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What is chloride attack in reinforced concrete?

Reinforced concrete is a common construction material used for various structures such as bridges, buildings, and highways. However, it is susceptible to various forms of degradation over time, one of which is chloride attack. Chloride attack is a significant threat to the long-term durability and structural integrity of reinforced concrete structures.



Chloride attack occurs when chloride ions penetrate the concrete and come into contact with the steel reinforcement. Chloride ions can come from various sources, including de-icing salts, seawater, and industrial processes. Once the chloride ions reach the steel reinforcement, they can initiate corrosion, which can lead to cracking and spalling of the concrete.


The corrosion process is initiated when the chloride ions penetrate the passive layer that forms on the surface of the steel reinforcement. The passive layer is a thin layer of iron oxide that protects the steel from corrosion. However, once the chloride ions penetrate the passive layer, they react with the steel, causing it to corrode.


The corrosion of the steel reinforcement causes it to expand, which can lead to the formation of cracks in the surrounding concrete. These cracks can allow more chloride ions to penetrate the concrete, which can accelerate the corrosion process, leading to further deterioration of the structure.


To prevent chloride attack, various preventative measures can be taken during the design and construction phases. One of the most effective ways to prevent chloride attack is to use high-performance concrete that has a low permeability to chloride ions. Additionally, using corrosion-resistant steel reinforcement, such as stainless steel or epoxy-coated steel, can also help to prevent chloride attack.


Other preventative measures include using protective coatings, such as sealants or coatings, to prevent chloride penetration and regular maintenance and inspections to detect and repair any signs of corrosion.


Chloride attack is a significant threat to the long-term durability and structural integrity of reinforced concrete structures. Preventative measures, such as using high-performance concrete, corrosion-resistant reinforcement, and protective coatings, can be taken to prevent chloride attack. Regular maintenance and inspections are also crucial in detecting and repairing any signs of corrosion before significant damage occurs.

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