Bitumen is one of the oldest building materials known to mankind. Nowadays, its use involves quite a variety of options. There are many varieties of this material.
Bitumen substances are organic materials, which include several types.
- Natural bitumen. It is a viscous substance or solid material that consists of carbohydrate compounds and their derivatives. The ways of their formation are natural oxidative processes of oil polymerization. They are widespread in the places where oil is located. Pure natural bitumen is a rather rare substance.
- Asph alt varieties. This type is found more often than the previous one. It is found in porous rocks. They are crushed and turned into powder. This is how road bitumen is obtained.
- Oil. This is an artificial type of material. It is obtained in the process of oil refining. In accordance with the type of technological cycle, such bitumens are divided into residual, oxidizing and cracking.
Bitumen has the followingcomposition in the classic version:
- up to 80% carbon;
- up to 15% hydrogen;
- 2 to 9% sulfur;
- no more than 5% oxygen;
- 0 to 2% nitrogen.
The listed substances are in the form of compounds of hydrocarbons, sulfur, oxygen and nitrogen.
All elements can be classified into three groups.
1. The solid component is high molecular weight hydrocarbons called asph altenes. Paraffins also belong to the solid constituents.
2. Resins are amorphous materials that are dark brown in color.
3. Oil fractions are various hydrocarbons that have a density less than 1.
Bitumen is a rather complex substance with a certain ratio of all components. An increase in asph altenes in its mass will lead to an increase in hardness, brittleness and softening point.
Paraffins also reduce the plasticity of bitumen, therefore, during production, attention is paid to reducing their content to 5% or less.
Scope of application
Depending on the physical properties, the following areas of application of bitumen are distinguished:
- road construction;
- roof device;
- electric cable production;
- tire-rubber technology;
- paint and varnish products;
- production of coal briquettes;
- oil refining.
In carrying out construction work on their own, bitumen is the mostdemanded material for waterproofing various objects, especially cellars and cellars.
In the construction of roads, oil road bitumen (GOST 22245-90) is used. There are several brands of this material.
To choose the right variety, you should decide on the type of climate zone.
For natural conditions, which are characterized by temperatures in the cold season, on average, not higher than -20 ˚С, road bitumens such as BND 200/300, BND 130/200, and BND 90 are suitable in accordance with GOST. 130.
For regions where average temperatures in the cold season range from -10 to -20 ˚С, oil road bitumens of the II and III climatic road zones are provided. These include the above varieties, as well as BND 60/90.
If the average monthly temperatures in the cold season are in the range from -5 to -10 ˚С, then GOST provides for the use of such oil road bitumens as all of the above types, as well as BND 40/60, BN 90/130, BN 130/200, BN 200/300.
For areas where winter is characterized by average monthly temperatures not lower than +5 ˚С, oil road bitumens of such types as BND 40/60, BND 60/90, BND 90/130, BN 60/90, BN are suitable 90/130.
There are varieties that are used to build not only roads, but also residential buildings. These are generic brands. There are only three brands that include suchpetroleum bitumen, like BN 70/30, BN 90/130, BN 50/50.
As well as oil road bitumen, the GOST of which regulates the conditions for the use of each variety, GOST 6671-76 applies to construction bitumen.
The lower the ambient temperature, the more elastic the material must be used for construction. This will ensure its durability and longevity.
Petroleum roofing materials
For various roofing works, special bitumen is used. Its properties and scope are regulated by GOST 9548-74. This standard implies the use of three varieties of this roofing material:
- BNK 90/30 - has such a scope as the formation of the cover layer of the roof.
- BNK 40/180 - used for impregnation.
- BNK 45/190 - selected for roofing and roof material.
Factors affecting the type of road material
Road bitumen, the GOST of which provides for several types of such a substance, is characterized by many different properties. Each gives certain qualities to the material.
The most important of them, which determine the scope of bitumen, are plasticity, softening point, brittleness, flashing, viscosity, adhesive qualities.
High temperatures increase bitumen viscosity. When cold, the material loses this quality and becomes brittle when it reaches the thermal limit.
Adding to the composition of the material helps to increase plasticityoils. The more frost resistance of oil road bitumen, the higher its quality class.
Flash point is also a very important indicator for a material such as road bitumen. GOST provides for a standard value of this indicator of +200 ˚С and higher. The higher the flash point, the lower the fire hazard of the substance.
The adhesion index will help you find out how well the bitumen adheres to the base surface. The higher this value, the stronger the material adheres to the surface.
In the construction of roads and other facilities, bitumen heating technology is used. This process is carried out in accordance with certain rules. The technique of using the material is embedded in the characteristics of such a substance as bitumen. GOST reveals its most important properties.
To heat the material used in construction and repair, a special boiler with thick metal walls and a hermetically sealed lid is used. The thickness of the material will prevent it from burning.
Fills 2/3 of the container. The bitumen is broken into small pieces before loading.
Heating is done over low heat, and the material is melted to a homogeneous mass. When foreign impurities appear, they are removed with a special sieve. The maximum heating temperature is +200 ˚С.
When the heating temperature is from +160 to +170 ˚С bitumen will melt in about 3 hours. If you increase it to the limit value, the warm-up process will be only 1hour.
Road oil bitumen does not tolerate an increase in heating above +200 ˚С, because their properties will deteriorate from this. At +220 ˚С, coke will start to form.
When the bitumen is overheated, an unpleasant yellow-green smoke is formed, and when the border reaches +240 ˚С, the substance may even flare up. The lid of the cauldron is then closed to put out the flames.
After overheating and flashing, road bitumen becomes brittle and is no longer suitable for construction or repair work.
Storage and transport
Storage of bitumen takes place in special tanks. They are equipped with mechanisms for mixing the heated substance. This technique must have special ways of supplying water vapor to prevent flashing of vapors from the material.
To empty the tanks, they have a bottom with a slope.
Equipment transporting liquid road bitumen is equipped with special pumps that pump the substance.
If the material is transported in solid form, special collapsible forms are used.
During transportation and storage, all fire safety requirements are met, since bitumen is a highly flammable substance. By following all safety rules, you can not be afraid of unpredictable situations when working with this material. Having studied the properties and varieties of the material, you can correctly apply it in the construction of various objects.
Bitumen is a substance that hassuch positive qualities as moisture resistance, strength, resistance to climatic influences, low sound and heat permeability, as well as low current conductivity. Thanks to these properties, it is a very popular and reliable building material.