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Last edited 24 Dec 2019
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 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.
The majority of bitumen used is obtained from crude oil and forms as a residue after the distillation process (sometimes called ‘refined bitumen’).
 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 a 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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