Mortar used for construction work in waterlogged areas & exposed positions is of proportion (A) 280.Indentations on the bricks provided to form a key for holding the mortar is called as
- A1 : 1
- B1 : 2
- C1 : 3Correct
- D1 : 4
Solution
Concept
A rich cement mortar of 1:3 is used in waterlogged areas and exposed positions for strength and water resistance.
Step-by-step solution
1. Leaner mortars like 1:6 are used for ordinary brickwork. 2. Waterlogged areas and exposed positions need a dense, strong and less porous mortar. 3. The standard recommendation is cement mortar 1:3. 4. So option C is correct.
Explanation
In waterlogged or exposed places, mortar must resist water and weather. A 1:3 cement mortar is dense and strong enough for this. Richer mixes like 1:1 or 1:2 are costly and shrink more.
Why the other options are wrong
A and B: 1:1 and 1:2 are very rich, costly mixes used only for special work like guniting or water-tight joints. D: 1:4 is weaker and more porous, used for general masonry.
Shortcut
Waterlogged or exposed work means cement mortar 1:3.
Common mistake
Thinking the richest mix (1:1) is always best. It is costly and cracks due to shrinkage.
Correct answer: C) 1 : 3