Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Green Plant Extract as a passivationpromoting Inhibitor for Reinforced Concrete  [PDF]
Abdulrahman A. S.,Mohammad Ismail
International Journal of Engineering Science and Technology , 2011,
Abstract: The present corrosion inhibitors in market for the protection of steel reinforcement in concrete exposed to chloride attack are toxic to the environment and compromises sustainability drives. There is the needs to develop inhibitor that are eco-friendly and sustainable. In this work the ability of hydrophobic green plant extracts inhibitor (Bambusa arundinacea) to repassivates the chloride induced corrosion of steel was studied. Its efficacy and effectiveness was also compared with calcium nitrite inhibitor. Concrete mix was designed to 30MPa with 0.45 W/C ratios and 1.5% weight of cement content of chloride was added to initiate corrosion.Inhibitors additions were 2%. Electrochemical impedance spectroscopy, linear polarization resistance and Field emission spectroscopy (FESEM) were used to monitor corrosion behavior of steel at 180 days exposure period. Corrosion rate of the inhibitors studied showed that Bambusa Arundinacea is superior as compared to calcium nitrite as results of its high concrete resistivity, chloride binding property and polarization resistance. Bambusa Arundinacea may be considered a better substitute for nitrite based corrosion inhibiting admixtures for durable concrete structures due its versatility.
Effect of chemical admixture on corrosion resistance of reinforced steel rods in concrete  [PDF]
R. Manoharan,P. Jayabalan,K. Palanisamy
Journal of Engineering and Applied Sciences , 2009,
Abstract: Water reducing admixture is widely used in concretes with less water-cement ratio, to improve some properties like strength and workability. In addition, this admixture has effect on corrosion resistance of embedded re-bars in concrete. In this work, the corrosion rate of mild steel rod, CTD (Cold Twisted Deformed) rod and TMT (Thermo Mechanically Treated) rod were observed by adding water reducing admixture in M25 concrete mix. By varying the percentage of admixture, the study was carried out for a period of 14 months. The corrosion rates were measured at different intervals by conducting electrochemical tests like ACI test, LPR test, and OCP test and by weight loss test (gravimetric method). In most of the time and cases, the corrosion rate was found to be less for 0.5% of water reducing admixture. Corrosion resistance of TMT rod is better than other rods like mild steel and CTD rods.
Influence of chemical bonding of chlorides with aluminates in cement hidratation process on corrosion steel bars in concrete  [PDF]
Biki? Farzet H.
Hemijska Industrija , 2010, DOI: 10.2298/hemind1001047b
Abstract: The presence of chlorides in concrete is a permanent subject of research because they cause corrosion of steel bars. Chlorides added to the concrete during preparation, as accelerators of the bonding of cement minerals process, enter into reaction with aluminates, creating a phase known as chloroaluminate hydrates. In everyday conditions the product of chemical bonding between chlorides and aluminates is usually monochloridealuminate C3A·CaCl2·Hx, better known as Friedel's salt. In this paper, the influence of chemical bonding of chlorides with aluminates during the process of cement hydration on corrosion of steel bars in concrete was investigated. The process of chlorides bonding with aluminates yielding monochloride aluminate is monitored by XRD analyses. It was found that the amount of chlorides bonding with aluminates increases with an increase of temperature, and as a result, reduces the amount of 'free' chlorides in concrete. Potentiodynamic measurements have shown that increase in temperature of the heat treatment of working electrodes by chlorides leads to a reduction of steel bars corrosion as a result of either the increase of the monochloride-aluminate content or the decrease of free chlorides amount. Chlorides bound in chloroaluminate hydrates do not cause activation of steel bars corrosion in concrete. It was also proven that the increase of free chlorides concentration in the concrete leads to intensification of steel bars corrosion. This additionally approves that free chlorides are only the activators of process of steel bars corrosion in the concrete.
Mix design of steel fiber reinforced concrete
Moreno, E.,Fernández Cánovas, M.
