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Drying and autogenous shrinkage of pastes and mortars with activated slag cement

MELO NETO, Antonio A.; CINCOTTO, Maria Alba; REPETTE, Wellington
Fonte: PERGAMON-ELSEVIER SCIENCE LTD Publicador: PERGAMON-ELSEVIER SCIENCE LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.14%
Activated slag cement (ASC) shows significantly higher shrinkage than ordinary Portland cement agglomerates. Cracking generated by shrinkage is one of the most critical drawbacks for broader applications of this promising alternative binder. This article investigates the relationship between ASC hydration, unrestrained drying and autogenous shrinkage of mortar specimens. The chemical and microstructure evolution due to hydration were determined on pastes by thermogravimetric analysis, conduction calorimetry and mercury porosimetry. Samples were prepared with ground blast furnace slag (BFS) activated with sodium silicate (silica modulus of 1.7) with 2.5, 3.5 and 4.5% of Na2O, by slag mass. The amount of activator is the primary influence on drying and autogenous shrinkage, and early hydration makes a considerable contribution to the total result, which increases with the amount of silica. Drying shrinkage occurred in two stages, the first caused by extensive water loss when the samples were exposed to the environment, and the second was associated with the hydration process and less water loss. Due to the refinement of ASC porous system, autogenous shrinkage is responsible for a significant amount of the total shrinkage. (C) 2007 Elsevier Ltd. All rights reserved.

Do Low-shrink Composites Reduce Polymerization Shrinkage Effects?

TANTBIROJN, D.; PFEIFER, C. S.; BRAGA, R. R.; VERSLUIS, A.
Fonte: SAGE PUBLICATIONS INC Publicador: SAGE PUBLICATIONS INC
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.2%
Progress in polymer science has led to continuous reduction of polymerization shrinkage, exemplified by a new generation of ""low-shrink composites"". The common inference that shrinkage stress effects will be reduced in teeth restored with such restoratives with lower shrinkage was tested in extracted human premolars. Mesio-occluso-distal slot-shaped cavities were cut and restored with a conventional (SupremePlus) or low-shrink (RefleXions, Premise, Kalore, and LS) composite (N = 5). We digitized the coronal surfaces before and 10 min after restoration to determine cuspal deflection from the buccal and lingual volume change/area. We also determined the main properties involved (total shrinkage, post-gel shrinkage, degree of conversion, and elastic modulus), as well as microleakage, to verify adequate bonding. It was shown that, due to shrinkage stresses, buccal and lingual surfaces pulled inward after restoration (9-14 microns). Only Kalore and LS resulted in significantly lower tooth deformation (ANOVA/Student-Newman-Keuls post hoc, p = 0.05). The other two low-shrink composites, despite having the lowest and highest total shrinkage values, did not cause significant differences in cuspal deflection. Deflection seemed most related to the combination of post-gel shrinkage and elastic modulus. Therefore...

Polymerization stress, shrinkage and elastic modulus of current low-shrinkage restorative composites

BOARO, Leticia Cristina Cidreira; GONCALVES, Flavia; GUIMARAES, Thayse Costa; FERRACANE, Jack Liborio; VERSLUIS, Antheunis; BRAGA, Roberto Ruggiero
Fonte: ELSEVIER SCI LTD Publicador: ELSEVIER SCI LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.27%
Objective. To compare currently available low-shrinkage composites with others regarding polymerization stress, volumetric shrinkage (total and post-gel), shrinkage rate and elastic modulus. Methods. Seven BisGMA-based composites (Durafill/DU, Filtek Z250/FZ, Heliomolar/HM, Aelite LS Posterior/AP, Point 4/P4, Filtek Supreme/SU, ELS/EL), a silorane-based (Filtek LS, LS), a urethane-based (Venus Diamond, VD) and one based on a dimethacrylate-derivative of dimer acid (N`Durance, ND) were tested. Polymerization stress was determined in 1-mm high specimens inserted between two PMMA rods attached to a universal testing machine. Total volumetric shrinkage was measured using a mercury dilatometer. Maximum shrinkage rate was used as a parameter of the reaction speed. Post-gel shrinkage was measured using strain-gages. Elastic modulus was obtained by three-point bending. Data were submitted to one-way ANOVA/Tukey test (p = 0.05), except for elastic modulus (Kruskal-Wallis). Results. Composites ranked differently for total and post-gel shrinkage. Among the materials considered as ""low-shrinkage"" by the respective manufacturers, LS, EL and VD presented low post-gel shrinkage, while AP and ND presented relatively high values. Polymerization stress showed a strong correlation with post-gel shrinkage except for LS...

