How to protect concrete reinforcement from corrosion
As previous article we talked about What cause corrosion in concrete reinforcement, now we will talk about how to protect concrete reinforcement from corrosion. This is really important. When you have a building stands in a extreme weather condition, this corrosion problem cannot taken so lightly. We have to do many steps how to protect concrete reinforcement from corrosion.
How to protect concrete reinforcement from corrosion? The following methods will help to protect concrete reinforcement from corrosion.
1. Concrete Quality Improvement.
By adopting the rich mix: Higher cement content and lower w/c ratio give stronger and impermeable concrete.
Adopting the best mix proportion: By designing the best suitable mix proportion the impermeable concrete can be produced.
Efficient compaction during casting: This gives dense concrete with minimum voids.
Leak proof formwork: This reduces the leakage of cement slurry during casting of concrete.
Adopting salt free sand: The salt content of mix can be reduced by washing the sand properly.
Using plasticizers: The use of plasticizers improves the workability without increasing the water content
Using sulphate resisting cement and Pozzolana cement.
2. Increase the thickness of Concrete Cover.
Extra cover depth lengthens the time for ingress of corroding agents. Such a remedy increases weight due to additional concrete requiring changes in structural design. Increased cover thickness should be provided when surfaces of concrete members are exposed to the action of harmful chemicals, acids, vapors, saline atmosphere, sulphurous smoke etc.
As per observation, the increase in cover thickness may be between 15 mm and 40 mm, the total cover thickness should not exceed 50 mm. concrete cover more than 50 mm is not recommended as it may give rise to increase crack widths which may further allow direct ingress of deleterious materials to the reinforcement.
3. Concrete Coating and Sealer.
When untreated reinforcing bar is used, the best method is to apply protective coatings to concrete surface to seal entry of moisture, carbon dioxide and chlorides.
The dry concrete surface should be roughened by chiseling. Then, a workable mixture of 1:3 cement sand mortar should be applied on the concrete surface after watering over the surface properly by trowelling to a thickness of 6 mm. The surface should be finished with neat cement slurry consisting of water and cement in the ratio 2:1.
In this type of treatment, Zinc itself becomes a sacrificial anode and then protects the bar from corrosion for five years approximately. This method is used when no superior treatment is available.
5. FUSION BONDED EPOXY COATING (FBEC)
Today the world over, fusion bonded epoxy coating (FBEC) has proved to be most effective, reliable and long-term economical method of anti corrosive treatment for reinforcing bar.
It is applied directly on the reinforcing steel which prevents corrosion by isolating and insulating the steel from the corrosive environment. These coatings protect against external and internal corrosive agents.
6. Reinforcement Bars Coating.
The corrosion of rebars can be prevented by applying proper coating to rebars. The coating can be one of the following:
- Chemical compound.
- Metallic epoxy coating.
- Fusion bonded epoxy.
7. Proper Storage and handling.
Steel reinforcement should be stored in such a way as to avoid distortion and to prevent deterioration and corrosion. It is desirable to coat reinforcement with cement wash before stacking to prevent scaling and rusting.
In case of long storage, reinforcement bars should be stacked above ground level by at least 150 mm. Also in coastal area or in case of long storage; a coat of cement wash shall be given to prevent scaling and rusting.
The article about How to Protect Concrete Reinforcement From Corrosion above is written by Sanjay Kumar, Virendra Kumar, M. Prasad and it is originally published on NSCP – 2001. For more updates about Civil Engineering articles, please subscribe.