Materiales de Construccion , 1997,
Abstract: Mix design of steel fiber reinforced concrete (SFRC) is concerned with achieving a workability, homogeneity, durability and strength suitable for its use. Variables defining any mix design of SFRC are commented below, as well as their influence on some properties of fresh and hardened SFRC. A special attention is paid to concrete, since it's the main use of steel fibers in Spain now, followed by paving construction. El objetivo de una correcta dosificación de hormigón reforzado con fibras metálicas (HRFA) es conseguir una mezcla que mantenga una docilidad, homogeneidad, durabilidad y resistencia adecuadas a su uso. A continuación se estudian las variables que definen una dosificación de HRFA, así como su influencia en las propiedades del HRFA fresco y endurecido. Se presta una especial atención al hormigón proyectado ya que es la principal aplicación de las fibras metálicas en Espa a, seguido por la construcción de pavimentos.
Passivating action of an organic inhibitor on the steel of reinforced concrete  [cached]
Anzola, E.,Malavé, R.,Barrios, V.,Villarroel, D.
Revista de Metalurgia , 2003,
Abstract: An electrochemical evaluation has been made on a concrete mix with an organic inhibitor added, in order to establish its contribution to the formation of a protective film on the steel surface. Concrete cylinders (6" x 3"), each with a 3/8" steel bar and two graphite electrodes embedded, with two water/cement ratios (0.40 and 0.55) were used as testing samples. Reinforced steel bars, both chemically cleaned and in the as rolled condition, embedded in salted and unsalted concrete mixes, were used to test if chemical adsorption occurs in each condition. Samples were soaked into brine solution during 365 days as to simulate a sea environment. During exposure period readings of potential, corrosion rate and potentiodynamical cyclic curves were made. It can be concluded that the organic inhibitor needs a low water/cement ratio mix (0.40) in order to react via a chemical adsorption on the steel, being more effective on cleaned surfaces. El objetivo del trabajo es hacer una evaluación electroquímica para inferir sobre la formación de la película pasivante en la superficie del acero, por parte de un inhibidor orgánico adicionado a la mezcla de concreto. Para esto se elaboraron probetas de concreto armado de 3 x 6 pulgadas con acero de refuerzo de 3/8 pulgadas de diámetro y dos electrodos de grafito en su interior, usando mezclas de relación agua/cemento 0,40 y 0,55; con y sin sal. Se utilizó acero limpiado por medios químicos y también en condiciones normales de uso. Las probetas se colocaron en agua salada durante 365 d, realizándoseles mediciones de potencial, velocidad de corrosión y curvas cíclicas potenciodinámicas. Se puede decir que el inhibidor actúa solo para relaciones agua/cemento de 0,40, observándose mejores resultados en las probetas con acero limpiado, indicando que el estado superficial del acero influye en la reacción de quimiadsorción del inhibidor.
Corrosion of Steels in Steel Reinforced Concrete in Cassava Juice
G.O. Oluwadare,O. Agbaje
Journal of Applied Sciences , 2007,
Abstract: The corrosion of two types of construction steels, ST60Mn and RST37-2 , in a low cyanide concentration environment (cassava juice) and embedded in concrete had been studied. The ST60 Mn was found to be more corrosion resistant in both ordinary water and the cassava juice environment. The cyanide in cassava juice does not attack the steel but it provides an environment of lower pH around the steel in the concrete which leads to breakdown of the passivating film provided by hydroxyl ions from cement. Other factors such as the curing time of the concrete also affect the corrosion rates of the steel in the concrete. The corrosion rate of the steel directly exposed to cassava juice i.e., steel not embedded in concrete is about twice that in concrete. Long exposure of concrete structure to cassava processing effluent might result in deterioration of such structures. Careful attention should therefore be paid to disposal of cassava processing effluents, especially in a country like Nigeria where such processing is now on the increase.
