Why Clear cover is provided in RCC :
The result is going to be something like this. In order to protect the reinforcement from this phenomenon called corrosion and to provide fire resistance to bars embedded in concrete, nominal cover is provided for Reinforced Concrete Structures.
Item-wise clear cover provided in RCC as Below :
Note : In Order to protect R/f from this phenomenon called corrosion and provide fire resistance to bar embeded in concrete
The result is going to be something like this. In order to protect the reinforcement from this phenomenon called corrosion and to provide fire resistance to bars embedded in concrete, nominal cover is provided for Reinforced Concrete Structures.
Concrete cover is the least distance between the surface of embedded reinforcement and the outer surface of the concrete.
Why do we provide cover then?
- To protect the reinforcement steel from environment in order to prevent the corrosion
- To give reinforcing bars sufficient embedding to enable them to be stressed without slipping
- And to provided insulation from fire or heat.
However
each national code suggests different cover depths like American code
suggest for 40-50 mm cover where as UK code suggest for 25-50 mm.
You
may think now like this " the more cover is the safer the reinforcement
is". However this is not true, because as the cover depth increase it
leads to increased crack width in flexural RCC members and crack width
greater than 0.3 mm permit ingress of moisture and chemical attack to
the concrete, resulting in possible corrosion of reinforcement and
deterioration of concrete. Therefore, thick covers defeat the very
purpose for which it is provided. There is a need for judicious balance
of cover depth and crack width requirements
Item-wise clear cover provided in RCC as Below :
sr no Item Cover Provided.
1 Raft foundation Bottom and side 75 mm
2 Raft Foundation top 50 mm
3 Footings 50mm
4 Beam 25 mm
5 Column 40 mm
6 Slab 15-20mm
7 Staircase 15 mm
8 Retaining wall 20-25 mm
1 Raft foundation Bottom and side 75 mm
2 Raft Foundation top 50 mm
3 Footings 50mm
4 Beam 25 mm
5 Column 40 mm
6 Slab 15-20mm
7 Staircase 15 mm
8 Retaining wall 20-25 mm
Note : In Order to protect R/f from this phenomenon called corrosion and provide fire resistance to bar embeded in concrete