SAND

Sand is a natural product which is obtained as nalla sand, river sand and pit sand. Though sea sand should not be used for the below described reasons:

1. It contains salt and thus structure will remain damp. The mortar is affected by blisters appear and efflorescence.

2. It contains shells and other organic matter which is decomposing after some time, reducing the life of the mortar.

By crushing hard stones, Sand can be obtained artificially. Generally artificial sand is obtained as a by-product whereas crushing stones to get jelly (coarse aggregate).

Sand is used in mortar and concrete for the below described purpose:

1. It sub-divides the paste of binding material into thin films and permits it to spread and adhere.

2. It fills up the gap between the building blocks and spreads the binding material.

3. It increases the density of the mortar.

4. It prevents the shrinkage of the cementing material.

5. It permits carbon dioxide from the atmosphere to reach some depth and thereby improve setting power.

6. The cost of cementing material per unit volume is reduced because this low cost material increases the volume of mortar.

7. Silica of sand contributes in the formation of silicates resulting into the hardened mass. The properties of good sand are following:

1. Should be free from organic or vegetable matter.
2. Should be chemically inert.
3. Should be free from salt.
4. Should be well graded.
5. Should contain sharp, angular and coarse grains.
6. Should be hard.