Download or read book valuation de l efficacit inhibitrice de Na3PO4 contre la corrosion des armatures du b ton written by Haifa Nahali and published by . This book was released on 2015 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt: L'objectif principal de cette thèse est d'étudier l'efficacité d'un inhibiteur à base de phosphate, Na3PO4, sur l'amorçage de la corrosion des armatures du béton. L'étude a été réalisée moyennant des méthodes électrochimiques et d'analyse de surface associées à l'émission acoustique et à la technique de la cellule de diffusion. L'évaluation de l'efficacité de l'inhibiteur en milieu simulant le béton a été réalisée en utilisant une nouvelle méthode de prétraitement de l'armature et de suivi de la corrosion. Il apparaît qu'en présence de Na3PO4 le rapport critique [Cl-] / [OH-] d'amorçage de la corrosion par piqûre atteint une valeur (R=15) nettement supérieure à celle sans utilisation de Na3PO4 (R ~ 0,6). L'inhibition est due à la formation d'un film renfermant des composés phosphatés (FePO4, (PO4)2Fe3,8H2O) qui bloque les sites anodiques actifs de l'acier, et augmente de façon significative sa résistance à la corrosion localisée. Pour un rapport R > 15, la dépassivation est liée à la présence d'une forte teneur en chlorure dans le milieu et conduit à terme, à la destruction quasi générale du film formé au préalable sur la surface de l'acier.La technique de cellule de diffusion a permis d'étudier, principalement, la cinétique de diffusion des ions Cl- dans un mortier confectionné sans et avec Na3PO4. La présence du phosphate dans le mortier entraîne une réduction du coefficient de diffusion des ions chlorures, et un accroissement important de la période d'amorçage du processus de corrosion. Enfin, l'inhibiteur adjuvant engendre la formation de nouveaux produits à base de phosphate dans le mortier (principalement : Ca3H2(P2O7)2, H2O et CaHPO4, 2H20). La disparition des hydrates usuels du ciment entraine une légère diminution de la résistance à la compression du béton, et de son module d'élasticité. Néanmoins, la présence de ces composés phosphatés bloque les pores du mortier et freine la diffusion des chlorures. Il s'ensuit une amélioration de la résistance de la corrosion du mortier armé en milieu 3 % NaCl. L'ensemble de ces résultats a montré clairement que cet adjuvant demeure recommandé pour la protection des armatures contre la corrosion en milieu chloruré.
Download or read book Etude du comportement la corrosion des armatures tendues dans le b ton contamin par des ions chlorure written by Hela Ben Mansour and published by . This book was released on 2018 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: La corrosion dans le béton précontraint est considérée parmi les pathologies les plus dangereuses dans le secteur du génie civil. En effet ce phénomène se caractérise par la gravité de ses conséquences économiques et sécuritaires. L'objectif de ce travail consiste à évaluer l'efficacité d'un inhibiteur à base de phosphates Na3PO4.12H2O contre la corrosion des aciers de précontrainte. L'étude a été d'abord menée en milieu synthétique simulant le béton chloruré sur des armatures tendues à 80% Rm, puis d'une part sur des éprouvettes en mortier précontraint conçues à l'échelle laboratoire, et d'autre part en utilisant la technique de cellule de diffusion pour tester l'efficacité de l'inhibiteur à long terme. Les résultats issus de l'étude réalisée dans le milieu simulant ont révélé que la présence des phosphates entraine l'augmentation du seuil critique d'amorçage de corrosion localisée R=[Cl-]/[OH-] jusqu'à la valeur de 5 au lieu de 0,4. Ceci semble être dû à deux actions inhibitrices des phosphates à savoir : la stabilisation de la couche protectrice à base d'oxyde de fer et la formation de composés phosphatés très peu solubles qui bloquent les sites anodiques actifs, augmentant ainsi la résistance de l'acier à la corrosion localisée. L'emploi de Na3PO4.12H2O en tant qu'adjuvant diminue légèrement la résistance à la compression du mortier. Cependant les composés phosphatés provenant de la réaction de l'inhibiteur avec les hydrates de ciment colmatent les pores du mortier et freinent la diffusion des chlorures. Ceci améliore le comportement à la corrosion des armatures enrobées de mortier précontraint. Enfin, lorsque le triphosphate de sodium est utilisé comme inhibiteur migrateur ou comme moyen de prétraitement des armatures, la technique de la cellule de diffusion a montré son efficacité à long terme, grâce à l'augmentation de la période précédant l'amorçage d'une corrosion localisée, où l'armature est en état passif.
