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Last edited 14 Mar 2022
Bitumen, sometimes called ‘tar’ or ‘pitch’ and is a petroleum-based hydrocarbon that occurs naturally as a concentrated substance in oil sands and pitch lakes. It is either a liquid – in which case it will be sticky, black, and highly viscous – or adopts a semi-solid form.
In its natural state, the high viscosity of bitumen prevents it from flowing through a pipe and so it must be heated and even sometimes diluted with lighter oils. Bitumen may also include contaminants such as vanadium and nickel, oxygen, sulphur, and nitrogen which must be removed during the refining process.
 Different Types of Bitumen
- Natural bitumen or gilsonite, which is found as a glossy black solid. It is classified using the percentage of ash.
- Bitumen extracted from oil: This bitumen is prepared by blowing oxygen into the vacuum bottom and is divided into the following types:
Types of bitumen include:
- Penetration bitumen: This bitumen is divided by penetrometer according to the degree of hardness and softness. The most common types of bitumen include: 30/40 40/50 50/60 60/70 85/100
- Viscosity bitumen: These bitumens are classified into 4 groups according to their viscosity properties: VG10, VG20, VG30, and VG40.
- Cutback bitumen: It is formed from a combination of bitumen and a solvent such as Naphtha.
- Emulsion bitumen: It is produced from the combination of bitumen, water, and emulsifier. This bitumen should be used soon because the emulsifier loses its property. It is divided into two types, cationic and anionic. Each type is classified based on setting time.
- Oxidized Bitumen: It is produced by blowing hot air into bitumen. Oxidized bitumen is classified into different groups based on the degree of penetration and softening point.
 Uses of bitumen
The vast majority of applications for bitumen products are in construction; one of the most useful qualities of bitumen – and the products derived from it – is as a barrier to water penetration. Around 10% of the global bitumen production goes into roofing, and another 5% goes into sealing and insulating materials such as paint, pipe coatings, and carpet tiles.
In the production of asphalt for road and highway surfacing, bitumen is used as a binder and combined with aggregates to create the top wearing surface. One of the main advantages of bituminous asphalt is that it is easily and relatively cheaply patched and repaired.
Other bitumen-based products include:
- Bituminous felt – used to surface and waterproof roofs, particularly in ‘built-up roofing’ where several layers of bituminous felt are bound together to form a water-resistant surface.
- Bituminous paints – which have good anti-corrosion properties, good moisture, and chemical resistance as well as being flexible and durable.
- Bituminous plastics – used for casings, etc.
NB The SuDS Manual published by CIRIA in 2015 defines bitumen as: ‘A hydrocarbon binder. A virtually non-volatile adhesive material derived from crude petroleum that is used to coat mineral aggregate for use in construction and maintenance of paved surfaces.’
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