Corrosion Behaviour and Chloride Attack of Reinforcing Steel in Presence of Concrete Admixtures

材料科学技术学报 , 1998,
Abstract: Corrosion and electrochemical behaviour of reinforcing steel embedded in cement pastes with and without concrete admixtures used in Egypt to modify concrete properties have been studied. The influence of the admixtures on the corrosion resistance of the steel against chloride attack has been studied using impressed current and impressed voltage techniques. The results indicate that the type and concentration of the admixture used have an important effed on the extent of chloride induced corrosion of the steel. The mechanism of corrosion of steel due to chloride attack is discussed.
Studies and research work on the reinforcement steel and concrete surface corrosion protection methods
Gheorghe Croitoru
Urbanism. Arhitectura. Constructii , 2013,
Abstract: Methods for reinforcement steel corrosion protection and concrete surface protection are analyzed. Knowing the corrosion process mechanism reinforcement steel can be protected by different protection methods even in the presence of crevices larger than those anticipated by design. The selection of the corrosion protection method depends on the reduction level of the reinforcement steel corrosion which in its turn is determined by the atmospheric conditions. The selection of the accelerated corrosion test conditions was made revealing the mechanism of the processes that take place at the steel reinforcement surface under natural weathering conditions. Crevices ranging from 0.05mm to 1.00mm or larger were opened by bending reinforced concrete girders on special equipment and were maintained all over the period of the corrosion resistance study.
AFM study of steel corrosion in aqueous solutions in concrete
Díaz-Benito, B.,Velasco, F.,Guzmán, S.,Calabrés, R.
Materiales de Construccion , 2011,
Abstract: Early corrosion stages are studied in carbon steel by means of a solution simulating that contained in concrete pores. Non-carbonated solution contains 5% NaCl. The atomic force microscopy (AFM) technique is used to study material performance after different immersion times (up to 48 h). Obtained data are compared to electrochemical ones (corrosion potential and polarization resistance). Analysis of images and roughness evolution along time shows that steel initially tends to reach passivity, although the passive layer rapidly loses its protective character due to chloride attack. Este trabajo estudia los primeros estados de la corrosión de un acero al carbono en una disolución que simula la existente en los poros del hormigón, sin carbonatar, con un 5% de NaCl. Para ello, se ha empleado la técnica de microscopía de fuerza atómica (AFM), estudiando el comportamiento del material tras diferentes tiempos de inmersión, hasta 48 h, en la disolución. Estos datos se comparan con datos electroquímicos (potencial de corrosión y resistencia de polarización). El análisis de las imágenes y la evolución de la rugosidad con el tiempo muestran que el acero tiende inicialmente a pasivarse, pero la capa pasiva pierde rápidamente su carácter protector debido al ataque de los cloruros.
A Novel Optical Fiber Sensor for Steel Corrosion in Concrete Structures  [PDF]
Christopher K.Y. Leung,Kai Tai Wan,Liquan Chen
Sensors , 2008, DOI: 10.3390/s8031960
Abstract: Steel corrosion resulting from the penetration of chloride ions or carbon dioxide is a major cause of degradation for reinforced concrete structures,. The objective of the present investigation was to develop a low-cost sensor for steel corrosion, which is based on a very simple physical principle. The flat end of a cut optical fiber is coated with an iron thin film using the ion sputtering technique. Light is then sent into a fiber embedded in concrete and the reflected signal is monitored. Initially, most of the light is reflected by the iron layer. When corrosion occurs to remove the iron layer, a significant portion of the light power will leave the fiber at its exposed end, and the reflected power is greatly reduced. Monitoring of the reflected signal is hence an effective way to assess if the concrete environment at the location of the fiber tip may induce steel corrosion or not. In this paper, first the principle of the corrosion sensor and its fabrication are described. The sensing principle is then verified by experimental results. Sensor packaging for practical installation will be presented and the performance of the packaged sensors is assessed by additional experiments.
Page 1 /100
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.