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Auswahl der wissenschaftlichen Literatur zum Thema „Concrete“
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Zeitschriftenartikel zum Thema "Concrete"
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Bergmann, Ana Claudia, Gustavo Savaris, Carlos Eduardo Tino Balestra und Lucia Bressiani. „CONCRETOS AUTOADENSÁVEIS E CONVENCIONAIS: ANÁLISE DAS PROPRIEDADES EM ESTADO FRESCO E ENDURECIDO“. REEC - Revista Eletrônica de Engenharia Civil 15, Nr. 2 (12.05.2020): 167–78. http://dx.doi.org/10.5216/reec.v15i2.50695.
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RESUMO: Os concretos autoadensáveis destacam-se por suas características essenciais: capacidade de preenchimento de fôrmas, habilidade passante e resistência à segregação, permitindo assim o aumento da qualidade de peças estruturais de concreto, assim como a otimização de sua execução. Contudo, para obtenção de suas características essenciais, um fator é imprescindível trata da utilização de materiais finos, com o objetivo de controlar os efeitos negativos de segregação e exsudação à que o concreto fresco é suscetível a apresentar. Neste contexto, o presente trabalho tem por objetivo comparar as propriedades no estado fresco e endurecido de um concreto autoadensável, utilizando cinza volante como material fino, com um concreto convencional, produzidos com materiais disponíveis na região de Toledo-PR. Os resultados demonstraram que o concreto autoadensável apresentou melhor desempenho quanto às propriedades mecânicas em relação ao concreto convencional. As imagens obtidas por meio da microscopia eletrônica de varredura corroboraram para sustentar as afirmativas acerca da melhora nas propriedades mecânicas do concreto autoadensável, uma vez que foi evidenciada uma menor quantidade de vazios graças à atividade pozolânica da cinza volante. Neste sentido, este trabalho contribui para a difusão do concreto autoadensável e seu uso em construções usuais, resultando em estruturas de concreto duráveis e confiáveis, reduzindo a necessidade de manutenções.
ABSTRACT: The self-consolidating concretes stand out for their essential characteristics: flowability, passing ability and segregation resistance, allowing the increase of the structural elements quality, as well as the optimization of their production. However, in order to obtain its essential characteristics, the main factor is the use of fines, in order to control the negative effects of segregation and bleeding to which fresh concrete is susceptible. In this context, the aim of this paper is to compare the properties, in the fresh and hardened states, of self-consolidating concretes, using fly ash as fine material with the properties of a conventional concrete, produced with materials available in the Toledo-PR, Brazil. The results showed that the self-consolidating concrete presented better performance in relation to the mechanical properties compared to conventional concrete. Using scanning electronic microscopy the affirmations about the improvement in the mechanical properties of self-consolidating concrete were proven, since a smaller amount of voids was evidenced due to the pozzolanic activity of fly ash. In this sense, this work contributes to the diffusion of self-consolidating concrete in the literature and its use in usual constructions, resulting in durable and reliable concrete structures, reducing the maintenance works.
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Žiogas, Vigantas Antanas, Svajūnas Juočiūnas und Giedrius Žiogas. „HYDROTECHNICAL CONCRETE WITH LOCAL AGGREGATES AND THEM USING FOR MONOLITHIC STRUCTURES“. Engineering Structures and Technologies 1, Nr. 2 (30.06.2009): 102–10. http://dx.doi.org/10.3846/skt.2009.13.
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The article discusses the technological peculiarities of construction monolithic hydrotechnical concrete structures, use of local aggregates for producing special concretes, methods of determining water impermeability of concretes as well as the evaluation of the methods mentioned above. The article presents the requirements for the granulometric composition of aggregate mixes for the production of flowing concrete mixes used for the construction of monolithic hydrotechnical structures. The possibilities and expediency of using local crushed gravel with increased amounts of weak particles for hydrotechnical structures are discussed. The mass loss of weak particles is slight compared with the whole mass of aggregates, and the total mass loss of crushed gravel it occurs due to micro-cracks present in particles. The frost resistance mark of crushed gravel and its suitability for hydrotechnical concretes should be determined by evaluating the amount of weak particles and their frost resistance. The article discusses concrete impermeability data received by means of two methods (according to LSTST 1974:2005 and LSTST EN 12390–8 requirements). Theoretical water penetration depths have been calculated. Determination of water impermeability according to LSTST 1974:2005 is recommended for C25/30 and lower compressive strength class concretes with W≤8. The LSTST EN 12390–8 water impermeability determina-tion method is recommended for C25/30 and higher compressive strength class concretes whose water impermea-bility mark is W≥8. For the construction of certain hydrotechnical structures water impermeable concretes whose water penetration depth should not exceed 20mm are recommended for use instead of the W6 and W8 concretes. Technological peculiarities and potential technological-organizational solutions for high walls of a water treatment plant have been discussed. The analysis of potential concreting methods of the reservoir’s high walls has been made as well as that of the key parameters of the continuous concreting process and their interaction. Dependences for the estimation of continuous concreting volumes and permissible concreted segment lengths have been proposed by evaluating the beginning of the intensive formation structure of concrete, number of layers in the height of the concreted wall and concreting intensity.
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Meesaraganda, Lakshmi Vara Prasad, Endow Ayar Mazumder und L. Ramaprasad Reddy. „Durability Studies of Conventional Cement Concrete and Geopolymer Concrete“. Materials Science Forum 1116 (05.03.2024): 97–103. http://dx.doi.org/10.4028/p-o39dkm.
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The service life of structural members is significantly impacted by the durability of the concrete and that they are made of. The embedded reinforcing steel in durable concrete is protected from corrosion, and the possibility of concrete spalling in the concrete as a result of chemical attack is reduced. This study investigates the effectiveness of geopolymer concretes prepared using fly ash or a mixture of fly ash and slag (SLG). The performance of OPC concrete is likewise evaluated for comparing the durability of geopolymer concretes. This is done in order to compare the two types of concrete. All of the prepared specimens were submerged in theee types of distinct solutions up to 9 months. Four different types of solutions are (i) sodium chloride with 5% concentration, (ii) sodium sulphate 5% concentration, (iii) combination of magnesium sulphate with sodium sulphate with 5% concentration both, and sulphuric acid 3% concentration. The variation in properties were evaluated throughout the duration of the exposure period. According to the findings, it has been demonstrated that Na2SO4 (sodium sulphate) has the most significant effect on the geopolymer concretes, whereas sulphuric acid has the greatest potential to break down OPC concrete. With the effect of sulfuric acid, the strength reduction was 26.57% for OPC concrete and where as for flyash & SLG concretes it is 10.87% & 7.26% respectively. According to the findings, the durability performance of geopolymer concrete is, in general, better to that of cement concrete.
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Pani, Luisa, Lorena Francesconi, James Rombi, Fausto Mistretta, Mauro Sassu und Flavio Stochino. „Effect of Parent Concrete on the Performance of Recycled Aggregate Concrete“. Sustainability 12, Nr. 22 (12.11.2020): 9399. http://dx.doi.org/10.3390/su12229399.
