Epoxy-Coated Reinforcing Bars

Virmani, Y.P., Clear, K.C. and Pasko, T.J. (1983). Time to Corrosion of Reinforced Steel in Concrete Slabs, Vol. 5, Calcium Nitrite Admixtures or Epoxy Coated Reinforced Bars as Corrosion Protective Systems, FHWA-RD-83-012, FHWA, US Department of Transportation, 71. 

Corrosion Evaluation of Epoxy-coated Metallic-clad and Solid Metallic Reinforcing Bars in Concrete, US Department of Transportation, Federal Highway Administration, Publication FHWA-RD-98-153, December 1998. 

Coated reinforcement MacroceU formation may be important in the case of epoxy-coated rebars (Section 15.4) in chloride-contaminated concrete if there are defects in the coating and the coated bars are electricaUy connected with uncoated passive steel bars in deeper parts of the structure. Small anodic areas are created at the defect points of coated rebars in contact with chloride-contaminated concrete, while the uncoated passive rebars provide a cathodic surface of much greater size. In these situations the macroceU can result in considerable anodic current densities and can significantly accelerate the attack on corroding sites. This is why coated rebars should be electrically isolated from uncoated bars. 

The cost of various techniques can only be given very roughly, and any estimate will be incomplete, since the actual cost will vary from one application to another. Furthermore, different types of prevention mechanisms are not directly comparable. Beyond this, it can be said that with respect to normal carbon-steel reinforcement, use of galvanized and epoxy-coated bars costs about twice as much, and the cost of stainless-steel reinforcement is about 5 to 10 times higher. The use of nitrite inhibitors in higher doses costs approximately 30 /m of concrete (volume). Coatings may vary from 7 to 50 /m of concrete surface, hydrophobic treatment costs about 10 /m. Cathodic prevention varies from 50 to 100 /m. ... 

Epoxy coating of reinforcing bars is a protective technique developed in the 1970s in North America. Laboratory results confirmed the effectiveness of the epoxy-coated bars, in many cases, in preventing corrosion of reinforcement in carbonated or chloride-contaminated concrete [46]. Recently, however, doubts have arisen about their long-term durability in very aggressive environments, doubts borne out above all by negative experience reported on structures in tropical environments [47-49]. 

Requirements for epoxy-coated reinforcing bars are reported in different international standards and recommendations the first dates back to 1981 (ASTM A775-81) and more recent national standards in European countries are based on it, even though their requirements are much more rigorous. 

It is, furthermore, important to pay attention to those cases in which, for economical reasons, coated steel is used only in the most critical areas of the stracture. In these cases it is important to ensure that epoxy-coated bars are electrically insulated from the uncoated reinforcement, in order to avoid macrocells. 

Some of the reinforcing steel bar alloys are cold-worked steel epoxy-coated steel 30400 stainless steel 30453 stainless 31600 stainless 31653 stainless Duplex S31803. Table 5.9 shows the corrosion resistance of some steels. 

Lempton, R. D. Jr., and Schemberger, D. 1996. Improving the Performance of Fusion-Bonded Epoxy Coated Steel Reinforcing Bars, CORROSION 96, Paper No. 323, NACE International, Conferences... 

There are particular problems when the reinforcing steel is not of the conventional type of steel bars embedded directly into the concrete. There are problems for galvanized steel bars with respect to reference electrode and corrosion rate measurement because the zinc affects the readings in poorly understood ways. However, when the bar is coated in epoxy or the reinforcement is in the form of wires in ducts the problems are multiplied as described later. 

Since the maximum voltage that can be generated with zinc anodes is extremely unlikely to generate hydrogen embritdement, galvanic systems have been used to protect prestressed concrete members. They are also used on fusion bonded epoxy coated steel reinforced piles as the effects of electrical discontinuity between bars is unlikely to lead to significant stray current induced corrosion as the currents and potentials are low. 

Epoxy coatings are applied to reinforcing steel in a factory process. The bar is grit blasted clean, it may then be pretreated and it is then heated in an... 

ASTM A775-81. Standard Specification for Epoxy-coated Steel Reinforcing Bars, American Society for Testing Materials. 

Concrete should not be relied upon as an electrical insulator. Reinforcing bars should be coated with, for example, epoxy resin. They should not be connected to building steel and should not be allowed to form a continuous path along the length or the width of the building. The joints between sections of precast reinforced concrete should be insulated. 

Walkways are fabricated with FRP grating. All concrete surfaces in the cell room are constructed with fusion-bonded epoxy coated steel reinforcing bars, and Type V... 

Epoxy coatings are applied to reinforcing steel in a factory process. The bar is grit blasted clean it may then be pretreated and it is then heated in an induction furnace and passed into a coating unit that sprays a fine epoxy powder at the bar The powder fuses onto the hot bar, is cured and quenched before passing out of the process (Figure 9.2a). 

Rebars are polymer fibre reinforced-concrete composites, and they are used as primary structures. It is estimated that replacement of steel reinforcing bars by non-corrosive polymer fibres, i.e., by Kevlar or carbon fibres (which gives rise to Kevlar or C-composite bars) for concrete structures produces structures with one-quarter the weight and twice the tensile strength of the steel bar. It is known that, corrosion of steel reinforcement from carbonation or chloride attack can lead to loss of the structural integrity of concrete structures, and such a danger is non-existent for rebars. Thermal expansion coefficient (TEC) values of these fibres are closer to concrete than that of steel, which provides an another advantage and they have the same surface deformation patterns as the steel bars. In addition, they can provide more economy than epoxy-coated steel bars. 

Epoxy coated carbon steel reinforcing bars... 

Fusion-Bonded Epoxy Coating of Steel Reinforcing Bars... 

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