Frequently Asked Questions (FAQs)

About

Yes! According to the CRSI Manual of Standard Practice reinforcing steel should be welded according to the American Welding Society, AWS D1.4/D1.4M. If the steel used for the coated bars meets ASTM A706, the bars are intended for welding without preheating and therefore should be specified for applications that require an appreciable amount of welding. ASTM A615 reinforcing bars can be welded, but may require preheating the bars up to 500° F. After completion of the welding on epoxy-coated bars, the damaged areas shall be repaired using patch materials meeting ASTM A7.

Epoxy-Coated Steel Reinforcing Bars was first used in 1973 on the Schuykill Bridge near Philadelphia, Pennsylvania.

In 2008, more than 60,000 bridges with Epoxy-Coated Steel Reinforcing Bars were listed in the National Bridge Inventory.

Structures built with Epoxy-Coated Steel Reinforcing Bars have longer lives than structures built with black steel.

  • Epoxy-Coated Steel Reinforcing Bars protect even in cracked concrete.
  • Life-cycle analysis shows that Epoxy-Coated Steel Reinforcing Bars provide the lowest cost.
  • Unlike corrosion protection systems used within the concrete mixture, Epoxy-Coated Steel Reinforcing Bars are readily identified at the job site.

  • Continuous reinforced concrete pavement
  • Parking garages
  • Piers and docks
  • Water towers
  • Columns and parapets
  • Dowels
  • Repair

Epoxy-Coated Steel Reinforcing Bars are produced and inventoried nationwide. Currently, 37 plants are certified under the CRSI Fusion-Bonded Epoxy Coating Applicator Plant Certification Program. For the most current CRSI certified Epoxy-Coated Steel Reinforcing Bar Manufacturers please see www.crsi.org under the Certification tab.

Specification

Epoxy-Coated Steel Reinforcing Bars are covered in ASTM A775 and A934 Standard Specifications for Epoxy-Coated Steel Reinforcing Bars.

  • Fabrication and handling of Epoxy-Coated Steel Reinforcing Bars are 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.

Follow design requirements for Epoxy-Coated Steel Reinforcing Bars, as outlined in ACI 318.

  • Purchase from a CRSI certified manufacturer.
  • Consider use of a CRSI certified fabricator.
  • Use the Epoxy-Coated Steel Reinforcing Bars 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.

The development length for Epoxy-Coated Steel Reinforcing Bars is longer.

  • Maintain concrete cover.

Yes. Epoxy-Coated Steel Reinforcing Bars are manufactured using reinforcing bars that are made using almost 100% recycled steel.

  • Epoxy-Coated Steel Reinforcing Bars can also be recycled after use.
  • Epoxy-Coated Steel Reinforcing Bars produce no VOCs during manufacture or use.
  • Structures that use Epoxy-Coated Steel Reinforcing Bars are more durable that those that do not.

Generally, Epoxy-Coated Steel Reinforcing Bars will cost 25 percent to 50 percent more than uncoated bars. However, that increase represents a minute incremental addition to the bridges total cost.

  • In 1998, the cost of three bridges containing Epoxy-Coated Steel Reinforcing Bars 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.

1991

Process

Epoxy thickness variability Epoxy-Coated Steel Reinforcing Bars eased by 23 percent.

  • Backside contamination was reduced from 40 or 50 percent to 15 percent.
  • Chloride contamination is measured and reduced.

According to the National Bridge Inventory, Epoxy-Coated Steel Reinforcing Bars have been used in more than 60,000 decks while galvanized has been used in only 950.

  • Epoxy-Coated Steel Reinforcing Bars are readily available from certified plants, while galvanized rebar is not.
  • Epoxy-Coated Steel Reinforcing Bars have outperformed galvanizing in almost every laboratory corrosion test of Epoxy-Coated Steel Reinforcing Bars.
  • Galvanized coating quality depends on the steel quality, while Epoxy-Coated Steel Reinforcing Bars do not.
  • Galvanizing may result in brittle bars that break during bending.
  • Epoxy-Coated Steel Reinforcing Bars do not have these embrittlement issues.

Stainless-steel bars cost up to five times as much as black bars and may increase the total structural cost by 10 percent or more.

  • Additional funding often is not available for these products.
  • Stainless-steel bars use materials from hard-rock mining operations, while Epoxy-Coated Steel Reinforcing Bars use 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 Bars have demonstrated long-term field performance.

  • Epoxy-Coated Steel Reinforcing Bars have 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.

FRP bars require extensive redesign due to differences in stress/strain values for these bars.

The following ASTM specifications are to be used when specifying Epoxy-Coated Steel Reinforcing Bars.

  • ASTM A775/A775M (Coating Application and Powder Qualification).
  • ASTM A 934/A934M.
  • 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.

Application

In Section 6 of ASTM D3963 “Standard Specification for Fabrication and Jobsite Handling of Epoxy-Coated Reinforcing Steel Bars” it is required that: “Placed coated bars shall be covered with opaque polyethylene or similar protective material if cumulative environmental exposure of the coated bars, including previously uncovered storage time, of greater than two months prior to concrete embedment is expected.”   The provision for two-months of exposure was developed from testing conducted by C-SHRP where bars were left exposed and then tested. (See: “http://www.cshrp.org/products/outdoor.pdf“) It is known that extended exposure is often unforeseen and that bars may be exposed for longer periods than that suggested by ASTM D3963. Fusion-bonded epoxy coatings may undergo surface discoloration and chalking from exposure. The Epoxy Interest Group of CRSI cannot endorse the use of products in non-specified manners; however, should extended exposures occur, it is strongly recommended that the bars be carefully inspected and any site of damage or localized corrosion be repaired following Section 7 of ASTM D3963 using a 2-part epoxy, recommended for use on epoxy-coated steel reinforcing.

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[1]. 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.

Answering this question requires an understanding of the concrete, the coating and the localized environment; however, epoxy-coated bars are routinely specified for structures with a desired 75 year design life and often for structures with a 100-year design life, given an appropriate concrete.

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.

Mesh is coated according to ASTM A 884 Standard Specification for Epoxy-Coated Steel Wire and Welded Wire Reinforcement. During the manufacturing process, sharp edges and undercutting, such as found at the welded intersections of welded wire reinforcement, present areas that make coating more difficult, resulting in minor coating voids at these locations.

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.

Repair materials for epoxy-coated bars are required to meet either ASTM A775, A934 or D3963. All three of these ASTM standards require use of a 2-part epoxy coating material. Materials from spray cans cannot meet these standards and thus should not be used for repair of epoxy-coated bars.

A study was recently conducted by the University of Kansas for the FHWA and Kansas DOT that compared the life-cycle costs of epoxy-coated reinforcing steel, uncoated and stainless steel reinforcing bars in bridge decks. This study found that the initial costs of stainless steel in bridge decks was $319/yd2, compared with $189 and $196/yd2 for decks containing uncoated and epoxy-coated reinforcing steel, respectively. Thus, use of stainless steel was $130/yd2 greater than that of the deck containing epoxy-coated bar. Life cycle costs for the epoxy-coated reinforcing steel was the lowest at $237/yd2 compared with $319 and $444 /yd2 for decks containing uncoated and stainless steel reinforcing bars. Thus, the epoxy-coated bars were $82/yd2 less than that of the stainless steel reinforcing over a 75-year design life.

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.

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