Asphalt, bitumen and tars are used for the construction of pavements and all these have few similar properties, however there are few differences too. In this short write up, we will compare the properties.
What is asphalt?
Asphalt consists of mixture having lime, silica, alumina and asphaltic bitumen. It will be in solid state at lower temperature, while it will be in liquid state at higher temperature.
Asphalt is available in following 2 different ways:
- Natural asphalt
This natural asphalt can be obtained from the nature directly from the 2 resources – rocks and lakes.
Rock asphalt will contain 10 – 15% of calcareous matter and pure bitumen.
Lake asphalt will contain pure bitumen of 40 – 70 %.
- Residual asphalt
You can obtain residual asphalt artificially by distilling crude petroleum oil along with asphaltic base.
Following are the available asphalt forms used by bitumen sealing services.
- Cutback asphalt
It is available in liquid state which is dissolved in volatile solvent for getting this cutback asphalt.
- Asphalt emulsion
This is obtained with addition of water of 50 to 60% to asphalt along with 1% emulsifying agent. This agent will form water proof film as water evaporates. Hence, in cold conditions it is used.
- Asphalt cement
To obtain asphalt cement, natural asphalt will be subjected to high-pressure air at high temperature.
- Mastic asphalt
By heating the natural asphalt along with mineral fillers and mastic asphalt will be obtained.
What is bitumen?
By partially distilling crude petroleum, bitumen is obtained. Also, it is called mineral tar which is present in the asphalt too. It will contain 87% of carbon, 11% of hydrogen and 2% of oxygen.
Following are 5 types of forms of bitumen:
- Cutback bitumen
This cutback bitumen can be obtained by distilling asphaltic bitumen along with addition of petroleum or coal.
- Bitumen emulsion
By dissolving fine bitumen in the aqueous medium bitumen emulsion can be obtained. Also, suitable stabilizing agents will be added to the solution.
- Plastic bitumen
Mostly plastic bitumen will contain 40 to 45% inert filler, bitumen and thinner. It will be used as a sealing material for cracks, leakages in masonry structures.
- Blown bitumen
This is special kind of bitumen that is manufactured by putting bitumen to air at heavy pressure at very high temperature.
- Straight run bitumen
This straight run bitumen can be obtained by distilling bitumen into certain definite viscosity.
What is tar?
It is very high viscous liquid that contains carbon content of very high amount.
Tars are available in following 3 forms:
- Coal tar
While producing coal gas, coal tar is obtained as by-product. It can be utilized for laying macadam roads and preserving timber.
- Wood tar
By distilling resinous woods such as pines, wood tar can be obtained. With distillation of the resinous wood will provide creosote oil that has very good property of preservation. Hence, wood tar is quite suitable for wood preservation.
- Mineral tar
By exploitation of kerogens, mineral tar can be produced. Kerogens can be obtained from bituminous shale that just rocks.