Network structures of Bis-GMA/TEGDMA resins differ in DC, shrinkage-strain, hardness and optical properties as a function of reducing agent

FURUSE, Adilson Y.; MONDELLI, Jose; WATTS, David C.
Fonte: ELSEVIER SCI LTD Publicador: ELSEVIER SCI LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.23%
Objectives. To evaluate the influence of different tertiary amines on degree of conversion (DC), shrinkage-strain, shrinkage-strain rate, Knoop microhardness, and color and transmittance stabilities of experimental resins containing BisGMA/TEGDMA (3: 1 wt), 0.25wt% camphorquinone, 1wt% amine (DMAEMA, CEMA, DMPT, DEPT or DABE). Different light-curing protocols were also evaluated. Methods. DC was evaluated with FTIR-ATR and shrinkage-strain with the bonded-disk method. Shrinkage-strain-rate data were obtained from numerical differentiation of shrinkage-strain data with respect to time. Color stability and transmittance were evaluated after different periods of artificial aging, according to ISO 7491: 2000. Results were evaluated with ANOVA, Tukey, and Dunnett`s T3 tests (alpha = 0.05). Results. Studied properties were influenced by amines. DC and shrinkage-strain were maximum at the sequence: CQ < DEPT < DMPT <= CEMA approximate to DABE < DMAEMA. Both DC and shrinkage were also influenced by the curing protocol, with positive correlations between DC and shrinkage-strain and DC and shrinkage-strain rate. Materials generally decreased in L* and increased in b*. The strong exception was the resin containing DMAEMA that did not show dark and yellow shifts. Color varied in the sequence: DMAEMA < DEPT < DMPT < CEMA < DABE. Transmittance varied in the sequence: DEPT approximate to DABE < DABE approximate to DMPT approximate to CEMA < DMPT approximate to CEMA approximate to DMAEMA...

Estudo da retração em argamassa com cimento de escória ativada.; Shrinkage of alkali-activated slag.

Melo Neto, Antonio Acácio de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 19/11/2002 PT
Relevância na Pesquisa
37.23%
O uso de escória de alto forno como aglomerante alternativo ao cimento portland tem sido objeto de vários estudos no Brasil e no exterior. Além de representar vantagens ao meio ambiente por ser um resíduo, a escória apresenta boas possibilidades de emprego, principalmente pelo baixo custo e por suas vantagens técnicas das quais se destacam a elevada resistência mecânica, a boa durabilidade em meios agressivos, o baixo calor de hidratação. No entanto, o emprego deste material carece de estudos detalhados da retração, muito superior à do cimento portland. Este trabalho teve como objetivo estudar a cinética das retrações autógena e por secagem não restringidas do cimento de escória ativada em função, principalmente, do tipo e teor de ativadores empregados. Para a retração autógena, o corpo-de-prova foi selado com papel alumínio protegido internamente com plástico. As medidas estenderam-se de 6 horas até 112 dias. O fenômeno da retração também foi analisado com base nos resultados dos ensaios de porosimetria, calorimetria, termogravimetria e difração de raios X. Foram empregados como ativadores: silicato de sódio, cal hidratada + gipsita, cal hidratada e hidróxido de sódio. Como referência foi adotado o cimento portland da alta resistência inicial CPV-ARI. De acordo com os resultados obtidos...

