What Is Asphalt?
A mechanical mixture of inert mineral, say like, brownish alumina, lime, silica, etc. and the asphaltic bitumen. The colour is usually black or brownish-black.
At low temperatures, it usually remains at soil but becomes liquid at a temperature of about 50° C to 100 ° C
Types of Asphalt
There two types of asphalt, namely.
• Natural Asphalt
• Residual Asphalt
It occurs as fossil deposits in places like lakes Trinidad at a depth of 3 to 6m. It contains 40 % to 70 % pure bitumen with about 30 percent contained.
It is obtained from the distillation of petroleum oil with an aspheric base. The residue left will also be asphalt.
Forms of Asphalt
The usual forms of asphalt are as follows
• Mastic Asphalt
• Asphaltic Cement
• Cut- back Asphalt
• Asphaltic Emulsion
On heating the natural asphalt with sand and mineral fillers, mastic asphalt is produced. The resulting product is a void less impermeable mass.
The hardness and melting point of mastic asphalt can be controlled during its manufacture. It may either be in a solid or semi-solid state.
But when heated to a suitable temperature it can be sufficiently fluid so as to be able to spread by a hand float. It is used as a material for damp-proofing and water-proofing.
It is prepared by blowing air through melted asphalt at high temperatures. The asphalt is oxidized and the resulting product is plastic in nature and it is highly resistant to varying dimatic conditions.
It is used for flooring, roofing, water-proofing, and filler in expansion joints in concrete.
Cut- back Asphalt
A liquid asphalt; prepared by dissolving asphalt in a volatile solvent. It can be applied at normal temperature in cold conditions.
It is used for preparing bituminous paints, repairing roofs, etc.
It is produced by mixing asphalt with 50 to 60 percent water in the presence of 1 percent of the emulsifying agent.
When water evaporates, the emulsion breaks and it forms a water-proofing layer. It can be applied in cold conditions.
Properties of Asphalt
Properties of asphalt are as follows:
• A good insulation of electricity, heat, and sound
• A tough and durable material.
• A Water-proof material that can be elastic cleaned.
• It is resilient and reasonably elastic.
• It is non- inflammable and non-absorbent.
• It is not attacked by acids and is safe against vermin.
Uses of Asphalt
The asphalt is widely used for various engineering purposes. Some of the purposes are listed below:
• As a water-proof layer for tanks, of roofs, basements, swimming pools, etc.
• As damp-proof courses.
• As flooring materials.
• For preparing paints felt flashing.
• For constricting roads and pavements, etc.
• Taking of basement floors (building water barriers in basements)
What Is Bitumen?
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.
Type of Bitumen
Following are the types of Bitumen
• Blown Bitumen.
• Cutback Bitumen.
• Straight Run Bitumen.
• Penetration Grade.
• Bitumen Emulsion.
• Residual Bitumen.
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.
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.
The basic form of bitumen and has to be heated before application.
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.
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.
Comparison Between Asphalt and Bitumen
|1.||And Asphalt colour Blackish brown||Bitumen Colour Dark with slight reddish time|
|2.||Asphalt carbon content is low||Bitumen carbon content is midium (moderate)|
|3.||Asphalt Solid or semisolid sate||Bitumen usually solid in state.|
|4.||Here, Asphalt effect on heating Burns with a smoke flame and becomes plastic||Bitumen effect on heating time bitumen is melt|
|5.||Asphalt setting time very less||Bitumen setting time very less|
|6.||Asphalt adhesive power is very less compared to bitumen||Bitumen adhesive power is high compared Asphalt|
|7.||Asphalt resistance to acid effect is more||Bitumen resistance to acid effect is more|
|8.||Molecular weight range for road Asphalt is 400 to 5000||Molecular weight range for road bitumen is 400 to 5000|
|9.||Installation is comparatively costlier.||Cheap to install compared to asphalt.|
|10.||It shows less resistance to weathering
|It shows more resistance to weathering action|
|11.||Asphalt use for As damp proof course, for paints, as roofing felt and for road works.||Bitumen normally use as damp proof course and as roofing felt.|
|12.||Less sensitive to temperature compared to bitumen pavements. Negative impacts are seen only in extremely high or low temperature.||Pavements are susceptible to high temperature, which can make it slick and soft.|