#bitumen_emulsion

Bitumen is a black, pasty material used in moisture insulation and asphalt construction.

There are different types of bitumen, each of which has a specific application.

Bitumen is a black to dark brown hydrocarbon that dissolves completely in carbon sulfide and carbon tetrachloride.

It is solid at room temperature, but as the temperature rises, it becomes a paste and then liquefies.

Bitumen is a derivative of oil.

Crude oil:

Crude oil is a thick, flammable liquid in the color of garlic or dark green or black.

Oil is found in the upper layers of parts of the Earth's crust.

Oil contains a complex mixture of various hydrocarbons.

With the development of drilling technology in the mid-nineteenth century and the technology of oil distillation and refining in the late nineteenth century and its use in non-fuel cases, an astonishing leap occurred.

So that today the petrochemical industry has a fundamental role in meeting the general needs of society. Most scientists consider the origin of oil to be plants and organic organisms in the early oceans.

Remnants of animals and plants that lived in the sea millions of years ago have been buried by mudstones and sediments for millions of years.

They are converted to oil under high pressure and temperature, lack of oxygen and for a long time.

If these conditions are present, along with a suitable reservoir rock, a large amount of oil will accumulate in the oil basin.

If oil accumulates in a place, that place is called an "oil pool."

From a total of several oil basins, an "oil field" is obtained.

The porous rock containing oil is called "reservoir rock".

From the history and definition of bitumen, it is believed that the name (Bitumen) is derived from Sanskrit and from the word (Jate) meaning (Pitch).

It is also claimed to be the Latin equivalent of Pixtu-men, which was later abbreviated to Bitumen and then translated from French into English.

Bitumen has been used as a waterproofing and bonding agent for more than 5,000 years.

The oldest recorded use dates back to 3800 BC by the Sumerians.

The first emulsion was recorded in 1922 by Hugh Allen Mackey.

At that time, the automobile industry was thriving and many roads were being built.

Emulsion production in France, known as the birthplace of this technology, increased from 10,000 tons in 1923 to 300,000 tons during World War II.In 1970 it reached 1,200,000 tons.

Bitumen in road construction Bitumen in road construction means black adhesives used in road construction, which include bitumen and tar materials. The main property of bitumen is that it sticks the stone grains together and turns them into a single body. Bitumen is a black body made of a large number of hydrocarbons.

Pure bitumen is solid or semi-solid at ambient temperature and is liquefied by heat. Bitumen dissolves in mineral oils and solvents such as carbon sulfide, carbon tetrachloride and ethylene trichloride. Tar, which is black but brown in color, is obtained by distilling gases from heating coal, wood, and schist rocks. This substance is called raw tar and is obtained by refining that tar. Tar is produced in very small quantities in Iran and its use in road construction works is not common in the country. Types of bitumen There are two main types of bitumen used in road construction. If it is obtained from a mine, it is called natural or mineral bitumen, and if it is obtained from the refining of crude oil, it is called petroleum bitumen or refinery. Petroleum bitumen should be used in road construction. If the use of mineral bitumen is in the desired projects, the mixing ratio of petroleum or mineral bitumen should be specified in the private technical specifications.

Petroleum bitumens Bitumens obtained from crude oil refining are divided as follows according to the type and conditions of its use in road construction and other industrial uses.

Pure bitumen Bitumens that are obtained directly from the refinery vacuum in the distillation tower or briefly exposed to the aeration process are called pure bitumens. These bitumens should be homogeneous and free of water and should not foam at 176 degrees Celsius. Pure bitumen deforms into a thick, watery liquid due to pressure and heat, and is elastic and springy at low temperatures.

Soluble bitumen Soluble bitumen, or back bitumen, is obtained by dissolving pure bitumen in solvents or petroleum oils. The type and quality of soluble bitumen depends on the quality of the original pure bitumen, the type and amount of solvent. The higher the amount of petroleum solvents in the bitumen solution, the greater its fluidity. Usually, the percentage of solvent used in soluble bitumens varies from 20 to 50%. Soluble bitumen is used in road construction for surface coatings, infiltration, surface asphalt, cold factory asphalt or on-site mix. Soluble bitumens are divided into the following three groups according to the setting speed and the type of solvent.

Instant soluble bitumens If gasoline is used to dissolve pure bitumen, dissolved bitumen is called quick-setting. Because the solvent in the bitumen evaporates shortly after the consumption of bitumen and the main bitumen remains. Quick bitumen is classified into four types in terms of RC-70, RC-250, RC-800, RC-3000.

Solution bitumen Slow bitumen is made by dissolving pure bitumen in kerosene, which is slower and longer than gasoline. Slab contraction joints should intersect at the openings for columns, and should intersect at the openings for columns, at a minimum of 30 to a maximum of 6,000 cm.

Delayed bitumen solution In addition to dissolving pure bitumen in refractory oils and petroleum solvents, such as diesel or black oil, retardant soluble bitumens can be obtained directly from the distillation of crude oil, such as pure bitumen, from which solvent oils have not yet been separated. It takes a long time for these bitumens to fully set after consumption. In fact, retarded bitumens do not evaporate under normal climatic conditions, but undergo molecular deformation that is relatively gradual and long.

Blown bitumen Pure bitumens are pressurized at 200 to 300 ° C to combine the hydrogen atoms in the bitumen molecules with oxygen in the air, resulting in polymerization reactions that produce heavier hydrocarbons with lower penetration and softer points than bitumen. Have an initial net.

