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‣ Assessment of the compatibility of wood and plastic with cement for their recycling in cement composites

Andrade, André; Caldeira, Fernando
Fonte: Edições Universidade Fernando Pessoa Publicador: Edições Universidade Fernando Pessoa
Tipo: Artigo de Revista Científica
Publicado em //2010 Português
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The compatibility between maritime pine wood and cement, and between plastic (LDPE) and cement, was assessed for the recycling of wood and plastic in cement composites. Temperature vs. time profiles of cement setting were registered and compatibility indices were calculated. Results indicate that recycling of plastics in plastic-cement composites does not pose any questions regarding chemical compatibility. However, maritime pine hinders cement setting in some extent. So, in order to manufacture wood-cement composites with recycled wood, physico-mechanical properties of composites must be assessed, too. Foi avaliada a compatibilidade entre a madeira de pinho bravo e o cimento, e entre plástico (LDPE) e cimento, com vista à sua reciclagem na forma de aglomerados com cimento como ligante. Obtiveram-se perfis de temperatura versus tempo da presa do cimento, e calcularam-se índices de compatibilidade. O plástico não tem problemas de compatibilidade com o cimento, e, como tal, a reciclagem de plásticos nesta forma será possível. No caso do pinho, a madeira de facto retarda a presa do cimento em certa extensão. Portanto, as propriedades físico-mecânicas de aglomerados cimento-madeira também deverão ser testadas se se pretender reciclar madeira desta forma.

‣ Effect of cement type and water storage time on the push-out bond strength of a glass fiber post

REIS, Kátia Rodrigues; SPYRIDES, George Miguel; OLIVEIRA, Jonas Alves de; JNOUB, Alexandre Abrão; DIAS, Kátia Regina Hostilio Cervantes; BONFANTES, Gerson
Fonte: Fundação Odontológica de Ribeirão Preto Publicador: Fundação Odontológica de Ribeirão Preto
Tipo: Artigo de Revista Científica
Português
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This study investigated the effects of the cement type and the water storage time on the push-out bond strength of a glass fiber post. Glass fiber posts (Fibrekor, Jeneric Pentron) were luted to post spaces using a self-cured resin cement (C&B Cement [CB]), a glass ionomer cement (Ketac Cem [KC]) or a resin-modified glass ionomer cement (GC FujiCEM [FC]) according to the manufacturers’ instructions. For each luting agent, the specimens were exposed to one of the following water storage times (n=5): 1 day (T1), 7 days (T7), 90 days (T90) and 180 days (T180). Push-out tests were performed after the storage times. Control specimens were not exposed to water storage, but subjected to the push-out test 10 min after post cementation. Data (in MPa) were analyzed by Kruskal-Wallis and Dunn`s test (α=0.05). Cement type and water storage time had a significant effect (p<0.05) on the push-out bond strength. CB showed significantly higher values of retention (p<0.05) than KC and FC, irrespective of the water storage time. Water storage increased significantly the push-out bond strength in T7 and T90, regardless of the cement type (p<0.05). The results showed that fiber posts luted to post spaces with the self-cured resin cement exhibited the best bonding performance throughout the 180-day water storage period. All cements exhibited a tendency to increase the bond strength after 7 and 90 days of water storage...