Influência de aditivos redutores e compensadores de retração em argamassas e pastas com cimento de escória ativada.; Effect of shrinkage compensating and reducing admixtures in alkali activated slag mortars and pastes.

Melo Neto, Antônio Acacio de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 11/12/2007 PT
Relevância na Pesquisa
37.24%
O objetivo desta tese foi o estudo da influência do aditivo redutor de retração (SRA) e o aditivo compensador de retração (SCA) em argamassas e pastas de cimento de escória ativada com silicato de sódio. A metodologia foi centrada na análise da retração por secagem e autógena, com o estudo de outras características que influenciam no fenômeno da retração, como as propriedades mecânicas. Para o avanço no conhecimento do efeito dos aditivos no comportamento do cimento de escória, foi caracterizada a microestrutura com a determinação da análise por termogravimetria, porosimetria e difração de raios X. Neste estudo foram empregados os seguintes teores de aditivo, porcentagem relativa à massa de aglomerante: 0,5%, 1%, 1,5% e 2% do aditivo SRA e 5%, 10% e 15% do aditivo SCA. Para a análise da influência da relação a/agl foram empregadas três teores: 0,40, 0,48 e 0,56. No estudo das amostras de referência, sem a utilização de aditivo, observou-se que o aumento da relação a/agl causa o aumento da retração por secagem e da retração autógena do cimento de escória ativada. A diminuição da resistência mecânica com o aumento da relação a/agl, o que torna o esqueleto sólido mais susceptível à deformações...

Estudo da fissuração associada à retração em argamassas para reparo em estruturas de concreto.; A study on shrinkage related cracking on mortars for the repair of concrete structures.

Grullón Peña, Manuel Ramón
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 15/12/2004 PT
Relevância na Pesquisa
37.14%
A durabilidade das estruturas de concreto tem se tornado um assunto de interesse mundial nas últimas duas décadas. Os custos econômicos associados a reparos de estruturas de concreto são cada vez maiores, e cada vez mais a incidência de insucessos nessas intervenções corretivas que não resultam adequadas é reportada. No Brasil a técnica de intervenção corretiva mais utilizada é a de reparos localizados com argamassas base cimento modificadas com polímeros. Uma das patologias mais comumente apresentada quando do uso deste tipo de intervenção é a fissuração associada à retração. O presente trabalho pretende avaliar a influência das variáveis mais importantes e até de alguns parâmetros de dosagem, na fissuração devido à retração de argamassas de reparo. Para tal foi estudada uma família de argamassas com mesma consistência de traços 1:1,0, 1:1,5, 1:2,2 e 1:3,0; utilizando para estas um teor fixo de polímero e de aditivo superplastificante com relação à massa do cimento. Foram também avaliadas três argamassas de base cimento modificadas com polímeros disponíveis no país e comercializadas para o reparo de estruturas de concreto, de modo a classificar e comparar estas quanto à fissuração, em relação àquelas dosadas em laboratório. Para avaliar a tendência à fissuração das argamassas foram realizados ensaios de retração potencial livre...

Análise da deformabilidade por fluência e retração e sua utilização na monitoração de pilares de concreto.; Analysis of creep and shrinkage and its utilization in health monitoring of reinforced concrete column.

Kataoka , Luciana Tiemi
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 12/08/2010 PT
Relevância na Pesquisa
37.14%
Esta pesquisa consiste no estudo da deformabilidade de estruturas de concreto, decorrente da retração e fluência. Este estudo envolve aspectos de caracterização do concreto por meio de ensaios em laboratório de retração, de fluência e de suas propriedades mecânicas (resistência à compressão, resistência à tração por compressão diametral e módulo de elasticidade). Por meio dessa caracterização, foram obtidos parâmetros experimentais de fluência e retração baseados em traços de concreto utilizados em obras que possam ser confrontados àqueles indicados pelas normas vigentes. Além disso, nove protótipos de pilares com duas taxas de armadura foram mantidos sob carga constante em um ambiente controlado de temperatura e umidade relativa durante 91 dias. O principal objetivo deste ensaio foi o estudo da influência da taxa de armadura na redistribuição de esforços do concreto para armadura devido às propriedades de fluência e retração em protótipos de pilares. Para prever esta redistribuição de esforços, foram feitas simulações numéricas utilizando o Método dos Elementos Finitos. As simulações consideraram tanto os modelos de previsão de fluência e retração disponível no programa quanto os resultados provenientes da caracterização laboratorial. Além disso...

