It is a non-crystalline solid or viscous material derived from petroleum, by natural or refinery process and substantially soluble in carbon disulfide. It is asphalt in a solid state and mineral tar in a semi-fluid state. Bitumen is brown or black in color.
Bitumen is the binding material that is present in asphalt. It is a hydrocarbon. It is obtained by partial distillation of crude oil. It contains 87 percent carbon, 11 percent hydrogen, and 2 percent oxygen.
Asphalt, bitumen and tar are called bituminous materials, which are essentially hydrocarbon materials.
Properties and characteristics of bitumen
Below is a summary table that describes the properties and characteristics of bitumen, and that compares them with asphalt and tar because these are also bituminous or asphaltic materials.
| Property | Asphalt | Bitumen | Tar |
|---|---|---|---|
| Color | blackish brown | Dark with a slight reddish tint | dark black |
| carbon content | Bass | Moderate | Tall |
| Condition | solid and semisolid | Solid | viscous and liquid |
| Effect on temperature | burns with a smoky flame and turns to plastic | it melts | It becomes more fluent |
| setting time | Minor | Minor | Higher |
| adhesive power | Bass | Medium | Tall |
| Acid resistance | Medium | Medium | Bass |
| Applications | As a moisture-proof course, for paints, as a roofing felt and for road works. | As a moisture-proof course and as a roofing felt | To preserve the wood |
Composition and components of bitumen
The main component is petrolene, a yellowish oily substance, excess of which causes bitumen to melt at low temperatures, and asphaltenes, a hard black substance, excess of which makes bitumen brittle and non-plastic.
Its compositions are 87 percent carbon, 11 percent hydrogen, and 2 percent oxygen.
Characteristics of bitumen
Bitumen is not affected by light, air or water individually, but in combination they can make it brittle, porous and susceptible to rust, forming blisters and cracks.
It becomes soft at temperatures between 30°–100°C (no sharp melting point) and therefore should be protected from exposure to heat.
It is insoluble in water and quite resistant to most acids.
Although bitumen is combustible, composite products, such as mastic asphalt, do not ignite easily.
Physical properties of bitumen
The various properties are viscosity, ductility, and softening point.
Goo : It depends a lot on the temperature. At a lower temperature, bitumen has a high viscosity and acquires the properties of a solid body, while with increasing temperature, the viscosity of bitumen decreases and it turns into a liquid state.
Plasticity : depends on the temperature, the composition of the group and the nature of the structure. Viscous bitumens that contain solid paraffins at low temperatures are very ductile.
softening point : is related to viscosity. The bitumen needs sufficient fluidity before the specific application.
Endurance : It is strong, not rigid, and as such is capable of absorbing shock and adapting to movement in the structure due to temperature, settlement, or shrinkage.
bitumen classification
natural bitumen
Pure natural bitumen rarely occurs. Limestone, sandstone and bitumen-impregnated soils are frequently found.
It originates from the accumulation of oil in the upper layers of the earth’s crust through migration, filling the pores and cavities of the rocks, under the action of high temperatures and pressures.
Natural bitumen is dark brown in color which gradually softens when heated and becomes a liquid and when cooled it solidifies.
It is insoluble in water, but it dissolves in carbon disulfide, chloroform, benzene, and very little in gasoline.
Natural bitumen can be extracted from bituminous rocks by blowing into boilers or by dissolving it in organic solvents (extraction).
petroleum bitumen
They are the product of the processing of crude oil and its resinous residues. These are classified as residual asphalts, oxidized, cracked and extracted bitumens.
| residual asphalt | they are solid substances of black or dark brown color at normal temperatures, obtained by atmospheric vacuum distillation of petroleum with high resin content after coating gasoline, kerosene and fractions. |
| rusty bitumen | they are produced by blowing air through oil residues. Oxygen from the air combines with hydrogen from the waste to give water vapor. Oil residues thicken due to polymerization and condensation. |
| cracked bitumen | It is obtained by the cracking (decomposition at high temperature) of petroleum and petroleum oils that allow a high gasoline yield. Blowing air through the debris produces oxidized cracked bitumens. |
based on consistency
At 18°C, they are classified into solid, semi-solid and liquid bitumen.
Based on the application
they are classified as road construction bitumen, construction bitumen and roofing bitumen.
Types of bitumen
bitumen emulsion
It is a liquid product that contains bitumen to a large extent in an aqueous medium. Bitumen which is in a very finely divided state (globules about 2 microns in diameter) is kept suspended in the aqueous medium with the help of some suitable stabilizing agents. Depending on the stability of the protective coating of the emulsifying agent, emulsions are classified as fast-setting, medium-setting, and slow-setting. These emulsions are always stored in airtight drums.
bitumen blowing
it is obtained by passing pressurized air at a higher temperature through the bitumen. It can be used as roofing and moisture-proof felts, in the manufacture of asphalt for pipes and joint fillers, as a heat-insulating material, etc.
reduced bitumen
It is obtained by flowing asphalt bitumen in the presence of some suitable liquid distillates of coal tar or petroleum. It is mainly used in road construction and soil stabilization (2–4%). Trims are commercially manufactured in the following three groups.
1. Fast-setting trim containing naphtha or gasoline.
2. Medium-setting trim containing kerosene.
3. Slow setting reductions containing light oils as fluxing agents.
Each of the clip groups above is subdivided into six categories from 0 to 5.
The six different viscosities are named with the numbers from 0 to 5 in increasing order of viscosity.
plastic bitumen
consists of bitumen, thinner and a suitable inert filler. The amount of inert filler is approximately 40 to 45 percent. It is used to fill cracks in masonry structures, to stop leaks, etc.
linear bitumen
It is the bitumen that is distilled to a defined viscosity or penetration without further treatment.
Applications
The bitumen is used for the manufacture of roofing and moisture-proof felts.
Plastic bitumen for leaks, waterproof wrapping paper, asphalt for pipes, joint filler, bituminous filling compounds for cable boxes, for sealing accumulators and batteries.
It is also used for fixing roofing felts, dam protection felts, and for thermal insulation materials for buildings, refrigeration equipment, and cold storage.