Epoxy coated rebar

Epoxy coated rebar

corrosion-resistent epoxy coating

Epoxy-Coating protects the steel using several mechanisms. If undamaged, the coating prohibits the passage of chloride ions, thus protecting the steel from corrosion damage. If minor holes or damage are present in the coating and sufficient chloride ions are available in the concrete, then localized corrosion may occur. For the corrosion reaction to proceed, a cathode is required. If all bars are coated, then only very small cathodes are present, substantially reducing the corrosion rate. Tests conducted for the FHWA demonstrated that if both top and bottom mats were coated, the corrosion rates of Epoxy-Coated Steel Reinforcing Bars were 40 to 50 times less than that of similar uncoated bars.

Epoxy-Coated rebar may be used in any concrete subjected to corrosive conditions. These may include exposure to deicing salts or marine waters.
. Bridges (decks, piers, etc.)
. Marine structures (seaports, airports, tunnels, etc.)
. Pavements (highway, airport runway, etc.)
. Parking structures
. Buildings (seaside, power plants, etc.)
. Repair


Standard

ASTM A775/A775M, ASTM A934/A934M


Rebar diameter

8mm ~ 40mm (1/3" ~ 1 1/2")


Powder brand

Jotun, Valspar


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Manufacturing process

 
Surface preparation
Surface preparation

Rebars are blast-cleaned to a near white metal finish using abrasive grit.

Heating
Heating

Bars are heated to approximately 230°C, typically using electrical induction heaters.

Powder application
Powder application

The heated steel is passed through a powder-spray booth where the dry epoxy powder is emitted from a number of spray guns.

Cure
Cure

Water cooling.

The sustainable choice for concrete structures


Black Epoxy coated Galvanized Stainless
ITEM
ASTM A615 ASTM A775/A934 ASTM A767
ASTM A955
%recycled
>75 >97 >97 >99
Durability Low High Moderate Very High
Cost Low Low Moderate High

Available alloys and dimensions

Grades
ASTM A615 BS 4449
Canadian
HRB 400
GR 60
B500
400R/400W
HRB 500
GR 75 500R/500W

GB/T 1499.2
BS 4449
ASTM A615
Canadian Sizes
6
6

8
8



#3
10 10




10M
12 12



#4
14




#5
16 16
15M
18 #6



20M
20 20

22
#7
25 25
25M


#8
28
#9




30M
32 32 #10

36 #11
35M
40 40

50 50


 

Frequently Asked Questions

 
1When was Epoxy-Coated Steel Reinforcing Bar first used?
Epoxy-Coated Steel Reinforcing Bar was first used in 1973 on the Schuykill Bridge near Philadelphia, Pennsylvania, USA.
2Why should I use Epoxy-Coated Steel Reinforcing Bar?
Structures built with Epoxy-Coated Steel Reinforcing Bar have longer lives than structures built with black steel.
*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.
3Where can Epoxy-Coated Steel Reinforcing Bar be used?
*Bridge decks
*Continuous reinforced concrete pavement
*Parking garages
*Piers and docks
*Water towers
*Columns and parapets
*Dowels
*Repair
4What specifications cover Epoxy-Coated Steel Reinforcing Bar?
Epoxy-Coated Steel Reinforcing Bar is covered in ASTM A775 and A934 Standard Specifications for Epoxy-Coated Steel Reinforcing Bars.
5What design issues should be considered if I specify Epoxy-Coated Steel Reinforcing Bars rather than black reinforcement?
The development length for Epoxy-Coated Steel Reinforcing Bar is longer.
*Maintain concrete cover.
6Epoxy-Coated Steel Reinforcing Bar cost?
Generally, Epoxy-Coated Steel Reinforcing Bar will cost 25 percent to 50 percent more than uncoated bars. However, that increase represents a minute incremental addition to the bridges total cost.
7How does Epoxy-Coated Steel Reinforcing Bar compare with galvanized reinforcing bar?
According to the National Bridge Inventory, Epoxy-Coated Steel Reinforcing Bar has been used in more than 60,000 decks while galvanized has been used in only 950. *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 Bar does not.
*Galvanizing may result in brittle bars that break during bending.
*Epoxy-Coated Steel Reinforcing Bar does not have these embrittlement issues.
8How does Epoxy-Coated Steel Reinforcing Bar compare with Fiber Reinforced Polymer (FRP) bars?
FRP bars require extensive redesign due to differences in stress/strain values for these bars.
9What is the difference between ASTM A775 vs. ASTM A934?
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.
10How long will structures with epoxy-coated bars last?
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.
11How do the initial and life-cycle cost of epoxy-coated reinforcing bars compare with other materials?
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.
12Epoxy-coated Reinforcing Steel in Repair of 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.
13Can I weld epoxy-coated reinforcing steel?
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.

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