Mitigação da retração autógena em concretos de alta resistência contendo aditivo redutor de retração e seus efeitos na macro e microestrutura; Mitigation of autogenous shrinkage in high strength concrete using shrinkage-reducing admixture and its macro and microstructural effects

Lopes, Anne Neiry de Mendonça
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Tese de Doutorado Formato: application/pdf
POR
Relevância na Pesquisa
37.16%
O desenvolvimento do concreto de alta resistência - CAR foi um importante avanço na tecnologia de concreto, entretanto, a despeito de suas inúmeras vantagens como material estrutural, o seu emprego tem sido limitado, por ter se revelado mais susceptível à fissuração nas primeiras idades. Isto se deve à ocorrência do fenômeno da retração autógena, particularmente mais intenso nestes concretos que nos de resistência normal, uma vez que no CAR, há significativamente maior quantidade de material cimentício e menor quantidade de água, o que dá origem a uma estrutura porosa muito refinada logo nas primeiras idades, gerando altas magnitudes de tensões capilares. Além do estudo sobre o entendimento do fenômeno, as pesquisas atualmente têm buscado formas de mitigá-lo a fim de contribuir para estruturas mais duráveis. Diante do exposto, esta pesquisa investigou o comportamento do CAR, no tocante às propriedades mecânicas, elásticas e viscoelásticas e à durabilidade, quando empregado um aditivo redutor de retração - ARR que pode se configurar como estratégia mitigadora para a redução da retração autógena, bem como verificar a sua influência sobre a microestrutura e hidratação da pasta de cimento. Os resultados indicam que o ARR é eficaz na redução da retração autógena e retração por secagem...

Assessment of measures to mitigate concrete shrinkage

Nunes, Júlio; Camões, Aires
Fonte: CI-Premier Pte Ltd Publicador: CI-Premier Pte Ltd
Tipo: Conferência ou Objeto de Conferência
Publicado em //2013 ENG
Relevância na Pesquisa
37.29%
Publicado em "Proceedings of the 5th International Conference on The Concrete Future", ISBN 978-981-07-6067-0; Concrete can have high tendency to shrink over time and this can cause its cracking and thus jeopardize its durability and increase significantly maintenance, repair or rehabilitation costs. In this context, this study intends to evaluate measures to mitigate concrete shrinkage through the incorporation of different percentages of fly ash (FA), shrinkage reducing admixtures (SRA) or superabsorbent polymers (SAP). For this, one has developed an experimental campaign on mortar specimens that consisted in the manufacture and subsequent shrinkage measurement of free specimens and sealed ones made with the different selected mix-designs. Shrinkage was recorded along time up to 304 days of age and not only the total shrinkage was evaluated so as the autogeneous and drying shrinkage also. For the case of FA addition, one has studied different percentages of cement replacement by weight: 20, 40 and 60 %. The SRA type and content was selected based on previous study which permits to obtain the best shrinkage performance. As for the mortar containing SAP one has adopted a dosage currently used. As a complement to the shrinkage measurements...

