Corrosion of reinforced concrete structure with steel rebars is a matter of greatconcern. In RCC structure, reinforced steel bars undergo distress due to embedded steel bars. Though, initially, when steel bars are reinforced, steel does not corrode as the concrete aggregates which consists of oxides of calcium, has alkaline condition (pH between 10-12.5). In this pH range, the steel forms a passive layer and hence does not corrode.
However, as the time passes moisture (from rain or high humid conditions) and pollutants such as chlorides (from coastal environment), carbon dioxide, sulphur dioxide (urban environment), penetrate through the concrete cover, reach concrete/steel interface, reduce pH below 10, it leads to the initiation of corrosion process.
Corrosion results in the formation of voluminous corrosion products (hydro-oxides, carbonates or sulphates) leading to stress generation and thereby causing distress, initially in the form of a pin holes, followed by small cracks and finally to the spallation of plaster, exposing the rebars.
Read More: Durable concrete structures
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