Download or read book valuation de l efficacit de traitements pour la pr vention ou la mitigation de la corrosion de l acier d armature dans les l ments en b ton arm written by Nicolas Rouleau and published by . This book was released on 2013 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Corrosion Inhibitors for Steel in Concrete written by Bernhard Elsener and published by CRC Press. This book was released on 2001 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt: The use of inhibitors for rehabilitation of reinforced concrete structures is a new field of application and this new volume provides a State of the Art Report on this subject. Corrosion of steel in concrete is one of the major problems for infrastructure such as bridges, tunnels, housing etc. since it leads to spalling of the concrete and loss in cross section of the steel that may cause structural and safety problems. The steel in concrete generally resists corrosion as a result of a passive layer that develops on the metal surface in the alkaline environment of the concrete. Corrosion can occur if these conditions are disturbed, for example, in the presence of chlorides or with carbonation of concrete. Traditional repair methods consist in removing the deteriorated concrete and replacing it but these can be laborious, noisy and very costly. To avoid these disadvantages new methods have been developed in recent years. These include electrochemical procedures and, increasingly, the use of inhibitors. The use of inhibitors for rehabilitation of reinforced concrete structures is a new field of application and this new volume provides a State of the Art Report on this subject.The report, under the editorship of Prof. Bernhard Elsener, was prepared by a Task Group of the EFC Working Party on Corrosion of Reinforcement in Concrete. In a literature review it describes inorganic and organic chemicals that have been proposed and examined as well as the commercial corrosion inhibitors that are available on the market. Protection mechanism and possible effects of inhibitors on concrete properties are described. Practical experience with inhibitors for steel in concrete and the long term effectiveness are considered. The various test methods for evaluating the behaviour of the inhibitors are described and critically assessed. In a rapidly evolving field this State of the Art Report, based mainly on independent not commercial literature, will be of value to corrosion engineers and civil engineers concerned with maintenance and repair of reinforced concrete structures.
Download or read book Contemporary Topics about Phosphorus in Biology and Materials written by David Churchill and published by BoD – Books on Demand. This book was released on 2020-09-09 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book addresses a diverse set of topics regarding phosphorus chemistry, namely phosphates and closely related chemical systems. Divided into two sections, chapters cover such topics as phosphate dynamics and phosphates in biomaterials. This volume is a useful reference for scholars and researchers and will inspire readers to make future discoveries in the field.
Download or read book Flame Retardant and Thermally Insulating Polymers written by Yanfei Xu and published by BoD – Books on Demand. This book was released on 2021-09-08 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polymers have infiltrated almost every aspect of modern technology, as they have wide applications ranging from building insulation and firefighter uniforms to the Boeing 787 Dreamliner aircraft and electronics packaging. However, common polymers are flammable. Inflammability and thermal insulation properties in polymers are important for specific applications. This book discusses recent advances in developing eco-friendly, flame-retardant, and thermally insulative polymer-based materials. It not only focuses on developments of high-performance flame retardants, but also examines flame retardant behaviors in polymers. Eco-friendly polymers with superior flame retardancy, extraordinary thermal insulation, and excellent mechanical strength will provide new opportunities for existing and future applications.
Download or read book Advances in Geopolymer Zeolite Composites written by Petrica Vizureanu and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Geopolymers and zeolites as eco-friendly materials can participate in cutting-edge research and applications due to their tailored properties, including superabsorbent capacity, heavy metals encapsulation, flame retardancy, mechanical performance, electrokinetic behaviour, corrosion resistance, and thermal properties. This book joins activities and knowledge of researchers from multiple fields to present a comprehensive overview of the advances in synthesis and characterization of geopolymers and zeolites, including base chemistry concepts, nanoscale characterization, and applications in top-level industry.
Download or read book Piezoelectric Actuators written by Hu Huang and published by BoD – Books on Demand. This book was released on 2021-12-08 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt: Taking advantage of high resolution, rapid response, and compact structure, piezoelectric actuators are widely employed for achieving precision positioning in both scientific research and industrial application. With the development of science and technology, the requirements for precision positioning are increasing. Accordingly, great efforts have been made to improve the performances of piezoelectric actuators, and significant progress has been achieved. This book discusses some recent achievements and developments of piezoelectric actuators, in terms of piezoelectric material, driving principle, structural design, modeling, and control, as well as applications.
Download or read book Botany written by Bimal Kumar Ghimire and published by BoD – Books on Demand. This book was released on 2021-11-24 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book integrates knowledge of plant biotechnology, plant physiology, and the environment. It presents new information about soil organic carbon sequestration using plant species (tropical grasses) that have potential in climate change mitigation. It also presents scientific knowledge on the multipurpose role of microRNA (miRNA), focusing mainly on stress tolerance in crop plants. Chapters discuss uses, methods, and advantages of recombinant DNA technology and novel plant biotechnology applications for plant-based vaccines. This volume brings together knowledge about non-edible plants seeds as potential sources of biodiesel production to mitigate the global energy crisis.
