what is clear cover? why it is provided?
The cover is the minimum distance from
the reinforcement to the outer surface of the concrete. The clear cover is
measured from the outer surface of the lateral tie/ or stirrup to the outer
surface of the concrete. The clear cover is provided to protect reinforcement
from corrosion and provide resistance towards fire damage.
The clear cover also enhance the
durability of the structure.
The clear cover distance is ensured by
providing cover blocks between reinforcement and shuttering before pouring
concrete.
cover blocks are generally made up of
cement mortar. Cover blocks are generally square or rectangular in plan with or
without binding wire embedded in them which will be tied to the reinforcement
at the time of placing.
The thickness of clear cover depends on
the type of exposure that the concrete has with the surrounding environment. If
the concrete is exposed to marine or aggressive environment or it is inside the
soil having harmful chemical higher clear should be provided.
The thickness of clear cover depends on
the type of work done. It varies for 20mm – 75mm.
The minimum clear cover provided are given below:-
1)Footing
50mm
2)Strap
beam=50mm
3)Concrete
slab=20mm
4)Column
=40mm
5)Shear
wall= 25mm
6)Beams=25mm
7)Slab=20mm
8)Retaining
wall 25mm
9)Water
retaining structure=30mm