Stainless Steel Reinforcement Bars...

Stainless Steel Reinforcement Bars  Premature deterioration of reinforced concrete structures is a serious problem worldwide due to corrosion of the embedded steel. The affected reinforced concrete structures are mainly those which are situated in an aggressive marine environment, and road bridges to which de-icing salts are applied during winter periods. Corrosion of the steel is initiated when the chloride ion from the salt (sodium chloride) permeates through the concrete to the level of the reinforcement steel which is attacked on contact. The solution, now favoured by highways authorities in Europe and North America, is to use stainless steel for rebars that has proven to be highly resistant to chloride ion. Stainless steel reinforcement bars or simply called stainless steel rebars are more expensive than carbon steel rebars. They do not corrode for the design life of the structure which is normally taken as 125 years in the case of highway bridges. The reductions on ongoing repair and maintenance costs that are usually incurred in case of carbon steel rebars are significant. Environmentally, the reduced downtime for maintenance and repair impacts upon traffic flow and disruption thus making the use of stainless steel rebars highly attractive. Only a small percentage of the steel rebars needs to be stainless steel to achieve a significant increase in durability. Stainless steel rebars can readily be used with conventional carbon steel rebars in reinforced concrete without causing galvanic effects. Stainless steel rebars are cost effective when used in the elements of the concrete structure at highest risk to corrosion (with carbon steel used for the balance of the reinforcement) or, where repair is difficult and expensive. Further by using stainless steel rebars, the concrete mix can also be simplified as it not necessary to provide passivity to the steel...

Galvanized Steel Reinforcement Bars...

Galvanized Steel Reinforcement Bars  Galvanized steel reinforcement bars (also called galvanized steel rebars) are the normal reinforcement steel bars which are coated with a protective layer of zinc (Zn) metal. Zn coating is usually carried out by hot dip galvanizing process. The Zn coating serves as a barrier to the corrosive environment which the rebars are exposed to when embedded in concrete. In addition to the barrier protection, Zn also provides cathodic protection where Zn corrodes preferentially when in contact with unprotected steel. This means that in case of any gap in Zn coating the surface of bare steel is protected by the surrounding Zn. The reaction between steel and molten Zn produces a coating on the steel made up of a series of iron -zinc alloy layers (gamma, delta and zeta) which grow from the steel-zinc interface with a layer of essentially pure Zn (eta) at the outer surface. What distinguishes galvanizing from other types of coatings is that the coating is metallurgically bonded to the steel. It actually becomes an integral part of the steel, as compared to the paints and epoxy coatings which are simply attached to the steel surface by physical bonding. The alloy layers in the coating are harder than the base steel resulting in a coating that is not only firmly adhered to the steel but is tough and hard and can resist abrasion and fairly heavy handling. It also allows the galvanized rebar to be handled, transported and fabricated in the same manner as ordinary steel. A typical galvanized coating structure is shown in Fig 1.  Fig 1 Galvanized coating structure  The first regular use of galvanized coating was done in USA during 1930s. Since then, and especially during the last 25 -30 years, it is being...

Steel Reinforcement Bars and its Important Characteristics...

Steel Reinforcement Bars and its Important Characteristics Steel reinforcement bar is also known as rebar, reinforcing bar, reinforcing steel and reinforcement steel. It is a versatile constructional material which is widely used in the construction industry for making of the reinforced concrete. Reinforcement concrete (RC) is a composite material made up of concrete and some form of reinforcement – most commonly steel rods, bars, wires or mesh of steel rods and steel wires. The steel reinforcement bars usually consists of such shape and size that they may easily be bent and placed in the concrete so as to form a monolithic structure. The properties of thermal expansion for both steel and concrete are approximately the same. This along with excellent bendability property makes steel the best material as reinforcement in concrete structures. Another reason steel works effectively as reinforcement is that it bonds well with concrete. When passive reinforcement (steel bars) is employed, the structure is known as reinforced concrete structure. In pre-stressed concrete structure, the reinforcement (steel wire) is stressed prior to subjecting the structure to loading, which may be viewed as active reinforcement. Passive steel reinforcing bars, also known as rebars, should necessarily be strong in tension and, at the same time, be ductile enough to be shaped or bent. Steel rebar is most commonly used as a tensioning devise to reinforce concrete to help hold the concrete in a compressed state. Concrete is a material that is very strong in compression, but virtually without strength in tension. To compensate for this imbalance in a concrete slab behavior, reinforcement bar is cast into it to carry the tensile loads. The surface of the reinforcement bar may be patterned to form a better bond with the concrete. Reinforced concrete gets its strength from...

Fusion Bonded Epoxy Coated Reinforcement Bar...

Fusion Bonded Epoxy Coated Reinforcement Bar Fusion bonded epoxy coating, also known as fusion bond epoxy powder coating and commonly referred to as FBE coating, is an epoxy based powder coating that is widely used to protect concrete reinforcement bars from corrosion. FBE coatings are thermoset polymer coatings. The most widely used types include acrylic, vinyl, epoxy, nylon, polyester, and urethane. Most popular for reinforcement bars is epoxy coating. The name fusion bond epoxy is due to resin cross linking and the application method, which is different from a conventional paint. FBE coatings are 100 % solid coatings applied as dry powders and formed into a film by heating. The fusion bonded epoxy coating process for reinforcement bars was developed in United States in 1960s and its use was strongly recommended in coastal areas. Since Its introduction, FBE coating formulations had gone through vast improvements and developments. Today, various types of FBE coatings, which are tailor made to meet various requirements are available. Modern application techniques for applying powders fall into four basic categories. These are (i) fluidized bed process, (ii) electrostatic bed process, (iii) electrostatic spray process, and (iv) plasma spray process. The electrostatic spray process is the most commonly used method of applying powders. In this process, the electrically conductive and grounded object is sprayed with charged, non conducting powder particles. The charged particles are attracted to the substrate and cling to it. The epoxy powder is applied by electrostatic spray on hot steel on preset temperature level. The powder, when in contact with hot bar, melts flows, gels, cures, cools and produces a well adhered continuous corrosion resistant protective coating. The thermosetting of the epoxy is an irreversible process and provides a good protection to reinforcement bars against corrosion. It prevents attack of chloride ion on the metallic surface and the occurrence...