Stone : building structures are composed of different types of materials

                  Introduction:

                                                                                   Stone

All the building structures are composed of different types of materials. These materials are either called building materials or materials of construction. It is very essential for a builder, may be an architecture or engineer or contractor, to become conversant thoroughly with these building materials. The knowledge of different types of material, their properties and uses for different purposes provides and important tool in the hands of the builders in achieving economy in material cost. The material cost in a building ranges 30 to 50 percent cost of total cost construction. In addition to material economy, the correct use of material results in better structural strength, functional efficiency and esthetic appearance

Qualities of a good building stone:

The following are the qualities or requirements of a good building stone.

1.      Crushing strength: For a good building stone, the crushing strength should be greater than l000kg per cm².

2.      Appearance: Good building stone should be a uniform colour, and free from clay holes, spots of other colour bands etc capable of preserving the colour for longtime.

3.      Durability: A good building stone should be durable. The factors like heat and cold alternative wet and dry, dissolved gases in rain, high wind velocity etc affect the durability.

4.      Fracture: For good building stone its fracture should be sharp, even and clear.

5.      Hardness: The hardness greater than 17, treated as hard used in road works. It is between 14 to 17, medium hardness, less 14 said be poor hardness.

6.      Percentage wear: For a good building stone, the percentage wear should be equal to or less then 3 percent.

7.      Resistance to fire: A good building stone be fire proof. Sandstone, Argillaceous stone resists fire quite well

8.      Specific gravity: For a good building stone the specific gravity should be greater then 8.7 or so.

9.      Texture: A good building stone should have compact fine crystalline structure should be free from cavities, cracks or patches of stuff or loose material.

10.  Water absorption: For a good building stone, the percentage absorption by weight after 24 hours should not exceed 0.60.

11.  Seasoning: Stones should be well seasoned before putting into use. A period of about 6 to 12 months is considered to be sufficient for proper seasoning.

12.  Toughness Index: Impact test, the value of toughness less than 13 – Not tough, between 13 and 19 – Moderate, greater than 19- high