Volumetric polymerization shrinkage of contemporary composite resins

Nagem Filho,Halim; Nagem,Haline Drumond; Francisconi,Paulo Afonso Silveira; Franco,Eduardo Batista; Mondelli,Rafael Francisco Lia; Coutinho,Kennedy Queiroz
Fonte: Faculdade De Odontologia De Bauru - USP Publicador: Faculdade De Odontologia De Bauru - USP
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/2007 EN
Relevância na Pesquisa
37.16%
The polymerization shrinkage of composite resins may affect negatively the clinical outcome of the restoration. Extensive research has been carried out to develop new formulations of composite resins in order to provide good handling characteristics and some dimensional stability during polymerization. The purpose of this study was to analyze, in vitro, the magnitude of the volumetric polymerization shrinkage of 7 contemporary composite resins (Definite, Suprafill, SureFil, Filtek Z250, Fill Magic, Alert, and Solitaire) to determine whether there are differences among these materials. The tests were conducted with precision of 0.1 mg. The volumetric shrinkage was measured by hydrostatic weighing before and after polymerization and calculated by known mathematical equations. One-way ANOVA (a or = 0.05) was used to determine statistically significant differences in volumetric shrinkage among the tested composite resins. Suprafill (1.87±0.01) and Definite (1.89±0.01) shrank significantly less than the other composite resins. SureFil (2.01±0.06), Filtek Z250 (1.99±0.03), and Fill Magic (2.02±0.02) presented intermediate levels of polymerization shrinkage. Alert and Solitaire presented the highest degree of polymerization shrinkage. Knowing the polymerization shrinkage rates of the commercially available composite resins...

The effect of fibers on the loss of water by evaporation and shrinkage of concrete

Pillar,N. M. P.; Repette,W. L.
Fonte: IBRACON - Instituto Brasileiro do Concreto Publicador: IBRACON - Instituto Brasileiro do Concreto
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2015 EN
Relevância na Pesquisa
37.23%
Shrinkage is one of the least desirable attributes in concrete. Large areas of exposed concrete surfaces , such as in shotcrete tunnel linings, where it is practically impossible to make a moist cure, are highly susceptible to plastic shrinkage at early ages. The autogenous and drying shrinkage can lead to states of greater than threshold strength, causing fracture, mechanical damage and lack of durability of concrete structures. The addition of fibers can greatly reduce plastic shrinkage, but has limited effect in mitigating autogenous and drying shrinkage. To evaluate the performance of polypropylene and steel fibers to understand their effect on shrinkage of concrete, a study was carried out to relate the loss of water from the paste and the shrinkage during the first 28 days of age, and compare it with a control mix without fiber. The loss of water was obtained by the weight loss of the specimens at different ages, since the only component that could contribute for the loss of weight was the water lost by the paste of the concrete. And the paste itself is the only source of shrinkage. Uniaxial compressive tests from very early ages enabled the determination of time when plastic shrinkage ended. It was observed that the control concrete mix lost three times more water and developed plastic and drying shrinkage 60 % higher than the fiber reinforced concrete mixes. It was possible to demonstrate that the reduced loss of water caused by the incorporation of fibers is related to the mitigation of plastic shrinkage. It was observed that the fibers are effective to restrain the movement of water through the cement paste in the plastic state...

Analysis of soil shrinkage data

Groenevelt, P.; Grant, C.
Fonte: Elsevier Science BV Publicador: Elsevier Science BV
Tipo: Artigo de Revista Científica
Publicado em //2004 EN
Relevância na Pesquisa
37.16%
A precise mathematical formula for, and accurate curve-fitting of, shrinkage data are prerequisites for the evaluation of an array of structural properties as functions of the water content (moisture ratio) of non-rigid (swelling) soils. Such a formula is used here, together with its first (slope) and second (curvature) derivatives. The structural property that is of particular interest in this paper is the “shrinkage limit”, which occurs at the water content where the curvature of the shrinkage line (dry side) reaches its maximum value. Using a set of experimental data, found in the literature, it is shown here, that beyond the shrinkage limit (on the dry side), a secondary shrinkage process may be initiated, leading to a second (lower) shrinkage limit that would not usually be noticed.; http://www.elsevier.com/wps/find/journaldescription.cws_home/503318/description#description; P. H. Groenevelt and C. D. Grant