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Recycling concrete construction waste is a promising way towards sustainable construction. Indeed, replacing natural aggregates with recycled aggregates obtained from concrete waste lowers the environmental impact of concrete constructions and improves natural resource conservation. This paper reports on an experimental study on mechanical and durability properties of concretes casted with recycled aggregates obtained from two different parent concretes, belonging to two structural elements of the old Cagliari stadium. The effects of parent concretes on coarse recycled aggregates and on new structural concretes produced with different replacement percentages of these recycled aggregates are investigated. Mechanical properties (compressive strength, modulus of elasticity, and splitting tensile strength) and durability properties (water absorption, freeze thaw, and chloride penetration resistance) are experimentally evaluated and analyzed as fundamental features to assess structural concrete behavior. The results show that the mechanical performance of recycled concrete is not related to the parent concrete characteristics. Furthermore, the resistance to pressured water penetration is not reduced by the presence of recycled aggregates, and instead, it happens for the chloride penetration resistance. The resistance to frost–thawing seems not related to the recycled aggregates replacement percentage, while an influence of the parent concrete has been assessed.
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Kaitukov, Batraz, Mihail Stepanov und Pavel Kapyrin. „The choice of concrete mixers for the concrete preparation“. MATEC Web of Conferences 178 (2018): 06016. http://dx.doi.org/10.1051/matecconf/201817806016.
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The production of commodity concretes is a large segment of the construction industry and a testing base for concrete mixers. The choice of high-reliable concrete mixers for high-quality production of various brands of concrete is topical. When choosing concrete mixers, the most important is condition for improving the quality of mixing. Solving this problem, the analysis of various parameters and structural designs of concrete mixers is carried out. Dependencies are established that show the properties of concrete of various brands with their composition and technical characteristics of concrete mixers. Variants of rational selection of concrete mixers that provide high uniformity of concretes and a combination of the components of the mixture are proposed. The capacities of various concrete mixers for the preparation of commodity concrete are determined and the optimum rotational speeds of the working elements of concrete mixers are determined. Reasonable speeds of movement of working elements are revealed and dependences of the Reynolds number on frequency of rotation of a drum between capacity and diameter of a drum of a concrete mixer are established. This method of selecting rational concrete mixers allows reducing operating costs and improving the quality of concrete.
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Stehlík, Michal. „TESTING THE STRENGTH OF CONCRETE MADE FROM RAW AND DISPERSION-TREATED CONCRETE RECYCLATE BY ADDITION OF ADDITIVES AND ADMIXTURES“. Journal of Civil Engineering and Management 19, Nr. 1 (16.01.2013): 107–12. http://dx.doi.org/10.3846/13923730.2012.734853.
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Today, concrete comprises more than 65% of the total volume of building constructions. As it undergoes degradation and buildings require refurbishment, the volume of concrete increases at disposal sites. Due to a lack of non-renewable resources and due to high prices of energies, the reuse of concrete seems to be more than desirable. It is common knowledge that in concretes made from recycled concrete, the strengths of the original concretes can hardly be achieved. The addition of dispersion additives and mineral admixtures into the freshly mixed concrete can contribute to improving the mechanical properties of concretes made from recycled concrete. Potential composite action of the recyclate, mineral admixtures and dispersion additives in increasing the compressive strength of concretes made from recycled concrete remains to be a question.
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Santor, M. S., A. L. G. Gastaldini, C. Crauss, G. T. Dos Santos und F. C. Rossini. „Influência de materiais de proteção na resistividade elétrica do concreto“. Revista ALCONPAT 2, Nr. 1 (30.01.2012): 46–56. http://dx.doi.org/10.21041/ra.v2i1.26.
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RESUMOA durabilidade das estruturas de concreto armado é resultado da ação protetora do concreto sobre a armadura. Quando a passivação do aço deixa de existir a estrutura torna-se vulnerável ao fenômeno da corrosão, cuja propagação, após iniciada é essencialmente controlada pela resistividade elétrica do concreto. O objetivo deste trabalho foi avaliar a alteração na resistividade elétrica de concretos produzidos com diferentes tipos de cimento, CP II F, CP IV e CP V, submetidos a tratamento superficial com produto obturador dos poros e argamassa polimérica. Para efeito de análise os resultados foram comparados com os mesmos concretos sem aplicação do produto. Esses tratamentos foram realizados em concretos confeccionados com resistências à compressão na idade de 28 dias de 21,6MPa, 26,6 MPa e 31,6 MPa. Para todos os tipos de cimento utilizados e níveis de resistência adotados o tratamento superficial com argamassa polimérica resultou em maiores valores de resistividade elétrica.Palavras chave: Concreto; durabilidade; material de proteção superficial; resistividade elétrica.ABSTRACTThe durability of concrete structures is a result of the protective action of concrete on the reinforcement. When there is no passivation of steel, the structure becomes vulnerable to corrosion, and once corrosion starts its propagation is essentially controlled by the electrical resistivity of concrete. The objective of this study was to evaluate the change in electrical resistivity of concretes produced with different types of cement: CP II F, CP IV and CP V that were surface-treated with pore filler and polymer mortar. For analysis purposes, the results were compared with those of the blanks that were not subjected to surface treatment. These treatments were performed in concretes with the following compressive strengths at the age of 28 days: 21.6 MPa, 26.6 MPa and 31.6 MPa. For all types of cement used and strengths adopted, surface treatment with polymer mortar led to higher electrical resistivity values.Key words: Concrete; durability; surface protection material; electrical resistivity.
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Wang, Chong, Chang Hui Yang, Chao Jun Wan und Yan Feng Tian. „Comparison of Fluidity between Metakaolin and Silica Fume Concretes“. Key Engineering Materials 477 (April 2011): 95–101. http://dx.doi.org/10.4028/www.scientific.net/kem.477.95.
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Aiming at preparing the high performance concrete with metakaolin (MK) replacing silica fume (SF), comparison of fluidity between MK concrete and SF concrete was investigated in this paper. Slump, spread, and slump loss with time of fresh concrete under the condition of superplasticizer adding were tested, which containing with 5 to 15 wt. % replacement of MK, SF, combination of MK and ground granulated blastfurnace slag (GGBS), or combination of SF and GGBS, respectively. The mechanism for exploring fluidity difference of MK concrete and SF concrete were researched by measuring ζ potential and superplasticizer adsorption. The results indicate that concretes containing with 5 to 15 % MK were provided with better workability than concretes with SF. Fluidity of MK concretes incorporating with 5 to 15 % GGBS was better than that of SF concretes. Incorporating with 5 to 15% replacement, MK-cement-superplasticizer system present higher ζ potential, and lower superplasticizer adsorption than SF-cement-superplasticizer, which is an answer to why MK concrete has better fluidity than SF concrete. Physical filling effect of mineral additives is also is helpful to concrete fluidity.
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Dobshits, Lev M. „Physical and mathematical modeling of frost resistance for cement concretes“. Structural Mechanics of Engineering Constructions and Buildings 19, Nr. 3 (30.09.2023): 313–21. http://dx.doi.org/10.22363/1815-5235-2023-19-3-313-321.
