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Behaviour of continuous concrete beams reinforced with FRP barsEl-Mogy, Mostafa 09 December 2011 (has links)
The non-corrodible nature of FRP bars along with their high strength, light weight and ease of installation made it attractive as reinforcement especially for structures exposed to aggressive environment. In addition, the transparency of FRP bars to magnetic and electrical fields makes them an ideal alternative to traditional steel reinforcement in applications sensitive to electromagnetic fields such as magnetic resonance imaging (MRI) units.
Continuous concrete beams are commonly-used elements in structures such as parking garages and overpasses, which might be exposed to extreme weather conditions and the application of de-icing salts. In such structures, using the non-corrodible FRP bars is a viable alternative to avoid steel-corrosion problems. However, the linear-elastic behaviour of FRP materials makes the ability of continuous beams to redistribute loads and moments questionable. The objective of this research project is to investigate the flexural behaviour of continuous concrete beams reinforced with FRP and their capability of moment redistribution. An experimental program was conducted at the University of Manitoba to realize the research objectives. Ten full-scale continuous concrete beams were constructed and tested to failure in the laboratory. The specimens had a rectangular cross-section of 200×300 mm and continuous over two spans of 2,800 mm each. The main investigated parameters were the amount and material of longitudinal reinforcement, the amount and material of transverse reinforcement and the spacing of used stirrups. The experimental results showed that moment redistribution in FRP-reinforced continuous concrete beams is possible if the reinforcement configuration is chosen properly, and is improved by increasing the amount of transverse reinforcement.
A finite element investigation was conducted using ANSYS-software. A 3-D model was created to simulate the behaviour of continuous beams reinforced with FRP. The model was verified against the experimental results obtained from the present study. This verified model was used to investigate the effect of the concrete compressive strength, longitudinal reinforcement ratio, midspan-to-middle support reinforcement ratio and the amount of transverse reinforcement on the behaviour of FRP-reinforced beams. The analytical results of this parametric investigation along with the experimental results were used to propose an allowable limit for moment redistribution in FRP-reinforced continuous concrete beams.
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Influence of steel fibres on response of beamsBelghiti, Moulay El Mehdi. January 2007 (has links)
The following thesis presents the results of six full scale beams tests as part of a research program conducted at McGill University on the effect of steel fibres on the shear capacity of a beam with an aid ratio greater than 2.5. The test specimens had the following dimensions: 4400 mm long, 300 mm wide and 500 mm long. The beams had 4-25M bottom reinforcing bars and 2-20M top reinforcing bars. Two series were designed with different reinforcing details: the "BA" series contained transverse reinforcement spaced at 275 mm center to center while the "BB" series had no transverse reinforcement. The specimens were cast in three batches of two specimens from each series, with each batch containing concrete with respectively 0%, 0.5% and 1% fibres content by volume. The beams were simply supported and were tested with two equal point loads located at 500 mm from the centre of the beam. / This research project demonstrated a clear improvement of the shear capacity resulting from the use of steel fibres for the beams without transverse reinforcement. For the beams with transverse reinforcement, displacement ductility was highly increased. This suggests that fibres have the potential to reduce the congestion of the reinforcement if fibres are designed to replace partially closely spaced transverse reinforcement. Also, it was noted that a redistribution of stresses occurred resulting in the formation of more well-controlled cracks. Finally, the strength predictions using the method developed by Aoude (Aoude, 2007) agree very well with the experimental results.
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More than just “Hello” and “Nihao”: Exploring bars and intercultural communication in a touristic town, Yangshuo, ChinaZhou, Lingxu 18 March 2011 (has links)
The purpose of this research is to explore the communication and interaction between westerners and Chinese people in western bars in the touristic town of Yangshuo in southern China. Yangshuo is worldly famous for its breath-taking Karst Mountains, rice fields and water buffalos. It has attracted millions of visitors annually, both domestic and international. The tourist center of Yangshuo consists of a main street, West Street, and many other small streets around it. In recent years, bars and night clubs have been established, bringing a more modern and western atmosphere to the main tourist streets that are paved in marble and lined with ancient buildings. This research is focused on bars, western bars in particular, as a unique setting for intercultural communication and interaction.