Analysis of shrinkage in prestressed concrete slabs and beams

Warner, R.F.
Fonte: Engineers Australia Publicador: Engineers Australia
Tipo: Artigo de Revista Científica
Publicado em //2014 EN
Relevância na Pesquisa
37.24%
A step-by-step method of analysis is used in this paper to study the long-term effects of shrinkage in prestressed concrete members, and in particular shrinkage warping and loss of prestress. The step-by-step method is also being used in a parallel study of creep in prestressed concrete beams. A simple, closed-form equation is derived for the long-term shrinkage curvature in the cross-section of a rectangular prestressed member that contains tensile and compressive reinforcing steel. This allows the shrinkage deflection of the member to be calculated by first evaluating curvatures at key sections and then integrating. A simple, closed-form equation is also derived for the long-term loss of prestress due to shrinkage. Numerical studies show that tensile and compressive reinforcement strongly influence both the curvature and the prestress loss due to shrinkage. An assumption made in the analyses is that shrinkage occurs uniformly throughout the concrete. This is the basis of the current AS 3600 shrinkage clauses, and hence also of most current shrinkage design calculations. In reality, shrinkage in concrete members is non-uniform and non-linear. The paper concludes with a discussion of non-uniform shrinkage, and gives an outline of how the step-by-step method can be used to analyse non-uniform shrinkage.; RF Warner

Untersuchung der Ionentransportmechanismen, die für die Volumenveränderung kultivierter Parietalzellen bei Stimulation der Säuresekretion verantwortlich sind; K+ and Cl- channels mediate shrinkage during stimulation of acid secretion in cultured parietal cells

Heinzmann, Alexander Tobias
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
Relevância na Pesquisa
37.2%
Untersuchung der Ionentransportmechanismen, die für die Volumenveränderung kultivierter Parietalzellen bei Stimulation der Säuresekretion verantwortlich sind Im Rahmen des Säuresekretionsvorganges der Parietalzelle spielen außer der H+/K+-ATPase noch zahlreiche weitere Ionentransportprozesse eine bedeutende Rolle. In der vorliegenden Arbeit wurden eine Parietalzell-Primärkultur mit den Agonisten der Säuresekretion Forskolin (10-5 M) und Carbachol (10-4 M) stimuliert, um die Änderungen der Säuresekretion und die Volumenveränderungen unter Beeinflussung der verschiedenen Ionentransporter, insbesondere von K+ und Cl- Kanälen, zu beobachten. 293B (10 μM), ein Hemmstoff des KCNQ1 K+ Kanals, führte nicht zur Zellschwellung, verringerte aber die Schrumpfung durch Forskolin stärker als die durch Carbachol. 50 nM ChTX führte ebenfalls nicht zur Zellschwellung, hatte keinen Einfluss auf die Schrumpfung nach Forskolin-Stimulation und blockierte einen Großteil der Carbachol-induzierten Schrumpfung. NPPB (300 μM), ein Cl- Kanalblocker führte ebenfalls nicht zur Schwellung, verhinderte aber die stimulations-assoziierte Zellschrumpfung beider Agonisten nahezu vollständig. Die Hemmung der Säureproduktion durch 293B, ChTX und NPPB folgte dem gleichen Muster wie die Hemmung der initialen Zellschrumpfung nach Stimulation. 10 μM SCH28080...

