A 1st class brick immersed in water for 24 hours, should not absorb water (by weight) more than A. 10% B. 15% C. 20% D. 25%

The correct answer is A. 10%.

A first-class brick should not absorb more than 10% of its weight in water when immersed for 24 hours. This is according to the Indian Standard IS: 1050-1981, “Specification for Ordinary Bricks”.

The absorption of water by a brick is a measure of its porosity. A porous brick will absorb more water than a non-porous brick. The absorption of water can affect the strength and durability of a brick.

A brick that absorbs too much water can become weak and brittle. It can also be more susceptible to frost damage.

Therefore, it is important to choose bricks with low absorption rates for use in areas where they will be exposed to water.

Here is a brief explanation of each option:

• Option A: 10%. This is the correct answer. A first-class brick should not absorb more than 10% of its weight in water when immersed for 24 hours.
• Option B: 15%. This is too high. A first-class brick should not absorb more than 10% of its weight in water when immersed for 24 hours.
• Option C: 20%. This is too high. A first-class brick should not absorb more than 10% of its weight in water when immersed for 24 hours.
• Option D: 25%. This is too high. A first-class brick should not absorb more than 10% of its weight in water when immersed for 24 hours.