Ce travail de recherche est axé sur la compréhension du comportement en flexion, statique et instantané, des structures multimatériaux acier-béton collées du génie civil. La première étape consiste à mener une analyse expérimentale et numérique par éléments finis non linéaire sur la caractérisation de la connexion. L’essai Push-Out a été retenu : deux dallettes de béton C25/30 sont connectées à un profilé métallique. Nous faisons varier la géométrie des dallettes et du joint de colle. La ruine est cohésive dans le béton proche de l’interface par cisaillement. Un effet favorable du frottement entre dallette et presse peut se développer et induire le développement de contraintes de compression et augmenter la contrainte de cisaillement moyenne à l’interface. Les dimensions des éprouvettes et du joint de colle influent sur la charge de ruine. Ainsi, l’essai Push-Out est, dans l’état actuel de connaissances, difficile à utiliser pour la caractérisation de la connexion collée acier-béton en vue du dimensionnement de structures. La seconde partie est consacrée à l’analyse du comportement de poutres mixtes acier béton collées. Un essai sur poutre constituée de prédalles et d’une dalle de compression confirme que le collage est une alternative aux connexions traditionnelles. Nous développons aussi un modèle de calcul en variables généralisées et en variables locales en 3D non linéaire. La modélisation par éléments finis apporte plus de précisions, notamment sur l’état de contraintes à proximité de l’interface et à l’approche de la ruine. Les dimensions du joint de colle et la plastification du profilé influent sur la zone de rupture dans le béton. / This PhD thesis investigates the connection of steel-flexural members by bonding and focuseson static and instantaneous behavior. First, experimental and numerical analyses are performed. A push out test is used : two concrete blocks are connected to steel members. The influence of the concrete blocks and bonding joint geometry is examined. Cohesive shear failure appears in concrete near the interface. Failure can occur when the average shear strain is twice the tension limit of concrete, which can be explained by favorable slipping between the concrete block and the support. In this case, the bonding joint is not only solicited in shear but also in compression. Results depend on the length of bonding joint and concrete blocks geometry. So, push out test cannot be now used to characterize the bonding connection between steel and concrete in order to design structures. The second is about the analysis of the behavior of steel concrete composite beams. A precast beam with compressive concrete was tested. Results show that a bonding connection can be an alternativesolution regardless of the slab manufacturing. We develop two numerical models. The first one is based on multi-layer beam modeling and the second one is a nonlinear 3D finite element model. The stress distribution close to the interface and near failure is more accurate with the finite element model than with the generalized model. Bonding joint geometry and plastification of steel girder have an influence on the failure region in the concrete.

Ce travail porte sur la compréhension du comportement en flexion, statique instantané, en fatigue et en fluage des structures multi matériaux du génie civil, constituées d'acier et de béton et assemblées par un adhésif de type époxy. L'analyse et la résolution du problème posé se feront à deux échelles : au niveau de l'interface et à l'échelle d'un élément de structure. De plus, l'attention sera tout particulièrement portée sur le comportement au cours du temps (fluage, relaxation, retrait…), la fatigue et la durabilité sous différents environnements. La première étape consiste à mener une analyse expérimentale sur la caractérisation de la connexion acier-béton, à l'échelle de l'interface, en vue de repérer les principaux facteurs influençant leur comportement mécanique. Pour cela, L'essai push out, analogue à celui utilisé pour caractériser les connecteurs des ponts mixtes, a été plus particulièrement utilisé. Des essais de vieillissement accéléré par immersion dans un bain d'eau chaude ont été réalisés. Ils n'ont pas diminué la contrainte de cisaillement moyenne à rupture de façon significative mais ont en revanche modifié le mode de ruine qui devient mixte (adhésif et cohésif dans la colle). Cette modification est à la fois due au primaire et à l'adhésif lui-même dont les performances intrinsèques diminuent avec le vieillissement. A l'échelle d'un élément de structure, nous avons enrichi les données expérimentales existantes sur le comportement instantané des poutres mixtes acier-béton collées avec la réalisation de 7 essais de flexion avec deux modes de sollicitation (flexion 3 et 4 points). Ces essais nous donnent une base solide pour nos essais en fatigue et sous fluage. On constate que le mode de ruine est mieux prédit en se basant sur une comparaison entre la contrainte de cisaillement dans les poutres avec les contraintes de cisaillement limite déduites des essais push-out. Cette conclusion