‣ Radiopacity of Portland Cement Associated With Different Radiopacifying Agents

DUARTE, Marco Antonio Hungaro; KADRE, Guaniara D`arc de Oliveira El; VIVAN, Rodrigo Ricci; TANOMARU, Juliane Maria Guerreiro; TANOMARU FILHO, Mario; MORAES, Ivaldo Gomes de
Fonte: ELSEVIER SCIENCE INC Publicador: ELSEVIER SCIENCE INC
Tipo: Artigo de Revista Científica
Português
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This study evaluated the radiopacity of Portland cement associated with the following radiopacifying agents: bismuth oxide, zinc oxide, lead oxide, bismuth subnitrate, bismuth carbonate, barium sulfate, iodoform, calcium tungstate, and zirconium oxide. A ratio of 20% radiopacifier and 80% white Portland cement by weight was used for analysis. Pure Portland cement and dentin served as controls. Cement/radiopacifier and dentin disc-shaped specimens were fabricated, and radiopacity testing was performed according to the ISO 6876/2001 standard for dental root sealing materials. Using Insight occlusal films, the specimens were radiographed near to a graduated aluminum stepwedge varying from 2 to 16 mm in thickness. The radiographs were digitized and radiopacity compared with the aluminum stepwedge using Digora software (Orion Corporation Soredex, Helsinki, Finland). The radiographic density data were converted into mmAl and analyzed statistically by analysis of variance and Tukey-Kramer test (alpha = 0.05). The radiopacity of pure Portland cement was significantly lower (p < 0.05) than that of dentin, whereas all cement/radiopacifier mixtures were significantly more radiopaque than dentin and Portland cement alone (p < 0.05). Portland cement/bismuth oxide and Portland cement/lead oxide presented the highest radiopacity values and differed significantly from the other materials (p < 0.05)...

‣ Influência da cal hidratada nas idades iniciais da hidratação do cimento Portland - estudo em pasta.; Influence of hydrated lime on initial stages of hydration of Portland cement - paste study.

Quarcioni, Valdecir Angelo
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 04/04/2008 Português
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O progresso científico e tecnológico das últimas décadas registra um avanço significativo no processo de obtenção da cal, porém, há uma lacuna de conhecimento de base referente à sua ação quando empregada em conjunto com o cimento Portland. O uso da cal nas argamassas mistas de acabamento tem sido associado positivamente apenas à plasticidade no estado fresco e à sua deformabilidade no estado endurecido. Maiores informações são necessárias sobre a ação da cal na evolução das propriedades da argamassa no estado fresco, vinculadas à hidratação do cimento. Este conhecimento é importante para o desenvolvimento de formulações que atendam ao desempenho desejado em diferentes aplicações. O entendimento do mecanismo de hidratação do cimento em presença da cal constitui uma plataforma para estudos de adições minerais ativas ao clínquer, com adição de cal hidratada como fonte externa de cálcio, na produção de novos materiais cimentícios sustentáveis. O estudo em pasta realizado teve como foco a interação cimento-cal visando identificar os fenômenos químicos e físicos relevantes que se sucedem à adição de água ao sistema. Foram caracterizadas as idades iniciais de hidratação do cimento por meio de ensaios de calorimetria de condução...

‣ Aplicação da difração de raios-X e método de Rietveld no estudo de Cimento Portland; Application of X-ray diffraction and Rietveld method in Portland Cement study

Gobbo, Luciano de Andrade
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 19/06/2009 Português
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O projeto desenvolvido enfocou a aplicação da difração de raios-X e método de Rietveld (DRX-Rietveld) na caracterização e quantificação do Cimento Portland, constituindo-se em contribuição pioneira sobre o tema em âmbito nacional. Foram estudadas amostras de pozolanas naturais e artificiais, subprodutos industriais de grande disponibilidade na indústria nacional, tais como escórias de alto-forno provenientes das siderúrgicas e cinzas volantes das termelétricas. Adicionalmente, foram estudadas amostras dos componentes utilizados para composição de cimentos laboratoriais, tais como clínqueres, calcários e fosfogesso, e por fim, cimento Portland com adições, preparados em laboratório. Também foram realizados ensaios para acompanhamento da hidratação do cimento Portland com uso da difração de raios-X e método de Rietveld. O cimento Portland é o material composto de clínquer, gesso e eventuais adições, tais como calcário, pozolanas e escórias. O clínquer de cimento Portland é o material sinterizado e peletizado, resultante da calcinação de uma mistura adequada de calcário e argila e, eventualmente, de componentes corretivos. O método de Rietveld, foi introduzido por Hugo Rietveld em 1969, tendo em base a simulação de todo o perfil difratométrico a partir de parâmetros estruturais das fases constituintes...