First of all, this research introduces a background of intercultural communication definitions, the link between bars and tourism in China, as well as international tourism in China. With the goal of understanding the intercultural phenomena in bars through conversations and observations, I explored the role of bars in the community, the social and intercultural situations in bars, and the reflection and outcome of those communication and interaction. Field work was conducted in July and August 2010, by using both qualitative and quantitative research methods: questionnaire survey and ethnographic participant observation. I was able to obtain a broad perception of the subject as well as detailed description from participants, including myself.
A broad range of literature related to bars and spaces in leisure and tourism, as well as in the fields of intercultural communication, intercultural host-guest relationship in tourism, tourism and cultural understanding, and tourist experience were reviewed. The gaps in the literature were identified. Limited research was done by addressing the actual situations of intercultural communication and linking the social and intercultural theories with actual practice, especially in a tourism context. Also, the role of western bars, as a new form of recreational, cultural and social space in China needed more attention.
Chapter four and five present major findings of this research. Informants were divided into five groups: western tourists, local westerners (westerners who have become residents), Chinese tourists, Chinese students studying English in Yangshuo, and local residents. Preliminary findings from questionnaire survey indicate that westerners and Chinese people have difference reasons for visiting Yangshuo and going to bars. Bars have both social and recreational functions for westerners but are of less interest to and have more limited functions as attractions to Chinese tourists. Local residents have the least interest in western bars but Chinese students often go to them, mainly to practice English with foreigners. Detailed analysis of qualitative data suggests intercultural communication and interaction have difference purposes and styles for the different groups. Students, locals who work in the bars and local westerners have most contact with western tourists. Chinese tourists tend to interact with westerners in non-verbal ways, such as in games and photo-taking. Language is a major communication barrier but westerners made more effort to overcome this, reflecting both desire and need as visitors in a foreign land.
The research findings can seek theoretical explanation through many social and intercultural theories. They suggest tourist-host interaction and communication has been overrated, especially when tourists are travelling in a different culture. The level of contact and cultural understanding is relatively superficial, but more meaningful than mere commercial exchanges. The trend of globalization and cultural homogeneity was well recognized by both cultural groups. The acknowledgement of cultural difference and interaction between customers should be encouraged and facilitated in bars, in order to create an authentic bar experience and nurture effective intercultural communication.
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Bond and Flexural Behaviour of Self Consolidating Concrete Beams Reinforced and Prestressed with FRP BarsKrem, Slamah 10 April 2013 (has links)
Self consolidating concrete (SCC) is widely used in the construction industry. SCC is a high performance concrete with high workability and consistency allowing it to flow under its own weight without vibration and making the construction of heavily congested structural elements and narrow sections easier. Fiber reinforced polymer (FRP) reinforcement, with its excellent mechanical properties and non-corrosive characteristic, is being used as a replacement for conventional steel reinforcement. In spite of the wide spread of SCC applications, bond and flexural behaviour of SCC beams reinforced or prestressed with FRP bars has not been fully studied. Furthermore, the ACI 440.1R-06 equation for determining the development length of FRP bars is based on Glass FRP (GFRP) bars and may not be applicable for Carbon FRP (CFRP) bars.
This research program included an experimental and analytical study to investigate the flexural and bond behaviour of SCC beams reinforced with FRP bars and SCC beams prestressed with CFRP bars. In the experimental phase, fifty-six beams were fabricated and tested. Sixteen of these beams were prestressed with CFRP bars and forty beams were reinforced with non-prestressed GFRP or CFRP bars. Four concrete batches were used to fabricate all the specimens. Three mixes were of self consolidating concrete (SCC) and one mix was of normal vibrated concrete (NVC). The test parameters for the non-prestressed beams were the concrete type, bar type and bar diameter, concrete cover thickness and embedment length while the test parameters for the prestressed beams were the concrete type and the prestressing level (30%, 45% and 60%). The transfer length of the prestressed CFRP bars was determined by means of longitudinal concrete strain profile and draw-in methods. All beams were tested in four-point bending to failure. Measurements of load, midspan deflection, bar slip if any at the beam ends, strain in reinforcing FRP bar at various locations, and strain in concrete at the beam midspan were collected during the flexural test.
