Concrete Cover/ Purpose

The concrete cover is the least distance between the
outer surface of concrete and the surface of the reinforcement.

In all reinforced concrete elements, a minimum
thickness of concrete cover must be provided.

The main reasons to provide concrete cover is to
prevent the steel reinforcement from corrosion due to environmental effects.

To provide thermal insulation to protect the
reinforcement bars from a fire.

 To provide
sufficient embedding to reinforcing bars to enable them to be stressed without
slipping.

Generally, the thickness of cover depends on
environmental conditions and type of structural member.

The thickness of the concrete cover is calculated
according to following considerations as per Indian standard code.

The thickness of concrete cover should not be less than
the diameter of the bar.

The minimum thickness of concrete cover of normal
weight aggregate concrete is provided in accordance with exposure conditions.

The table available in the video below the concrete cover for various exposure conditions.

However,
for longitudinal reinforcement in a column, the thickness of the concrete cover
is should not be less than 40 mm or diameter of reinforcement.  

Whereas,
columns with dimensions less than 200 mm, whose reinforcements are not
more than 12 mm.

Then,
the concrete cover of 25 mm is adopted.

The
minimum thickness of concrete cover for footing is normally provided with 50
mm.

The
minimum concrete cover in the fire-prone places is provided with special consideration.

The table displayed in the below video displays the minimum
thickness of concrete cover to satisfy the accepted period of fire resistance.