Laboratory study of geosynthetic clay liner shrinkage when subjected to wet/dry cycles

Bostwick, LAURA
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado Formato: 9577750 bytes; application/pdf
EN; EN
Relevância na Pesquisa
37.26%
Geosynthetic Clay Liners (or GCLs) are often used in conjunction with a geomembrane for landfills and heap-leach pads, where their function is to minimize leakage that may occur through holes in the geomembrane. GCLs are installed with overlapping panels and powdered bentonite placed between the overlaps to provide a better seal. Recent field exhumations of GCLs installed beneath a geomembrane left exposed to solar radiation have shown panel shrinkage; in some cases, this shrinkage was enough to leave exposed areas unprotected by the GCL. One hypothesized cause of this shrinkage is cyclic wetting and drying of the GCL. To investigate the hypothesis that wet/dry cycles have the potential to cause irrevocable shrinkage of GCL panels, a total of 8 different products were tested under idealised conditions in the laboratory. Shrinkage was measured using both hand measurements and digital image correlation techniques. A number of variables were tested for their effects on panel shrinkage, including mass per unit area, size and aspect ratio, restraint, moisture content and wetting conditions, and GCL type. Wet/dry cycles were found to cause sufficient shrinkage to explain the shrinkage observed in all but one field case. The shrinkage of any particular product was found to be variable. In particular the shrinkage was found to be sensitive to the distribution of the mass of bentonite within a specimen with the highest shrinkage being observed when there was the greatest variability in mass distribution. It is shown that some GCL products are more prone to shrinkage than others. Consideration is also given to the potential effectiveness of heat-tacking of GCL seams to reduce panel shrinkage in the field. Specimens of GCL which had been heat-tacked in the field were tested under similar cyclic conditions as used in the abovementioned laboratory tests...

Effect of light-curing units and activation mode on polymerization shrinkage and shrinkage stress of composite resins

LOPES, Lawrence Gonzaga; FRANCO, Eduardo Batista; PEREIRA, José Carlos; MONDELLI, Rafael Francisco Lia
Fonte: Faculdade De Odontologia De Bauru - USP Publicador: Faculdade De Odontologia De Bauru - USP
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.16%
The aim of this study was to evaluate the polymerization shrinkage and shrinkage stress of composites polymerized with a LED and a quartz tungsten halogen (QTH) light sources. The LED was used in a conventional mode (CM) and the QTH was used in both conventional and pulse-delay modes (PD). The composite resins used were Z100, A110, SureFil and Bisfil 2B (chemical-cured). Composite deformation upon polymerization was measured by the strain gauge method. The shrinkage stress was measured by photoelastic analysis. The polymerization shrinkage data were analyzed statistically using two-way ANOVA and Tukey test (p<0.05), and the stress data were analyzed by one-way ANOVA and Tukey's test (p<0.05). Shrinkage and stress means of Bisfil 2B were statistically significant lower than those of Z100, A110 and SureFil. In general, the PD mode reduced the contraction and the stress values when compared to CM. LED generated the same stress as QTH in conventional mode. Regardless of the activation mode, SureFil produced lower contraction and stress values than the other light-cured resins. Conversely, Z100 and A110 produced the greatest contraction and stress values. As expected, the chemically cured resin generated lower shrinkage and stress than the light-cured resins. In conclusion...

Effect of light-curing units and activation mode on polymerization shrinkage and shrinkage stress of composite resins

Lopes,Lawrence Gonzaga; Franco,Eduardo Batista; Pereira,José Carlos; Mondelli,Rafael Francisco Lia
Fonte: Faculdade De Odontologia De Bauru - USP Publicador: Faculdade De Odontologia De Bauru - USP
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2008 EN
Relevância na Pesquisa
37.16%
The aim of this study was to evaluate the polymerization shrinkage and shrinkage stress of composites polymerized with a LED and a quartz tungsten halogen (QTH) light sources. The LED was used in a conventional mode (CM) and the QTH was used in both conventional and pulse-delay modes (PD). The composite resins used were Z100, A110, SureFil and Bisfil 2B (chemical-cured). Composite deformation upon polymerization was measured by the strain gauge method. The shrinkage stress was measured by photoelastic analysis. The polymerization shrinkage data were analyzed statistically using two-way ANOVA and Tukey test (p<0.05), and the stress data were analyzed by one-way ANOVA and Tukey's test (p<0.05). Shrinkage and stress means of Bisfil 2B were statistically significant lower than those of Z100, A110 and SureFil. In general, the PD mode reduced the contraction and the stress values when compared to CM. LED generated the same stress as QTH in conventional mode. Regardless of the activation mode, SureFil produced lower contraction and stress values than the other light-cured resins. Conversely, Z100 and A110 produced the greatest contraction and stress values. As expected, the chemically cured resin generated lower shrinkage and stress than the light-cured resins. In conclusion...