montre la pertinence des essais push-out dans l'objectif de les prendre comme critère de dimensionnement. Aussi, et contrairement aux travaux antérieurs, nous pouvons conclure que la contrainte moyenne de cisaillement à l'interface entre le béton et l'acier est supérieure à la résistance en traction du béton utilisé. Pour le comportement à long terme, trois poutres ont été testées sous charge cyclique pour plus de 2 million de cycles et à plusieurs niveaux de charge. Une autre poutre a subi une charge constante pendant 7 mois pour étudier l'influence de fluage sur ce type de structure. Après les essais de fatigue et fluage, le comportement des poutres est analogue à celui des poutres de référence. Nous avons toujours une ruine par rotule plastique et non par cisaillement du joint de colle ce qui confirme sa bonne résistance vis-à-vis ces deux phénomènes / This PhD thesis focuses on understanding the static, fatigue and creep behavior of composite-flexural members made of steel and concrete and assembled by adhesive epoxy. The analysis and resolution of the problem will be carried out at two levels: the interface and the structural element. In addition, attention will be particularly focused on the time-dependent behavior (creep, relaxation, shrinkage ...), fatigue and durability in various environments. The first step is to conduct an experimental analysis on the characterization of the steel-concrete connection in order to identify the main factors influencing their mechanical behavior. To do this, a Push-out test, similar to that used to characterize a steel-concrete element with studs, was especially used. An accelerated aging test, by immersion in a hot water bath, has been made. They have not decreased significantly τu but changed the failure mode which becomes mixed (adhesive and cohesive in the adhesive). This change is due to a decrease of the intrinsic performance of the primary and the adhesive with aging. From a structural point of view, we have improved the existing experimental data on the instantaneous behavior of steel-concrete bonded beams by performing seven beam tests with two modes of loading (3 and 4 point bending test). These tests give us a solid foundation for our fatigue and creep tests. It is found that the failure mode is better predicted based on a comparison between the shear stress in beams with shear limit provided by push-out tests. This finding indicates the relevance of the push-out tests as a design criterion. Also, unlike previous work, we can conclude that the average shear stress at the interface between the concrete and steel is greater than the tensile strength of the concrete used.For the long-term behavior, three beams were tested under cyclic loading for over 2 million cycles with several load levels. Another beam has been test with a constant load for 7 months to investigate the influence of creep on this type of structure. After fatigue and creep tests, the behavior of the beam is similar to that of reference beams. We have always a failure with plastic hinge and not a shear failure which confirms the good resistance of the adhesive joint in case of creep or fatigue

Atualmente, a alvenaria estrutural é utilizada em empreendimentos habitacionais de larga escala, nos quais as exigências de racionalização, controle, rapidez e custo são mais bem contemplados pelo sistema. No Brasil, existem empreendimentos de até 16 pavimentos construídos com blocos de alta resistência e alto controle tecnológico. A construção de edificações com maiores alturas exige o aumento da capacidade de absorção de esforços de compressão e tração. Para isso, são inseridas barras de aço nos vazados dos blocos e consolidadas com graute, a fim de aumentar a capacidade portante do conjunto. Entretanto, a influência da aderência graute/ bloco cerâmico no comportamento mecânico da alvenaria estrutural ainda é uma dúvida, visto que a NBR 15812 - 1 (ABNT, 2010) não especifica um valor de resistência para aderência graute/ bloco cerâmico, somente para graute/ aço. Frente a essa constatação, a presente pesquisa tem o objetivo de avaliar a influência da aderência graute/ bloco cerâmico estrutural no comportamento mecânico do conjunto, para determinar um valor de tensão de aderência que possa contribuir com a NBR 15812-1 (ABNT, 2010) Para isso, foram utilizados quatro tipos de blocos cerâmicos, com variação da geometria interna dos vazados e resistência mecânica à compressão. O graute foi padronizado em somente uma resistência, sendo essa de 30 MPa. Para desenvolvimento da pesquisa, inicialmente foi realizada a caracterização dos materiais e, posteriormente, realizados ensaios de push-out, resistência à compressão de blocos preenchidos com graute e microscopia óptica. Os resultados revelaram que a aderência graute/ bloco cerâmico estrutural é superior à resistência mecânica à tração do bloco cerâmico, e que a ruptura do conjunto ocorre primeiramente no bloco. Os resultados também constataram aumento da resistência mecânica à compressão axial nos blocos preenchidos com graute. / Currently, structural masonry is used in large-scale