The concrete compressive strength at flexural tests of SCC mix-1, mix-2, and mix-3 were 62.1MPa, 49.6MPa and 70.9MPa, respectively and for the NVC mix was 64.5MPa. The material test results showed that SCC mixes had lower modulus of elasticity mechanical properties than the NVC mix. The modulus of elasticity of the SCC mixes ranged between 65% and 82% of the NVC mix. The modulus of rupture of the SCC mixes was 86% of the NVC mixes.
The test results for beams prestressed with CFRP bars revealed that the variation of transfer length of CFRP bars in SCC versus their prestressing level was nonlinear. The average measured transfer lengths of 12.7mm diameter CFRP bars prestressed to 30%, 45% and 60% was found to be 25db, 40db, 54db, respectively. Measured transfer lengths of the 12.7mm diameter CFRP bar prestressed to 30% in SCC met the ACI440.4 prediction. However, as the prestressing level increased, the predicted transfer length became unconservative. At a 60% prestress level, the measured/prediction ratio was 1.25. Beams prestressed with CFRP bars and subjected to flexural testing with shear spans less than the minimum development length had local bar slippage within the transmission zone. Beams that experienced local bond slip, their stiffness was significantly decreased. A modification to the existing model used to calculate the transfer and development lengths of CFRP bars in NVC beams was proposed to account for the SCC.
The test results for beams reinforced with FRP bars indicated that the average bond strength of CFRP bars in NVC concrete is about 15% higher than that of GFRP bars in NVC. The ACI 440.1R-06 equation overestimated the development length of the CFRP bars by about 40%, while CAN/CSA-S6-06 equation was unconservative by about 50%. A new factor of (1/1.35) was proposed to estimate the development length of the CFRP bars in NVC when the ACI440.1R-06 equation is used.
Beams made from SCC showed closer flexural crack spacing than similar beams made from NVC at a similar loading. The deflection of beams made from SCC and reinforced with CFRP bars was found to be slightly larger than those made from NVC. The average bond stresses of GFRP and CFRP bars in SCC were comparable to those in NVC. However, FRP bars embedded in SCC beams had higher bond stresses within the uncracked region of the beams than those embedded in NVC beams. In contrast, FRP bars in SCC had lower bond stresses than FRP bars in NVC within the cracked region. The average bond strength of GFRP in SCC was increased by 15% when the concrete cover thickness increased from 1.0db to 3.0db. Cover thicknesses of 2db and 3db were found to be sufficient to prevent bond splitting failure of GFRP and CFRP bars in SCC, respectively. Bond splitting failure was recorded when the cover thickness dropped to 1.5db for the GRP bars and to 2.0db for the CFRP bars. An insignificant increase in average bond stress was found when the bar diameter decreased from 12.7mm to 6.3mm for the CFRP bars, and a similar increase occurred in GFRP bars when the bar diameter decreased from 15.9mm to 9.5mm.
New models to calculate the development length of GFRP and CFRP bars embedded in SCC were proposed based on the experimental results. These models capture the average bond stress profile along the embedment length. A good agreement was found between the proposed model and the experimental results.
Analytical modeling of the load-deflection response based on the effective moment of inertia (ISIS Canada M5) was unconservative for SCC beams reinforced with CFRP bars by 25% at ultimate loading. A new model for bond stress versus Ma/Mcr (applied moment to cracking moment) ratio was developed for GFRP and CFRP bars in SCC and for CFRP bars in NVC. These bond stress models were incorporated in a new rigorous model to predict the load-deflection response based on the curvature approach. The FRP bar extension and bond stress models were used to calculate the load-deflection response. With these models 90% of the calculated deflections were found to be within ± 15% of the experimental measured results for SCC beams reinforced with FRP bars.
