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Which of the following are correct for cover to reinforcement? 1. The reinforcement shall have a minimum clear cover of 20 mm or diameter of such bar whichever is More. 2. At each end of reinforcing bar not less than 25 mm nor less than twice the diameter of such bar 3. Increased cover thickness may be provided when surface of concrete is exposed to the action of harmful chemicals.

Which of the following are correct for cover to reinforcement? 1. The reinforcement shall have a minimum clear cover of 20 mm or diameter of such bar whichever is More. 2. At each end of reinforcing bar not less than 25 mm nor less than twice the diameter of such bar 3. Increased cover thickness may be provided when surface of concrete is exposed to the action of harmful chemicals. Correct Answer 1, 2 and 3

Statement I: True

As per IS 456:2000, Cl 8.4, the minimum value of nominal cover is based on exposure conditions as mentioned below:

Exposure condition

Minimum nominal cover

Mild

 20 mm

Moderate

30 mm

Severe

45 mm

Very Severe

50 mm

Extreme

75 mm

 

Also, in any case, cover shall not be less than the maximum bar diameter or 20 mm, whichever is more.

Statement II & III: True

As per SP -34:1987, Cl: 4.1, the following are some provisions for nominal cover:

1. At each end of the reinforcing bar not less than 25 mm, or twice the diameter of such bar whichever is greater.

2. For a longitudinal reinforcing bar in a beam not less than 25 mm or the diameter of such a bar, whichever is greater.

3. For tensile, compressive, shear, or other reinforcement in a slab not less than I5 mm or the diameter of such reinforcement, whichever is greater.

4. For any other reinforcement not less than 15 mm or the diameter of such reinforcement, whichever is greater.

5. The nominal cover may be increased, when the surfaces of concrete members are exposed to the action of harmful chemicals (as in the case of concrete in contact with earth contaminated with such chemicals), acid, vapor, saline atmosphere, sulphurous smoke. It is to be increased by 15 to 15 mm. However, in any case cover should exceed by 75 mm. 

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