housing projects, in which the requirements of rationalization, control, speed and cost are better covered by the system. In Brazil there are projects of up to 16 floors built with high resistance and high technological control blocks. The construction of buildings with higher heights requires the increase of the capacity of absorption of compression and traction forces. For this, steel bars are inserted into hollow blocks which are then consolidated with grout in order to increase the load-bearing capacity of the assembly. However, the influence of ceramic block/grout adhesion in the mechanical behavior of structural masonry is still unknown since the NBR 15812-1 (ABNT, 2010) standard does not specify a resistance value for grout/ceramic block adhesion, only for grout/steel adhesion. In view of this finding, the present research has the objective of evaluating the influence of the structural ceramic block/grout adhesion on the mechanical behavior of the assembly in order to determine a value of adhesion tension that can contribute to the NBR 15812-1 (ABNT, 2010) standard For this purpose four types of ceramic blocks with a variation in the internal geometry of the hollow spaces and mechanical strength to compression were used. Grout was standardized in only one strength of 30 MPa. For development of the research, initially the characterization of the materials was performed and, subsequently, the tests of push-out and compressive strength of grout-filled blocks and light microscopy. The results showed that the grout/ceramic block adhesion is superior to the mechanical tensile strength of the ceramic block and, therefore, the rupture of the assembly will occur first in the block. The results also showed a significant increase of the mechanical resistance to axial compression in blocks filled with grout.

Cast-in-place concrete in composite with steel sections is commonly used in bridge deck constructions. The shear transfer between the concrete and steel section is achieved by shear connectors and the strength calculation of conventional shear connectors, i.e. shear studs, is provided in various design codes in North America. Due to the fact that the strength equation is largely based on experimental results, the applicability of the equation is only warranted where the design matches the experimental configuration of the test specimens. Thus, the codes specify detailing requirement for the stud height and the elevation of the reinforcement mesh in relation to the stud height. However, these requirements, in particular, the elevation of the reinforcement mesh, may be difficult to meet accurately in construction practice. The implications of not meeting the mesh requirement to the strength of the shear stud and the remedy solutions are examined in this study. An experimental program involving the test of thirty-three push-out specimens was designed and conducted with a focus on the shear studs' performance. Testing parameters included reinforcement mesh position, shear stud height, presence of stud head, shear stud spacing, and steel flange surface treatment. In addition, the performance of a new type of shear studs, referred to as adjustable studs, was also studied experimentally. The ultimate load and load vs. slip curves were presented and discussed in the forms of tables and graphs. The failure modes were noted and the relationship between the failure modes and the ultimate capacity was discussed. Ultimate loads obtained from specimens were then used to assess the efficacy of code suggested values. Results showed that depending on the elevation of reinforcement mesh, three failure modes were observed including concrete related failure, combined concrete failure and bent studs and stud shear-off from the steel flange. The elevation of the reinforcement mesh had a significant effect on the ultimate load of the specimen. As the mesh elevation increased from intercepting the stud to being in flush with the top of the stud to above the stud, the ultimate load decreased. Specimens with unheaded shear studs had lower ultimate load than specimens with headed shear studs. Flange treatment had an impact on the ultimate load, where the coating on flanges resulted in a decrease in the ultimate load. Test results also showed that the close placement of the shear studs result in a reduction on the ultimate load when the other parameters were kept the same. In the comparison between conventional and adjustable shear studs, specimens with adjustable studs shared similar failure mode to those with conventional studs, but attained on average lower load capacity. The comparison with the code suggested values showed that the code suggested value is only ensured when double-layer reinforcement mesh is used and placed at code specified elevation. A single layer mesh intercepting the studs resulted in the ultimate load slightly lower than the code value. The code values for adjustable studs are markedly higher than the experimental value, which raises the question whether the code equation for conventional studs is directly transferrable to adjustable studs.