‣ Desenvolvimento e caracterização de um cimento ósseo esponjoso para preenchimento de falhas ósseas. Análise morfométrica e ensaio mecânico; Development and characterization of a cancellous cement repair of bone defects. Morphometric analisys and mechanical testing

Cimatti, Bruno
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 28/06/2012 Português
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Introdução: O tratamento dos tumores ósseos benignos é frequentemente realizado por abordagem intralesional com curetagem do tumor e preenchimento da falha óssea com substâncias biológicas ou sintéticas. Entre as biológicas estão os vários tipos de enxertos e o maior representante das sintéticas é o cimento ósseo ou polimetilmetacrilato (PMMA). O uso do cimento ósseo compacto pode apresentar problemas devido à necrose térmica, ao afrouxamento asséptico, à incapacidade de remodelação e à elasticidade inadequada em relação ao osso normal. O desenvolvimento de um cimento ósseo esponjoso que atenda a estas demandas mecânicas e biológicas e que seja de fácil manipulação no ambiente cirúrgico tem estimulado alguns pesquisadores. Basicamente, é possível formar poros no interior do cimento por mistura de substâncias hidrossolúveis ou por reação química produtora de gás. Objetivo: Desenvolver e caracterizar fisicamente e mecanicamente um cimento ósseo com poros intercomunicantes de aspecto estrutural esponjoso. Material e métodos: A produção de cimento esponjoso foi realizada misturando-se o PMMA com bicarbonato de sódio e ácido cítrico. Foram confeccionados 90 corpos de prova com 40 mm de altura por 20 mm de diâmetro distribuídos em 6 grupos (n=15): G1 formado por cimento esponjoso em que antes da polimerização do cimento foram adicionados bicarbonato de sódio e ácido cítrico na proporção de 10% em relação ao componente sólido do cimento (polímero); G2 - cimento esponjoso na proporção de 20%; G3 - cimento esponjoso na proporção de 30%; G4 - cimento ósseo de PMMA compacto; G5 - formado por cimento de poliuretana de mamona (Bioósteo®) na proporção de 20%; G6 formado de corpos de prova cilíndricos de osso esponjoso extraído com trefina de côndilos tibiais proximais de bovinos. A qualidade do cimento esponjoso foi avaliada por macroscopia...

‣ Effects of cement thickness and bonding on the failure loads of CAD/CAM ceramic crowns: Multi-physics FEA modeling and monotonic testing

May, Liliana G.; Kelly, J. Robert; Bottino, Marco A.; Hill, Thomas
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: E99-E109
Português
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Objective. To determine the influence of cement thickness and ceramic/cement bonding on stresses and failure of CAD/CAM crowns, using both multi-physics finite element analysis and monotonic testing.Methods. Axially symmetric FEA models were created for stress analysis of a stylized monolithic crown having resin cement thicknesses from 50 to 500 mu m under occlusal loading. Ceramic-cement interface was modeled as bonded or not-bonded (cement-dentin as bonded). Cement polymerization shrinkage was simulated as a thermal contraction. Loads necessary to reach stresses for radial cracking from the intaglio surface were calculated by FEA. Experimentally, feldspathic CAD/CAM crowns based on the FEA model were machined having different occlusal cementation spaces, etched and cemented to dentin analogs. Non-bonding of etched ceramic was achieved using a thin layer of poly(dimethylsiloxane). Crowns were loaded to failure at 5 N/s, with radial cracks detected acoustically.Results. Failure loads depended on the bonding condition and the cement thickness for both FEA and physical testing. Average fracture loads for bonded crowns were: 673.5 N at 50 mu m cement and 300.6 N at 500 mu m. FEA stresses due to polymerization shrinkage increased with the cement thickness overwhelming the protective effect of bonding...

‣ Cementation of fiber post: influence of the cement insertion techniques on the bond strength of the fiber post-root dentin and the quality of the cement layer.

