Bitumen
Bitumen is the heaviest fraction of crude oil and one of its most complex components, dark in color, in solid, semi-solid or viscous forms and of natural or manufactured origin. The main components of bitumen are composed of hydrocarbon compounds with high molecular weight, including oily substances, resins and asphaltenes. This material has a very complex chemical composition and has physical properties such as adhesion and moisture resistance and is soluble in carbon disulfide and CO2. In some countries, the word asphalt is used synonymously with the word bitumen, but in Iran, asphalt is more commonly used to mean a mixture of bitumen and sand used in road construction. Some of them are produced using residues from the distillation of fuel oil. Others are made by using hydrocarbon waste from various industries, including acidic hydrocarbon waste from the re-refining process of engine oils, which are known as acid sludge.
1- Petroleum bitumens are produced from three processes: direct extraction, (Straight Run), aeration (Air Blowing), and blending (Blending).
- Straight Run Process: When the characteristics of the refinery vacuum distillation tower residual cut are similar to the characteristics of bitumen, a process cut called bitumen is received as the final product.
- Air Blowing Process: When the refinery vacuum distillation tower residual cut (VB) does not have the same characteristics as bitumen, in this case VB is transferred to the bitumen unit as the initial feedstock and is produced with the aeration process in the reactor along with oxidation, dehydrogenation, and polymerization reactions and by controlling the operating parameters of bitumen with different grades. This process is carried out in two ways: continuous process and batch process.
- Blending process: The process of mixing different cuts of petroleum products (with optimal formulation), achieving standard bitumen specifications
2- Types of bitumen
There are mainly two types of bitumen used in road construction: if obtained from a mine, it is natural or mineral bitumen, and if obtained from refining crude oil, it is called petroleum bitumen. Petroleum bitumen should be used in road construction, natural bitumen can only be used in combination with petroleum bitumen in some cases as a modifier of petroleum bitumen.
3- Types of petroleum bitumen:
- Pure bitumen (Asphalt Cement):
Bitumens that are obtained directly in the distillation tower in the vacuum of the refinery or are briefly subjected to the aeration process are called pure bitumens. These bitumens must be homogeneous and free of water, and their heating temperature should never exceed 175 degrees Celsius.
- Blown asphalt:
Pure bitumen is exposed to air under pressure and at a temperature of 200 to 300 degrees Celsius so that the hydrogen atoms in the bitumen molecules combine with oxygen in the air and, by creating polymerization reactions, heavier hydrocarbons are obtained that have a lower penetration degree and a higher softening point than the original pure bitumen. These bitumens are less sensitive to heat compared to pure bitumens and their penetration degree is lower. Blown asphalts are not widely used in road construction. These bitumens are used to fill cracks in concrete pavements and fill joints in concrete surfaces.
- Liquid asphalt:
Soluble bitumens or recycled bitumens are obtained by dissolving pure bitumens in solvents or petroleum oils. Soluble bitumens are used in road construction for surface coating, penetration, surface asphalt, cold factory asphalt or asphalt mixed on site. These types of bitumens are divided into three groups: fast-setting bitumens, slow-setting bitumens, and long-setting bitumens, depending on their setting speed and solvent type.
1- Petroleum bitumens are produced from three processes: direct extraction, (Straight Run), aeration (Air Blowing), and blending (Blending).
- Straight Run Process: When the characteristics of the refinery vacuum distillation tower residual cut are similar to the characteristics of bitumen, a process cut called bitumen is received as the final product.
- Air Blowing Process: When the refinery vacuum distillation tower residual cut (VB) does not have the same characteristics as bitumen, in this case VB is transferred to the bitumen unit as the initial feedstock and is produced with the aeration process in the reactor along with oxidation, dehydrogenation, and polymerization reactions and by controlling the operating parameters of bitumen with different grades. This process is carried out in two ways: continuous process and batch process.
- Blending process: The process of mixing different cuts of petroleum products (with optimal formulation), achieving standard bitumen specifications
2- Types of bitumen
There are mainly two types of bitumen used in road construction: if obtained from a mine, it is natural or mineral bitumen, and if obtained from refining crude oil, it is called petroleum bitumen. Petroleum bitumen should be used in road construction, natural bitumen can only be used in combination with petroleum bitumen in some cases as a modifier of petroleum bitumen.
3- Types of petroleum bitumen:
- Pure bitumen (Asphalt Cement):
Bitumens that are obtained directly in the distillation tower in the vacuum of the refinery or are briefly subjected to the aeration process are called pure bitumens. These bitumens must be homogeneous and free of water, and their heating temperature should never exceed 175 degrees Celsius.
- Blown asphalt:
Pure bitumen is exposed to air under pressure and at a temperature of 200 to 300 degrees Celsius so that the hydrogen atoms in the bitumen molecules combine with oxygen in the air and, by creating polymerization reactions, heavier hydrocarbons are obtained that have a lower penetration degree and a higher softening point than the original pure bitumen. These bitumens are less sensitive to heat compared to pure bitumens and their penetration degree is lower. Blown asphalts are not widely used in road construction. These bitumens are used to fill cracks in concrete pavements and fill joints in concrete surfaces.
- Liquid asphalt:
Soluble bitumens or recycled bitumens are obtained by dissolving pure bitumens in solvents or petroleum oils. Soluble bitumens are used in road construction for surface coating, penetration, surface asphalt, cold factory asphalt or asphalt mixed on site. These types of bitumens are divided into three groups: fast-setting bitumens, slow-setting bitumens, and long-setting bitumens, depending on their setting speed and solvent type.
