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The cover of longitudinal reinforcing bar in a beam subjected to sea spray should not be less than which one of the following?

The cover of longitudinal reinforcing bar in a beam subjected to sea spray should not be less than which one of the following? Correct Answer 70 mm

Explanation:

Concrete surfaces exposed to seawater spray, corrosive fumes, or severe freezing conditions whilst wet will correspond to Very severe exposure.

From the below table, Corresponding to very severe exposure, the nominal concrete cover should not be less than 50 mm.

So, out of the above options, The cover of the longitudinal reinforcing bar in a beam subjected to sea spray should not be less than 70 mm.

Note:

Since the minimum value is 50 mm that's why 25 and 40 mm will be below the criteria and 90 mm is too large to consider. Hence most appropriate answer is 70 mm.

The minimum clear cover depends upon the exposure condition and fire resistance.

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

 

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

Note:

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

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