Bitumens

The Babylonians and Assyrians cemented stone slabs as well as bricks with bitumen (which is sometimes also referred to as asphalt), a mixture of a black or brown natural organic material with a pitchy luster and comminuted mineral. Bitumen is a thermoplastic solid material when heated above 50°C, it softens and becomes a thick, viscous liquid that reverts to a solid on cooling. It is composed of a natural mixture of hydrocarbons (organic sub-sfances composed of carbon, hydrogen, and oxygen) that occurs in natural 

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In the U.S. and elsewhere the term asphalt is commonly applied to the material known in Britain as bitumen or asphaltic bitumen. 

Athabasca tar sands Naturally occurring mixtures of bitumen and sand found in Northern Alberta. 

In France, bitumen belong to a category of products called "hydrocarbon binders . They are defined and classified in the French Standard, NF T 65000. The hydrocarbon binders comprise ... 

The term bitumen is used in France to designate petroleum products, as in Great Britain and Germany. In the United States on the other hand, the equivalent material is designated by the expression asphalt-cement . In France, asphalt is a mastic, a mixture of bitumen and powdered minerals, poured in place. This mixture can be either natural or reconstituted by an industriai process. Asphait (French meaning) is utilized on roads, particularly in urban centers as well as for sidewalk surfacing. 

The standard NF T 65-001 gives a classification for bitumen as a function of their hardness. This is measured using a needle penetrability test, which measures the penetration depth of a weighted needle into the bitumen. Five grades have been defined. 

The standard NF T 65-003 defines in the same manner three grades of fluxed bitumen. 

The standard NF T 65-004 classifies the types of composite bitumen it distinguishes three grades of bitumen-tars by their pseudo-viscosities and two grades of bitumen-coal tar pitch by their penetrabilities. 

The standard NF T 65-011 distinguishes the bitumen emulsions by their ionic nature (anionic or cationic), their stability with respect to agglomerates and weight content of base binder. There are 20 grades of emulsions. 

There are several processes to manufacture bitumen from crude oil ... 

The distillation of crudes chosen for their yield in heavy fractions is the most common means. Bitumen is extracted from the residue from a vacuum distillation column (a few dozen mm of mercury), the latter being fed by atmospheric distillation residue. Unlike the practice of a decade ago, it is now possible to obtain all categories of bitumen, including the hard grades. 

Solvent deasphalting. This is an extraction of the heaviest fractions of a vacuum residue or heavy distillate. The extract is used to produce the bitumen. The separation is based on the precipitation of asphaltenes and the dissolution of the oil in an alkane solvent. The solvents employed are butane or propane or a butane-propane mixture. By selecting the proper feedstock and by controlling the deasphalting parameters, notably temperature and pressure, it is possible to obtain different grades of bitumen by this process. 

Road paving. This includes bitumen, cutbacks and fluxed bitumen as well as emulsions. Each of these products is subject to very special application techniques. This list is completed by the use of poured asphalt, even though this product is better suited to smaller surfaces sidewalks, courts, etc., than to pavements. Since the middle of the 1980 s, air-blown bitumen is no longer used for road construction. 

The industrial applications, for which blown bitumen are very often used. Some of the industrial applications are given below ... 

Waterproofing, whether it has to do with protecting civil engineering structures or roofs or terraces. Poured asphalt, often placed in layers with kraft paper, oxidized bitumen or modified bitumen can be used, generally with copolymer. The modified bitumen are used for the making prefabricated multi-layer waterproofing composites. 

Filler for cracks and fissures, particularly in highways. Mixtures of bitumen, heavy oils, polymer or sulfur are used. 

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