Orientador: Milton Carlos kuga / Resumo: O objetivo do presente estudo foi avaliar os efeitos do álcool isopropílico, soro fisiológico, ácido citríco 10% e ácido peracético 1% como soluções de irrigação intermediária entre o hipoclorito de sódio 2,5% (NaOCl) e o digluconato de clorexidina 2% (CHX) sobre a dentina de canais radiculares. Inicialmente cento e vinte caninos humanos extraídos foram preparados até o instrumento F5 e irrigados com NaOCl a 2,5% e EDTA 17%. Sessenta dentes foram divididos em 6 grupos (n = 10), de acordo com o protocolo de irrigação intermediária: G1 (controle negativo, EDTA 17% e NaOCl 2,5%); G2 (controle positivo, CHX); G3 (soro fisiológico); G4 (álcool isopropílico); G5 (ácido cítrico); G6 (ácido peracético) . Em seguida, os espécimes foram clivados e a dentina do canal radicular analisada através de microscopia eletrônica de varredura (MEV), nos segmentos cervical-médio e médio-apical, a fim de detectar a presença de debris e smear layer. Em seguida foi realizada análise de EDS para detectar a quantidade de Cl, Ca, P e O. Outros 60 dentes foram tratados igualmente ao estudo anterior, obturados adicionando rodamina ao cimento obturador para posterior análise de confocal, a fim de analisar a penetrabilidade do cimento endodôntico na dentina radicular, e então submetidos ao teste de push out, nos terços cervical, médio e apical radicular. Os espécimes foram avaliados utilizando uma máquina universal de ensaios mecânicos. Análises estatística foram submetidas aos testes de Kruskal –Wallis, Du... (Resumo completo, clicar acesso eletrônico abaixo) / Doutor

O objetivo do presente estudo foi avaliar o efeito da aplicação de clorexidina após o condicionamento ácido na preservação da camada híbrida, avaliando a resistência de união imediata e a longo prazo de pinos de fibra de vidro cimentados à dentina radicular. Setenta e dois dentes unirradiculares superiores humanos foram selecionados. Os canais radiculares foram alargados para receberem os pinos de fibra de vidro e aleatoriamente divididos em três grupos (n=24). No Grupo Controle (Gcontrol), o pino de fibra de vidro foi cimentado de acordo com as instruções do fabricante, utilizando um sistema adesivo convencional de três passos e um cimento resinoso dual. Os grupos tratados com digluconato clorexidina GCHX0.2 e GCHX2 receberam a aplicação de solução de clorexidina 0,2% e 2%, respectivamente, após o condicionamento com ácido fosfórico e os pinos foram cimentados utilizando o mesmo sistema adesivo e cimento utilizados no Gcontrol. As raízes foram seccionadas transversalmente ao longo eixo do dente, em fatias de 0,68 (± 0,09) mm. Metade dos dentes foi submetida ao ensaio de push-out após 24 horas e a outra metade, após seis meses de armazenamento em água destilada, a 37°C. Os valores foram analisados com ANOVA de duas vias e teste de comparações múltiplas de Tukey, com nível de significância de 5%. A aplicação de clorexidina não influenciou a resistência de união quando os dentes foram avaliados no mesmo período de armazenagem (p>0,05). O tempo de armazenamento diminuiu significativamente a resistência de união de 24 horas para 6 meses, em todos os grupos (p<0,05). A aplicação de clorexidina não preveniu significativamente a degradação da resistência de união de pinos de fibra cimentados em raízes de dentes humanos, após seis meses de armazenamento. / Introduction: This study evaluated the effect of chlorhexidine applied after dentin phosphoric acid etching on hybrid layer preservation, analyzing the immediate and long-term bond strength of a fiber post cemented to root dentin. Methods: Seventy-two single-rooted, human upper teeth were selected for analysis. Root canals were enlarged for fiber post cementation and were randomly divided into three groups (n= 24). After phosphoric acid etching, each group received a different dentin treatment. In the Control Group (Gcontrol), the fiber post was cemented according to the manufacture’s instruction, using a three-step etch-and-rinse adhesive and a dual-cured resin cement. The Chlorhexidine 0.2% Group (GCHX 0.2) and the Chlorhexidine 2% Group (GCHX 2) received an application of a chlorexidine digluconate solution of 0.2% and 2%, respectively, after phosphoric acid etching, and the post was cemented using the same adhesive and cement that was used in the Gcontrol. Teeth were sectioned transversally in slices of 0.68 (± 0.09) mm. Half of the teeth were submitted to push-out bond strength after 24 hours and the other half were submitted after six months of distilled water storage at 37°C. Data were analyzed by using the two-way analysis of variance (ANOVA) and a post hoc tests using the Tukey multiple comparison test at α = 0.05. Results: Chlorhexidine application had no influence on bond strength when teeth were stored for the same period of time (p>0.05). The storage time significantly decreased the bond strength values of 24 hours to six months, in all groups (p<0.05). Conclusion: After six months, chlorhexidine application did not effectively arrest bond strength degradation of fiber post cemented in human roots.

