The Characteristics of Good Building Stones

Stone is a naturally available building material, which has been formed the early age of civilization. It is available in from in the form of rock, which is cut to the required size and shape and used as a building block. Stone has been used to build a small residential building to large places and temples.

Stones should possess fine-grained texture. It should be free from soft patches, flows and cracks The strength of stone should be ascertained if it is to be subjected to any excessive or unusual stresses. The shade of the stone should be uniform and pleasing. Freshly  broken surface should be bright and cracks

The stone should be strong, hard and durable. the hardness of stone is often of importance, especially if it is to be subjected to a considerable amount of wear and friction, as in pavements.

It should be easily workable before seasoning. the appearance of stone is often a matter of importance, especially in the facework of conspicuous buildings. In order that the appearance may be preserved, a good weathering stone should be selected, free from flaws, clay holes, etc.

It should have good resistance to smoke, fire and acidic atmosphere, It should not absorb more than 5% of water by weight when kept immersed in water for 24 hrs. In the attrition test, the stone should not show wear of more 2%

The Characteristics of Good Building Stones

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

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

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

Weight: The weight of a stone for building has occasionally to be considered. In marine engineering works it is often advisable to use heavy stones to resist the force of the sea. A light stone would be best adapted for arches, while heavy stones would add to the stability of retaining walls.

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.

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

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

Percentage wear: For a good building stone, the percentage wear should be equal to or less than 3 per cent.

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

Specific gravity: For a good building stone the specific gravity should be greater than 8.7 or so. The specific gravity should not be less than 2.5.

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

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

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.

Toughness Index: It should become hard after seasoning. This seasoning gets rid of the moisture, sometimes called “quarry sap,” which is to be found in all stone when freshly quarried. Toughness index should be more than 19. Impact test, the value of toughness less than 13 – Not tough, between 13 and 19 – Moderate, greater than 19- high