Michida, S. M.; Souza, R. O.; Bottino, M. A.; Valandro, L. F.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 633-636
Português
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The aim of this study was to assess the influence of resin cement insertion methods on the bond strength of a fiber post to root dentin and quality of the cement layer. Forty bovine single-roots (length =16 mm) were randomly allocated into four groups, according to the cement insertion methods (N.=10): Gr1- Lentulo drill #40, Gr2- Centrix syringe, Gr3- Explorer #5, Gr4- fiber post. The root canals were prepared at 12 mm, using preparation bur # 3 of a cylinder quartz-FRC post (Aesthet post-plus, Bisco). The fiber posts were cemented using a multi-step etch-and-rinse adhesive system (All Bond 2®, Bisco) and a dual-cured resin cement (Duolink, Bisco). Each root was cut into seven samples: four samples of 1.8 mm thickness for push-out testing, and three with 0.5 mm for cement layer quality analyzing. One-way ANOVA was used for the push-out test values and the One-Way Kruskal-Wallis (P<0.05) and Dunn (10%) tests for the cement layer analyzes. ANOVA showed that the cement layer quality was affected by the cement insertion methods (P=0.0044): Gr1 (3.8 ± 1.3a), Gr2 (3.2 ± 1.3a), Gr3 (5.2 ± 1.5a,b) and Gr4 (5.2 ± 1.5b) (Dunn test), whereas the bond strength (MPa) was not affected by cement insertion methods: G1 (4.2 ± 1.3), G2 (3.2 ± 1.8)...

‣ Recycling of textile wastes in fibre-cement composites

Monteiro, H.; Caldeira, F.; Pinto, J.; Varum, H.
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Conferência ou Objeto de Conferência
Português
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Changing wastes into raw materials is one of the most favoured options for waste management, as it diverts wastes from landfill and saves resources. Fibres, either vegetable (cellulosic) or synthetic, may be added to cement pastes in order improve the properties of concrete or mortar by reinforcement. At the same time, if our source of fibres is wastes, then such processes make ways for recycling. In this work we studied the compatibility of residues from the nonwoven textile industry with Portland cement, with the aim of manufacturing fibre-cement composites. The temperature of cement setting was monitored and when fibre or other materials were added to cement pastes. The textile waste from needling machines investigated here is not compatible with cement. The reason is ascribed to a higher cotton content (65%), which enables cation exchange to occur in cement suspensions, and that disturbs cement setting reactions. On the other hand, however, synthetic fibres do not seem to hinder cement setting.

‣ Effect of eugenol-based endodontic cement on the adhesion of intraradicular posts

Alfredo,Edson; Souza,Emanuel Soares de; Marchesan,Melissa Andréia; Paulino,Silvana Maria; Gariba-Silva,Ricardo; Sousa-Neto,Manoel Damião
Fonte: Fundação Odontológica de Ribeirão Preto Publicador: Fundação Odontológica de Ribeirão Preto
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2006 Português
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The present study evaluated, in vitro, the influence of an eugenol-based endodontic sealer (EndoFill) on the adhesion of intra-radicular posts cemented with a resin-based cement (Enforce) ou a zinc phosphate cement. Twenty-four single-rooted maxillary canines were divided into 2 groups (n=12) and obturated with either gutta-percha points plus EndoFill or gutta-percha points alone (no cement). In each group, half of intracanal posts (n=6) were cemented with Enforce resin-based cement and half with zinc phosphate cement. Specimens were submitted to pull-out test in an Instron machine and tensile force was applied at a crosshead speed of 0.5 mm/min until post dislodgement. The maximum forces required for post removal was recorded (N) and means were submitted to statistical analysis by Kruskal-Wallis test (p<0.01). Posts cemented with zinc phosphate cement were significantly more retentive (353.4 N) than those cemented with Enforce (134.9 N) (p<0.01). Regarding the influence of the eugenol-based cement (EndoFill) on post retention, there was statistically significant difference (p<0.01) only between the groups cemented with Enforce, i.e., in the canals filled with EndoFill + guta-percha there was lower bond strength than in the canals filled with gutta-percha points alone (101.5 and 168.2 N...