Blowed bitumen is not widely used in road construction. These bitumens are used to fill cracks in concrete pavements and to fill joints in concrete surfaces. The elasticity of blown bitumens is usually increased by the use of special chemical additives, and this condition remains constant even at low temperatures where pure bitumen becomes brittle. This type of blown bitumen, which is somewhat similar to rubber, is used to cover the floor of water pipes.

Functional bitumens Functional classification for bitumen selection in road construction has been developed by SHRP. In this classification, which is based on recognizing the behavior of bitumen and its functional characteristics, with the characteristics of resistance to deformation, resistance to cracking due to cold, resistance to cracking due to fatigue, prediction of how hard bitumen in the asphalt plant When preparing the asphalt mixture, how the bitumen hardens over time and with the tests specified in the specifications, and the appropriate bitumen according to the temperature of the project site, traffic, loading speed and geographical location selected It becomes.

Bitumen type and traffic conditions Traffic conditions including the type and amount of heavy traffic, how to load (fast, slow or static loading) and the total number of equivalent axes of 80 kN and traffic are effective in choosing the type of bitumen in each project. In general, the heavier the traffic, the denser and more directed it is, and the steeper and more steep the slopes and the more exposed to the intense sun, the harder the bitumen is used.

Application of cold asphalt in road construction: Cold asphalt (Cold Mix) is a mixture of rock materials and bitumen or bitumen emulsion whose raw materials are mixed at room temperature. Cold asphalt is prepared by mixing aggregates with soluble bitumen or bitumen at room temperature. And at the same temperature it spreads and condenses. The mixing time with bitumen can be wet, but with soluble bitumen, it must be dried at room temperature or under heat. Cold asphalt can be transported and then spread over long distances or stored in a workshop and used later. Stay with us until the end of this article.

What is cold asphalt? Its use in road construction Cold asphalt is prepared by mixing aggregates with soluble bitumen, bitumen or tar at ambient temperature and spreading and compacting at the same temperature. Aggregates can be wet when mixed with bitumen, but for soluble bitumen, the moisture content of the material must be dried at room temperature or under heat. Cold asphalt mixtures prepared with concentrated soluble bitumens such as 3000-MC or 3000-SC are practically mixed with bitumen at a temperature of 95 ° C or higher and spread and compacted within the same temperature.

Classification of cold asphalt Cold asphalts can be classified according to the following factors:

1- Method of preparing and applying asphalt 2- Cold asphalt granulation

Classification of cold asphalt in terms of method of preparation and implementation Cold asphalt can be divided into two categories according to the method of preparation and implementation:

Factory cold asphalt Cold asphalt mixed on site Factory cold asphalt Cold asphalt is prepared in fixed and central asphalt factories and then transported to the place of consumption for distribution. In cold asphalt plants, the necessary controls are observed to regulate granulation, distribution of aggregates and mixing with bitumen similar to hot asphalt. Of course, when using emulsion bitumen, provided that the moisture content of the material is not more than 3%, the heating or drying steps of the aggregates are often removed from the mentioned operation cycle. Stone materials are heated either under the conditions of using soluble bitumens or emulsion bitumens.

Cold asphalt mixed in place Cold asphalt mixed in place is divided into two categories:

A- The type of mixture in place, where the aggregates are spun along the path and sprayed with bitumen, and then the mixing and spreading operation is done with a grader or similar equipment. Cold asphalt prepared with soluble bitumen, the prepared asphalt mixture should be turned over and over again by machines (loaders and graders) in the open air as necessary to reduce the amount of solvent in the soluble bitumen.

B- The type of mixture in the mobile workshop, where the bitumen and aggregates are mixed in mobile factories and the prepared mixture is transported to the place of consumption for distribution.

Scope of application of cold asphalt Cold asphalt has three uses, which are:

Cold asphalt in road construction Maintenance of pavements In special cases such as the floor of sports venues Application of cold asphalt in road construction Cold asphalt is used in all layers of pavement, provided that all design criteria and traffic restrictions of the route are observed. This type of asphalt can be used in surface layers, bitumen base and foundation for light and medium traffic and in bitumen base layer for heavy and very heavy traffic. Cold asphalt is used in the surface layer in light and medium traffic conditions and its implementation. For conditions Heavy traffic is possible as a base layer. If the traffic situation changes from light to medium to heavy for the route in which this type of asphalt is used as a surface layer, hot asphalt should be used as a cover to prevent damage.

Breaking and Curing

Breaking

If the bitumen emulsion is to perform its ultimate function as a binder, water must separate from the bitumen phase and evaporate. This separation is called “breaking”. Emulsions are formulated to break according to their intended use. The two mechanisms by which bitumen emulsions break are chemically and evaporative. For the slow-setting grades, the breaking mechanism is mainly evaporation. For the medium-setting and rapid-setting grades, the breaking mechanism is mainly chemical. A rapid set emulsion will have a shorter breaking time, whereas a medium or a slow set material may take considerably longer. For dense mixtures, more time is needed to allow for mixing and placement. Therefore, emulsions used for mixture are formulated for delayed breaking.

The specific type and concentration of emulsifying agent primarily controls the rate of breaking. However, other factors discussed below, also play an important role in breaking the emulsion. In order to achieve optimum results, it is necessary to control all of these factors to meet the specific requirements of the field use of bitumen emulsion. Contact the supplier for more information regarding the optimum use of emulsions.