Question

Minimum clear cover (in mm) to the main steel bars in slab, beam, column and footing respectively are

• A. 10, 15, 20, 25
• B. 15, 25, 40, 40
• C. 20, 25, 30, 40
• D. 20, 35, 40, 75

Answer 1

The correct option is B 15, 25, 40, 40

In $\text{IS: 456- 1978,}$ the clear covers are specified as:
(i) For a longitudinal reinforcing bar in a column, not less than 40 mm, or less than the diameter of such bar.
(ii) For longitudinal reinforcing bar in a beam, not less than 25 mm, or less than the diameter of such bar.
(iii) For tensile, compressive, shear or other reinforcement in a slab, not less than 15 mm, or less than the diameter of such bar.
(iv) In other cases the clear cover to the reinforcement bars shall not be less than 40 mm or diameter of such bar whichever is more.
The minimum clear cover should not exceed 75 mm in any case.
According to $\text{IS 456:2000}$ nominal cover shall not be less than the diameter of bar. The nominal cover is specified to meet durability requirement in Table 16 on page 47 of the IS Code. To meet specified period of fire resistance the clear covers are given in Table 16A on page 47.
For longitudinal reinforcing bars the nominal cover shall not be less than 40 mm.
For footings minimum cover shall be 50 mm.