Analytical modeling of the load-deflection for NVC and SCC beams prestressed with CFRP bars are proposed done. The moment resistance was calculated using Sectional Analysis approach. The deflection was calculated using simplified and detailed methods. The simplified method was based on the effective moment of inertia while the detailed method was based on effective moment of inertia and effective centroid. The experimental results correlated well with the detailed method at higher loads range.
This study provided an understanding of the mechanism of bond and flexural behaviour of FRP reinforced and prestressed SCC beams. The information presented in this thesis is valuable for designers using FRP bars as flexural reinforcement and also for the development of design guidelines for SCC structures.
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Investigating The Extrusion Of Alumina Silicate Pastes For Synthesis Of Monolith Zeolite AOzcan, Aysenur 01 August 2005 (has links) (PDF)
Zeolites are highly porous materials that are most commonly used in granular or beaded forms. In general, zeolite granules, beads or monoliths are manufactured by using an inorganic binder which helps to cement zeolite crystals together. However, this inorganic binder decreases the purity of the zeolite structures and accessibility to the zeolite pores. A new and relatively easy method was offered for the production of binderless zeolite A tubes and bars from amorphous alumina silicate extrudates in this study. Amorphous alumina silicate powder, which is obtained by filtering the homogenous hydrogel with a composition of 2.5Na2O:1Al2O3:1.7SiO2:150H2O, is mixed with an organic binder (HEC-Hydroxyethyl Cellulose) to obtain the paste. The paste is then extruded through a die of a home-made extruder into bars and tubes. These extrudates were dried at room temperature for 24 hours, then calcined at 600oC for 2
hours and finally synthesized at 80oC for 72 hours in hydrothermal conditions to convert amorphous alumina silicate to zeolite.
The most appropriate amorphous alumina silicate powder (A) / 4wt% HEC solution (H) ratio to prepare paste, hence to prepare bars and tubes was found as 0.82. The crystallinity of bars and tubes was 91% and 97%, respectively, and zeolite A was the only crystalline material. The bars and tubes were composed of highly intergrown zeolite A crystals with high porosity. Porosity of the bars is approximately 39% and porosity of the tubes is 29%, with a narrow pore size distribution. Bars have macropores of 2 & / #956 / m, while the macropores of the tubes are 3-4 & / #956 / m. The BET surface area of the bars was 411 m2/g and of tubes was 439 m2/g, which are comparable with the commercial zeolite A beads. Bars had a crushing strength of 0.42 MPa, which is sufficiently high to handle.
In conclusion, zeolite A bars and tubes, with their high purity, macroporous structure and high mechanical strength, can be used in adsorption and ion exchange processes. The developed synthesis method can be scaled up to prepare honeycomb monoliths that provide higher surface are per unit volume with an appropriate extruder die.
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Non-linear overload behaviour and ductility of reinforced concrete flexural members containing 500MPa grade steel reinforcement /Gravina, Rebecca Jane. January 2002 (has links) (PDF)
Thesis (Ph.D.)--University of Adelaide, Dept. of Civil and Environmental Engineering, 2002. / Includes corrigenda (inserted at front) and list of publications published as a result of this research. Includes bibliographical references (leaves 192-199).
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The role of experience in the development of bar managers' social competencies /Dhaya, Jateen January 2007 (has links)
Thesis (M.Com. (Management)) - Rhodes University, 2008.
