Bitumen is one of the derivatives of oil in black and pasty form, which has many applications in asphalt, road construction, insulation and roof waterproofing. This material has many types of its own and each one of them is used in different industries according to its unique physical characteristics.
It varies as a hydrocarbon from black to brown and is completely soluble in carbon sulfide and carbon tetra chloride. This material is in solid shape in room temperature and ambient conditions and by increasing temperature, its shape will change to liquid and paste form. One of the main reasons for the diversity in its types is due to the existence of two significant properties in this material, including its permeability and adhesion.
The highest consumption is for road construction and is used as an additive in asphalt and the second most usage is for insulation and roof waterproofing. In general, the main applications are as follows:
– Roads and road construction
– Use in industry
– Insulation and waterproofing
– Electrical insulation
In the laboratory, its degree of penetration is measured to determine its hardness. In this method, a needle with a load of 100 g is inserted in 5 seconds at a temperature of 25 °C and the penetration rate is measured in tenths of a millimeter. The lower the penetration, the harder the bitumen.
The temperature at which its gases ignite is called the degree of ignition, and the maximum amount that can be heated is limited to its ignition temperature.
The lower its fluidity, the higher its solid properties. It is worth noting that at higher temperatures this substance is less psychoactive and this property is measured in the laboratory using special device.
Its ductility is as high as its length in the laboratory when it is drawn at a cross-sectional area of 1 cm2 at a rate of 5 cm / min.
5. Weight loss:
Weight loss in bitumen is due to the evaporation of oil compounds and oils. This property is also one of its important characteristics so that it can be measured in an oven up to 163 °C for 5 hours.
It is the temperature at which the solid flows from solid to liquid. The higher the degree of softness, the less sensitive it is to temperature, and the softness in most of them is between 60 and 70 degrees Celsius.
The amount of impurities left over from dissolving a sample of it in a solvent of carbon sulfur or tetra chlorocarbon is called purity.
The production of this material is done by distilling crude oil and this type is also called petroleum bitumen or distillation. Its oil type includes two stages of crude oil distillation in the distillation tower. The first stage of distillation involves the separation of light petroleum materials, including: gasoline and propane, and at this stage the pressure is close to one atmosphere.
The next step involves the separation of heavy materials such as diesel and kerosene, which is done at a pressure close to vacuum pressure, and in the final process a mixture of very fine asphaltene particles remains, which is immersed in a grease-like liquid like malt.
In addition to the production process in refineries, this material is produced in mineral form and in nature in the form of gradual conversion of crude oil and evaporation of its volatile materials after many years. This type is more durable than other petroleum bitumen and can also exist pure in nature, such as Behbahan Bitumen Lake in Iran or Bitumen Lake in Trinidad, USA.
Bitumen is a hydrocarbon material that has special properties. This material is more diverse than crude oil and is classified into the following three methods depending on its origin:
This type of bitumen is a naturally occurring hydrocarbon that was first found in the Bonita River in northeastern Utah, which is hardened crude oil known as asphalt and euthanasia. This type of bitumen can be soluble in aliphatic and aromatic solvents and is also used as a diluent for dilute petroleum derivatives due to its high compatibility.
It is in the form of a shiny, black and crispy clump and is brown in the form of micronized powder. Natural bitumen is found in the vertical layers of the earth’s surface and can now be mined using excavators and other up-to-date tools. In the United States, natural bitumen is called Gilsonite, which is produced by the American company Gilsonite with different grades.
The name is so well known that some people mistakenly call natural bitumen Gilsonite. One of the features of this type of bitumen is its low ash content, which has nothing to do with the mine, and in the United States, due to the high production technology, it is possible to process this product completely.
This type is referred to as solid bitumen, also known as asphaltite, and is distinguished from other types by its unique properties. This type of material is a type of natural hydrocarbon resin and is known as the best natural insulation. It has a shiny, black clump and has a high solubility in organic solutions, high purity, high molecular weight, constant properties and high nitrogen.
This type has a degree of softness between 130 and 250 degrees Celsius and is used for many purposes, including asphalt and road construction. Natural bitumen in Iran can be found in Moghan valley and Poshtkuh of Ilam bitumen castle.
During its natural formation, after the evaporation of crude oil, due to factors such as temperature, time and processes such as reaction with sulfur, oxidation, polymerization, the condensation of this material, it will form in liquid and solid shape. These types are semi-solid in liquid form and crispy lumps in solid state. Natural bitumen is classified as lake and rock bitumen as follow:
When crude oil rises to the ground’s broken bases and the material in it evaporates, it is covered as a lake on the ground. This species is found in various parts of the world, including Venezuela’s Trinidad Bitumen Lake with an area of 10 to 15 million cubic meters, as well as Venezuela’s Lake Bermuda. To use this type, it is heated to a temperature of 160 degrees Celsius and after evaporation of the water in it, it is passed through a sieve and the impurities in it are separated.