‣ Effect of cement type and water storage time on the push-out bond strength of a glass fiber post

Reis,Kátia Rodrigues; Spyrides,George Miguel; Oliveira,Jonas Alves de; Jnoub,Alexandre Abrão; Dias,Kátia Regina Hostilio Cervantes; Bonfantes,Gerson
Fonte: Fundação Odontológica de Ribeirão Preto Publicador: Fundação Odontológica de Ribeirão Preto
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2011 Português
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This study investigated the effects of the cement type and the water storage time on the push-out bond strength of a glass fiber post. Glass fiber posts (Fibrekor, Jeneric Pentron) were luted to post spaces using a self-cured resin cement (C&B Cement [CB]), a glass ionomer cement (Ketac Cem [KC]) or a resin-modified glass ionomer cement (GC FujiCEM [FC]) according to the manufacturers’ instructions. For each luting agent, the specimens were exposed to one of the following water storage times (n=5): 1 day (T1), 7 days (T7), 90 days (T90) and 180 days (T180). Push-out tests were performed after the storage times. Control specimens were not exposed to water storage, but subjected to the push-out test 10 min after post cementation. Data (in MPa) were analyzed by Kruskal-Wallis and Dunn`s test (α=0.05). Cement type and water storage time had a significant effect (p<0.05) on the push-out bond strength. CB showed significantly higher values of retention (p<0.05) than KC and FC, irrespective of the water storage time. Water storage increased significantly the push-out bond strength in T7 and T90, regardless of the cement type (p<0.05). The results showed that fiber posts luted to post spaces with the self-cured resin cement exhibited the best bonding performance throughout the 180-day water storage period. All cements exhibited a tendency to increase the bond strength after 7 and 90 days of water storage...

‣ VIABILIDADE DO USO DE CINZAS DE BAGAÇO DE CANADE- AÇÚCAR (CBC) RESIDUAIS DO ESTADO DE GOIÁS COMO ADIÇÃO MINERAL AO CIMENTO PORTLAND; FEASIBILITY OF THE USE OF SUGAR CANE BAGASSE ASH (CBC) FROM GOIÁS STATE TO REPLACE PORTLAND CEMENT

SOUSA, Lara Rubia Lopes de
Fonte: Universidade Federal de Goiás; BR; UFG; Mestrado em Engenharia Civil; Engenharias Publicador: Universidade Federal de Goiás; BR; UFG; Mestrado em Engenharia Civil; Engenharias
Tipo: Dissertação Formato: application/pdf
Português
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Aiming to reduce the generation of waste in industrial and agriculture processes, especially the pollutants, and reuses them best, whether in the production process or as raw material in the preparation of other materials, it has increasingly invested in searches for the processing of waste in industrial by-products of commercial interest. With increasing energy demand in the world, Brazil is an ecologically correct fuel producer, such as ethanol and bio diesel. In the State of Goiás there is a large potential for growth of industry cultivating sugar-cane, responding to sustainable energy issues. Furthermore, the recent national development policies point to the expansion of the sugaralcohol sector in the state. With the intensification of the industrial process of sugar-cane in Goiás, it is, increasingly, the occurrence of problems associated with disposal of waste generated by this sector. Much of that waste can be used to produce new building materials and meet the growing demand for alternative technologies, simpler, efficient and concerned about the sustainability of production processes. The research on the use of sugar-cane bagasse ash (CBC) as mineral addition to cement is still incipient. However, studies indicate the feasibility of using ash in conjunction with Portland cement. Additions are mineral materials with pozzolanic properties...

