What is Building stones?

 

BULLDING  STONES

 A building stone is obtained from the rocks in the earth. It is  a naturally occurring substance. Stone is considered to the king of engineering materials. And where durability and permanency of a  structure  are required.it continues to enjoy its superiority  over all other rival materials of engineering construction. Stones were used in early days for  structure.

Properties of Building Stones:When stones are selected   for use in structural and building constructions,the follow ing properties are to be considered:

Structure: This rwlates to the manner in which the particles that go to form a stone are arranged.Igneous stones possess unstratifed structure which yield much strength and durability. Stratified structure is a characteristic  feature of sede mentary stone. This is why sedimentary stone are not strong and durable and also they split very easily. Metamorphic stone have foliated structure which yield much strength and durability like igneous stones.

Texture:It is the arrangement , size and shape of the constituent minerals of a stone. Texture of a stone has a  direct relation with its hardness. Stones with crystalline or homogenous texture are close grained and compact and  better suited for resisting the weathering action of the atmospheric agencies.

Appwarance and Colour:stones with uniform colours  are  found generally strong ang durable. Better architectural aspects of structures are also produced by using highly coloured stones Red and Brown shades indicate the presence of harmful matters such  as oxides of iron,loose-earth particles,etc.Stones containing higher percentages of iron should never be used because; they are liable to be disfigured from unsightly rusts and stains formed bu the oxidation of iron under atmospheric conditions.

Porosity :The porosity of a stone is denied as the percentage of total volume occupied by poor- space. Porous stones are always weak. So, they should never be used in the face- works of buildings because they get decomposed and design deintegrated  by rainwater which is chemically very active.

 Absorption: When a stone is kept under  water for a couple of hours. It absorps water. A      porous stone will absorb more water when soaked. Absorption of water by marbel stones is only 1% by volume. Hence, it is a very strong stone .on the other hand the absorption of water by sands tone is 20%  by volume. This indicates that sandstone is porpous and hence very weak. So, absorption is good property of a stone to see whether it is strong or weak.

Strength: Stones are subject to direct compressive loads in structures. So, their  compressive or crushing strength is to be determined. Stones are very strong in composition.Granite stone has a compressive strength of 5.000 to 7.000 psi.The texture, specific gravity and proceed porosity of a stone greatly affect its compressive strength. It the texture is even, specific gravity is high and porosity less, the stone is considered to be very strong under compressive forces.

 Density: The density of a stone is determined by dividing the total weight of stone by total volume.A denser stone will have higher specific gravity which yields higher strength. Densest stones are used in foundation works whereas light stones are used in ornamental works.

 Toughness: This is the residence of stone to impact. This property is particularly important where the stones are subjected to severs use in impact. A good stone should be very tough.

 Abrasion Reistance: This is the property of stone to resist abration wear and tear. The stone that will be used in road construction should have very good abrasive resistance.

 Permeability: This is the capacity of stone to transmit a fluid through it. A  porous stone is more permeable and hence very weak. A good stone should be impermeable in nature .

 Heat Resitance: Stone is a poor conductor of heat. Heat brings about rapid destruction of stone structures by disintegration and decomposition. Limestones and marbless begin to calcite between a temperature of 600 to 800 c and trap stones resist heat from fire very well, but granites disintegrate very quickly. stand stone are very good in resisting heat in short. most of the stones are very good heat resistants.

 Electrical Conductivity: Stones are poor conductors of electricity. When dry they offer a very high resistance but when wet their resistance becomes less. In an-electric installation marbles and Slater are used because they are non conductor of electricity.

 Seasoning Qualities: Stones contain a higher percentage of moisture when quarried. This makes the stones soft an easer to cut so,stons should be roughly dressed just immediate after quarrying and final dressing and polishing should be done at the work side. Before use the stones must be seasoned to remove moisture by leaving them in the sun for about six months. otherwise the stones will disintegrate and destory the durability and also the quality of the work.

Facility of Working: Economy in the cost of dressing stones plays a vital role in engineering constructions by stones. Hard stones are very difficult to dressand hence very costly. Whereas soft stones can be dressed more economically.