Due to the fact that this type has a penetration rate of 2 cm and a softness of 95 °C, it has a lot of hardness that cannot be used. Therefore, it is mixed on ratio of 1:1 with bitumen with a penetration rate of 200 and a bitumen with a penetration rate of 50, which can be easily used in the asphalt mixture in road construction. This type has good quality in different climatic conditions, also the asphalt prepared by this method has a longer lifespan.
Rock bitumen generally consists of two groups of limestone and sandstone, in which crude oil penetrates in it and over time, volatile substances evaporate and the rest is formed naturally. In this type, during use, first it is crushed, soft and heated and spread on the road surface, and the amount of bitumen in this type of rock varies by 7 to 80%. Lorestan’s rock bitumen in Iran contains between 70 and 80 percent bitumen which is known in the United States as Gilsonite. Today, in addition to road construction, rock bitumen is also used in various other uses.
Oil bitumen is solid and semi-solid, which is produced directly through the distillation of crude oil and the process of blowing air. This type of heavy residue is formed by the distillation of crude oil, and the amount of bitumen in crude oil varies from zero to half. refineries must choose their crude oil with a certain sensitivity because it has a great impact on the quality of the bitumen produced.
Distillation is an important process in the crude oil process. In the first stage, the crude oil is heated in the distillation tower to a temperature between 650 and 800 degrees Fahrenheit and then transferred to the separation column.
In this case, the light cuts remain at the top solution of the tower and its residue, which is bitumen-shaped and is referred to as atmospheric residue is at bottom of tower.
Due to the fact that many crude oils contain high boiling point cuts, not all of them can be used in atmospheric distillation. A secondary separation tower that operates in vacuum conditions is used to separate these cuts and provide the appropriate quality bitumen. The residue from this process is called direct extraction bitumen, which has little effect on the properties of bitumen in the production of asphalt using vacuum distillation other than permeability.
Other factors affecting the quality of bitumen include the source of the crude oil used. Although the bitumen obtained in the vacuum tower can be used, but in most cases, it does not have the appropriate and practical properties and corrections should be made on it and the most important of which are blowing air as follows:
This type was first discovered in 1890 by the reaction of hot bitumen with oxygen, and a lot of research is been done on the process and design of the devices required in the reaction. In the aeration process, hot bitumen is exposed to air. And due to the contact of air with bitumen, it hardens and its thermal sensitivity decreases.
The amount of improvement in this process has a great impact on the type of feed, temperature, viscosity, time, aeration ratio and type of equipment.
The use of this type has many applications in asphalt and road construction and insulation, asphalt bricks and many other applications. Aeration in this way includes dehydrogenation, polymerization and oxidation, in which some oils are converted to resin and some resins are converted to asphaltene. This process results in the formation of a gel-like colloidal structure that is one of the technical indicators of blown bitumen.
In this process, the amount of combined oxygen is only 5 to 25 percent and remains bonded in the bitumen, and the rest is released as water vapor and other gases. The amount of oxygen in the product increases with increasing aromatic content of the feed, increasing aeration and decreasing the temperature of the process.
This type has a lower degree of penetration and a higher soft spot than the original pure bitumen obtained from the distillation of crude oil, and its thermal sensitivity has also been reduced. Due to the fact that this process is hot, it is very important to control the temperature and adjust the amount of feed. This process is performed continuously and discontinuously as follows:
In this process, the initial feed is filled to the desired level in the tower after the initial heating, and aeration begins when the temperature reaches a temperature between 190 and 240 degrees Celsius. Due to the fact that this process is thermal, the temperature resulting from the reaction causes the bitumen temperature to reach 240 to 260 degrees Celsius, which is maintained in this range.
After sampling, the operation is stopped at different time intervals until the desired specifications are obtained. Depending on different technical specifications, this operation can vary between 3 to 24 hours.
The bitumen aeration tower has a height of 12 meters and a diameter of 3.65 meters and the air is injected from the bottom of the tower through the distribution pipes. The reaction variables cause the production of bitumen with different technical characteristics.
Additional vapors released from the top of the tower include decomposed oil, air, light water vapor particles, and other gases and light hydrocarbons. One of the obvious points of production in this method is the ability to produce a product with different technical specifications.
The start of the continuous process is the same as discontinuous, and when the technical specifications reach the desired level, the finished product is taken out through the height controller and the feed is entered separately with flow control. In this process, temperature control is performed using methods such as initial feed heating in the furnace, heat exchanger or cooling using water injection.
The effective blowing temperature in this method is 260 °C and this method will be more useful if the goal is to produce the product with specific technical specifications and in bulk. Currently, in Iran, two types of 60/70 and 85/100 are produced by direct and semi-blown methods. Bitumen has different physical properties and is generally classified into the following four main types:
Cutback bitumen is used in road construction because it is not possible to use it in solid form. This type is obtained by dissolving pure bitumen with oil and petroleum solvents. The quality and type of it depends on the quality of the pure bitumen, the amount and type of solvent.
