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Definition of bitumen


Definition of bitumen
The term ‘bitumen’ is used in this Article to describe refined bitumen, a hydrocarbon product produced by removing the lighter fractions (such as liquid petroleum gas, petrol and diesel) from crude oil during the refining process.
In North America, bitumen is commonly known as asphalt binder or asphalt. For the purpose of this article, the term ‘bitumen’ is used.
A comprehensive definition of refined bitumen is used in the industry document The Bitumen Industry – A Global Perspective (Eurobitume and the Asphalt Institute, 2011) and is reproduced here verbatim:

Bitumen is an engineering material and is produced to meet a variety of specifications based upon physical properties. Bitumen is the residual product from the distillation of crude oil in petroleum refining. The basic product is sometimes referred to as ‘straight run’ bitumen and is characterised by CAS# 8052-42-4 or 64741-56-6 which also includes residues obtained by further separation in a deasphalting process. Bitumen can be further processed by blowing air through it at elevated temperatures to alter its physical properties for commercial applications.
The general characteristics of oxidized bitumen are described by CAS# 64742-93-4. The vast majority of petroleum bitumens produced conform to the characteristics of these two materials as described in their corresponding CAS definitions.
Bitumen is produced to grade specification either directly by refining or by blending.
Bitumen should not be confused with coal derived products such as coal tar or coal tar pitches. These are manufactured by the high temperature pyrolysis (.8008C) of bituminous coals and differ from bitumen substantially in comparison and physical characteristics. The differences between bitumen and coal-tar products are well defined in the literature.
Similarly, bitumen should not be confused with petroleum pitches (CAS# 68187-58-6), which are often aromatic residues, produced by thermal cracking, coking or oxidation from selected petroleum fractions.
The composition of petroleum pitches differs significantly from bitumen.
Bitumen also should not be confused with natural or lake asphalt such as Trinidad Lake Asphalt, Gilsonite, rock asphalt and Selenice. These products are unrefined and not produced by refining of crude oil. They often contain a high proportion of mineral matter (up to 37% by weight) and light components, leading to a higher loss of mass when heated. Bitumen is manufactured during the distillation of crude oil. It is generally agreed that crude oil originates from the remains of marine organisms and vegetable matter deposited with mud and fragments of rock on the ocean bed. Over millions of years, organic material and mud accumulated into layers some hundreds of metres thick, the substantial weight of the upper layers compressing the lower layers into sedimentary rock. Conversion of the organisms and vegetable matter into the hydrocarbons of crude oil is thought to be the result of the application of heat from within the Earth’s crust and pressure applied by the upper layers of sediments, possibly aided by the effects of bacterial action and radioactive bombardment. As further layers were deposited on the sedimentary rock where the oil had formed, the additional pressure squeezed the oil sideways and upwards through porous rock. Where the porous rock extended to the Earth’s surface, oil seeped through to the surface. Fortunately, the majority of the oil and gas was trapped in porous rock, which was overlaid by impermeable rock, thus forming gas and oil reservoirs. The oil remains here until its presence is detected by seismic surveys and recovered by drilling through the impermeable rock.