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Etude expérimentale du frottement entre l’acier et un matériau fragile sous haute vitesse et haute pression / Experimental study of the friction between steel and a brittle material under high velocites and high pressureDurand, Bastien 04 December 2013 (has links)
L’objectif de la thèse est la caractérisation expérimentale du frottement entre l’acier et un matériau fragile. Les pressions et les vitesses de glissement qu’on cherche à atteindre sont respectivement de l’ordre de 10 à 100 MPa et l’ordre de 10 à 100 m/s. Les tribomètres classiques ne peuvent pas être utilisés car les pressions qu’on cherche à atteindre sont suffisamment élevées pour mener le matériau fragile à rupture. Pour pallier cette difficulté, le matériau doit être confiné. Un échantillon cylindrique du matériau est alors inséré dans un tube en acier qui fait à la fois office de confinement et de surface de frottement. Avec cette configuration, comme nous ne pouvons pas effectuer de mesures directes au niveau de l’interface, les paramètres de frottement sont identifiés à partir de mesures indirectes et de modèles analytique et numérique. Deux types de dispositifs ont été conçus pour effectuer à la fois des essais d’orientation en quasistatique et des essais sur barres de Hopkinson. Les essais quasi-statiques permettent une identification fiable du frottement et montrent que des pressions de 100 MPa peuvent être obtenues avec notre configuration sans dégrader le matériau fragile. En revanche, les essais sur barres de Hopkinson ne donnent pas satisfaction. Un dispositif spécifiquement adapté à la dynamique rapide a alors été conçu. Il permet d’identifier le frottement sous des pressions de 100 MPa et des vitesses de10 m/s. / The aim of the thesis is the experimental characterisation of the friction between steel and a brittle material. The desired pressures and the desired sliding velocities are respectively of the order of 10-100 MPa and 10-100 m/s. Usual tribometers cannot be used because the desired pressures are high enough to fracture the brittle material. The material has to be confined to overcome this difficulty. A cylindrical sample of the material is therefore inserted into a steel tube which acts both as a confinement and a sliding surface. Such a configuration does not enable to carry on direct measurements on the interface, the friction parameters are thus identified from indirect measurements and from analytical and numerical models. Two types of set-up have been designed to carry on both quasi-static tests and tests on split Hopkinson pressure bars. Quasi-static tests enable a reliable identification of friction and show that the desired pressures can be reached with our configuration whilst retaining the brittle material integrity. Unfortunately, the results obtained with split Hopkinson pressure bars are not satisfactory. A set-up specifically adapted to dynamic situations has thus been designed. It enables identification of friction under pressure of 100 MPa and velocities of 10 m/s.
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Barras de cereais com amnêndoas de chichá, sapucaia e castanha-do-gurguéia, complementadas com casca de abacaxi / the cereal bars from almonds to chichá, sapucaia and chestnut-of-gurguéia, supplemented with pineapple bark.Carvalho, Michelle Garcêz de January 2008 (has links)
CARVALHO, Michelle Garcêz de. Barras de cereais com amnêndoas de chichá, sapucaia e castanha-do-gurguéia, complementadas com casca de abacaxi. 2008. 92 f. : Dissertação (mestrado) - Universidade Federal do Ceará, Centro de Ciências Agrárias, Departamento de Tecnologia de Alimentos, Fortaleza-CE, 2008 / Submitted by Nádja Goes (nmoraissoares@gmail.com) on 2016-06-21T13:50:58Z