‣ The Construction of Sustainability in the Cement Industry: Audit Culture, Materiality and Affective Processes

Resendez de Lozano, Laura
Fonte: Universidade Rice Publicador: Universidade Rice
Português
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Introducing sustainability policies in the cement industry involves changing not only production technologies, but the organizational culture of a mature industry that is characterized by huge CO₂ emissions and significant environmental impacts. This research attempts to understand the transition process of the industry and its employees as the process is taking place. The actors involved are strongly influenced by often contradictory forces: On one hand the naturalized market dynamics in the context of the automobile dependent society and widespread networks of highways and other concrete structures, and on the other, the growing concern of preserving resources for future generations as a shared responsibility that raises awareness of the negative environmental impacts of cement production. The fieldwork component of the project was comprised of two complementary parts: First, an ethnographic study of how the abstract goal of becoming sustainable is given meaning as it is implemented in Cemex, one of the largest companies in the cement industry at the global level. Second, an analysis of the audit culture mechanisms present in the production of knowledge among experts involved in designing sustainability assessment mechanisms for infrastructure projects. The latter component took place among experts in the academy and in the Texas Department of Transportation...

‣ Screw and Edge Dislocations in Cement Phases: Atomic Modeling

Chen, Lu
Fonte: Universidade Rice Publicador: Universidade Rice
Português
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Cement is the key strengthening and the most energy-intensive ingredient in concrete. With increasing pressure for reducing energy consumption in cement manufacturing, there is an urgent need to understand the basic deformation mechanisms of cement. In this thesis, we develop a computational framework based on molecular dynamics to study two common types of defects, namely screw and edge dislocations, in complex, anisotropic crystalline polymorphs of cement clinkers and cement hydration products. We found the likelihood of these defects in regions with higher Young moduli. We also found the preferred cement polymorphs that require less energy for grinding via analysis of Peierls stresses. Together, the results provide a detailed understanding of the role and type of defects in cement phases, which impact the rate of hydration, crystal growth and grinding energy. To our knowledge, this is the first study with atomic-resolution on deformation-based mechanisms in cement crystalline phases.

‣ Existing and Potential Technologies for Carbon Emissions Reductions in the Indian Cement Industry : A Set of Technical Papers Produced for the Project 'Low Carbon Technology Road Map for the Indian Cement Industry'

World Bank
Fonte: Washington, DC Publicador: Washington, DC
Tipo: Economic & Sector Work :: Commodities Study; Economic & Sector Work
Português
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This set of technical papers was commissioned by the Cement Sustainability Initiative (CSI) members in India. CSI is a member-led program of the World Business Council for Sustainable Development (WBCSD). The report represents the independent work of the CII - Godrej Green Business Centre (CII, Godrej GBC), a center of excellence of Confederation of Indian Industry (CII) and the National Council for Cement and Building Materials (NCB). The author of each paper is shown after its title. It aims to identify, describe and evaluate technologies, which may contribute to increased energy efficiencies and reduced greenhouse gas emissions from cement production in India today and in the longer-term. The results have been reviewed by CII, NCB, CSI member companies and stakeholders like the International Energy Agency (IEA). All papers follow the same format, outlining the current status of the technology, the impact on energy consumption, anticipated benefits from implementation, the CO? reduction potential, main parameters influencing implementation...

‣ Resistência à compressão não confinada de misturas de solo-cimento visando à aplicação do sistema de estabilização Dry-Mix; Unconfined compressive strength in a soil-cement mixture for stabilization system Dry-Mix

Débora Regina Dias
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 15/12/2011 Português
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Este trabalho vem contribuir com a técnica de tratamento de solos moles por meio do sistema de estabilização Dry-Mix, analisando parâmetros de resistência à compressão não confinada de corpos-de-prova, devidamente preparados com misturas plásticas de solo mole, aglomerante (cimento Portland) e água, em laboratório. O solo utilizado era oriundo da região da Baixada Santista, localizada no Estado de São Paulo. Duas diferentes dosagens de cimento, 100 e 200 kg de cimento por m³ de solo, além de dois diferentes tipos de cimento CP III e CP V, foram utilizadas neste estudo. Os corpos-deprova foram ensaiados à compressão não confinada nas idades de cura de 7, 28, 90 e 180 dias, e submetidos aos ensaios de ultrassom, durante 28 dias. As dosagens inferiores a 100 kg de cimento por m³ de solo apresentaram resultados de resistência à compressão não confinada inferiores a 200 kN/m², não sendo recomendadas para o tratamento Dry-Mix. Os módulos de elasticidade apresentaram valores crescentes até a idade de 28 dias, indicando perda da rigidez após essa idade de cura. Nos ensaios de ultrassom, foram observados resultados significativos somente para os corpos-de-prova com a dosagem de 200 kg de cimento por m³ de solo. Os resultados de resistência à compressão simples foram submetidos a uma análise estatística...