The degree of lubrication of this type depends on the amount of petroleum solvent in them, and the higher this amount, the higher its lubricity, and typically the amount of these solvents is between 10 and 50 percent.
Lack of access to heating devices, decomposition of bitumen at high temperatures, lack of penetration into porous minerals, safety of workers, time consuming, cooling during work and fire have caused soluble bitumen to be used in some cases. In order to adhere well to wet materials, the acidity of this type must be appropriate.
This type of road construction is usually used to cover the surface of asphalt, cold asphalt or mixed on site. This type is classified into three categories according to the rate of traction and solvent type: RC (Rapid), MC (Medium) and SC (Slow).
The emulsion type contains a two-phase mixture in which the inner phase is dispersed in the form of fine particles in the outer phase. The diameter of these particles is between 0.1 and 5 microns and the diameter of the particles is larger than the true solution and colloidal state.
The amount of emulsifier material used is between 0.3 to 0.5 percent by weight and the amount of water used is 30 to 50 percent. The emulsifier is usually an alkaline salt of organic acid or ammonium salt, which has a great effect on the charge of its particles.
In this way, the particles repel each other due to the induced load and float in the water in the form of spheres with a diameter between one hundred and one thousand.
If the emulsifier material is not used, it will increase the contact surface between the two phases and increase the interfacial energy, which is not a stable suspension. The two phases of the system return to a stable state. The use of this type reduces environmental pollution and reduces the risk of ignition in transportation due to the fact that oil and flammable solvents are not used.
This type is used in cold asphalt and if the environment is wet, water should be added to it and its content should be increased to 65%. Emulsions are generally classified into the following categories:
– In terms of types, they are divided into two categories: water in oil and oil in water
– In terms of suspended solids, they are classified into three categories: cationic, anionic and non-anionic
– Due to the speed of breaking and separating of the two phases, they are classified into three groups: early breaker, slow breaker and late breaker
Its main applications are in road construction, surface asphalt, cold asphalt, slag coat, single coat, protective coating of tanks and insulation. And its highlights are the following:
– Ease of transportation in bulk and drum
– Use in low thickness asphalt
– Speed of asphalt operation due to drying less than 2 hours
– Can be used on any type of asphalt, including streets, highways and airports
– Can be used at ambient temperature and between 5 and 80 degrees Celsius
– No need for heat during transport, spraying and maintenance
– Permeability due to high fluidity
– The complexity of the machines used
– Compatibility with the environment
– Failure against rocks and air
– Not toxic and odorless
– No flare during transportation
– Change the color from brown to black after breaking and ready for use in asphalt
– Long shelf life of at least 3 months
– Apply indirect heat if the temperature drops below 5 °C
Due to the fact that the pure bitumen obtained from the refinery does not have the required quality and specifications used in various applications, researchers are always trying to improve its quality. Impregnating bitumen not only helps to improve its quality, but also increases its lifespan and reduces maintenance costs.
Weaknesses in major bitumen include low elasticity, temperature sensitivity, and limited performance at different temperatures. Different additives are used to improve its performance. The main usable additives are polymers, including SBS and SIS.
The main properties of this types are good performance and adhesion properties at low and high temperatures, good resistance to lubrication and temperature changes, low sensitivity to temperature, tensile strength, good tensile performance and increased stiffness at high temperatures.
This type, also known as Latin Tar, is similar to petroleum type due to its similarity in appearance and use. The production base of this type is different from its oil type and has different physical properties. Depending on the type of process, this type of bitumen can be formed from burning or carbonizing coal and can be obtained at temperatures of 600 °C.
This type has a lower percentage of aromatics, which after separating the oil slices and cooling the steam, the remaining materials contain coal bitumen.
Due to the era of the Industrial Revolution and the discovery of significant amounts of oil and gas, the use of Coal was almost abandoned in the production of bitumen, and its consumption declined sharply.
Two types are produced diametrically by burning or carbonizing coal. In one of these processes, the temperature is heated to 1200 °C, and the bitumen obtained from this method has a high percentage of aromatics, and in the other method, it is heated only up to 600 °C, and the result has less aromatic than the previous process.
After this process, the product is cooled and the remaining liquid is known as Crude Tar, then distillation is done and after separating the oil cuts, coal bitumen or Pitch is obtained and the resulting diameters are combined with the oil cuts. An oil is obtained that is classified in the BS standard with eight grades.
Currently, more than 90% of this type is used in road construction, charcoal electrodes, glazes, charcoal soil and pipe coatings. The use of this type in road construction has been used only in surface coatings, which is a better performance and at lower temperatures as a solution, which causes more adhesion.
The only disadvantage of this type compared to its oil type is its sensitivity to higher temperatures. Due to the development of chemical adhesion production factors and environmental problems, the use of Tar method has become much more limited.