The basic problem in Reinforced concrete structures is the corrosion of steel reinforcement. The main cause of this corrosion is intrusion of water inside the RC structures. The corrosion of steel reinforcement can be judged by peculiar cracking of concrete structures. At last stage of corrosion, the steel reinforcement becomes exposed and the extent of corrosion can be seen as rust. Corrosion of steel reinforcement usually occurs more in externally located RC members as compared to internally located RC members.
Types of Corrosion in Concrete Reinforcement:
There are two types of corrosion:
- Crevice Corrosion
- Pitting Corrosion
Reasons of Corrosion of Reinforcement:
There are two main reasons behind the corrosion of steel reinforcement:
- Localized damaging to the film over the steel due to chloride ions
- Increase in the concentration of carbon dioxide in the environment that leads to corrosion of steel in concrete
Repairs to Corroded Reinforced Concrete structures:
- For inspection, it is necessary to expose the corroded locations up to such an extent that these locations can be seen through naked eye.
- First step in treatment of rusting on reinforcement is cleaning of rust with the wire brush.
- After cleaning, tamp the surface with hammer having the weight at least 5 lbs.
- Then rub the surface with wire brush or hessian rope. In the market, many rust removing chemicals are also available. Those chemicals can be used if cleaning of rust is to be done more effectively.
- In important members (members that has to carry heavy load) of RC structures, sand blasting can be used for cleaning of rust.
- If the cleaned surface is found heavily corroded, then the surface can be coated with black ship paint (that paint is marine paint).this paint usually seals off he steel surface and prevent the further corrosion.
- Corroded members which are critical in the whole structure such as columns should be additionally reinforced by using hooked or anchorage connections or by using beams. Corroded slabs can be additionally reinforced by using wire mesh (which is locally said to be as Jali).