Permeability of High-Performance Fiber Reinforced Concrete Immersed in High Concentration Sodium Chloride Solution

This paper aims to study the permeability of High-Performance Concrete containing natural pozzolan and reinforced with fibers in high concentration sodium chloride solution. Optimized finely ground natural pozzolan was employed as 6% of partial substitution of the cement. Polypropylene fibers with 6 mm and 12 mm lengths were introduced individually for a volume fraction of 0.1% and 0.15% respectively. Then, in combination with a total fiber content of 0.25%. The effect of sodium chloride attack on the performance of concretes was assessed through the measurement of the compressive strength, splitting tensile strength, sorptivity, rapid chloride permeability test, apparent and intrinsic gas permeability, and visual inspection at various testing ages (28, 90, 180, and 365 days). A total of four (04) types of concretes were cast: one (01) High-Performance Concrete (HPC), and three (03) High-Performance Fiber Reinforced Concrete (HPFRC) stored in tap water and sodium chloride environment. From the experiments performed, it can be concluded that the polypropylene fibers introduction into HPC favorably affect its chemical resistance to chloride attack and long-term durability. The difference in the permeability of HPC and HPFRC stored in tap water and chloride environment is not significant. Furthermore, the visual investigation of HPFRC after 365 days of immersion in sodium chloride environment showed no sign of degradation. Based on the results obtained in this study, we recommend the use of hybrid fiber-reinforced concrete (F0-0.25%) as a low permeable material in a severe chloride environment

Corrosion processes controlled by phosphonic acid nano-layers

Self assembled monolayers (SAM) formed by fluoro-phosphonic and undecenyl-phosphonic acids on carbon steel surfaces as anticorrosive nanocoatings were investigated. The anticorrosive efficacy of these SAM layers was followed by atomic force microscopy, when the change in the surface morphology caused by layer deposition and corrosion processes was monitored. The corrosion process was determined by electrochemical potentiodynamic polarization and cyclic voltammetry. Results showed that both chemicals produced good protection against corrosion as anodic inhibitors specially with increasing the time of layer formation which results in a more compact molecular film. According to the AFM images, the fluoro-phosphonic acid self-assembled molecular layer can control the general as well as the pitting corrosion, but the SAM layers of the undecenyl-phosphonic acid cannot inhibit the pitting corrosion. The AFM measurements confirmed the electrochemical results

"I Am the Wild Machinist ... Reconstructing the Present": The Flâneur-Cruiser in Samuel R. Delany’s Dhalgren

This thesis aims to better understand queer theories of time and space in relation to the experiences of those who loiter, who lounge, who fuck against the rush of straight time and space. The project does so via an investigation of the related figures of the flâneur and the cruiser, considering what latent potentials they hold for queer futurity. This research examines these themes in the science fiction novel Dhalgren by Samuel R. Delany, as well as Delany’s autobiographical writings. I posit that, through a total rejection of straight and capitalist time, Dhalgren’s fictional city of Bellona and its residents effectively put into practice a queer world that theorists such as José Esteban Muñoz conceive as impossible in our own here and now. Moreover, by way of this imaginative turn, Delany crystalizes a clear image of the world that cruisers and flâneurs alike are striving towards – a world where all are free to wander idly and to desire publicly without legal or moral consequence

Comportement d’un béton à hautes performances à base de laitier en milieu sulfatique

L'utilisation de béton à hautes performances (BHP) intégrant des ajouts cimentaires comme les cendres volantes, les fumées de silice ou le laitier hydraulique cimentaire a augmenté considérablement au cours des deux dernières décennies. Les ouvrages en BHP durent plus longtemps et entraînent des frais d'entretien moins élevés que ceux en béton ordinaire. De plus, le BHP utilise moins de ciment, ce qui diminue les émissions de CO2. Une plus vaste utilisation du béton à hautes performances intégrant des ajouts cimentaires pourrait donc entraîner des bénéfices tant environnementaux que financiers et construire des ouvrages plus durables. A l’état actuel, la recherche sur les bétons à hautes performances en Algérie est surtout axée sur leurs formulations en vue de produire des bétons de meilleures résistances et durables. Cependant, une composition optimale dépend de plusieurs paramètres, en particulier du choix des ingrédients. L'effet des ajouts cimentaires et leur finesse reste peu entrepris. C'est pourquoi nous nous proposons dans ce travail, de formuler des bétons à hautes performances avec et sans ajout cimentaire et de traiter l’influence du laitier de l’usine sidérurgique d’El-hadjar (Algérie), finement broyé et substitué à une partie de ciment, sur les caractéristiques physico-mécaniques des bétons élaborés.Mots clés : BHP - Laitier - Durabilité - Sulphate

