Question

Consider the following statements:

1. Bricks in masonry arc bound by mortar.

2. Mortars make bricks damp. proof.

3. Strength of brick in masonry is improved by plastering.

4. Addition of lime improves workability.

5. Marine constructions need sulphate-resistant cement mortar.

Which of the above statements are relevant for 'cement mortar?
1. 1, 2 and 3
2. 2, 3 and 4
3. 1, 4 and 5
4. 3, 4 and 5

Answer 1

Correct Answer - Option 3 : 1, 4 and 5

Concept:

Bricks masonry is made of brick units, bonded together with mortar. Mortar acts as a cementing material and unites the individual brick units together to act as a homogenous mass.

Mortars does not make bricks damp proof. Mortar only acts as a cementing material.

Strength of brick in masonry does not depend upon plastering.

Strength of brick masonry depends upon type and strength of bricks, shape and size of masonry, uniformity of bricks, mix of mortar, method adopted for laying bricks.

Addition of lime improves workability.

Sulphate resisting cement:

OPC is highly susceptible to the attack of sulphates especially to that of MgSO₄ which attacks both lime and calcium aluminate resulting in formation of CaSO₄ and calcium sulphoaluminate.Volume of which is 227% more than the original volume that causes volume changes in cement and leads to development of cracks in it.

In order to avoid this sulphate resisting cement is used which is produced by reducing the percentage of lime and alumina in such a way that the proportion of C3A is not more than 5% and proportion of twice of C3A and C4AF is not more than 25%.

Applications:

1. Foundation works

2. Sewage treatment works

3. Marine construction

4. Where pipes are to be laid in marshy areas.

So here statement 1, 4 and 5 are correct.