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The key factor of engineering structures made of concrete and reinforced concrete is insufficient frost resistance of concretes. It is important to identify the causes and prevent concrete damage caused by frost. The research provides the basic points of the developed physical and mathematical theory of cement concretes frost resistance. Under consideration are the processes occurring during cyclic freezing and thawing of concrete in a water-saturated state. The results of the performed theoretical and experimental studies are presented. The criterion of concrete frost resistance, which estimates the pore structure of concrete, was derived on the basis of the obtained results. The suggested criterion has a close correlative relation with the frost resistance of concrete. Using this interrelation, the method was proposed for accelerated determination of actual frost resistance of concrete, as well as the method of selection concretes' compositions for a specified design frost resistance of concretes. The methods of accelerated determination of concrete frost resistance, as well as ways to increase it, are described. The developed physical and mathematical model was used to carry out computational modeling for freezing of an extended concrete structure. This made it possible to determine the changes in humidity, temperature, and pressure in concrete during cyclic freezing and thawing at different distances from the surface of its freezing and also draw graphs of changes in these parameters. The recommendations on assignment of concrete design grades by frost resistance for various elements of concrete and reinforced concrete structures are given.
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Flohr, Alexander, und Andrea Osburg. „Design and Development of Concretes for Special Rehabilitation Tasks“. MATEC Web of Conferences 199 (2018): 07001. http://dx.doi.org/10.1051/matecconf/201819907001.
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The requirements for concrete restoration are not only aspects of retrofitting or restoration of bearing capacity but also aspects of preservation of historic structures, such as industrial monuments or civil engineering structures and buildings of the 1960s [1]. Thereby the facsimile replication of the concrete surface is a particular challenge. For the manufacture of delicate and complex structures with restricted accessibility self-compacting concrete (SCC) is well suited [2]. A modification with polymers normally ensures the durability of repair mortars or concretes (PCC) [3]. The combination of PCC and SCC to the Polymer-modified Self-Compacting Concrete (PSCC) for the restoration of historic concrete constructions is the logical consequence, to combine the advantages of both materials and is therefore an interesting alternative to well established materials and methods. Historic concrete constructions are often manufactured of concretes with very stiff consistencies, the so called tamped concretes. So there is a need to develop materials and methods for the rehabilitation of structures made of tamped concrete. For this reason, first investigations have been performed to the recipe development and optimization of its composition, but also properties, furthermore to the design possibilities and how polymers influence the concrete properties. In Germany between 1920 and 1970 industrial buildings and hydraulic structures have been built with concretes, where the content of Portland cement clinker was nearly complete substituted by latent hydraulic materials. The binders of those concretes contain large quantities of blast furnace slag and calcium sulphate and are called super-sulphated cement (SSC). Because of the high sulphate content, the compatibility of concrete structure with SSC is not given to concretes or mortars with other cements. If there is an adequate range of moisture, harmful new formations of phases will occur in the contact zone between SSC-concrete and the other concrete. In the field of rehabilitation PCC are well established. These are polymer-modified mortars or concretes with Portland cement, which are not suitable for the rehabilitation of structures of SSC-concrete. An alternative is the polymer-modification of SSC-concretes with polymers.
Dissertationen zum Thema "Concrete"
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Tokudome, Shingiro. „Contribuição para o desenvolvimento do concreto auto-adensavel“. [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258503.
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Orientador: Vladimir Antonio PaulonDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil
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Resumo: A presente dissertação tem como objetivo o desenvolvimento da especialidade da tecnologia do concreto de elevado desempenho, o concreto auto-adensável. A tendência do mercado em construir cada vez mais estruturas arrojadas exige o desenvolvimento de tecnologias que coadunem com a realidade técnico-econômica da obra. A concretagem destas estruturas, quando realizada em formas irregulares e em armação densa, ocasiona, na maioria das vezes, problemas no adensamento, formando descontinuidade e/ou segregação na peça concretada. Contudo, quando executada em concreto auto-adensável, estas ocorrências tendem a diminuir. Este trabalho apresenta a confrontação da metodologia de avaliação do concreto autoadensável no estado fresco com o método da caixa L e o utilizado atualmente na Alemanha conforme a norma DIN 1045 -2 DAfStb- Richtlinie Selbstverdichtender Beton (SVB-Richtlinie), com o propósito de levar para a prática procedimentos simples e de fácil análise do controle de trabalhabilidade do concreto, e também a aplicação do concreto auto-adensável em estruturas de escala real para analisar a segregação do concreto quando lançados a 4,00 metros de altura.
Abstract: This study concerns a special kind of high performance concrete technology development, called self-compacting concrete. The growing market tendency to build bold structures requires construction technology development, which fits real technical-economical needs. The concrete placing in irregular shape structures, and reinforced concrete structures, most of time brings compacting problems and result on segregation, and/or not satisfactory concrete surfacing. However, the use of self-compacting concrete can reduce these problems. The main objective of this research is to compare L box method and the German standard DIN 1045 -2 DAfStb- Richtlinie Selbstverdichtender Beton (SVB-Richtlinie) for fresh self compacting concrete workability analysis, in order to propose the L box method as an practical and easy way test to control the fresh concrete quality. This study also provides an accurate description of self-compaction concrete history, its development and the advantages reached by the structures based on concrete selfcompacting concrete, as well. Furthermore this research sets a real beam and column structure concrete applications from 4,00 m high filling to analyze segregation behavior.
Mestrado
Edificações
Mestre em Engenharia Civil
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Ferraz, Andre Luiz Nonato. „Avaliação de retração e fluencias do concreto auto-adensavel para aplicação em elementos pre-moldados“. [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/257677.
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Orientadores: Newton de Oliveira Pinto Junior, Monica Pinto BarbosaTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
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Resumo: Foram avaliados neste trabalho, teórica e experimentalmente, o comportamento reológico e mecânico do concreto auto-adensável (C.A.A.), em específico suas características frente as deformações lentas, retração e fluência, e sua aplicabilidade em peças pré-moldadas. Foram desenvolvidos duas composições de concreto de classes de resistência distintas, 35 e 55 MPa. Na etapa de dosagem foram utilizados os procedimentos do método REPETTE-MELO, onde nas pastas e argamassas, foram realizados ensaios reométricos, ensaios de fluidez e Mini-Slump, e na definição do traço do C.A.A., ensaios de controle, tais como Slump-Flow, Funil em V, caixa em L, caixa em U e tubo em U, assim como ensaios das propriedades mecânicas tais como resistência à tração, resistência à compressão, e módulo de elasticidade. A avaliação do comportamento dos concretos frente a fluência se deu nas idades de 7, 14, 28, e 56 dias, segundo a NBR 8224 (ABNT, 1983), e frente a retração de acordo com a norma MERCOSUL NM 131:9. Os resultados experimentais foram comparados com valores de concretos convencionais disponíveis na literatura. Todos os ensaios foram realizados no Laboratório CESP de Engenharia Civil, e no Laboratório de Hidrologia da UNESP em Ilha Solteira-SP. No estudo da deformação rápida, ensaios de tração na flexão foram realizados aos 28 e 56 dias. Os coeficientes de fluência foram calculados quer seja através dos valores experimentais como pela NBR 6118 e comparados entre si, apresentando boa correlação, com diferenças menores que 10% para toda as idades. A composição do concreto auto-adensável foi implantada para fins de avaliação, junto a empresa de Pré- Moldados Protendit de São José do Rio Preto-SP, onde foram moldadas vigas, em escala real, as quais apresentaram melhor acabamento e se mostraram 50% mais economicas, em relação a mão-de-obra, quando comparada com a viga de concreto convencional. Os resultados obtidos mostram que as composições de concreto auto-adensável apresentam maiores valores de retração e fluência quanto comparados com concretos convencionais de mesma resistência mecânica. O C.A.A. de resistência à compressão igual a 55 MPa apresentou menor retração e fluência básica que o C.A.A. de resistência 35 MPa.
