One of the most common methods of combating steel rebar corrosion in precast concrete applications is the use of fusion-bonded, epoxy-coated rebar in construction and repair.
By Phillip Cutler, P.E.
According to the Concrete Reinforcing Steel Institute (CRSI), epoxy-coated reinforcing steel was first used in a bridge application in Pennsylvania in 1973. Why 1973? Well, earlier in our infrastructure history there was less concern about vehicles sliding on icy roads or snow and ice removal during the winter. It wasn’t until the 1950s that deicing chemicals were used to clear bridges and highways, but the result of using these chemicals sent repair costs skyrocketing due to corrosion problems. The country needed a better solution to reduce the problem and, out of many protective-coating options tested, fusion-bonded epoxy coating of rebar was the best fit.1
When precast project specifications call for the use of epoxy-coated rebar, precast concrete manufacturers need to be armed with the appropriate ASTM standards in order to satisfy contract documents and owner demands. The most widely used ASTM standards covering epoxy-coated rebar are ASTM A775, “Standard Specification for Epoxy-Coated Steel Reinforcing Bars” and ASTM A934, “Standard Specification for Epoxy-Coated Prefabricated Steel Reinforcing Bars.” The difference between these two standards is one key word – prefabricated. ASTM A775 covers fusion-bonded epoxy coated bar lengths while ASTM A934 covers fusion-bonded, epoxy-coated bar that is cut and bent into specific required shapes, sizes and lengths such as stirrups and hooks. This occurs prior to cleaning and the powder-coating application.
Manufacturing epoxy-coated rebar
Epoxy-coated rebar is manufactured in CRSI certified plants under strict controls for cleaning, pre-heating, electro-powder coating and curing processes. Bars are cleaned by grit blasting to remove all mill scale and oxidation and then electro-induction heated to around 450 F. The bars and specialty shapes then go through an electrostatic powder-coating process. The heat of the bars and shapes causes the powder to melt on contact, forming the polymer coating. In the final stages of the process, bars are air and/or water cooled prior to removal from the manufacturing line. This cooling process allows the bars to be handled and stacked without damaging the epoxy coating. Danielle Kleinhans, Ph.D., P.E., certification program administrator and structural/transportation engineer at CRSI, said CRSI’s certification program for the application of epoxy coating on reinforcing steel has been in effect since 1991. The program outlines basic requirements for the quality control program to ensure a plant and its employees are trained, equipped and capable of producing epoxy-coated rebar. Today, 38 certified plants are part of the coating certification program, and they have recently established a certification program for fabricators of epoxy-coated reinforcement as well.
“Most epoxy-coated rebar produced in the country is coated by CRSI certified plants, so the chance a precast concrete producer is receiving domestic, non-certified product is slim,” she said. “We view that as a good thing.”
Handling and storage
When handling epoxy-coated rebar, plants must take special care not to damage the coating. Handling requirements are covered by ASTM D3963. Using nylon strapping and multiple lift points along the bar will help to ensure the coating is not marred or damaged by cables or chains and is not allowed to sag and rub during offloading. Epoxy-coated rebar needs to be stored separately from non-epoxy-coated rebar and proper protective measures such as storage on wooden racks or plastic or rubber-coated steel racks avoids the possibility of surface damage. Bars that have damaged coatings need to be repaired using an approved repair material and process prior to being placed in formwork. If stored outside, Epoxy-coated rebar needs to be protected from direct sunlight – ultra-violet light degrades the epoxy coating over time – by tarps and/or covered storage areas. CRSI recommends that bar be exposed to ultra-violet light no longer than 30 days unprotected, Kleinhans said.
Cage fabrication and formwork
When assembling reinforcing cages using epoxy-coated rebar, technicians should exercise care in assembly as to not damage the epoxy coating. Fabrication of cages should be accomplished using appropriate coated tie wire. Cages can be supported in the proper position in the formwork using plastic chairs and stand-offs and/or precast concrete spacer blocks as with conventional black bar applications.
Designers of structures using epoxy-coated rebar usually follow the standard recommended practices of ACI and AASHTO. However, plant personnel should be aware that laps and splices for epoxy-reinforcing steel need to have larger lap and development lengths due to the bond differences between conventional black bar and epoxy-coated bar.
Applications for epoxy-
The use of epoxy-coated rebar is commonplace today for precast concrete applications in bridges and roadways, marine applications, parking structures, concrete repair and structures challenged with corrosion from deicing chemicals, continuous moisture exposure and/or salts. Kleinhans said there are more than 65,000 reinforced concrete bridges with epoxy-coated rebar nationwide.
“Based on survey results, epoxy coating is second only to increased concrete cover as a method to prevent reinforcement corrosion,” she said.
References for precast producers
Precast concrete producers can obtain many valuable references and resource documents from CRSI in regard to the use of epoxy-coated rebar in precast products. The product guide titled, “Specialty & Corrosion-Resistant Steel Reinforcement” is an authoritative and comprehensive reference covering steel bars specified with improved corrosion resistance. The “Manual of Standard Practice” is another great resource for the precast industry, providing detailed information on steel reinforcement.
Phillip Cutler, P.E., is NPCA’s director of quality assurance programs.
