Reinforcement epoxy coated

Xiaojun Wang, Chung DDL, Short carbon fiber reinforced epoxy coating as a piezoresistive strain sensor for cement mortar. Sensors and Actuators, A71(3), 208-212, 1998. 

Treadaway, K. W. J., Davies, H. and Brown B. L., Performance of fusion bonded epoxy coated steel reinforcement. Proceedings of the Institute of Structural Engineers (in press)... 

The MDB is a two-story, steel-framed building with thick, reinforced-concrete floors and most interior walls made of concrete and foam-core sandwich panels. Explosion containment rooms have 2-foot-thick reinforced concrete floors, walls, and ceilings. Because concrete is a porous material capable of absorbing agent, all concrete surfaces in the JACADS process areas were sealed with an epoxy coating. A total of 134,153 square feet of concrete will require decontamination (U.S. Army, 1999d). 

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. 

The use of epoxidized hyperbranched polyesters as toughening additives in carbon-fiber reinforced epoxy composites has been demonstrated (Boogh et al., 1995). Since a hyperbranched resin has a substantially lower viscosity and much shorter drying time than a conventional (less branched) resin of comparable molecular weight, hyperbranched polymers have been used as the base for various coating resins (Pettersen and Sorensen, 1994). 

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. 

Very high corrosion rates in the vicinity of defects in the coating can occur in the presence of macrocells. A typical situation is that of stractures in which epoxy-coated reinforcement in contact with chloride-contaminated concrete is coupled to non-coated reinforcement embedded in concrete that is uncontaminated or contains a level of chlorides below the critical level. In this case, the passive non-coated... 

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. 

S. R. Yeomans, M. P. Novak, "Further studies of the comparative properties and behaviour of galvanized and epoxy coated steel reinforcement , International Lead Zinc Research Organization (ILZRO) project ZE-341, Progress report... 

K. C. Clear, Effectiveness of epoxy-coated reinforcing steel , Concrete International, 1992, 5, 58—62. 

The data from the Concrete Reinforcing Steel Institute (CRSI) shows that more than 3.6 billion kg (4 million tons) of epoxy-coated rebar (150 million m reinforced concrete) were used as of 1998. A significant amount of the epoxy-coated rebar was used in bridge decks. Over time, the formulation of epoxy has been modified to achieve better performance of the epoxy coating. 

Epoxy coatings cost approximately 4.7-5.3/l while antifoulants are more expensive at 11.8-21.1/1. Environmental regulations have led to decreased amount of chemicals released from industrial installations along waterways, especially corrosives such as chlorine. The materials of construction for some water structures have also changed. Piers and docks are no longer constructed with wood, but instead are constructed with steel-reinforced concrete. To improve the lifespan of the structure and prevent corrosion of reinforcing steel, fusion-bonded epoxy-coated reinforcement or corrosion-inhibiting admixtures are sometimes utilized in the concrete mix. 

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... 

Prime coating is either a two-pack, zinc-rich epoxy primer with a DFT of ca. 30-40 pm, or a chromate-free, two-pack epoxy primer. Topcoats based on PVC copolymerisates, chlorinated rubber, silicone-reinforced epoxy esters, or alkyds were used for many years. Now, the standard European topcoat is based on acrylic resins with terminal epoxy groups that are cross-linked with amine adducts or aminoamide resins. 

A.M. Zayed, A.A. Sagues, Corrosion at surface damage on an epoxy-coated reinforcing steel, Corros. Sci. 30 (1990) 1025-1044. 

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