Abstract: This project analyzed, theoretically and experimentally, the mechanical and rheological behavior of the selfcompacting concrete (C.A.A.), specially its features according to slow deformation, shrinkage and creep, and its applicability in precast elements. Two compositions of concrete of different classes of resistance were developed, 35 MPa and 55 MPa. In the stage of the dosage, the procedures of the method REPETTE-MELO were used, rheometrical tests, fluidness tests and Mini-Slump were carried out on the pastes and the mortars, and control tests, such as Slump-Flow, funnel V test, box L, box U and tube U, and mechanical properties tests, such as tensile strength, compression strength and elasticity module were used to define the C.A.A. feature. The evaluation of the concrete behavior by creep happened at ages of 7, 14, 28, and 56 days, according to NBR 8224 (ABNT, 1983), and by shrinkage according to MERCOSUL NM 131:9. The experimental results were compared with values from conventional concrete available in the literature. All tests were performed at CESP Civil Engineer Laboratory, and at Hydrology Laboratory of the UNESP in Ilha Solteira-SP. In the fast deformation study, traction tests in flexion were performed at 28 and 56 days. The creep coefficients were calculated either through experimental values as by the NBR 6118 and compared each other, showing a good correlation, with differences smaller than 10% for all ages. The composition of self-compacting concrete was established for evaluation, in partnership with precast elements company Protendit of São José do Rio Preto-SP, where were shaped beams, in real scale, which showed better finishing and they showed themselves 50% more economical regarding labor, when compared with conventional concrete beam. The results reached show that the compositions of self-compacting concrete present higher values of shrinkage and creep when compared with conventional concrete of same strength. The C.A.A. that presented compression strength equal to 55 MPa showed a lower shrinkage and basic creep that C.A.A. strength of 35 MPa.
Doutorado
Edificações
Doutor em Engenharia Civil
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Bekoe, Patrick Amoah. „Concrete containing recycled concrete aggregate for use in concrete pavement“. [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0025075.
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Bolognini, Enio José [UNESP]. „Idealizações de um programa baseado em redes neurais para dosagem de concreto“. Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/144535.
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A produção de concreto está cada vez mais exigente. Medidas de prevenção e correção são empregadas na dosagem do concreto, gerando lucros e economia no preparo. A fim de obter economia e praticidade na dosagem de concretos, neste estudo foi desenvolvido, após a coleta de dados experimentais, a criação de rede neural artificial feedforward, utilizando algoritmo genético de retropropagação (backpropagation). A rede neural artificial (RNA) é composta de quatro camadas, entre entradas, pesos, bias, função de ativação sigmóide e saída desejada. O modelo conta com funções sigmoides, a fim de calcular e otimizar o erro através das camadas anteriores, até a entrada. Este modelo, por ser mais preciso, conta com certo momento e taxa de aprendizagem. A proposta da rede neural artificial (RNA) em feedforward, com o algoritmo genético de retropropagação (backpropagation), foi implementada em forma estrutural, e com uma interface gráfica, na qual o usuário final possa escolher a resistência desejada, tipo de cimento, tipo e dimensão de agregados graúdos, dimensão de agregados miúdos, tipo de concreto e aditivo, se for o caso de concretos de alta resistência (CAR). Nesta pesquisa, a coleta de dados, para armazenar no programa, foi realizada por meio de ensaios de caracterização dos materiais e de dosagem e resistência do concreto. A linguagem de programação Java foi utilizada para programar o algoritmo genético e a interface usuário. Foram realizados os testes e manutenção da ferramenta computacional, seguindo regras importantes no desenvolvimento de softwares. O resultado final, deste desenvolvimento, foi um software capaz de calcular a dosagem do concreto para o usuário, quando este insere valores de resistência à compressão axial desejada e o material que será usado na confecção do concreto.
The concrete production is increasingly demanding. preventive and corrective measures are used in concrete dosage, generating profits and savings in preparation. In order to achieve economy and practicality in the dosage of concrete in this study was developed after the collection of experimental data, the creation of artificial neural network feedforward using genetic algorithm backpropagation. The artificial neural network (ANN) is composed of four layers, between inputs, weights, biases, sigmoid activation functions and output desired. The model has sigmoid functions in order to calculate and optimize the error by the preceding layers, until the entrance. This model, to be more precise, has the right time and learning rate. The proposed artificial neural network (ANN) in feedforward, with the genetic algorithm backpropagation, was implemented in structural form, and with a graphical interface, in which the end user can choose the desired strength, cement type, and size of coarse aggregates, fine aggregates dimension, type of concrete and additives, if any of high strength concrete (CAR). In this research, data collection, to store the program, was carried out by means of characterization tests of materials and dosage and strength of concrete. The Java programming language was used to program the genetic algorithm and the user interface. testing and maintaining software tool were conducted following important rules in the software development. The end result of this development was an able to calculate the dosage of specific software for the user, when it enters resistance values to the desired axial compression and the material that will be used in the manufacture of concrete.
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Bolognini, Enio José. „Idealizações de um programa baseado em redes neurais para dosagem de concreto /“. Ilha Solteira, 2016. http://hdl.handle.net/11449/144535.
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Orientador: Maria da Consolação Fonseca de AlbuquerqueResumo: A produção de concreto está cada vez mais exigente. Medidas de prevenção e correção são empregadas na dosagem do concreto, gerando lucros e economia no preparo. A fim de obter economia e praticidade na dosagem de concretos, neste estudo foi desenvolvido, após a coleta de dados experimentais, a criação de rede neural artificial feedforward, utilizando algoritmo genético de retropropagação (backpropagation). A rede neural artificial (RNA) é composta de quatro camadas, entre entradas, pesos, bias, função de ativação sigmóide e saída desejada. O modelo conta com funções sigmoides, a fim de calcular e otimizar o erro através das camadas anteriores, até a entrada. Este modelo, por ser mais preciso, conta com certo momento e taxa de aprendizagem. A proposta da rede neural artificial (RNA) em feedforward, com o algoritmo genético de retropropagação (backpropagation), foi implementada em forma estrutural, e com uma interface gráfica, na qual o usuário final possa escolher a resistência desejada, tipo de cimento, tipo e dimensão de agregados graúdos, dimensão de agregados miúdos, tipo de concreto e aditivo, se for o caso de concretos de alta resistência (CAR). Nesta pesquisa, a coleta de dados, para armazenar no programa, foi realizada por meio de ensaios de caracterização dos materiais e de dosagem e resistência do concreto. A linguagem de programação Java foi utilizada para programar o algoritmo genético e a interface usuário. Foram realizados os testes e manutenção da ferramenta com... (Resumo completo, clicar acesso eletrônico abaixo)
Mestre
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Ore, Andrade Harold Oscar Rosil, und Diaz Miguel Angel Portillo. „Propuesta de diseño de mezcla para un concreto permeable de FC=175kg/cm² en veredas“. Bachelor's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2019. http://hdl.handle.net/10757/635423.
