros de 17...

Este trabalho tem por objetivo o estudo da viabilidade da utilização de cerâmica vermelha para a confecção de agregados leves de argila calcinada para utilização em concretos estruturais. Inicialmente, foram coletadas amostras de solo de cinco diferentes empresas produtoras de cerâmica vermelha do estado de São Paulo. As massas cerâmicas foram caracterizadas por meio das técnicas de limites de liquidez (LL) e plasticidade (LP), análise granulométrica, análise química e difração de raios X (DRX). Os corpos de prova confeccionados com essas massas cerâmicas, queimados à temperatura de 900ºC, foram caracterizados por meio da avaliação da retração linear, absorção de água, porosidade aparente, massa específica aparente, expansão por umidade e resistência à compressão. Após a caracterização dos corpos de prova de cerâmica vermelha, foram escolhidas duas amostras para a confecção dos agregados leves de argila calcinada. Em seguida, foram confeccionados corpos de prova de concreto com agregados leves de argila calcinada, argila expandida e brita. Os corpos de prova de concreto leve foram caracterizados pelos ensaios de slump, massa específica fresca, teor de ar incorporado, resistência à compressão...

Dissertação de mestrado em Engenharia Civil (área de especialização em Estruturas, Geotecnia e Fundações); Este trabalho pretende constituir prova das potencialidades da utilização madeira como material estrutural, quer em acções de reabilitação quer em construções novas. Para tal, numa primeira fase, realiza-se uma síntese das principais propriedades da madeira como material de construção. De seguida, descrevem-se os estudos experimentais realizados no Laboratório de Engenharia Civil da Universidade do Minho, e que se podem agrupar nas três seguintes etapas: validação da metodologia de cálculo estabelecida pelo Eurocódigo 5 para as ligações tipo cavilha, utilizando para o efeito a espécie de madeira mais comum em Portugal (pinus pinaster); estudo do comportamento das ligações mistas madeira-betão leve, verificando a adequação da metodologia proposta no Eurocódigo 5 sobre este tema; realização de ensaios de corte à escala real sobre alguns sistemas de ligação madeira-betão disponíveis no mercado. O trabalho incluiu, ainda, a apresentação da técnica construtiva das lajes mistas madeira-betão, descrevendo-se a evolução das tipologias, os vários sistemas de ligação possíveis e os procedimentos de cálculo. Por fim...

A lightweight concrete using granulated corn cob (without corn) as an aggregate is proposed in this research work. Taking into account that corn cob, after extracting the corn, is generally considered an agricultural waste, an interesting economic and sustainable benefit may result by using it as a building material. Therefore, it can be an alternative sustainable lightweight aggregate solution in comparison to the most currently applied ones such as expanded clay, particles of cork, particles of expanded polystyrene (EPS), among others. The density, the compressive strength and the thermal insulation properties of a corn cob concrete were experimentally quantified. An expanded clay concrete was also studied as reference. The main results obtained are presented and discussed showing that the proposed corn cob concrete may have the adequate material properties required for a lightweight concrete for non-structural application purposes.

A lightweight concrete using granulated corn cob (without corn) as an aggregate is proposed in this research work. Taking into account that corn cob, after extracting the corn, is generally considered an agricultural waste, an interesting economic and sustainable benefit may result by using it as a building material. Therefore, it can be an alternative sustainable lightweight aggregate solution in comparison to the most currently applied ones such as expanded clay, particles of cork, particles of expanded polystyrene (EPS), among others. The density, the compressive strength and the thermal insulation properties of a corn cob concrete were experimentally quantified. An expanded clay concrete was also studied as reference. The main results obtained are presented and discussed showing that the proposed corn cob concrete may have the adequate material properties required for a lightweight concrete for non-structural application purposes.

This study concerns the numerical simulation of effective elasticity modulus of lightweight concrete by means of Asymptotic Expansion Homogenization. Taking as input data the elastic properties of the aggregate and mortar employed in the concrete composition, it is possible to evaluate a homogenized elastic tensor for the resulting material. The present work deals with lightweight concretes made of the same mortar and five families of low density aggregates, with varying aggregate volumetric fractions. The multiscale model employed to represent the geometric and mechanical properties of the concrete is characterized by a great deal of simplicity. The validation of the adopted procedure consisted of comparisons of the numerical results with experimental measurements, showing good agreement.

Nowadays lightweight concrete is used on a large scale for structural purposes and to reduce the self-weight of structures. Specific grav- ity, compressive strength, strength/weight ratio and modulus of elasticity are important factors in the mechanical behavior of structures. This work studies these properties in lightweight aggregate concrete (LWAC) and normal-weight concrete (NWC), comparing them. Spe- cific gravity was evaluated in the fresh and hardened states. Four mixture proportions were adopted to evaluate compressive strength. For each proposed mixture proportion of the two concretes, cylindrical specimens were molded and tested at ages of 3, 7 and 28 days. The modulus of elasticity of the NWC and LWAC was analyzed by static, dynamic and empirical methods. The results show a larger strength/ weight ratio for LWAC, although this concrete presented lower compressive strength.