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Previous issue date: 2008 / The trend of consumption of healthy food, innovative and practical has led to growth increasing in recent years the market for the cereal bars. The cereal bars are formed by grain cereals, processed and clusters, and they can be incorporated different ingredients, such as integral cereals, dehydrated fruit or crystallized fruit, almonds and sugars. There are in the native Brazilian flora, some species still little known, but which have potential for the market of almonds, as chichá, sapucaia and chestnut-of-gurguéia. However, its observe also the importance of the use of waste generated from fruit processing, such as bark, stems and cake, these can be used in the human diet. Thus, the objective of this work was to develop the cereal bars from almonds to chichá, sapucaia and chestnut-of-gurguéia, supplemented with pineapple bark. Cereal bars were making with three formulations (A, B and C), which they were different by the amount added of hydrogenated vegetable fat and dust of the pineapple bark. Subsequently, nine types of the cereal bars were prepared, three with almonds, chichá, three with almonds, chestnut-do-gurguéia and three of sapucaia with almonds, which were evaluated microbiologically and sensorial. After the sensory evaluation, the cereal bars with higher notes of overall impression was chose, and those subjected to chemical analyses. The sapucaia highlighted is among the almonds evaluated, by presenting the greatest medium for most parameters evaluated. It was found by the parameter overall impression that among the formulations tested showed that the largest note of acceptance was the formulation B, between the cereal bars with the three almonds studied. The cereal bars, developed with almonds of chichá and sapucaia, in general, were more accepted than cereal bars with almonds of chestnut-do-gurguéia. With regard to minerals, the highest levels in the cereal bars prepared in this study were, respectively, potassium, sodium, iron and zinc. It is viable to use the almonds, chichá, sapucaia and chestnut-of-gurguéia, and the dust of the pineapple bark in the preparation of the cereal bars. / A tendência de consumo de alimentos saudáveis, inovadores e práticos tem levado ao crescimento cada vez maior nos últimos anos do mercado de barras de cereais. As barras de cereais são formadas por grãos de cereais processados e aglomerados, e a elas podem ser incorporados diferentes ingredientes, tais como cereais integrais, frutas desidratadas ou cristalizadas, amêndoas e açúcares. Existem na flora nativa brasileira, algumas espécies ainda pouco conhecidas, mas que apresentam potencialidades para o mercado de amêndoas, como o chichá, sapucaia e castanha-do-gurguéia. No entanto, observa-se também a importância da utilização dos resíduos gerados do processamento das frutas, como cascas, talos e bagaços, podem esses ser aproveitados na dieta humana. Assim, objetivou-se neste trabalho desenvolver barras de cereais a partir de amêndoas de chichá, sapucaia e castanha-do-gurguéia, complementadas com casca de abacaxi. Foram formuladas barras de cereais com três formulações (A, B e C), as quais se diferenciavam pela quantidade adicionada de gordura vegetal hidrogenada e pó da casca de abacaxi. Posteriormente, foram elaborados nove tipos de barras de cereais, sendo três com amêndoas de chichá, três com amêndoas de castanha-do-gurguéia e três com amêndoas de sapucaia, as quais foram avaliadas microbiologicamente e sensorialmente. Após a avaliação sensorial, escolheram-se as barras de cereais com maiores notas de impressão global, sendo essas submetidas a análises químicas. A sapucaia destacou-se, dentre as amêndoas avaliadas, por apresentar as maiores médias para a maioria dos parâmetros avaliados. Verificou-se através do parâmetro impressão global que dentre as formulações testadas a que exibiu a maior nota de aceitação foi a formulação B, entre as barras de cereais com as três amêndoas estudadas. As barras de cereais elaboradas com amêndoas de chichá e sapucaia de um modo geral foram mais aceitas do que as barras de cereais com amêndoas de castanha-do-gurguéia. No que se referem aos minerais, os de maior teor nas barras de cereais elaboradas neste estudo, foram, respectivamente, o potássio, sódio, ferro e zinco. Conclui-se ser viável a utilização das amêndoas de chichá, sapucaia e castanha-do-gurguéia, e do pó da casca de abacaxi na elaboração de barras de cereais.