Comportement des BHP de laitier soumis aux cycles immersion-séchage

This article is part of a summary of the work developed in conjunction with the Laboratory of Civil Engineering and Mechanical Engineering from INSA Rennes and Research Unit: Materials, Processes and Environment, University of Boumerdes. One of the objectives was indeed to promote, through studies of variants, the use of local cementitious additions in the formulation of high performance concretes (HPC). The binding contribution of mineral additions to the physical, mechanical and durability of concrete was evaluated by an experimental methodology to subjugate their original granular and pozzolanic effect. The results show that the contribution of couple cement -slag intensification of the matrix is higher than that obtained when the cement is not substituted by addition. Therefore, a significant improvement in performance of concretes was observed, despite the adverse action immersion cycles - drying maintained for 365 days.Cet article constitue une partie d’une synthèse des travaux élaborés conjointement au Laboratoire de Génie Civil et de Génie Mécanique de l’INSA de Rennes et l’Unité de Recherche : Matériaux, Procédés et Environnement de l’Université de Boumerdès. Un des objectifs visés était en effet de valoriser, par des études de variantes, l’utilisation des ajouts cimentaires locaux dans la formulation des bétons à hautes performances (BHP). La contribution liante des additions minérales aux propriétés physiques, mécaniques et de durabilité des bétons a été évaluée par une méthodologie expérimentale originale permettant de subjuguer leur effet granulaire et pouzzolanique. Les résultats obtenus montrent que la contribution du couple ciment - laitier à la densification de la matrice est supérieure à celle obtenue lorsque le ciment n’est pas substitué par l’addition. Par conséquent, une amélioration significative des performances des bétons formulés a été observée, ceci malgré l’action préjudiciable des cycles immersion - séchage maintenus pendant 365 joursCet article constitue une partie d’une synthèse des travaux élaborés conjointement au Laboratoire de Génie Civil et de Génie Mécanique de l’INSA de Rennes et l’Unité de Recherche : Matériaux, Procédés et Environnement de l’Université de Boumerdès. Un des objectifs visés était en effet de valoriser, par des études de variantes, l’utilisation des ajouts cimentaires locaux dans la formulation des bétons à hautes performances (BHP). La contribution liante des additions minérales aux propriétés physiques, mécaniques et de durabilité des bétons a été évaluée par une méthodologie expérimentale originale permettant de subjuguer leur effet granulaire. Les résultats obtenus montrent que la contribution du couple ciment - laitier à la densification de la matrice est supérieure à celle obtenue lorsque le ciment n’est pas substitué par l’addition. Par conséquent, une amélioration significative des performances des bétons formulés a été observée, ceci malgré l’action préjudiciable des cycles immersion - séchage maintenus pendant 365 jours

Experimental Contribution Concerning the Effect of Carbonation Reaction on the Oxygen Permeability of Concrete

Reinforced concrete (RC) structures are prone to steel corrosion that affects their service life. The two main processes, involved in the destruction of the steel-concrete self-protection are the carbonation and the penetration of chlorides. Understanding the behavior of these degrading phenomena is of paramount importance to enhance the field of predicting the service life of RC structures. In this investigation, a total number of 54 cylindrical specimens (150×100 mm2) and 54 cubic specimens (100×100 mm2) from six different concrete mixtures covering a range of water-to-cement ratio (w/c) between 0.76 and 0.36 was tested. The effect of the carbonation reaction on the concrete oxygen permeability (assessed by a recent method), compressive strength, and weight has been investigated. The obtained data were analyzed to establish correlations to predict the oxygen permeability of non-carbonated concrete with concrete characteristics such as w/c ratio and compressive strength. Test results show good correlations. The results of the accelerated carbonation test showed that compressive strength increases with carbonation. Concerning the effect of carbonation reaction on concrete oxygen permeability which is the main goal of this paper, test results showed that carbonation considerably affects the concrete permeability. This result was observed for all concrete mixtures. Moreover, the relationship between carbonation depth and concrete oxygen permeability in ordinary concrete differed than high performance concrete. Furthermore, the increase of the oxygen permeability observed after the carbonation has been justified by the analysis of the Scanning Electron Microscopy images that show the formation of larger pores in comparison with non-carbonated concrete

Evolution of durability and mechanical properties of ordinary portland cement concretes in sulphates attack

Concrete in sulphates environments often undergoes significant alterations that often have significant adverse results on its engineering properties. However, the choice of cement type is a very important factor for concrete exposed in aggressive environment. This research presents the effect of two types of cement on the mechanical and microstructure properties of ordinary concretes exposed in aggressive solution dosed with 5% of gypsum (Ca2SO4.2H2O). The tests studied in this experimental part were the compressive strength, flexural strength, thermogravimetry, mercury intrusion porosimetry and mass variations of the concrete. The results clearly show that the CEM I 42.5 is suitable for the formulation of concretes exposed to sulphate attack and their properties are better compared with the CEM II/A 42.5