‣ Effect of cement types on the tensile strength of metallic crowns submitted to thermocycling

Consani,Simonides; Santos,Julie Guzela dos; Correr Sobrinho,Lourenço; Sinhoreti,Mário Alexandre Coelho; Sousa-Neto,Manoel Damião
Fonte: Fundação Odontológica de Ribeirão Preto Publicador: Fundação Odontológica de Ribeirão Preto
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2003 Português
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The relationship between metallic cast crowns and tensile strength according to cement types submitted to thermocycling was studied. Seventy-two metallic crowns were cast with Verabond II Ni-Cr alloy and cemented in standardized preparations with 10º tapering. Three types of finishing line (45-degree chamfered, 20-degree bevel shoulder and right shoulder) were made with diamond burs on bovine teeth. Twenty-four metallic crowns in each group were randomly subdivided into three subgroups of 8 samples each according to the cement used: SS White zinc phosphate cement, Vitremer resin-modified glass ionomer cement, and Rely X resin cement and were submitted to thermocycling. Retention was evaluated according to tensile load required to displace the metallic cast crowns from tooth preparations with an Instron testing machine. ANOVA and Tukey's test showed a statistically significant difference among luting materials, with greater results for Rely X resin cement (24.9 kgf) followed by SS White zinc phosphate cement (13.3 kgf) and Vitremer resin-modified glass ionomer cement (10.1 kgf). The finishing line types did not influence the tensile resistance of the crowns fixed with the three cements. Increased tensile resistance of metallic crowns fixed on bovine teeth was obtained with resin cement...

‣ Manufacture of wood-cement composites from Acacia Mangium: mechanistic study of compounds improving the compatability of Acacia Mangium heartwood with Portland cement

Semple, Kate; Cunningham, Ross; Evans, Philip David
Fonte: Society of Wood Science and Technology Publicador: Society of Wood Science and Technology
Tipo: Artigo de Revista Científica
Português
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Numerous inorganic compounds were screened to identify those capable of minimizing the inhibitory effect of Acacia mangium heartwood on the setting of cement. It was hypothesized that the most effective compounds would be ones that could accelerate the hydration of cement and form complexes with inhibitory phenolic extractives found in the heartwood of A. mangium. Our hypothesis proved correct since compounds such as SnCl4, AlCl3, and FeCl3 and/or their ionic species that were able to bond with the phenolic heartwood constituents of A. mangium as well as accelerate cement hydration were generally more effective at strengthening cement hydration in the presence of A. mangium heartwood than compounds that simply accelerated cement hydration. Compounds containing Ni2+, Ag+, Fe3+, and Co2+, that bonded to phenolic constituents of A. mangium heartwood, but lacked the ability to strongly accelerate cement hydration increased maximum hydration temperature attained in wood-cement mixes. The findings suggest that complexation of phenolic heartwood extractives may be an important mechanism by which inorganic compounds reduce the inhibitory effect of certain wood species on the hydration of cement. A combination of compounds including a cost-effective accelerator (such as CaCl2 or MgCl2) and an efficient chelating agent (containing such ions as Al3+...

