Requirements of a Good Building Stone

        A good building stone should possess several characteristics such as high strength (i.e., crushing strength > 1000 kg/cm2), high durability, sufficient hardness (i.e., coefficient of hardness > 14), high resistance to wear, good fire resistance, specific gravity more than 2.7, crystalline structure, high impact value (i.e., toughness index > 13), low water absorption (i.e., Percentage absorption after 24 hours less than 0.6), facility for carving and dressing, weather resistance and better appearance. Generally stones from igneous and metamorphic rocks are heavier and more durable than stones from sedimentary rocks.

1. Appearance:

The stones to be used for face work must have a uniform and pleasing color. It must be free from cavities, cracks, flaws and patches of loose and soft material etc.

2. Strength:

A good building stone should have sufficient crushing strength to withstand the load of superstructure. In general, compressive strength should not be less than 100N/mm2. It should be strong.

3. Durability:

A good building stone must be durable enough to resist the effect of weathering agencies e.g. rain, wind, temperature etc. It should have fine grained, compact and crystalline structure.

4. Hardness:

The stone used in floors, pavements and aprons of bridges, should be able to resist the abrasive forces caused due to wear and friction. For good stone wear should be equal or less than 3%. It terms of co efficient of hardness, it should be more than 14.

5. Workability:

The stone to be used should be easy to cut and dress into different sizes and shapes.

6. Toughness:

Building stones should be tough enough to withstand stresses developed due to vibrations of machinery and moving loads over them. The stones used in the construction of roads should be hard as well as tough.

7. Seasoning:

The stone to be used for an important interior work should be well seasoned. Presence of moisture makes the stone soft and it is liable to an early decay when used in structural work.

8. Resistance to fire:

A good building stone should be able to resist high temperature. Its mineral constitutes should have equal co-efficient of expansion.

9. Porosity:

A good building stone should be less porous. It should not absorb more than 5% of water. Any stone absorbing 10% of water should be rejected.

10. Specific gravity:

The stone to be used on heavy engineering works docks, harbous, gravity dams etc. must have high specific gravity. In general, it varies from 2.4 to 2.8. For a good building stone specific gravity should be more than 2.7.

11. Texture:

A good building stone should have a close grained and compact texture. It should be free from cavities and cracks.

12. Availability:

It should be easily available and cheap.

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