The Role of Energy Supply in Economic Growth: Evidence from the Oil Importing Countries

The main purpose of this study is to explore and analyse relationships between energy supply and economic growth. Path analysis and structural equation modelling have been used to analyse the direct and indirect effects of energy supply on economic growth by identifying the form of the relationships between them and the role of mediating variables. Energy supply was found to be strongly correlated with economic growth and to have a number of other relationships and effects on the economy. It was also found that mediating variables had different relationships and effects on the economy based on the source of energy. This result confirms that changes in energy suppliers seem to reflect changes in the political ‎economy of the country rather than shifts in energy use. The influence of the ‎political economy and the preferential treatment of supplying energy to oil importing countries below ‎market price were found to have mixed effects on economic growth for both trade and budget path models.‎ Keywords: Energy supply, Economic growth, Structural equation, Path analysis. ‎ JEL Classifications: Q41, O4, Q43, C32. â€

Comportement des BHP de laitier soumis aux cycles immersion-séchage

This article is part of a summary of the work developed in conjunction with the Laboratory of Civil Engineering and Mechanical Engineering from INSA Rennes and Research Unit: Materials, Processes and Environment, University of Boumerdes. One of the objectives was indeed to promote, through studies of variants, the use of local cementitious additions in the formulation of high performance concretes (HPC). The binding contribution of mineral additions to the physical, mechanical and durability of concrete was evaluated by an experimental methodology to subjugate their original granular and pozzolanic effect. The results show that the contribution of couple cement -slag intensification of the matrix is higher than that obtained when the cement is not substituted by addition. Therefore, a significant improvement in performance of concretes was observed, despite the adverse action immersion cycles - drying maintained for 365 days.Cet article constitue une partie d’une synthèse des travaux élaborés conjointement au Laboratoire de Génie Civil et de Génie Mécanique de l’INSA de Rennes et l’Unité de Recherche : Matériaux, Procédés et Environnement de l’Université de Boumerdès. Un des objectifs visés était en effet de valoriser, par des études de variantes, l’utilisation des ajouts cimentaires locaux dans la formulation des bétons à hautes performances (BHP). La contribution liante des additions minérales aux propriétés physiques, mécaniques et de durabilité des bétons a été évaluée par une méthodologie expérimentale originale permettant de subjuguer leur effet granulaire et pouzzolanique. Les résultats obtenus montrent que la contribution du couple ciment - laitier à la densification de la matrice est supérieure à celle obtenue lorsque le ciment n’est pas substitué par l’addition. Par conséquent, une amélioration significative des performances des bétons formulés a été observée, ceci malgré l’action préjudiciable des cycles immersion - séchage maintenus pendant 365 joursCet article constitue une partie d’une synthèse des travaux élaborés conjointement au Laboratoire de Génie Civil et de Génie Mécanique de l’INSA de Rennes et l’Unité de Recherche : Matériaux, Procédés et Environnement de l’Université de Boumerdès. Un des objectifs visés était en effet de valoriser, par des études de variantes, l’utilisation des ajouts cimentaires locaux dans la formulation des bétons à hautes performances (BHP). La contribution liante des additions minérales aux propriétés physiques, mécaniques et de durabilité des bétons a été évaluée par une méthodologie expérimentale originale permettant de subjuguer leur effet granulaire. Les résultats obtenus montrent que la contribution du couple ciment - laitier à la densification de la matrice est supérieure à celle obtenue lorsque le ciment n’est pas substitué par l’addition. Par conséquent, une amélioration significative des performances des bétons formulés a été observée, ceci malgré l’action préjudiciable des cycles immersion - séchage maintenus pendant 365 jours

Distribution of the putative virulence factor encoding gene sheta in Staphylococcus hyicus strains of various origins

In the present study, Staphylococcus (S.) hyicus strains isolated in Russia (n = 23) and Germany (n = 17) were investigated for the prevalence of the previously described genes sheta and shetb. Sheta was detected in 16 S. hyicus strains. Sheta-positive strains were mainly found among strains isolated from exudative epidermitis, and frequently together with the exfoliative toxin-encoding genes exhD and exhC. Partial sequencing of sheta in a single S. hyicus strain revealed an almost complete match with the sheta sequence obtained from GenBank. None of the S. hyicus strains displayed a positive reaction with the shetb-specific oligonucleotide primer used in the present study. According to the present results, the exotoxin encoding gene sheta seems to be distributed among S. hyicus strains in Russia and Germany. The toxigenic potential of this exotoxin, which does not have the classical structure of a staphylococcal exfoliative toxin, remains to be elucidated