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El Perú presenta diversas eventualidades como las lluvias, que retrasan distintas actividades que promueven el crecimiento económico del país. Las zonas urbanas necesitan una mejora continua del entorno con mejores infraestructuras para promover el crecimiento y reducir los accidentes. En la actualidad, se necesita fomentar por el medio local soluciones innovadoras para la evacuación de altas precipitaciones.
El concreto permeable es un tipo de concreto cuya tecnología permite que el agua discurra a través de su estructura por la alta porosidad que posee a diferencia del concreto tradicional. Es fabricado de agregado grueso y material cementante, con un bajo porcentaje de finos de hasta el 10%.
Esta investigación consiste en proponer un diseño de mezcla de concreto permeable de f’c=175kg/cm² aplicado en veredas que satisfaga distintos requerimientos establecidos por las normas CE010 de Pavimentos Urbanos, ACI 211.3R, ACI 522R-10 y los propios de la zona de aplicación. Para ello se realizó una batería de 12 diseños de mezcla con relaciones a/c 0.30, 0.35 y 0.38; agregados de HUSO 7 y 67; cementos portland tipo 1 Sol y Quisqueya; y aditivo Z fluidizante SR. Se realizaron ensayos en estado fresco: Slump, peso volumétrico y contenido de vacíos; y en estado endurecido: Resistencia a la compresión y flexión, y permeabilidad. Finalmente se realizó un prototipo con el diseño que presentó mejores características con el propósito de validar la investigación y se realizo un comparativo entre las veredas de concreto permeable y tradicional.Peru presents various eventualities such as rainfall, which delay different activities that promote the country's economic growth. Urban areas need continuous improvement of the environment with better infrastructure to promote growth and reduce accidents. At present, innovative solutions for the evacuation of high rainfall need to be promoted through the local environment. Permeable concrete is a type of concrete whose technology allows water to flow through its structure due to the high porosity it possesses, unlike traditional concrete. It is made of coarse aggregate and cementitious material, with a low percentage of fines of up to 10%. This research consists in proposing a permeable concrete mix design of f'c = 175kg / cm² applied in sidewalks that satisfies different requirements established by the CE010 standards of Urban Pavements, ACI 211.3R, ACI 522R-10 and those of the area of application. For this, a battery of 12 mixing designs with a / c ratios of 0.30, 0.35 and 0.38; aggregates of HUSO 7 and 67; portland cements type 1 Sol and Quisqueya; and fluidizing Z additive SR. Fresh tests were performed: Slump, volumetric weight and void content; and in a hardened state: resistance to compression and flexion, and permeability. Finally, a prototype was made with the design that presented better characteristics with the purpose of validating the research and a comparison was made between the permeable and traditional concrete sidewalks.
Tesis
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Rosa, Alaor Leandro. „Estudo da influência da taxa de solicitação na resposta em fratura quase-frágil“. [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258103.
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Orientador: José Luiz Antunes de Oliveira e SousaTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
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Resumo: A pesquisa objeto desta tese refere-se a uma investigação dos processos de fratura no concreto de alta resistência (High Strength Concrete - HSC), com ênfase no estudo da influência da taxa de carregamento (medida como a taxa de deslocamento do ponto de aplicação de carga) nos ensaios de fraturamento e assim caracterizar sua ductilidade em tração. Neste trabalho um modelo de fratura dependente do tempo (modelo coesivo-viscoso) é apresentado e a influência da taxa de carregamento na resposta em fratura quase-frágil é estudada através de simulação numérica. O modelo de fratura dependente do tempo acopla um parâmetro viscoso, dado em função da velocidade de abertura da fratura, ao modelo clássico de fissura fictícia proposto por Hillerborg, tal que uma relação tensão-abertura de fissura dependente do tempo, (?, ?), represente uma zona coesiva-viscosa inserida em um meio elástico não-viscoso. O modelo coesivo-viscoso é implementado no arcabouço teórico do método dos elementos finitos com um método de cálculo iterativo que modela a fratura quase-frágil (comportamento não-linear) como uma superposição de problemas em mecânica da fratura elástica linear (Linear Elastic Fracture Mechanics - LEFM). O modelo numérico implementado é validado com os resultados experimentais obtidos de vigas prismáticas ranhuradas em flexão em três pontos (Three-Point Bend Test - TPBT), com taxas de carregamento variando da ordem de = 10-5 mm/s a 6 = 10+1 mm/s. Os resultados numéricos obtidos mostram que o modelo coesivo-viscoso implementado, apesar de sua simplicidade, reflete o fato experimentalmente documentado de que a nucleação e a propagação de uma fratura coesiva, bem como os fenômenos que governam os processos de fratura, são dependentes da taxa de carregamento. Assim, a diferença obtida por muitos pesquisadores na medida da energia de fratura não se deve unicamente à escala do protótipo ensaiado mas também à taxa de carregamento aplicada nos ensaios.
Abstract: This thesis addresses a numerical investigation to account for loading rate influence (measured as the load-point displacement rate) on the fracture processes of quasi-brittle materials such as high strength concrete (HSC). In this context, fracture tests are simulated by a proposed time-dependent cohesive model. The proposed model couples a viscous parameter, as a function of crack-opening rate, to the classical Hillerborg's fictitious crack approach such that a time-dependent stress crack opening law, (?, ?), represents a viscous-cohesive zone in an elastic, time-independent, body. The viscous cohesive representation is implemented in a finite element framework using a iterative method in such a way that the equations governing the quasebrittle crack propagation (non-linear behaviour) is sought from a triangular system of equations, obtained by superposing linear elastic fracture mechanics (LEFM) cases. To show the accuracy of the model, numerical simulations of notched beams in three-point bend test (TPBT) were performed. In the tests five different loading rates were employed (ranging from = 10-5 mm/s = 10+1 mm/s). The results numerically obtained match very well the experimental ones, particularly the maximum load for the several loading rates used in the tests. A parametric study has also been performed to point out which are the model, geometry and fracture parameters influencing the fracture process due to loading rate. The numerical results show that the model, although its simplicity, provides a general approach to reflect the experimentally documented fact that crack propagation and so the parameters governing the fracture processes in cementious materials depend on the loading rate. So, the differences obtained by several researches worldwide on the fracture energy measurement are not only due to the scale of the tested specimens, but also due to the loading rate influence.
Doutorado
Estruturas
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Souza, Adriana Aparecida Ambrosio de 1975. „Procedimento de ensaio para verificação em laboratório da tendência ao lascamento do concreto em situação de incêndio“. [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258256.