‣ Cement Hydration Tests Using Wood Flour may not Predict the Suitability of Acacia mangium and Eucalyptus pellita for the Manufacture of Wood-Wool Cement Boards

Semple, Kate; Cunningham, Ross; Evans, Philip
Fonte: Walter de Gruyter Publicador: Walter de Gruyter
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
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Wood-wool cement boards (WWCBs) are manufactured in many tropical countries which have extensive eucalypt and acacia plantations. Wood from such plantations could act as a potential raw material for WWCBs, but the suitability of most tropical eucalypts and acacias for the manufacture of such products is unknown. This study was undertaken to assess whether the standard laboratory test for wood-cement compatibility, which measures heat of hydration in wood flour-cement mixtures, is an appropriate method for screening tropical eucalypts and acacias for their compatibility with cement and suitability for the manufacture of WWCBs. Wood samples from a tropical eucalypt (E. pellita) and a tropical acacia (A. mangium) were tested in two forms, i.e. flour and wool, for their compatibility (expressed by maximum hydration temperature and CA-factor) with Portland cement. Form significantly influenced the effect of the wood on cement hydration, resulting in a different species compatibility ranking for flour and wool. As the heartwood content of wood-wool-cement hydration test samples increased, Tmax. and CA factor increased whereas the opposite occured for those containing wood flour. Tests using wood flour ranked E. pellita as being more compatible with cement than A. mangium whereas the ranking was reversed when wood-wool was used. Furthermore at low wood levels the compatibility of samples containing wood-wool or wood flour with cement was similar whereas at high wood levels...

‣ Wood-cement boards of Eucalyptus saligna with different chemical additives and methods of formation.; PAINÉIS CIMENTO-MADEIRA DE Eucalyptus saligna COM DIFERENTES ADITIVOS QUÍMICOS E MÉTODOS DE FORMAÇÃO

Castro, Vinicius Gomes; Universidade Federal do Paraná; Braz, Rafael Leite; Universidade Federal do Paraná; Azambuja, Rafael Rosa; Universidade Federal do Paraná; Loiola, Pedro Lício; Universidade Federal do Paraná; Iwakiri, Setsuo; Universidade Fede
Fonte: FUPEF DO PARANÁ Publicador: FUPEF DO PARANÁ
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; Artigo Avaliado pelos Pares Formato: application/pdf
Publicado em 17/09/2014 Português
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Este trabalho teve como objetivo avaliar o potencial de uso de diferentes aditivos químicos e métodos de formação na produção de compósitos cimento-madeira com clone de Eucalyptus saligna. Utilizou-se o cimento Portland tipo CP II-Z, como aglutinante mineral, e cloreto de cálcio (CaCl2) e cloreto de magnésio (MgCl2),como aceleradores de cura do cimento. Os painéis cimento-madeira foram produzidos pelo método de prensagem na prensa de pratos de 50,5 x 38,5 x1,5 cm, e pelo método de adensamento por vibrocompactação em dimensões de 35 x 7 x1,5 cm. Os painéis foram formados com densidade nominal de 1 g/cm³ e relação cimento:madeira de 2,75:1. Com base nos resultados, pode-se concluir que: (I) os testes de hidratação mostraram que a madeira é compatível com o cimento Portland tipo II; (II) o uso de cloreto de cálcio e de magnésio na proporção de 3% em relação à massa do cimento proporcionou incremento nas propriedades físicas e mecânicas dos painéis produzidos pelos dois métodos de formação avaliados; (III) os painéis produzidos pelo método de adensamento por vibrocompactação apresentaram menor densidade média, maior estabilidade dimensional e melhor tração perpendicular do que os painéis produzidos pelo método tradicional de prensa de pratos.Palavras-chave: Compósito cimento-madeira; vibro compactação; aceleradores de cura. AbstractWood-cement boards of Eucalyptus saligna with different chemical additives and methods of formation. The aim of this work was evaluate the potential use of different chemical additives and methods of formation for wood-cement composites with Eucalyptus saligna clones. Portland cement type II-Z was used as mineral bonding and Calcium chloride (CaCl2) and Magnesium chloride (MgCl2) as accelerator of the cement hydration. The wood-cement panels were produced by the cold press method with dimensions of 50.5 x 38.5 x1.5 cm...