What Is The Corrosion Of Reinforcement?
What Is The Corrosion Of Reinforcement?
Corrosion of reinforcement refers to the corrosion of the steel bars (reinforcement bars) that are used to provide strength and support to concrete structures, such as buildings and bridges.
This corrosion can lead to the weakening of the concrete structure and the potential failure of the structure if not addressed.
Factors that contribute to the corrosion of reinforcement include exposure to moisture, exposure to salts and chemicals, and a lack of proper maintenance.
To prevent or slow down corrosion of reinforcement, protective coatings can be applied to the steel bars and proper drainage and ventilation can be implemented in the concrete structure.
Corrosion of reinforcement is one of the most destructive and costly issues associated with reinforced concrete structures. It occurs when the steel reinforcing bars in the concrete are exposed to moisture, oxygen, and chlorides.
The corrosion process leads to rust formation on the metal rods and gradually weakens the structural integrity of the cement matrix that encapsulates them.
This corrosion can be accelerated by exposure to de-icing salts or seawater that naturally contains high chloride ions, oxidizing steel.
Corrosion of reinforcement is difficult to repair due to its complexity and often leads to partial or complete demolition for safety reasons if not addressed timely.
What Are The Effects Of Corrosion In Reinforcement?
Corrosion of reinforcement can have severe and catastrophic effects on reinforced concrete structures as it will lead to cracking, spalling, and delamination of the concrete cover and even contribute to the collapse of the corroded structure.
This is why it is so important to identify the source of corrosion and adequately preserve or repair all corroded steel reinforcement bars for a structure to withstand its design loads.
Reinforcement corrosion leads to an increase of rebar sectional area decreasing, resulting in decreased concrete cover thickness, loss of bond between rebar and concrete, overall weakening of the entire structure, and further contributing to corrosion deterioration.
In extreme cases, complete structural failure can occur due to reinforcement corrosion. Therefore, these potential effects must be considered when designing structures, and materials intended to prevent or reduce the effects from occurring should be used during construction.
What Are The Two Leading Causes Of Corrosion Of Steel Reinforcing In Concrete?
Two types of corrosion are typically observed in the steel reinforcement bars of reinforced concrete structures:
- Crevice corrosion, which occurs in small crevices within the concrete structure due to stagnated solutions.
- Pitting corrosion, which is related to the de-passivation of small areas on the steel reinforcement bars.
Both can corrode structural components that are not adequately protected, leading to structural failure if left unchecked.
How Do You Prevent Corrosion In Reinforced Concrete?
The best way to prevent corrosion in concrete is by a corrosion-inhibiting admixture.
Corrosion-inhibiting admixtures either extend the natural corrosion-inhibiting properties of the Portland cement or reduce the corrosion rate of the embedded metal, and some admixtures provide both benefits.
How Does Corrosion Of Steel Reinforcement Cause?
Corrosion of steel reinforcement in concrete is caused by the loss of alkalinity, which occurs when acid-forming gases (such as CO2 and SO2) react with the hydration products of cement in the form of calcium bicarbonate and leach away Ca(OH)2.
This leads to a decrease in pH level, ultimately resulting in oxidation of iron ions which corrode the steel, causing a significant weakening of structures and accelerated deterioration.
Concrete deterioration due to corrosion can cause structural failure, resulting in costly repairs or replacement.
How Can We Prevent The Corrosion Of Steel Reinforcement?
Cathodic protection is an effective way of preventing the corrosion of steel reinforcement. The most common method involves installing a zinc-based sacrificial anode system, which sacrifices itself instead of the steel material when corrosion occurs.
This approach is considered more efficient than the impressed-current cathodic protection method due to the practical difficulties involved with this latter technique.
Protective coating systems can also be applied to existing reinforced structures to protect them from environmental damage while avoiding physical interference with the structure.
Other solutions, such as galvanizing and using special alloys that resist corrosion, should also be considered to ensure the long-term durability of steel reinforcement in different environments.