Atualmente, a alvenaria estrutural é utilizada em empreendimentos habitacionais de larga escala, nos quais as exigências de racionalização, controle, rapidez e custo são mais bem contemplados pelo sistema. No Brasil, existem empreendimentos de até 16 pavimentos construídos com blocos de alta resistência e alto controle tecnológico. A construção de edificações com maiores alturas exige o aumento da capacidade de absorção de esforços de compressão e tração. Para isso, são inseridas barras de aço nos vazados dos blocos e consolidadas com graute, a fim de aumentar a capacidade portante do conjunto. Entretanto, a influência da aderência graute/ bloco cerâmico no comportamento mecânico da alvenaria estrutural ainda é uma dúvida, visto que a NBR 15812 - 1 (ABNT, 2010) não especifica um valor de resistência para aderência graute/ bloco cerâmico, somente para graute/ aço. Frente a essa constatação, a presente pesquisa tem o objetivo de avaliar a influência da aderência graute/ bloco cerâmico estrutural no comportamento mecânico do conjunto, para determinar um valor de tensão de aderência que possa contribuir com a NBR 15812-1 (ABNT, 2010) Para isso, foram utilizados quatro tipos de blocos cerâmicos, com variação da geometria interna dos vazados e resistência mecânica à compressão. O graute foi padronizado em somente uma resistência, sendo essa de 30 MPa. Para desenvolvimento da pesquisa, inicialmente foi realizada a caracterização dos materiais e, posteriormente, realizados ensaios de push-out, resistência à compressão de blocos preenchidos com graute e microscopia óptica. Os resultados revelaram que a aderência graute/ bloco cerâmico estrutural é superior à resistência mecânica à tração do bloco cerâmico, e que a ruptura do conjunto ocorre primeiramente no bloco. Os resultados também constataram aumento da resistência mecânica à compressão axial nos blocos preenchidos com graute. / Currently, structural masonry is used in large-scale housing projects, in which the requirements of rationalization, control, speed and cost are better covered by the system. In Brazil there are projects of up to 16 floors built with high resistance and high technological control blocks. The construction of buildings with higher heights requires the increase of the capacity of absorption of compression and traction forces. For this, steel bars are inserted into hollow blocks which are then consolidated with grout in order to increase the load-bearing capacity of the assembly. However, the influence of ceramic block/grout adhesion in the mechanical behavior of structural masonry is still unknown since the NBR 15812-1 (ABNT, 2010) standard does not specify a resistance value for grout/ceramic block adhesion, only for grout/steel adhesion. In view of this finding, the present research has the objective of evaluating the influence of the structural ceramic block/grout adhesion on the mechanical behavior of the assembly in order to determine a value of adhesion tension that can contribute to the NBR 15812-1 (ABNT, 2010) standard For this purpose four types of ceramic blocks with a variation in the internal geometry of the hollow spaces and mechanical strength to compression were used. Grout was standardized in only one strength of 30 MPa. For development of the research, initially the characterization of the materials was performed and, subsequently, the tests of push-out and compressive strength of grout-filled blocks and light microscopy. The results showed that the grout/ceramic block adhesion is superior to the mechanical tensile strength of the ceramic block and, therefore, the rupture of the assembly will occur first in the block. The results also showed a significant increase of the mechanical resistance to axial compression in blocks filled with grout.