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Orientador: Armando Lopes Moreno JúniorTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
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Resumo: O lascamento é um fenômeno complexo, estocástico, e que pode causar um efeito danoso a estruturas de concreto em situação de incêndio. O fenômeno do lascamento deve, portanto, ser considerado no projeto de construções em que a ação do fogo é levada em conta. Não existe um procedimento de ensaio normalizado para avaliação da tendência ao fenômeno do lascamento do concreto. Os resultados de outros pesquisadores mostram diferentes procedimentos, tamanho das amostras, preparo das amostras (execução e cura), tempo de exposição à temperatura, evolução da temperatura ao longo do tempo (taxas de elevação), quantificação do fenômeno (degradação das amostras em termos de fissuração e desprendimento de camada superficial das amostras), o que dificulta comparação dos resultados obtidos. Esta pesquisa apresenta um procedimento de ensaio para avaliar a tendência ao lascamento de misturas de concreto em situação de incêndio e mostra que este fenômeno está relacionado, principalmente, ao tipo de agregado utilizado e a umidade do concreto exposto à elevadas temperaturas. Como resultado pôde - se observar que um concreto preparado com agregado calcáreo apresenta maior lascamento de superfície, do que um concreto preparado com agregado basalto, mesmo este apresentando fissuração superficial. Ao final, concluí - se que o procedimento proposto é eficaz na avaliação e determinação do tipo de dano causado
Abstract: The spalling is a complex phenomenon, that may cause a damage effect on concrete structures in a fire situation. The spalling phenomenon should, therefore, be considered in the constructions design, in that the fire effect is taking account. It does not exist a standardization of tests proceeding for evaluation of spalling phenomenon tendency in concrete. The results of others researchers show different proceedings, specimens size, specimens preparation (execution and cure), fire resistance, temperature evolution in a time period, phenomenon amount (degradation of specimens about its cracking and come unstuck of superficial layer of the specimens), what make difficult the comparison of the obtained results. This research shows a test proceeding to evaluate the spalling tendency of concrete mixing under fire situation and also shows that this phenomenon is mainlly relating to the aggregate type used and to the concrete humidity under high temperatures. As a result it could observed that a concrete made with calcareous coarse aggregate shows higher surface spalling than a concrete made with basaltic coarse aggregate, even this specimen of concrete showing a superficial cracking. At the end, it did conclude that the proposal proceeding is efficient in the evaluation and determination of the damage
Doutorado
Estruturas
Doutor em Engenharia Civil
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Catoia, Thiago. „Concreto ultraleve® estrutural com pérolas de EPS: caracterização do material e estudo de sua aplicação em lajes“. Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-19122012-104222/.
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A utilização de concreto leve decorre especialmente dos benefícios promovidos pela redução da massa específica do material, tais como menores esforços nas estruturas, economia com fôrmas e cimbramento, além de diminuição dos custos com transporte e montagem de construções pré-fabricadas. Atualmente, além das questões técnicas e econômicas, a escolha dos materiais de construção deve levar em conta os aspectos ambientais. Portanto, o uso de poliestireno expandido (EPS) na produção de concreto pode abrir portas para o emprego de resíduos de materiais dessa natureza, e ainda usufruir de sua baixa massa específica nas aplicações estruturais. Este trabalho teve como objetivo determinar as principais características do concreto leve com pérolas (esferas) de EPS, também conhecido como Concreto Ultraleve® ou Concreflex®, características essas necessárias para projetar elementos estruturais, e analisar o comportamento de lajes produzidas com esse novo material. Mais especificamente, foram determinadas características mecânicas, tais como: resistência à compressão, módulo de elasticidade e resistência à tração, na compressão diametral e na flexão, além de características de deformação de longo prazo, como retração e fluência. Também foi determinada a massa específica e avaliada sua relação com as características mecânicas, além dos ensaios de modelos de lajes unidirecionais produzidas com esse concreto. Para analisar a possibilidade de aplicação prática do concreto leve com EPS em lajes, foram elaboradas tabelas para pré-dimensionamento de lajes unidirecionais e bidirecionais com o novo material, nas quais essas lajes foram comparadas com as de concreto comum. Com base no procedimento experimental e nos resultados dos ensaios, o objetivo de determinar as características necessárias para projetar elementos estruturais de Concreto Leve com EPS foi alcançado. Pode-se ainda afirmar que o concreto estudado, com aproximadamente metade da massa específica dos concretos convencionais, apresenta características compatíveis com a produção e o uso comercial de lajes maciças, principalmente pré-moldadas, o que pode ser estendido a outros elementos que não necessitem de concretos com resistência muito alta. Também foi avaliado o comportamento de modelos de lajes de concreto leve com poliuretano (PU), de maneira semelhante ao estudo realizado com EPS, incluindo a caracterização do concreto de cada modelo. Para complementar a análise de desempenho do concreto leve com EPS, apresentou-se um estudo de carbonatação, que comprovou a excelente condição desse novo material com relação à durabilidade.The use of lightweight concrete is mainly due to the benefits provided by reducing the density of the material such as smaller efforts on structures, economy of molds and scaffolding, as well as lower costs of transportation and erection of precast constructions. Currently, besides the technical and economic issues, the choice of building materials should take into account environmental aspects. Therefore, the use of expanded polystyrene (EPS) in the concrete production can open doors for the use of waste materials of this nature, and still to take advantage of its low density in structural applications. This study aimed to determine the main characteristics of the lightweight concrete with EPS beads (spheres), also named Ultra Lightweight Concrete, characteristics which are necessary to design structural members, and analyze the behavior of slabs produced with this new material. More specifically mechanical properties were determined, such as compressive strength, modulus of elasticity, and splitting and flexural tensile strength, as well as long term deformation properties such as shrinkage and creep. The density was also determined and evaluated its association with the mechanical characteristics, besides the tests of unidirectional slab models produced with this concrete. To analyze the possibility of use of the lightweight concrete with EPS in slabs, tables were compiled for pre-design of unidirectional and bidirectional slabs with this new material, in which these slabs were compared with those of common concrete. Based on the experimental procedure and results of tests, the aim of determine the characteristics necessary to design structural elements of lightweight concrete with EPS has been achieved. Can be also said that the studied concrete, with about half the density of conventional concrete, presents mechanical characteristics compatible with commercial production and use of slabs, mainly precast, conclusion which can be extended to other components that do not require concretes with very high strength. It was also assessed the behavior of slab models of lightweight concrete with polyurethane (PU) in a similar way to the study carried out with EPS, including the characterization of concrete for each model. To complement the performance analysis of the lightweight concrete with EPS a study of carbonation was presented, which proved the excellent condition of this new material with respect to durability.
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Lannon, Kristyna Tylova. „Using recycled concrete aggregate in pervious concrete“. [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0025119.
Der volle Inhalt der QuelleBücher zum Thema "Concrete"
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D, Williams Linda. Mezcladoras de concreto =: Concrete mixers. Mankato, Minn: Capstone Press, 2006.
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Nicotera, Fabio. Fabio Nicotera: Instabile concreto = concrete instability. Cinisello Balsamo, Milano: Silvana editoriale, 2019.
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Mackay, Calum Angus. Craiceann concrete =: Concrete skins. Derry: Orchard Gallery, 1992.
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Hughes, Barry P. Concrete and concrete structures. Birmingham: University of Birmingham, 1989.
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Mackay, Calum Angus. Craiceann concrete =: Concrete skins. Derry: Orchard Gallery, 1992.
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Theodor, Löffler, und Fraunhofer-Gesellschaft. Informationszentrum Raum und Bau., Hrsg. Concrete roads, concrete composition. Stuttgart: IRB Verlag, 1989.
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Ahrens, Donald L. Concrete and concrete masonry. St. Paul, Minn: Hobar Publicatons, 1996.
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Simenc, Christian. Concrete. Suresnes: B. Chauveau, 2008.
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Simenc, Christian. Concrete. Suresnes: B. Chauveau, 2008.
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Macdonald, Susan, Hrsg. Concrete. Oxford, UK: Blackwell Science Ltd, 2002. http://dx.doi.org/10.1002/9780470773659.