Volumetric polymerization shrinkage of contemporary composite resins

Nagem Filho, Halim; Nagem, Haline Drumond; Francisconi, Paulo Afonso Silveira; Franco, Eduardo Batista; Mondelli, Rafael Francisco Lia; Coutinho, Kennedy Queiroz
Fonte: Universidade de São Paulo. Faculdade de Odontologia de Bauru Publicador: Universidade de São Paulo. Faculdade de Odontologia de Bauru
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; ; Formato: application/pdf
Publicado em 01/10/2007 ENG
Relevância na Pesquisa
37.16%
The polymerization shrinkage of composite resins may affect negatively the clinical outcome of the restoration. Extensive research has been carried out to develop new formulations of composite resins in order to provide good handling characteristics and some dimensional stability during polymerization. The purpose of this study was to analyze, in vitro, the magnitude of the volumetric polymerization shrinkage of 7 contemporary composite resins (Definite, Suprafill, SureFil, Filtek Z250, Fill Magic, Alert, and Solitaire) to determine whether there are differences among these materials. The tests were conducted with precision of 0.1 mg. The volumetric shrinkage was measured by hydrostatic weighing before and after polymerization and calculated by known mathematical equations. One-way ANOVA (;a; or = 0.05) was used to determine statistically significant differences in volumetric shrinkage among the tested composite resins. Suprafill (1.87±0.01) and Definite (1.89±0.01) shrank significantly less than the other composite resins. SureFil (2.01±0.06), Filtek Z250 (1.99±0.03), and Fill Magic (2.02±0.02) presented intermediate levels of polymerization shrinkage. Alert and Solitaire presented the highest degree of polymerization shrinkage. Knowing the polymerization shrinkage rates of the commercially available composite resins...

Specific gravity and shrinkage coefficients of wood of six species of eucalypts cultivated on the coast of Santa Catarina.; MASSA ESPECÍFICA E RETRATIBILIDADE DA MADEIRA DE SEIS ESPÉCIES DE EUCALIPTO CULTIVADAS NO LITORAL DE SANTA CATARINA

Eleotério, Jackson Roberto; Universidade Regional de Blumenau; Reichert, Douglas; Hornburg, Kerling Fabiane; Meneguelli, Isalena
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 29/09/2014 POR
Relevância na Pesquisa
37.3%
This work aims at determining and comparing the basic and 12% moisture content specific gravity and radial, tangential and volumetric shrinkage coefficients of five species and a hybrid of eucalypts. The samples of Corymbia torelliana, Eucalyptus cloeziana, Eucalyptus pilularis, Eucalyptus resinifera were extracted from 17 years old trees; ones of Eucalyptus grandis from 14 years old trees and the ones of Eucalyptus grandis x Eucalyptus urophylla from eight years old trees, all of them planted on the North Coast of Santa Catarina State. The wood of the hybrid Eucalyptus grandis x Eucalyptus urophylla, of the Eucalyptus grandis and of the Eucalyptus pilularis can be classified as light, the others can be classified as moderately heavy. Independently on the shrinkage analyzed, the groups formed during the multiple mean comparing are the same. The radial shrinkage coefficient of Eucalyptus cloeziana and that of Eucalyptus resinifera are high. However, the tangential and volumetric shrinkage coefficients of Eucalyptus grandis and the volumetric shrinkage coefficient of Eucalyptus pilularis are low; the others can be classified as medium. The variation on specific gravity is not followed by proportional variation on the shrinkage coefficients...