Made available in DSpace on 2015-05-08T14:59:42Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 4158784 bytes, checksum: 614ac248aca292bc7e1a840fb03f4a7f (MD5) Previous issue date: 2012-08-13 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Oil has become one of the greater sources of energy in the contemporary world and ensures that its extraction is done without loss of production wells and structurally reliable is essential. Cementitious coatings of oil wells are used in order to ensure structural support of the wells and corrosion protection. In these structures, the adhesion between steel and cementitious material is responsible for ensuring the mechanical and the thermodynamical efficiencies, protecting them against corrosion, preventing the escape of fluids inside and isolating the hydraulic structure against infiltrations. The push-out test is used to measure the adherence between steel and cement. In this work, the numerical simulation of steel-cement interface was carried. For reproducing the mechanical behavior of this interface, a cohesive-zone model, formulated from the perspective of Damage Mechanics, combined with Coulomb's law for friction were used. The proposed model was implemented in CAST3M software. The numerical results obtained with the proposed model were compared with experimental results of push-out tests made with three different interface conditions. The comparison between the force versus displacement curves obtained experimentally and numerically validated the proposed model. / O petróleo tornou-se uma das principais fontes de energia do mundo contemporâneo e garantir que sua extração seja feita sem que haja perdas de produção e com poços estruturalmente confiáveis é fundamental. Os revestimentos cimentícios dos poços de petróleo são utilizados no intuito de garantir suporte estrutural aos poços e proteção contra corrosão. Nessas estruturas, a adesão entre o aço e o material cimentício é responsável por garantir a eficiência tanto do ponto de vista mecânico, garantindo suporte estrutural, quanto da estabilidade termodinâmica dos aços, protegendo-os contra a corrosão, impedindo a fuga de fluidos de seu interior e isolando hidraulicamente a estrutura contra infiltrações. O ensaio de arrancamento, também conhecido como push-out test, é utilizado no intuito de mensurar o nível de aderência entre o aço e o cimento. Neste trabalho, a simulação numérica da interface aço-cimento foi realizada. Para a reprodução do comportamento mecânico desta interface, utilizou-se um modelo de zona coesiva formulado sob a ótica da Mecânica do Dano combinado com a lei de Coulomb para o atrito. O modelo proposto foi implementado no software CAST3M. Os resultados numéricos obtidos com o modelo proposto foram comparados com resultados experimentais de ensaios de arrancamento feitos com três diferentes condições de interface: Tubo de aço limpo e seco (LS), tubo de aço borrifado com solução de NaCl em água (NaCl) e tubo de aço revestido por um cimento geopolimérico (GEO). A comparação entre as curvas força versus deslocamento, obtidas experimentalmente e numericamente, validaram o modelo proposto.

O objetivo do presente estudo foi avaliar o efeito da aplicação de clorexidina após o condicionamento ácido na preservação da camada híbrida, avaliando a resistência de união imediata e a longo prazo de pinos de fibra de vidro cimentados à dentina radicular. Setenta e dois dentes unirradiculares superiores humanos foram selecionados. Os canais radiculares foram alargados para receberem os pinos de fibra de vidro e aleatoriamente divididos em três grupos (n=24). No Grupo Controle (Gcontrol), o pino de fibra de vidro foi cimentado de acordo com as instruções do fabricante, utilizando um sistema adesivo convencional de três passos e um cimento resinoso dual. Os grupos tratados com digluconato clorexidina GCHX0.2 e GCHX2 receberam a aplicação de solução de clorexidina 0,2% e 2%, respectivamente, após o condicionamento com ácido fosfórico e os pinos foram cimentados utilizando o mesmo sistema adesivo e cimento utilizados no Gcontrol. As raízes foram seccionadas transversalmente ao longo eixo do dente, em fatias de 0,68 (± 0,09) mm. Metade dos dentes foi submetida ao ensaio de push-out após 24 horas e a outra metade, após seis meses de armazenamento em água destilada, a 37°C. Os valores foram analisados com ANOVA de duas vias e teste de comparações múltiplas de Tukey, com nível de significância de 5%. A aplicação de clorexidina não influenciou a resistência de união quando os dentes foram avaliados no mesmo período de armazenagem (p>0,05). O tempo de armazenamento diminuiu significativamente a resistência de união de 24 horas para 6 meses, em todos os grupos (p<0,05). A aplicação de clorexidina não preveniu significativamente a degradação da resistência de união de pinos de fibra cimentados em raízes de dentes humanos, após seis meses de armazenamento. / Introduction: This study evaluated the effect of chlorhexidine applied after dentin phosphoric acid etching on hybrid layer preservation, analyzing the immediate and long-term bond strength of a fiber post cemented to root dentin. Methods: Seventy-two single-rooted, human upper teeth were selected for analysis. Root canals were enlarged for fiber post cementation and were randomly divided into three groups (n= 24). After phosphoric acid etching, each group received a different dentin treatment. In the Control Group (Gcontrol), the fiber post was cemented according to the manufacture’s instruction, using a three-step etch-and-rinse adhesive and a dual-cured resin cement. The Chlorhexidine 0.2% Group (GCHX 0.2) and the Chlorhexidine 2% Group (GCHX 2) received an application of a chlorexidine digluconate solution of 0.2% and 2%, respectively, after phosphoric acid etching, and the post was cemented using the same adhesive and cement that was used in the Gcontrol. Teeth were sectioned transversally in slices of 0.68 (± 0.09) mm. Half of the teeth were submitted to push-out bond strength after 24 hours and the other half were submitted after six months of distilled water storage at 37°C. Data were analyzed by using the two-way analysis of variance (ANOVA) and a post hoc tests using the Tukey multiple comparison test at α = 0.05. Results: Chlorhexidine application had no influence on bond strength when teeth were stored for the same period of time (p>0.05). The storage time significantly decreased the bond strength values of 24 hours to six months, in all groups (p<0.05). Conclusion: After six months, chlorhexidine application did not effectively arrest bond strength degradation of fiber post cemented in human roots.

