Bitumen, properties, composition, production and application.
Bitumen is a solid or retinoid product, which is a mixture of hydrocarbons and their nitrogen, kislorodnykh, sulfur and metal-containing derivatives.
Bitumen (lat. bitūmen — mountain tar, asphalt) is a solid or retinoid product, which is a mixture of hydrocarbons and their nitrogen, kislorodnykh, sulfur and metal-containing derivatives. Bitumen is an amorphous substance, and, therefore, exhibits the properties of a liquid in a solid state and has no melting point.
Since ancient times, bitumen is one of the most common civil engineering materials. Natural bitumen, or “tar” was used for attaching the lugs of the ancient copies. Bitumen making pottery of ancient man waterproof (dishes of bitumen was preceded by clay). Also in ancient times, the natural bitumen is often used as a binder when working with mosaics and to create products from precious stones. In Ancient Egypt it was used for mummification and embalming.
Bitumens are natural and artificial.
Natural bitumens are an integral part of fossil fuels of organic origin. They are common in locations of oil. It is a natural derived oil formed in the process of natural, biochemical and chemical oxidative polymerization reactions in the oil. Depending on the composition of the original oils and conditions for their conversion, the bitumen is conventionally divided into classes such as: asphalt, Malta, asphaltenes, charity, ozokerite, luminocity, anthraxolite, Naftoli, Naftali.
The world’s reserves of natural bitumen are according to various estimates, around 500 – 1000 billion tons. Reserves of natural bitumen is poorly understood, therefore the range of stocks is large enough. In any case, the reserves of natural bitumen in several times more than the reserves of oil.
Artificial asphalts (bitumens technical) – are products of processing of crude oil, stone coal and oil shale. Artificial or technical bitumens are similar in chemical composition to natural bitumens. By kind of technological cycle of artificial bitumens are divided into oxidizing, residual and cracking.
The bitumens have a rather complex chemical composition. For example, they may consist of saturated hydrocarbons from С9Н20 to С30Н62.
All the various organic hydrocarbon compounds that form the bitumen can be classified into three groups: solid component, tar and oil fraction.
The hard part of the bitumen consists of high molecular weight hydrocarbons and their derivatives with a molecular weight of from 1000 to 5000 g/mol and a density of more than 1 g/cm3. They are all United under the common name of “asphaltenes”. In asphaltene contains karboidy insoluble in volatile solvents and oils, and carbenes, which can be dissolved only in СCl4. To the solid component of the bitumens include solid hydrocarbons called paraffins.
Resins are amorphous substances of a dark brown color with a molecular weight of from 500 to 1000 g/mol, the density is about 1 g/cm3.
Oil fraction of bitumen consists of different hydrocarbons with a molecular weight of from 100 to 500 g/mol and a density less than 1 g/cm3.
Properties of bitumen, as a dispersed system, are determined by the ratio of its constituent components: asphaltenes, paraffins, oils and resins. With increasing content of asphaltenes and resins increases the hardness, softening temperature and brittleness of the bitumen. And oil, which partly dissolve resin, make it fusible and soft. Ductility of bitumen increases with decreasing molecular weight resins and oils. The bitumen in the oil contains paraffin, which contributes to the deterioration of their properties, increasing brittleness at low temperatures. Therefore, it is necessary that the bitumen contained paraffin is not more than 5%.
From the point of view of the elemental composition of the bitumen contains the following chemical elements:
|The name of a chemical element:||%% content|
|Nitrogen, N||to 2|
The most valuable properties of bitumen and bituminous materials is their chemical resistance to aggressive substances, which corrode metals, cement concrete and other construction materials. Thus, the bituminous materials are good at resisting the action of alkalis with concentration no more than 45 %, phosphoric acid with a concentration of not more than 85% sulfuric acid concentration of not more than 50% of the bitumen are less resistant in the atmosphere, which contains nitrogen oxides and under the influence of concentrated solutions of acids. Bitumen soluble in organic solvents. Due to the inherent bitumen chemical resistance and cost effectiveness, bituminous materials are preferably used as chemical protection of concrete structures and steel pipes.
(depends on the temperature, pressure and chemical composition)
|from of 0.965 to 1.5|
(depends on the temperature, pressure and chemical composition)
|from 965 to 1500|
|Aggregate state||solid or resinoid substance|
|Thermal conductivity, W/(m∙°C)||0,17-0,27|
|Softening temperature*, oC*||35 (Malta) to infusible (kerity, anthraxolite, luminocity)|
|Specific heat, kJ/(kg∙K)||1,591-1,968|
|Electrical conductivity, Ohm-1∙cm-1||1∙10-14|
* Bitumen is an amorphous substance having no melting point. Its transition from solid to liquid is characterized by softening temperature. The softening temperature is usually determined using the “ring and ball”, which is placed in a container of water. The softening temperature determined by the temperature of the heated water, in which a metal ball under the action of its own weight passes through a ring, filled by the studied bitumen.
Pure natural bitumen occurs quite rarely. Mostly it is found in the tar Sands. Development of deposits of natural bitumens depends on the physical properties of the feedstock, the depth and conditions of occurrence.
The extraction of natural bitumen from tar Sands produce mostly mine or pit method. This method consists in the fact that the breed as a whole is retrieved to the surface and the bitumen is extracted with a solvent or hot water. Recovery of bitumen is between 85-90 %.
Downhole in-situ methods to develop deposits of liquid natural bitumen, lying at a depth of over 100 meters. This method extract the bitumen through wells drilled on the surface, by thermal effects on bitumen saturated rocks. The coefficient of extraction of bitumen is an average of 30 %.
There is another method of extraction of bitumen in the mines through a system of drainage wells, hewn from the mine workings. This mine drainage extraction method. The bitumen flows by gravity through the system of wells.
For the application of bitumen are divided into three main types: construction, road and roofing.
Construction bitumen – bitumen is used in construction and waterproofing work. Such bitumens are labeled as follows: bn 50/50, bn 70/30, bn 90/10.
Explanation: bn – bitumen, BND – a bitumen road, BNK – petroleum roofing bitumen, the first number is the designation of the softening temperature, the second marking penetration.
Road bitumens are the most popular type of bitumen used in road construction. They are characterized by a high coefficient of penetration. Their main difference from each other is the climatic zone in which they are applied.
Considering the regions, the use of bitumen, determine the maximum and minimum winter temperatures. Regions with low temperatures in the winter rarely rising above minus 20 ° C., used bitumen BND 90/130, BND 130/200, BND 200/300. Regions with moderate winter temperatures from -20 to 10 ° C suitable brand BND 60/90 and BND 90/130 above, BND 130/200, BND 200/300. In areas with winter temperatures ranging from -10 to -5 ° the roadbed is laid with the use of bitumen BND 40/60, BND 60/90, BND 90/130, BND 130/200, bn 90/130, bn 130/200, 200/300 bn. For warm places, where the average winter temperature is +5 OS use bitumen grades BND 40/60, BND 60/90, BND 90/130, bn 60/90, bn 90/130.
Roofing bitumen used in the manufacture of roofing materials: roofing material, rubemast, gidrostekloizol of paper, mastic, of rubiteks, bitumen paper, rubiteks, rubiteks, steklolenta, rubiteks primer. For impregnation use bitumen grades BNK 45/180 and BNK 45/90. To obtain a coating layer – bitumen grades BNK BNK 90/30 and 90/40.
Bitumen is also used in various sectors of the economy. For example, in foundry as one of the components of the model compounds at a precision molding as insulating material in electrical industry, for finishing various products from paper, wood, leather , etc.
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