By
Sourav Dutta
Manager-Civil
Ion Exchange India Limited
Now-a-days for controlling rust/corrosion of rebar some extra treatment is being carried out on rebar, making it more resistant to rusting/corrosion under unfavorable circumstances. Some of these treated rebars normally used are: (1) Fusion bonded epoxy coated rebar, (2) Cement-polymer composite coated rebar,(3) Corrosion resistant steel (CRS) rebar. The following comparison is being made aiming to give a clear cut idea on advantages/disadvantages of each type, which might help and give an idea to construction industry for decision making of selection of any particular type.
| Sl. No. | Parameter | Fusion bonded epoxy coated rebar | Cement-polymer composite coated (CPCC) rebar | Corrosion resistant steel (CRS) rebar |
|
1 |
Corrosion Resistance Technology | For protection of reinforcing bars against corrosion, epoxy coating is done on these bars by electrostatic spraying of fusion bonded epoxy powder. | For protection of reinforcing bars against corrosion, coating of rapid setting primer followed by a coat of cement polymer sealing product is done. | For protection of reinforcing bars against corrosion, chemical composition of rebar is made such as to develop inherent corrosion resising property. |
|
2 |
BIS code |
BIS13620-1993 |
No BIS code available. Developed by CECRI, Karaikudi. They have the detailed specification of chemicals and quality control with them. | No BIS code available for CRS yet. Complying to BIS1786-2008 500D. |
| 3 | Manufacturing process control | Difficult, as it needs to pass some critical procedures as per BIS. | Difficult, as it involves various steps like surface preparation, coating application on rebar. | Easier to control, as it is dependant on mother billet composition. |
|
4 |
Damage possiblity |
A coating of 0.1-0.3mm on external surface of rebar and liable to damage. Performance of the system depends upon least defect in the coating. |
It can be brush applied or sprayed and hence defects in the coating can be patch repaired. |
Inherent property of rebar itself. No chance of damage/change in property. |
| 5 | Bond strength of rebar | About 20% less strength than conventional reinforcing bars, due to the coating. | Has good bond strength and hence bond between coated rod and concrete unaffected, as per CECRI. | No effect on bond strength. |
|
6 |
Handing |
Special procedure is there for handling such rebar, otherwise the coating may get damaged. Even dropping or dragging such rebar is prohibited. |
Care to be taken while handling such rebar, otherwise the coating may get damaged. |
No restriction in handling procedure. |
|
7 |
Fabrication (Cutting) | Chance of damage in coating during fabrication. Exposed edge of rebar will be affected by corrosion. | Chance of damage in coating during fabrication. Exposed edge of rebar will be affected by corrosion. |
Normal practice like conventional rebar. |
| 8 | Bending | Chance of disbonding in coating during bending. | Chance of disbonding in coating during bending. Bending of rebar to be completed prior to coating. | Normal practice like conventional rebar. |
| 9 | Welding | Not advisable as coating get damaged during welding. | Not advisable as coating get damaged during welding. | No special care is required. |
| 10 | Usage of couplers | Threaded portion of rebar without coating for fixing couplers leads to corrosion. | Threaded portion of rebar without coating for fixing couplers leads to corrosion. | Threading and coupler usage is not an issue due to inherent property of rebar. |
|
11 |
Extent of protection |
No measurement of extent of protection to rebar due to the coating, as per BIS. Smallest damage in coating can initiate corrosion under severe environment. |
This system is newly developed by CECRI and the long term results are not known. |
About 25% lower rate of corrosion compared to conventional rebar. |
|
12 |
Cost saving |
Cost higher compared to conventional rebar typically by Rs 6000-13000/MT, due to the coating. Moreover, due to less bond strength, more development length required, leading to more cost. |
Cost higher compared to conventional rebar typically by Rs 5000-8000/MT, due to the coating. |
Cost higher compared to conventional rebar by Rs 2500-3000/MT. |
We at engineeringcivil.com are thankful to Er. Sourav Dutta for submitting this paper to us. We hope this paper will be helpful for the whole construction industry in general.
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