Atualmente, a alvenaria estrutural é utilizada em empreendimentos habitacionais de larga escala, nos quais as exigências de racionalização, controle, rapidez e custo são mais bem contemplados pelo sistema. No Brasil, existem empreendimentos de até 16 pavimentos construídos com blocos de alta resistência e alto controle tecnológico. A construção de edificações com maiores alturas exige o aumento da capacidade de absorção de esforços de compressão e tração. Para isso, são inseridas barras de aço nos vazados dos blocos e consolidadas com graute, a fim de aumentar a capacidade portante do conjunto. Entretanto, a influência da aderência graute/ bloco cerâmico no comportamento mecânico da alvenaria estrutural ainda é uma dúvida, visto que a NBR 15812 - 1 (ABNT, 2010) não especifica um valor de resistência para aderência graute/ bloco cerâmico, somente para graute/ aço. Frente a essa constatação, a presente pesquisa tem o objetivo de avaliar a influência da aderência graute/ bloco cerâmico estrutural no comportamento mecânico do conjunto, para determinar um valor de tensão de aderência que possa contribuir com a NBR 15812-1 (ABNT, 2010) Para isso, foram utilizados quatro tipos de blocos cerâmicos, com variação da geometria interna dos vazados e resistência mecânica à compressão. O graute foi padronizado em somente uma resistência, sendo essa de 30 MPa. Para desenvolvimento da pesquisa, inicialmente foi realizada a caracterização dos materiais e, posteriormente, realizados ensaios de push-out, resistência à compressão de blocos preenchidos com graute e microscopia óptica. Os resultados revelaram que a aderência graute/ bloco cerâmico estrutural é superior à resistência mecânica à tração do bloco cerâmico, e que a ruptura do conjunto ocorre primeiramente no bloco. Os resultados também constataram aumento da resistência mecânica à compressão axial nos blocos preenchidos com graute. / Currently, structural masonry is used in large-scale housing projects, in which the requirements of rationalization, control, speed and cost are better covered by the system. In Brazil there are projects of up to 16 floors built with high resistance and high technological control blocks. The construction of buildings with higher heights requires the increase of the capacity of absorption of compression and traction forces. For this, steel bars are inserted into hollow blocks which are then consolidated with grout in order to increase the load-bearing capacity of the assembly. However, the influence of ceramic block/grout adhesion in the mechanical behavior of structural masonry is still unknown since the NBR 15812-1 (ABNT, 2010) standard does not specify a resistance value for grout/ceramic block adhesion, only for grout/steel adhesion. In view of this finding, the present research has the objective of evaluating the influence of the structural ceramic block/grout adhesion on the mechanical behavior of the assembly in order to determine a value of adhesion tension that can contribute to the NBR 15812-1 (ABNT, 2010) standard For this purpose four types of ceramic blocks with a variation in the internal geometry of the hollow spaces and mechanical strength to compression were used. Grout was standardized in only one strength of 30 MPa. For development of the research, initially the characterization of the materials was performed and, subsequently, the tests of push-out and compressive strength of grout-filled blocks and light microscopy. The results showed that the grout/ceramic block adhesion is superior to the mechanical tensile strength of the ceramic block and, therefore, the rupture of the assembly will occur first in the block. The results also showed a significant increase of the mechanical resistance to axial compression in blocks filled with grout.