Frequently Asked Questions
- Epoxy-Coated Steel Reinforcing Bar protects even in cracked concrete.
- Life-cycle analysis shows that Epoxy-Coated Steel Reinforcing Bar provides the lowest cost.
- Unlike corrosion protection systems used within the concrete mixture, Epoxy-Coated Steel Reinforcing Bar is readily identified at the job site.
- Continuous reinforced concrete pavement
- Parking garages
- Piers and docks
- Water towers
- Columns and parapets
- Fabrication and handling of Epoxy-Coated Steel Reinforcing Bar is covered in ASTM D3963 Standard Specification for Fabrication and Jobsite Handling of Epoxy-Coated Steel Reinforcing Bars.
- Job site handling is also covered in the Appendix of ASTM A775.
- Purchase from a CRSI certified manufacturer.
- Consider use of a CRSI certified fabricator.
- Use the Epoxy-Coated Steel Reinforcing Bar in both top and bottom mats of decks.
- Minimize damage during transport, handling and placement.
- Repair damage using two-part epoxy coating, approved by bar supplier.
- Use plastic headed concrete vibrators during concrete placement.
- Maintain concrete cover.
- The bar is then heated to approximately 450° F and passed through a powder spray booth where electrically charged epoxy particles are attracted to the steel.
- The coating then undergoes a cross-linking process to form a uniform barrier over the steel.
- Epoxy-Coated Steel Reinforcing Bar can also be recycled after use.
- Epoxy-Coated Steel Reinforcing Bar produces no VOCs during manufacture or use.
- Structures that use Epoxy-Coated Steel Reinforcing Bar are more durable that those that do not.
- In 1998, the cost of three bridges containing Epoxy-Coated Steel Reinforcing Bar were considered and the increase in cost was between 0.49 percent and 2.16 percent of the total structure compared with structures that used uncoated bars.
- Backside contamination was reduced from 40 or 50 percent to 15 percent.
- Chloride contamination is measured and reduced.
- Epoxy-Coated Steel Reinforcing Bar is readily available from certified plants, while galvanized rebar is not.
- Epoxy-Coated Steel Reinforcing Bar has outperformed galvanizing in almost every laboratory corrosion test of Epoxy-Coated Steel Reinforcing Bar.
- Galvanized coating quality depends on the steel quality, while Epoxy-Coated Steel Reinforcing BarL does not.
- Galvanizing may result in brittle bars that break during bending.
- Epoxy-Coated Steel Reinforcing Bar does not have these embrittlement issues.
- Additional funding often is not available for these products.
- Stainless-steel bars use materials from hard-rock mining operations, while Epoxy-Coated Steel Reinforcing Bar uses scrap steel.
- Not all stainless steels have demonstrated good corrosion performance in concrete as it depends on the grade of stainless.
- Care must be taken to ensure that stainless-steel bars are not contaminated with black bar.
- Epoxy-Coated Steel Reinforcing Bar has outperformed ASTM A1035 (MMFX) in almost every lab test.
- Some laboratory tests indicated that the performance of ASTM A1035 (MMFX) is highly dependent on surface preparation, such as pickling, prior to placement in concrete.
- ASTM A1035 is only available from a single source and in limited supply.
- ASTM A775/A775M (Coating Application and Powder Qualification).
- ASTM D3963 (Fabrication and Field Requirements, Repair Material Qualification).
- Make sure that proper specifications are included for all stages of the project: coating application, fabrication, field handling, and material pre-qualification.
A: Two specifications are available for epoxy-coated reinforcing steel, ASTM A775 and ASTM A934. Reinforcing steel bars meeting ASTM A775/A775M Standard Specification for Epoxy-Coated Steel Reinforcing Bars are coated in a straight condition and then bent, whereas ASTM A934/A934M Standard Specification for Epoxy-Coated Prefabricated Steel Reinforcing Bars covers bars that are bent prior to coating.
