The bitumen is the binding material that is present in asphalt. It also sometimes called mineral tar. It is obtained by partial distillation of crude petroleum.
It is chemically a hydro-carbon. It is insoluble in water, but it completely dissolves in carbon disulfide chloroform, alkalies, alkaline, carbonates, petroleum spirit, and oil of turpentine.
It is found on analysis is composed of 87 percent carbon 11 percent and 2 percent oxygen by weight.
The bitumen is back or brown in colour, and it is obtained is solid or semi-solid or sate. Its applications are the same as the residual asphalt.
Soft bitumen can be modified by heating until it becomes a liquid and then passing air under pressure by which all the volatile compounds in it can be driven out. The product is called blown bitumen.
Cutback Bitumen
Bitumen combined with other petroleum distillates forms cutback bitumen. This may be regarded as a means of applying penetration-grade bitumen at lower temperatures.
Straight Run Bitumen
When bitumen distilled to a definite viscosity of penetration, which does not require further treatment like heating.
Penetration Grade
The basic form of bitumen and has to be heated before application.
Bitumen Emulsion
A product in liquid form, formed in aqueous medium and stabilizing agents. This also another means to obtain bitumen into a liquid form so that it can be easily applied at ambient temperature.
Residual Bitumen
It consists of bitumen thinner and suitable filler made into a plastic Conn. As it is plastic, it can be used for filling cracks in masonry, stopping leakages, etc.
Use of Bitumen
• Bitumen is used for the manufacture of roofing and damp proofing felts.
• For sealing accumulators and batteries.
• It also used for heat insulation materials for building, refrigeration, and cold storage.
What Is Tar?
Tar is a viscous black liquid made of hydrocarbons that can form in multiple ways. Because of this, the chemical composition of tar varies, though it is always made of organic matter of some sort.
It has many uses as a waterproofing and sealing agent. It is also used for many medicinal purposes.
Classified of Tar
Tat is classified on the basis of its sources.
• Coal Tar
• Mineral Tar
• Wood Tar
Coal Tar
A heavy, back, and strong-smelling liquid is known as coal tar. In closed iron vessels, the variety of tar is prepared by heating the coal.
The escaping gases are allowed to pass through the tube, which is kept cool by the circulation of water. The coal tax gets deposited in these tubes.
It is usually derived as a byproduct during the manufacture of coal gas. The coal tar is used for making macadam roads, preserving timber, etc.
Mineral Tar
Distillation of bituminous shales gives us mineral tar. It contains less matter.
Wood Tar
Distillation of pipes and resinous wood gives wood tar. In contains, creosote oil which can be obtained by further distillation of wood and hence is possessed stronger preservation property.
However, the wood creosote is not so good as coal tar creosote for the preservation of timber.
Use of Tar
For coating of sleepers, wooden poles, latrine walls, etc.
Bitumen Vs. Tar
Sr.No.
Bitumen
Tar
1.
Bitumen Colour Dark with slight reddish time
And Tar colour Deep dark
2.
Bitumen carbon content is midium (moderate)
Tar Bitumen carbon content is very high
3.
Bitumen usually solid in state.
Tar viscous liquid sate
4.
Bitumen effect on heating time bitumen is melt
Here, Tar effect on heating becomes more fluid when heated.
5.
Bitumen setting time very less respect to tar
Tar setting time is more compared to bitumen
6.
Bitumen adhesive power is high but not more than tar
Tar adhesive power is very high compared to bitumen
7.
Bitumen resistance to acid effect is more compared to tar
Tar resistance to acid effect is less compared to bitumen
8.
Bitumen is obtained from fractional distillation of crude oil
Tar is obtained by destructive distillation of coal or wood
9.
Molecular weight range for road bitumen is 400 to 5000
Molecular weight range for road tar is 150 to 3000
10.
Bitumen consists of large amount of aromatic hydrocarbon
Tar consist of large amount of oily matter with lower molecular weight
11.
It shows more resistance to weathering action
It shows less resistance to weathering
action
12.
Bitumen normally use as damp proof course and as roofing felt.
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