Rebar is a vital component for the strength of concrete structures. It prevents the concrete from cracking and distorting when placed under load. But, is epoxy coated rebar used in the same way, and what are its disadvantages?
The disadvantage of Epoxy Coated Rebar (ECR) is that if the coating is damaged, it may corrode under the epoxy coating. ECR is inspected before it is placed into the concrete, and damaged areas can be repaired. ECR is commonly found in marine structures due to its good corrosion resistance.
Read on to discover how epoxy coated rebar is made, its strengths and why it is banned in some areas.
What Is Epoxy Coated Rebar, And How Is It Manufactured?
A reinforcing Bar, or Rebar as it is more commonly referred to, provides extra strength and stability to concrete structures. Epoxy-Coated Rebar (ECR) performs the same function as regular rebar but has a coated layer that provides additional corrosion protection to the metal rebar.
ECR is becoming more prevalent as construction moves to more corrosion-prone areas, and additional protection is needed. ECR has excellent protection against corrosive fluids, extreme temperatures, and abrasion. The corrosion protection properties of ECR make it very well suited to the marine environment.
Epoxy Coated Rebar is coated with Fusion Bond, a dry powder at room temperature, and turns into a boding film when heated. The following processes are completed to coat the rebar with epoxy.
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- The rebar is cleaned to remove grease, salt, and rust contaminants. The cleaning process leaves the rebar shiny with a slightly rough exterior.
- The rebar is heated to 230°C (446°F) using electrical Induction Heaters.
- The heated rebar passes through a spray booth, where the dry epoxy powder is sprayed onto the rebar. The heat causes the dry epoxy powder to melt and cover the rebar surface with a 200 – 300 μm (micrometer) layer of epoxy.
- The ECR is then left to cure for an extra hour at 225°C (437°F) before passing through a cooling chamber.
- The cooled ECR is then inspected and tested.
What Quality Tests Are Conducted On Epoxy Coated Rebar?
Once the ECR has cooled, it is tested to determine the quality of the bar. These tests are conducted to ensure that the epoxy has bonded to the rebar and that no damages have been done to the ECR during the coating process. The Following tests are done on the newly coated rebar to ensure sufficient quality.
- Holiday detection (Detects scratches and imperfections)
- Coating thickness
- Impact strength
- Bendability
- Bond strength
- Alkali resistance
- Corrosion resistance
Why Is Epoxy Coated Rebar Banned In Certain Areas?
There are many misleading reports that ECR is illegal to use, but this is not the case. Although ECR is banned in Quebec, Canada, while many other areas have commenced studies into its corrosion resistance. ECR is still being used in regions that suffer from corrosion.
The biggest concern is that if the epoxy coating on the rebar is scratched or damaged during the installation process, it will corrode faster. This is very possible as the corrosive material will be able to do damage underneath the coating layer, thus making it very difficult to diagnose.
For this reason, many states have implemented more frequent and in-depth inspections of structures that have ECR.
These are other types of rebar that offer corrosion resistance:
- Glass Fiber Reinforced Polymer (GFRP) Rebar
- Galvanized Rebar
- Stainless-steel Rebar
What Applications Are Best Suited For Epoxy Coated Rebar?
Rebar is relatively inexpensive and offers excellent structural strength when combined with concrete. Over time concrete will crack due to external forces, thus allowing water and corrosive material to seep in and contact the rebar.
If the rebar starts corroding, the structure will be vulnerable and lose its strength. ECR prevents this from occurring as it offers an extra layer of protection from the elements and keeps the structure’s strength intact.
ECR is used in concrete that will be subjected to corrosive conditions. The following are structures and applications where ECR is commonly used:
- Underground Parking Structures
- Roadways
- Pavements
- Bridges
- Marine and Offshore structures
- Concrete that is exposed to salt
The Advantages And Disadvantages Of Epoxy Coated Rebar?
Epoxy Coated Rebar may have a declining reputation. Still, it is favored in many projects and totally excluded in others. Below are the advantages and disadvantages of ECR.
The Advantages Of Epoxy Coated Rebar
- Good Corrosion Protection
- Lower Maintenance Costs
- ECR can extend a structure’s service life
- 40-50 times more corrosion compared to standard rebar
- High Mechanical impact strength
- Higher quality due to the inspection process
The Disadvantages Of Epoxy Coated Rebar
- Does not bond as well to concrete as standard rebar
- 10% to 12 % higher cost compared to standard rebar
- Scratches easily
- The damaged coating may force sudden breaks in the infected area
- It cannot be stored in harsh environments
- More field handling is more labor intensive
Can Epoxy Coated Rebar Be Repaired?
When ECR is being installed, it must be inspected for cuts, scratches, or any other damage that may occur in the transportation, storage, or moving stages. If damage has been identified, it can be repaired depending on the severity.
A liquid two-part epoxy that hardens at ambient temperatures can be painted or sprayed on the damaged areas of the ECR. The same liquid epoxy is used after a piece of rebar has been cut to size or spliced together. These cut-offs and spliced areas will expose the rebar underneath the coating, thus, needing it to be coated. All repairs can be done on the job site with no additional tools.
Conclusion
Rebar is placed in concrete to increase its structural strength. Epoxy coated rebar (ECR) is used the same way but is used in areas that have high corrosion, such as bridges, pavements, and marine structures. The epoxy coating forms an additional layer of corrosion protection if the rebar is exposed to the elements.
ECR is banned in some areas because if the coating is damaged, it will corrode under the epoxy coating, making it much more difficult to detect. As a result of this, many states have increased the frequency of ECR inspections.