Der volle Inhalt der QuelleBuchteile zum Thema "Concrete"
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Bussell, Michael. „Concrete and Reinforced Concrete“. In Materials & Skills for Historic Building Conservation, 92–108. Oxford, UK: Blackwell Publishing Ltd, 2008. http://dx.doi.org/10.1002/9780470697696.ch5.
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Surahyo, Akhtar. „Concrete“. In Concrete Construction, 3–20. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-10510-5_1.
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O’Brien, James J. „Concrete“. In Construction Inspection Handbook, 269–322. Boston, MA: Springer US, 1997. http://dx.doi.org/10.1007/978-1-4615-6017-3_14.
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Munro, Rosalind. „Concrete“. In Selective Neck Dissection for Oral Cancer, 1–2. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-12127-7_65-1.
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Bailey, Harold, und David Hancock. „Concrete“. In Brickwork 1 and Associated Studies, 50–63. London: Macmillan Education UK, 1990. http://dx.doi.org/10.1007/978-1-349-11377-4_4.
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Gooch, Jan W. „Concrete“. In Encyclopedic Dictionary of Polymers, 164. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4419-6247-8_2791.
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Deplazes, Andrea. „Concrete“. In Constructing Architecture, 56–76. Basel: Birkhäuser Basel, 2005. http://dx.doi.org/10.1007/3-7643-7666-x_4.
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Levy, Sidney M. „Concrete“. In The Construction Superintendent’s Handbook, 138–55. Boston, MA: Springer US, 1992. http://dx.doi.org/10.1007/978-1-4684-8494-6_13.
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O’Brien, James J. „Concrete“. In Construction Inspection Handbook, 280–337. Boston, MA: Springer US, 1989. http://dx.doi.org/10.1007/978-1-4757-1191-2_12.
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Vieira, Manuel. „Concrete“. In Materials for Construction and Civil Engineering, 185–236. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-08236-3_4.
Der volle Inhalt der QuelleKonferenzberichte zum Thema "Concrete"
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Ondrejka Harbulakova, Vlasta, Adriana Estokova, Michaela Smolakova und Martina Kovalcikova. „Mathematical Investigation of Concrete Corrosion – a Sustainability Study“. In Environmental Engineering. VGTU Technika, 2017. http://dx.doi.org/10.3846/enviro.2017.038.
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The issue of sustainability is a major spur to innovation in the flied of civil engineering where the important role is decreasing the detrimental effects on environment and save raw materials and energy. Micro silica is a by-product of the industrial manufacture of ferrosilicon and metallic silicon in high temperature electric arc furnaces and is used as an additive for improving concrete properties. The paper presents the results of chemical corrosion and bio-corrosion tests on concrete samples with 5% addition of microsilica as well as on concrete samples with only Portland cement. Chemical corrosion, simulated by sulphuric acid with pH of 4.2, and bio-corrosion, simulated by sulphur-oxidising bacteria Acidithiobacillus thiooxidans, were investigated in terms of basic concrete’s elements leachability. Dissolved amounts of Si and Ca due to both chemical attack and biocorrosion were measured in the period of 3 months. The leaching trends were analysed using a mathematical approach for better interpretation of the results. The correlation analysis confirmed the different leaching trends comparing bio-corrosion and chemical corrosion processes. A high dependency was observed between leaching of Ca and Si from concretes prepared with ordinary cement. In case of concrete sample with microsilica addition no correlation was found out.
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Rempling, Rasmus, Mats Karlsson, Ignasi Fernandez, Carlos Gil, Ingemar Löfgren, Alexandre Mathern, Jonas Magnusson, Iad Saleh und Jan Suchorzewski. „The need for research and innovation to facilitate upscaling of low-carbon concrete“. In IABSE Congress, New Delhi 2023: Engineering for Sustainable Development. Zurich, Switzerland: International Association for Bridge and Structural Engineering (IABSE), 2023. http://dx.doi.org/10.2749/newdelhi.2023.1199.
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<p>For decades, research has been carried out with a focus on concrete structures during curing to mitigate the risk of thermal cracking. Computer programs and aids/tools have also been developed to assess stress and cracking risk analysis of concrete structures during curing. However, today with the recent introduction of low-carbon concretes to reduce the environmental impact of constructions, the reliability of the tools and working procedures, i.e. concrete characterization, is questioned, and a roadmap for research and innovation is called for. The project's primary purpose is to investigate the need for research and innovation regarding upscaling the usage of low-carbon concrete. The nature of the study is based on an industry-focused workshop with specialists from Scandinavia. Increased knowledge of hardening concrete's cracking risk-related properties is of the utmost importance for the construction industry as the need for its understanding has recently increased.</p>
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WYSOCZAŃSKI, Andrzej. „The Use of Additively Manufactured Concrete Objects“. In Terotechnology XIII, 101–10. Materials Research Forum LLC, 2024. http://dx.doi.org/10.21741/9781644903315-13.
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Abstract. Printed concrete elements are now becoming increasingly popular in industrial use within the construction field. This is primarily due to the versatility of 3D printers, which can form virtually any shape, including hollow ones, without the need for moulds. The concretes used in 3D printing can achieve up to six times greater strength than the popular C35/45 construction concretes, and the ability to use variable nozzles enables the printing of both large elements and fine details. However, the technology requires further research, particularly regarding the relationship between concrete strength and printing parameters, as well as the physical characteristics of the concrete mixture.
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Naus, D. J., und H. L. Graves. „A Review of the Effects of Elevated Temperature on Concrete Materials and Structures“. In 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/icone14-89631.
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Concrete’s properties are more complex than those of most materials because not only is concrete a composite material whose constituents have different properties, but its properties depend upon moisture and porosity. Exposure of concrete to elevated temperature affects its mechanical and physical properties. Elements could distort and displace, and, under certain conditions, the concrete surfaces could spall due to the buildup of steam pressure. Because thermally-induced dimensional changes, loss of structural integrity, and release of moisture and gases resulting from the migration of free water could adversely affect plant operations and safety, a complete understanding of the behavior of concrete under long-term elevated-temperature exposure as well as both during and after a thermal excursion resulting from a postulated design-basis accident condition is essential for reliable design evaluations and assessments of nuclear power plant structures. As the properties of concrete change with respect to time and the environment to which it is exposed, an assessment of the effects of concrete aging is also important in performing safety evaluations. The effects of elevated temperature on Portland cement concretes and constituent materials are summarized, design codes and standards identified, and considerations for elevated temperature service noted.
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Mohamad, Abdelrahman, Fouzia Khadraoui, Nassim Sebaibi, Mohamed Boutouil und Daniel Chateigner. „Water Sensitivity of Hemp-Foam Concrete“. In 4th International Conference on Bio-Based Building Materials. Switzerland: Trans Tech Publications Ltd, 2022. http://dx.doi.org/10.4028/www.scientific.net/cta.1.135.
