The emulsion 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 of Bitumen 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
This type, also known as Latin Tar, is similar to petroleum bitumen due to its similarity in appearance and use. The production base of this bitumen is different from its oil type and has different physical properties. Depending on the type of process, this type 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 tar bitumen 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 of bitumen 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.
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 polymer modified type 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.