In the early 1990s it was believed that bending of the coated bars would reduce the corrosion performance of coated bars. At that time, ASTM A775 required bars to pass a flexibility test that only bent the bars 120 degrees. Coatings would often crack or debond from the steel surface when bent to 180 degrees, reducing their corrosion performance. More recent ASTM A775 specifications require that the bars pass a 180 degree flexibility test. This improved specification has been met through improved surface preparation of the steel prior to coating and use of more flexible coatings.
According to the 2007 specifications, Coatings meeting A775 and A934 are required to pass an abrasion test meeting ASTM D4060. In this test, they are required to exhibit less than 100 mg of weight loss during 1000 cycles. Both standards also require coatings to be tested for impact according to ASTM G14 using a 4-lb tup. ASTM A775 requires coatings to pass an impact requirement of 80 in-lbf without shattering, cracking or bond loss, whereas ASTM A934 requires an impact of only 40 in-lbf. Thus, the general belief that coatings meeting ASTM A934 are tougher is not supported by the relevant ASTM specifications.
Side-by-side corrosion tests were conducted by McDonald et al. as part of a 5-year FHWA research program. These studies found no significant difference in the performance of either the flexible or non-flexible coatings.
For all coated bars, it is important that coated product be inspected after fabrication and prior to placement into the concrete to ensure that any damage is repaired. Further details on fabrication of epoxy-coated bars are presented in Appendix X1 of ASTM A775 and ASTM D3963.
In environments subjected to marine or deicing salts, corrosion initiates when sufficient chloride ions reach the reinforcing steel. The time for these salts to reach the bars is dependent on the concrete permeability and the amount of cracking in the concrete as well as the exposure conditions.
The permeability of concrete depends on the water-cement ratio as well as the presence of pozzolans including fly ash and silica fume or various concrete additives that impart water resistance. When uncoated reinforcing is placed in cracked concrete, corrosion initiates almost immediately the concrete is placed in contact with the salt solution; thus, the presence of cracks will significantly reduce the repair -free life of a structure. Epoxy-coated bars have been found to perform well in cracked concrete compared with the use of concrete modifications alone.
To optimize the design life of structures that use epoxy-coated bars it is recommended that high quality concrete is used with appropriate cover over the reinforcing and that cracks in the concrete are repaired.
Section 8.2.2 of ASTM A 884 requires the mesh to contain less than 1 holiday per foot. During evaluation of holidays, voids at the weld intersections are not be counted. Section 13.1 requires that all visible damaged coating be repaired with patching material. Based upon review of sections 8.2.2 and 13.1 as voids are not a result of damage, but occur as a normal part of the manufacturing process. Thus, voids do not require repair.
Once bars are stored outside, in humid or wet environments, corrosion may initiate at the void locations and red rust staining may occasionally be observed. It is important to determine the source of the corrosion staining. If they are occurring at void intersections, then repair is not required according to ASTM A884.
While the specifier may decide that repair of these intersections is important, this repair is over and above that required by the ASTM specifications and additional costs may be incurred by the owner. If repair is to be conducted it should be made using a two-part epoxy material, compatible with the coating and the concrete.
When sufficient chloride reaches the level of the reinforcing steel in concrete, corrosion of the steel occurs. The location that has the highest corrosion rate is generally the location with optimum levels of chloride and moisture. At this anode location, the steel releases electrons that are then consumed at the cathode, which may be in areas of the structure that can be substantially further away from the damage.
During a typical concrete repair, it is common only to remove the damaged concrete, where the steel corrosion has resulted in expansion that sufficiently damages the concrete. Unless precautions are taken as part of the repair process, corrosion damage in immediately surrounding areas may rapidly occur. This “ring anode” effect occurs as the area after the repair becomes the new anode, and the repaired area may become a strong cathode. At the cathode, electrons react with water and oxygen.
Due to the dielectric (non-conducting) coating on epoxy-coated bars, it is difficult for these bars to become cathodes. Thus, replacing exposed bars in the repair area with epoxy-coated bars substantially reduces the cathode and thus dramatically reduces the ring anode effect, leading to significantly enhanced repair life. Where bars are too short to be replaced or where areas of exposed uncoated reinforcing bars are present, it is recommended that they be coated with a repair material specifically designed to reduce the cathodic effect.