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The necessity to build energy-efficient and low environmental impact buildings favors the development of biobased light-weight materials as hemp-foam concretes. In this context, experimental protocols were developed to study the effects of hemp shiv and the production methods on the water sensitivity of bio-based foamed concrete (BBFC). Foam concrete incorporates several materials and compounds: cement, protein-based foaming agent, ground granulated blast–furnace slag, metakaolin as a binder, and hemp shiv as bio-based aggregates. The study investigated first the effect of the incorporation of hemp shiv (from 0 to 15 vol%) and then the elaboration method, comparing direct method versus preformed method on the resulting physical properties, the isotherms sorption-desorption and the capillary water absorption of hemp-foam concretes. We observe an increasing porosity of the concrete with hemp shives content. Additionally, hemp shives increase the adsorption and the capillary absorption of water. Moreover, the preformed method produces concretes more sensitive to water than the direct methods since it increases its porosities.
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Raijiwala, D. B., und H. S. Patil. „Geopolymer concrete A green concrete“. In 2010 2nd International Conference on Chemical, Biological and Environmental Engineering (ICBEE). IEEE, 2010. http://dx.doi.org/10.1109/icbee.2010.5649609.
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„Geopolymer Concrete - Sustainable Cementless Concrete“. In SP-261: 10th ACI International Conference on Recent Advances in Concrete Technology and Sustainability Issues. American Concrete Institute, 2009. http://dx.doi.org/10.14359/51663200.
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Ninan, Chinnu Mariam, K. P. Ramaswamy und R. Sajeeb. „Influence of Concrete Mixture Composition on Acid Resistance of Concrete: A Review“. In International Web Conference in Civil Engineering for a Sustainable Planet. AIJR Publisher, 2021. http://dx.doi.org/10.21467/proceedings.112.53.
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Cementitious materials are highly susceptible to rapid and severe degradation by a wide range of acids that are found immensely in ground water, sewage systems, industrial effluents, acid rain etc. which may cause microstructure deterioration. The factors influencing acid attack is generally categorised as material related factors and test related factors. Material related factors can be either related to acid solution or concrete mixture composition. Composition of concrete mixture greatly impacts the acid resistance of concrete. Factors related to composition of concrete mixture are type of cement, type and proportion of binders, water binder ratio, aggregate binder ratio and mineralogical nature of the aggregates. Even though the type of cement influences acid attack, the magnitude of variation is negligible. Consumption of calcium hydroxide and refinement of pore structure makes the use of supplementary cementitious materials favourable for acid resistance. Decrease in water binder ratio and increase in aggregate binder ratio reduces the porosity of concrete and thereby improves the acid resistance of concrete. Calcareous aggregates are preferred for concretes exposed to acids having less soluble salts and not preferred for acids forming soluble salts. This paper highlights the influence of composition of concrete mixture on acid resistance of concrete. A proper formulation of concrete is expected to enhance its acid resistance.
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Bäuml, Martin, Jakob Melchior und Felicia Constandopoulos. „Over-night Renewals of the Concrete Runway at Sabiha Gökcen International Airport Istanbul“. In 12th International Conference on Concrete Pavements. International Society for Concrete Pavements, 2021. http://dx.doi.org/10.33593/nj0oxhb0.
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Over the last couple of years, new rapid-hardening concretes were developed. They do not only stand out by their high early strength, in excess of 20 MPa already 90 minutes after setting, but are also adjustable to the needs of the construction site in regards to fresh concrete properties and setting behavior. This allows the rapid-hardening concrete to be placed using traditional means and the construction program to be optimized in order to perform the renewals during very short closure windows. After many years of usage, the single runway at Sabiha Gökcen International Airport Istanbul was in need of large-scale renewals due to severe damages in the high wear areas around the centerline. But, with it being the only runway at the airport, closing it for multiple weeks to perform the renewal was not an option. The nightly closure of only 5 hours, due to late-evening and early-morning flights, placed additional demands on the rapid-hardening concrete, the logistics of the construction site and the concrete's long-term durability for a permanent solution. This article presents the step-by-step over-night renewals at Sabiha Gökcen Airport, which is the largest project ever performed involving rapid-hardening concrete. Each night up to 5 slabs (94 m2) of the runway were replaced for a total area of 8700 m2 over 117 nights between March and September 2018. Such large area applications without affecting regular airport operations are possible thanks to the latest generation of rapid-hardening cement and this article shows these possibilities to project owners, design engineers, and contractors.
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Dahlenburg, Maximilian, Christian Maximilian Hechtl, Carla Matthaus und Johannes Fottner. „3D-Concrete Printing – Graded Concrete Extrusion“. In 2022 3rd International Conference on Computation, Automation and Knowledge Management (ICCAKM). IEEE, 2022. http://dx.doi.org/10.1109/iccakm54721.2022.9990494.
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Davaadorj, Otgonchimeg. Shear Stress Transfer Across Concrete to Concrete and Steel to Concrete Interfaces. Precast/Prestressed Concrete Institute, 2018. http://dx.doi.org/10.15554/pci.rr.conn-002.
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Skone, Timothy J. Concrete Production. Office of Scientific and Technical Information (OSTI), Februar 2016. http://dx.doi.org/10.2172/1509359.
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Author, Not Given. Concrete Biodecontamination. Office of Scientific and Technical Information (OSTI), Februar 2009. http://dx.doi.org/10.2172/950788.
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Abdellatef, Mohammed, Clifford Ho, Peter Kobos, Budi Gunawan, Jessica Rimsza, Hongkyu Yoon und Mahmoud Taha. Biopolymer Concrete. Office of Scientific and Technical Information (OSTI), September 2022. http://dx.doi.org/10.2172/1888878.
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Isgor, O. Cracking Susceptibility of Concrete Made with Recycled Concrete Aggregate. Portland State University Library, Dezember 2013. http://dx.doi.org/10.15760/trec.50.
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Krajcinovic, Dusanr. Micromechanics of Concrete. Fort Belvoir, VA: Defense Technical Information Center, Januar 1988. http://dx.doi.org/10.21236/ada193433.
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D.H. Tang. Concrete Chemical Evolution. Office of Scientific and Technical Information (OSTI), Juli 1998. http://dx.doi.org/10.2172/859060.
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Howard, Isaac, Thomas Allard, Ashley Carey, Matthew Priddy, Alta Knizley und Jameson Shannon. Development of CORPS-STIF 1.0 with application to ultra-high performance concrete (UHPC). Engineer Research and Development Center (U.S.), April 2021. http://dx.doi.org/10.21079/11681/40440.
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This report introduces the first release of CORPS-STIF (Concrete Observations Repository and Predictive Software – Structural and Thermodynamical Integrated Framework). CORPS-STIF is envisioned to be used as a tool to optimize material constituents and geometries of mass concrete placements specifically for ultra-high performance concretes (UHPCs). An observations repository (OR) containing results of 649 mechanical property tests and 10 thermodynamical tests were recorded to be used as inputs for current and future releases. A thermodynamical integrated framework (TIF) was developed where the heat transfer coefficient was a function of temperature and determined at each time step. A structural integrated framework (SIF) modeled strength development in cylinders that underwent isothermal curing. CORPS-STIF represents a step toward understanding and predicting strength gain of UHPC for full-scale structures and specifically in mass concrete.
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Bostick, W. D., S. A. Bush, G. C. Marsh, H. M. Henson, W. D. Box und I. L. Morgan. Electroosmotic decontamination of concrete. Office of Scientific and Technical Information (OSTI), März 1993. http://dx.doi.org/10.2172/10141134.
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Berry, E. E., und V. M. Malhotra. Fly ash in concrete. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 1986. http://dx.doi.org/10.4095/305031.
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