Question

A RCC slab under mild exposure condition having main longitudinal tensile reinforcement of diameter 12 mm, then minimum allowable nominal cover to satisfy durability requirement is
1. 10 mm
2. 15 mm
3. 20 mm
4. 25 mm

Answer 1

Correct Answer - Option 2 : 15 mm

Explanation:

Nominal Cover to Meet Fire Resistance:
The nominal cover is the design depth of concrete cover to all-steel reinforcements.

It shall be not less than the diameter of the bar.

Minimum values of the nominal cover of normal-weight aggregate concrete to be provided to all reinforcement to meet the specified period of fire resistance shall be given in the table below 

Member	Minimum Cover
Slab	20 mm
Beam	20 mm
Column	40 mm for d > 12 mm 25 mm for d < 12 mm
Footing	50 mm

 

Nominal Cover to Meet Durability Requirements:

Exposure	Nominal concrete cover  (in mm) not less than
Mild	20
Moderate	30
Severe	45
Very Severe	50
Extreme	75

Note:

For main reinforcement, up to 12 mm diameter bar for mild exposure the nominal cover may be reduced by 5 mm.