1 For additional historical information, visit epoxyinterestgroup.org and crsi.org.
“Specialty & Corrosion-Resistant Steel Reinforcement” CRSI
“Manual of Standard Practice” CRSI
“Epoxy-Coated Reinforcing Steel Bars In Northern America” David McDonald, Managing Director, Epoxy Interest Group of CRSI
ASTM A775, “Standard Specification for Epoxy-Coated Steel Reinforcing Bars”
ASTM A934, “Standard Specification for Epoxy-Coated Prefabricated Steel Reinforcing Bars”
My question is what type of hand tools is required for bending FBE coated rebars at sites.
Lap splice for #4/ 60 grade purple infusion epoxy coated rebar ?
Sara Geer says
Thank you for the comment Tavo. Lap splice lengths depend on the rebar grade, size, spacing and number of bars as well as concrete strength, type of concrete, concrete cover and the type of product. We would recommend reviewing local building codes and product specifications for specifics based on your criteria.
Epoxy-coated rebar is manufactured in CRSI certified plants under strict controls for cleaning, pre-heating, electro-powder coating and curing processes. Bars are cleaned by grit blasting to remove all mill scale and oxidation and then electro-induction heated to around 450 F. The bars and specialty shapes then go through an electrostatic powder-coating process.
When combining 2 rebars together that has epoxy coating, how far back do you remove the coating before performing the weld?
Kirk Stelsel says
Thank you for your question Dan. 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.
As far as removing the coating, there should be enough removed so that there is no epoxy remaining in the path of the weld. This depends on the size of the bar used, and unfortunately CRSI does not offer any measurements or tables on exactly how much epoxy to remove. I talked with Peter Fosnough of the Epoxy Interest Group, who gave me the following rule of thumb for welding epoxy coated rebar:
1. Remove any epoxy in the path of the weld.
2. Preheat the bar if necessary and perform the weld.
3. The heat from the weld will discolor or cause epoxy in the proximity of the weld to debond from the rebar. This epoxy should be removed. Sometimes, epoxy will discolor but remain bonded to the rebar in which case it can stay attached.
4. Apply the appropriate patching materials to the exposed areas of the rebar to ensure a new coat.
Jon Bean says
Can you weld epoxy rebar together?
For example, when fabricating a cage, does it always have to tied?
Sara Geer says
Thank you for the question Jon. According to the Concrete Reinforcing Steel Institute, the answer is yes, you can weld epoxy coated rebar, but you have to be certain of what type of steel is under the epoxy coating first, and the proper precautions must always be taken. From page 10 of the CRSI FAQ sheet, which can be found online, the question and answer below directly answers your question.
“Can I weld epoxy-coated reinforcing steel?”
“According to the CRSI Manual of Standard Practice reinforcing steel should be welded according to the American Welding Society, AWS D1.4/D1.4M Structural Welding Code – Reinforcing Steel. If the steel used for the coated bars meets ASTM A706/A706M, the bars are intended for welding without preheating and therefore should be specified for applications that require an appreciable amount of welding.”
“ASTM A615/A615M 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 Page 11 of 15 areas shall be repaired using patch materials meeting ASTM A775/A775M or A934/A934M.”
Teemu Tuominen says
I guess combining tradition rebars and coated ones would work also… using coated rebars on surface layers and uncoated rebars when they are deep enough in the structure that conrcete will protect them.. makes sense. Too bad I have never seen coated rebars here in Finland, we often switch to stainless steel rebars when in risk areas if we cant get enough concrete cover there. Intresting anyways 🙂
i have question regarding, the starter bar (both column / wall ) must be an epoxy bar if raft bar epoxy.
Sara Geer says
Thank you for the comment Kumar. If you have more information regarding the project or the application for the steel, I can pass that along to our Technical Services engineers for a response. Thank you.
Sam Davis says
Are there any other protecting coatings used besides epoxy?
Sara Geer says
Thank you for the comment, Sam. NPCA Technical Services engineer Alex Morales provided the following response:
“You are wise to ask if there are other coatings. Another option is to use galvanized rebar. Galvanization is the process of applying a zinc coating to the reinforcement which protects the steel from the cement matrix. Epoxy-coating is considered a barrier-type coating and some have said that galvanization is both a barrier and sacrificial coating. Proponents of galvanized bar point to the fact that the zinc coating has to be completely eroded away in order for the steel to be exposed.
Both epoxy-coated and galvanized bar help to protect reinforcing steel from any water intrusion, which can tend to oxidize and corrode steel. Coating of bars is particularly useful in brackish environments and when exposure to salt/chlorides is expected. NPCA does not promote one type over another, but we do expect that our certified plants follow specification and project requirements that specify the use of one or the other.”
Epoxy is a good solution for preventing rust over time. I used it to cover my garage floor and it turned out to be fab. Been around 2 years and my floor still looks good.
I tired the Rust-Oleum 251966.
Keep up with the good work. 🙂
Hello, could you please name some of the supplier in the USA of epoxy rebar?
we’re looking forward to buy 2 tons
Kirk Stelsel says
To find a manufacturer, you can use your member database at precast.org/find.