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Contribution à l'évaluation de l'état de dégradation de divers types de barres d'acier utilisées comme armatures dans des bétons carbonatés ou pollués par des chlorures / Assessment of the state of degradation of various types of steel bars used as reinforcement in concrete carbonated or contaminated by chloridesRivera-Corral, Jesus Octavio 29 September 2016 (has links)
Le béton armé est sans conteste le matériau le plus utilisé dans la construction, et permet de réaliser la plupart des infrastructures dans tous les pays du monde. Cependant, sa durabilité peut être compromise de façon prématurée par la corrosion des aciers, qui est la pathologie considérée comme la plus dangereuse vis-à-vis du maintien de l'intégrité des ouvrages de Génie Civil. Afin d'obtenir une meilleure résistance face au risque de corrosion, l'acier conventionnel (AC) peut être soumis à divers traitements, dont les plus connus sont le recouvrement superficiel par d'autres matériaux métalliques à base de zinc (AG), ou par des revêtements doubles métal-polymères (AD). Cependant, il existe aussi des barres d'acier thermiquement traitées (ATT) qui ne sont actuellement quasiment pas utilisées en tant qu'armatures. De ce fait, leur comportement face aux mécanismes de détérioration comme la corrosion en milieu cimentaire causée par les chlorures ou la carbonatation est encore très peu connu. Dans ce travail, le comportement des différentes barres d'acier mentionnées ci-dessus a été étudié. Des éprouvettes prismatiques de béton, incluant ces types d'armatures, ont été fabriquées avec deux rapports E/C : 0,45 et 0,65. Avant leur utilisation, les barres ont été caractérisées mécaniquement et métallographiquement. Ensuite, les éprouvettes ont été placées dans différentes conditions d'exposition : un environnement urbain/industriel ou côtier, et un environnement contrôlé en laboratoire. Des mesures du potentiel de corrosion, de résistance de polarisation linéaire, et de spectroscopie d'impédance électrochimique ont été mises en œuvre durant la période d'exposition. Pour chaque série, la teneur critique en chlorures a été déterminée, et la progression de la profondeur de carbonatation a été suivie. En outre, en induisant un couple galvanique par effet de la carbonatation, des mesures originales du comportement électrochimique de ces barres ont été effectuées puis une analyse, en s'appuyant sur une modélisation en éléments finis, en a été faite. Dans l'environnement contrôlé en laboratoire, l'ordre de dépassivation des différentes barres exposées a été observé de façon similaire pour les deux rapports E/C, à savoir : ATT, AC, AG et enfin AD. Une teneur critique en chlorures plus élevée a été obtenue pour les barres AG et AD. Cependant, lors de l'inspection visuelle, les dommages causés sur les armatures AG étaient plus élevés que sur les autres types de barres. Enfin, durant l'étape de propagation, la densité de courant de corrosion des barres ATT et des barres AG s'est révélée inférieure. / Corrosion of reinforcing bars in concrete is considered as the most important problem that affects the integrity of the civil structures. In order to obtain a better resistance to corrosion, various superficial processes as coatings with zinc (AG) or such as the dual covering metallic-polymeric (AD) are applicate to ordinary steel bars (AC). On the other hand, steel bars with thermal treatments (ATT), principally developed as an alternative to improve the mechanical properties without the use of ferroalloys, are not used in concrete. The behavior of these kinds of bars in front of mechanisms of deterioration as the corrosion induced by chlorides or carbonation has not yet been studied. In this work, all these various steel bars (AG, AD, AC and ATT) were embedded in prismatic specimens of concrete made with two ratio water/cement: 0.45 and 0.65. Previously, steels bars were characterized by mechanical tests and metallographic identifications. Then, specimens were placed in several sites of exposition: urban/industrial environment, or coastal environment, or controlled atmosphere in laboratory. During these expositions, measurements of corrosion potential, linear polarization resistance, and electrochemical impedance spectroscopy were regularly carried out. For each type of steel bar, chloride threshold level and progress of the carbonation depth were determined. Furthermore, by means of the induction of a galvanic couple during design of new samples, the electrochemical behavior of the steels bars AC, ATT and AG was followed up experimentally and then analyzed with finite element model. It was founded that the different steels bars exposed in controlled atmosphere of laboratory followed a same sequence in depassivation for both ratios water/cement: ATT, AC, AG and AD. The chloride thresholds were higher for steels bars AG and AD. However, visual inspection showed that the morphology of damages caused on AG bars was most important compared with the other steel bars. In the propagation phase, the corrosion current density of the ATT bars was lower, even to that obtained by the AG bars.
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