Corrosion in RCC Part – I

Corrosion in RCC rightsteel fe415

Thermo Mechanically treated steel bars created the current standard of reinforcement. Their excellent tensile strength and ductility make them ideal and preferred for construction of building structures. Building structures are always susceptible to environmental changes. No building will ever be the same once the environmental changes kick in. Out of all the changes, the most serious and devastating is corrosion.

The Universal Problem

TMT reinforced steels are available in many grades mainly Fe 415, Fe 500, Fe 550 and Fe 600. Each grade is used according to the design of the structure. With Reinforced concrete stronger support is ensured for the building structure. However strong the structure may be, over a certain period of time, the structure will start deteriorating by environmental factors. One of them is corrosion. Corrosion has become a serious, universal problem worldwide, with costly repairs resulting in a huge amount of money per year.

Corrosion

Corrosion is a phenomenon which results in the deterioration of a material when they are exposed to different environmental conditions. It is an electrochemical process in which results in the occurrence of chemical reactions and electrical current flow. With the tensile strength provided, RCC structures are meant to last for up to 100 years but recent studies have shown that within 20 years these structures start to deteriorate. Several factors are responsible for the early deterioration in reinforced concrete structures but in the majority of the cases, it is because of the corrosion of steel.

The Cause

When the steel bars are combined with the wet concrete, it rapidly forms a thin layer of oxide which strongly adheres to the steel bars and results in a protective alkaline environment from reaction with oxygen and water, i.e corrosion. The pH value for this environment is between 12-13. This state of the steel is known as passivation.

However, over the passage of time, due to carbonation process or chloride-induced corrosion, the pH value starts declines slowly and alkaline surrounding of the reinforcement bar is lost, starting the corrosion process, which in turn results in cracks and spalling of the concrete. In this case, the reinforced steel bars are literally exposed and loses the sole property it is designed for which is the strength. Corrosion, therefore, results in severe damages to the building structure.

The Damages caused to RCC by corrosion is yet to occur. Stay tuned to know about them in the next blog.

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