What is Tar ? | Comparison Between Asphalt, Bitumen and Tar Properties

In this article, we'll discuss what is tar and difference between asphalt, bitumen, and tar, their types, and comparisons of their properties are discussed. Asphalt, bitumen, also tar have similar properties commonly used for pavements construction.

what is tar

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What is Asphalt?

The asphalt is a mixture that consists of alumina, lime, silica, and asphaltic bitumen. At low temperatures, it is in solid-state and at high temperatures, it is in a liquid state.

Asphalt is presented in two different forms as follows.

1. Natural asphalt
2. Residual asphalt

Natural Asphalt

Natural asphalt is received directly from nature, mainly from the two resources lakes and rocks.

The lake asphalt includes 40 to 70 % of pure bitumen, which is boiled in the tank, and water content evaporates, and impurities are separated.

The last result is called asphalt, which can be used for laying roads etc.

Rock asphalt includes 10 to 15% of pure bitumen and calcareous matter. These rocks are crushed and heated and consolidate by sudden cooling. This type of asphalt is used for paving tiles etc.

Residual Asphalt

Residual asphalt is obtained artificially by the distillation of crude petroleum oil with an asphaltic base.

Forms of Asphalt

The available forms of asphalt are:

1. Cutback asphalt
2. Asphalt emulsion
3. Asphalt cement
4. Mastic asphalt

Cutback Asphalt

Cutback asphalt is in a liquid state. Asphalt is dissolved in a volatile solvent to make this type of asphalt. It is used for producing bituminous paint, repairing roofs, etc.

Asphalt Emulsion

The asphaltic emulsion is obtained by adding 50 to 60% water to the asphalt in presence of 1% emulsifying agent. The emulsifying agent forms a waterproof layer when water evaporates. So, it can be used in cold positions.

Asphalt Cement

Natural asphalt is controlled to high-pressure air under high temperatures to make asphalt cement. Asphalt cement is plastic in nature and it is used for flooring, roofing, waterproofing material, etc.

Mastic Asphalt

Mastic asphalt is obtained by heating natural asphalt with sand and mineral fillers. It is an impermeable thing that does not contain any voids.

Hardness and melting point of mastic asphalt can be managed while the process of heating. It is in solid-state, and by heat, it can be brought to a liquid state. It is used for DPC.

What is Bitumen?

This is binding material present in asphalt. Sometimes it is also known as mineral tar. Bitumen is produced by partial distillation of crude petroleum. The bitumen is produced in solid or semi-solid state and black or brown in color.

Types of Bitumen

There are different types of bitumen available in industry with different properties, specifications, and uses based on requirements of consuming industry.

Usually, types of bitumen can be identified like below;

1. Cutback bitumen
2. Bitumen emulsion
3. Plastic bitumen
4. Blown bitumen
5. Straight run bitumen

Cut-back Bitumen

This form of bitumen is produced by fluxing asphaltic bitumen in the presence of some liquid distillates of petroleum or coal tar. Cut-back bitumen can be used as bitumen paint in cold.

Cutback bitumen is obtained from the distillation of asphaltic bitumen with the addition of coal tar or petroleum. Cut back bitumen can be used as paint in cold weather conditions.

Bitumen Emulsion

It is a liquid compound that contains a large amount of bitumen in the aqueous medium. It is suspended by some appropriate stabilizing agents in the aqueous medium.

Plastic Bitumen

Plastic bitumen majorly contains inert filler about 40 to 45% and bitumen and thinner is the other material.

Normally, this type of bitumen is use as sealing material for leakages, cracks in wall, etc.

Blown Bitumen

Blown bitumen is a special form of bitumen. It is manufactured by subjecting bitumen to air under heavy pressure at high temperatures. It can be used as DPC material, heat insulating material, etc.

Straight Run Bitumen

Straight run bitumen is obtained by the distillation of bitumen into definite viscosity. It is also available as rocks.

What is Tar?

Tar is a highly viscous liquid that contains a high amount of carbon content. It is used for laying surface layer for pavements, preserving wood, etc..

Types of Tar

General forms of tar are as follows.

1. Coal tar
2. Wood tar
3. Mineral tar

Coal Tar

Coal tar is the by-product obtained during the production of coal gas. It is used for preserving timber, laying macadam roads, etc.

The process consists of coal heated in closed iron vessels and the evaporated gases are collected in tubes. These tubes are circulated with cooling water. So, some matter is deposited in these tubes and it is nothing but coal tar. It is dense and strong-smelling liquid. It is in black color.

Wood Tar

Wood tar is obtained by the distillation of resinous woods like pines etc. The distillation of resinous wood provides the creosote oil which has very good preservative property. So, wood tar is well suitable for preserving wood.

Mineral Tar

Mineral tar is produced by the exploitation of kerogens. Kerogens are generally obtained from bituminous shale’s which are nothing but rocks. The volatile content of mineral tar is very less.

Comparison Between Asphalt, Bitumen and Tar Properties

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what is tar