BITUMEN

Ashalt, bitumen and tar are referred as bituminous materials, which are essentially hydrocarbon materials. The asphalt is a mixture of inert mineral matter lime alumina, lime, silica etc. and a hydrocarbon known as asphaltic bitumen. In some places like Trinidad and Bermudez, asphalt is available in nature at a depth of 3 to 60 metres. It is known as natural asphalt. Common variety used all over the world is residual asphalt, which is obtained by fractional distillation of crude petroleum oil. Bitumen is the binding material which is present in asphalt. It is a hydrocarbon. It is obtained by partial distillation of crude oil. It contains 87 per cent carbon, 11 per cent hydrogen and 2 per cent oxygen. Tar is obtained in the distructive distillation of coal, wood or other organic materials. When coal or wood is heated to redness in an closed chamber, it yields volatile product and residue coke. After separating and cooling volatile product gives tar.

Comparison between asphalt, bitumen and tar is given below figure.






ASBESTOS

Asbestos is a general name for several varieties of fibrous minerals which are available in nature. But presently, most of the commercial asbestos produced is ‘chriotile’ [Mg6SiO11(OH)6.H2O].


Properties of Asbestos:-

1. It is flexible, soft and non-porous.
2. It is fire proof and acid proof material.
3. It is a good insulator of heat and electricity.
4. When it is mixed with cement and water, it retains shape firmly.
5. Its colour is brown or grey.
6. It can be cut into pieces or can be drilled.
7. It possesses high tensile strength in the direction of its fibres.
8. Its specific gravity is 3.10.


Uses of Asbestos:-

1. Asbestos cement sheets are the cheapest roofing materials.
2. Asbestos cement pipes are used as down take pipes of rain water from the roof.
3. With bitumen it forms good damp proof layer.
4. It is used for preparing fire proof ropes and clothes.
5. It is used as covering material for fuse and electric switch boxes.
6. It is useful for insulating boilers, furnaces etc.