Abstract not available.; Kim Hung Mo, U. Johnson Alengaram, Phillip Visintin, See Heng Goh, Mohd Zamin Jumaat

Indiana Geological Survey Report of Progress 12; Laboratory tests show that some Indiana shales are potential sources of manufactured lightweight aggregate. Bloating, the process by which lightweight aggregates are manufactured, is caused by various constituents acting singly or in combination. Chemical composition and mineral composition of the shales and particle-size distribution of the mineral constituents are interrelated, and all of these factors contribute to the bloating of shales. This study was made to test the potential use of some Indiana, shales as raw materials for manufacturing lightweight aggregate. Such aggregate was produced in Ohio, Illinois, and Kentucky before any interest was shown in Indiana. A new plant is now producing lightweight aggregate from shale of the Borden group near Brooklyn, Ind., but other plants are needed to meet the increasing demand for lightweight concrete in the State. It is hoped that this report will stimulate interest in developing lightweight aggregate from shale and will enable future producers of lightweight aggregate in Indiana to evaluate better the location, thickness, extent, and physical properties of various shale formations.; Indiana Department of Conservation

A research work was performed in order to assess the potential application of processed granulate of corn cob (PCC) as an alternative lightweight aggregate for the manufacturing process of lightweight concrete masonry units (CMU). Therefore, CMU-PCC were prepared in a factory using a typical lightweight concrete mixture for non-structural purposes. Additionally, lightweight concrete masonry units based on a currently applied lightweight aggregate such as expanded clay (CMU-EC) were also manufactured. An experimental work allowed achieving a set of results that suggest that the proposed building product presents interesting material properties within the masonry wall context. Therefore, this unit is promising for both interior and exterior applications. This conclusion is even more relevant considering that corn cob is an agricultural waste product.; En este trabajo de investigación se evaluó la posible aplicación de granulado procesado de la espiga de mijo como un agregado ligero alternativo en el proceso de fabricación de unidades de mampostería de hormigón ligero. Con esta finalidad, se prepararon en una fábrica diversas unidades de mampostería no estructural con granulado procesado de la espiga de mijo. Además, se fabricaran unidades de mampostería estándar de peso ligero basado en agregados de arcilla expandida. Este trabajo experimental permitió lograr un conjunto de resultados que sugieren que el producto de construcción propuesto presenta interesantes propiedades materiales en el contexto de la pared de mampostería. Por lo tanto...

The mechanical characteristics of the lightweight aggregate concretes (LWAC) strongly depend on the proportions of aggregates in the formulation. In particular, because of their strong porosity, the lightweight aggregates are much more deformable than the cementations matrix and their influence on concrete strength is complex. This paper focuses on studying the physical performance of concrete formulated with substitution of 30% of coarse aggregates by limestone dust. In this article an attempt is made to provide information on the elastic properties of lightweight concrete (LWC) from tests carried out under uniaxial compression conditions. The results of Young modulus, Poisson's ratio, and compressive and flexural tensile strength tests on concrete are presented. The concretes obtained present good mechanical performances reaching 34.99 MPa compressive strength, 6.39 MPa flexural tensile strength and in front of 36 MPa Young modulus.

Forty-eight samples of Delaware clays were collected and tested jointly by the Delaware Geological Survey and the U. S. Bureau of Mines. Clays potentially useful for face brick are common. The nonmarine Cretaceous Potomac Formation is a potential economic clay at virtually all locations sampled. Some Miocene and Pleistocene clays are also possibilities for brick clays. Other Potomac clays are potential sources for glazed tile, sewer pipe, refractory brick, and stoneware. Coastal marsh clays, frequently containing much organic debris, are potential source material for lightweight aggregate used in lightweight, strong concrete products. Lightweight aggregate has the potential for augmenting dwindling reserves of crushed stone and gravel aggregate.; In cooperation with the United States Bureau of Mines, Curtis Edgerton, Geologist, Pittsburgh Office

This work proposes a methodology to predict the elastic modulus of lightweight aggregate concretes. To this end an analytical formula is achieved by curve fitting experimental results from 135 concrete samples made of 45 different mixes. The validation of the proposed methodology is carried out by applying the obtained analytical formula to a set of 90 concrete samples made of 30 different mixes. Comparisons with other methods applied to predicting the elastic modulus of lightweight aggregate concretes indicate that the results show good agreement and suggest that the proposed methodology could be applied in practical situations.

Lytag, manufactured first by pelletisation of a mixture of fly ash, bentonite and water, and then by sintering the spherical pellets at about 1 300°C, is used as coarse aggregate for producing lightweight plain and structural concrete mixtures. The weight of lightweight concretes is reduced significantly without compromising the structural integrity. The reduced dead load results in significant savings in the cost of foundations and reinforcement, as well as reduction in the sizes of columns, beams and slabs, which in turn reduce the overall volume of concrete and the costs of formwork and scaffolding. This paper reports on the results of an experimental study which consisted of designing, preparing and testing different mixtures of lightweight aggregate concrete considering four dosages of Lytag, used as coarse aggregate. It was found that the density and workability of concrete mixtures significantly decreased with increase in the dosage of Lytag. Concrete mixtures containing Lytag were found to be stronger than normal weight concrete. However, the strength of the lightweight aggregate concrete is found to be maximum at an optimum dosage of the Lytag.