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What is Bitumen?

Bitumen is one of the derivatives of Crude Oil and is normally produced in oil refinery or found naturally in nature.  It is a sticky, black, paste-like solid material (can behave as a liquid over high temperature also) that is applied in insulating moisture and Asphalt making.

It is a strong and durable glue-like material that holds together a wide variety of other materials without overlapping in their properties. For Pars Bitumen, the main reason for its wide application is its Durability, which is essential for large engineering projects such as roads and waterways that must last 20 years or more.

How is Bitumen Produced?

Pars Bitumen, Bitumen is usually obtained from the distillation of crude oil. Such bitumen is called petroleum bitumen or distillate bitumen. Oil bitumen is the product of two stages of crude oil distillation in the distillation tower.

At Pars Bitumen, in the first stage of distillation, light substances such as gasoline and propane are separated from crude oil. This process is carried out at a pressure close to one atmosphere (unit).

 In the second stage, heavy compounds such as diesel and kerosene are removed. This process takes place in a pressure close to vacuum. Finally, a mixture of very fine solid particles called asphaltene remains, which is immersed in a grease-like fluid called maltene.

But some types of bitumen are obtained in nature as a result of the gradual transformation of crude oil and the evaporation of its volatile substances over many years. Such bitumen is called natural bitumen or Gilsonite and it is more durable than petroleum bitumen. Such bitumen may exist in pure form in nature such as Bitumen mines in Gilane Gharb Iran.



What is Vacuum Batuum?

Vacuum Batuum is a black substance taken from crude oil in the lowest bottom level of oil refinery distillation Tower. The raw materials for bitumen production that remain in the refinery due to the bottom of the distillation tower are called Vacuum Batuum (VB).

The crude oil is converted into different types of materials in the distillation tower, and these materials are obtained at different boiling points. The material remained at Bottom of distillation Tower is similar to bitumen and called Vacuum Batuum(VB).

 At present, various methods are used to convert Vacuum Batuum into bitumen in Pars Bitumen and it is known as bitumen production feed. This material consists of hydrocarbons with carbon number more than 35 and in addition to bitumen production, it is also used in some base oil production facilities.

Passing air through the vacuum batuum inside the bitumen tower, in which case the oxidation process is achieved, improves its properties and viscosity, and causes maltene molecules to change to asphaltene molecules, which causes the degree of penetration to decrease and the inertia point to increase, and different types of bitumen with Penetration grade is obtained, depending on the amount of aeration, the penetration grade decreases or increases.

In our factory, Pars Bitumen, as a result of aeration, the residue properties are improved, and the most important effect of air blowing on the baton vacuum is the conversion of maltene light molecules into heavier molecules, i.e. asphaltene, which increases its penetration degree and softening point. The vacuum batuum temperature inside the bitumen production tower is 240 to 320 degrees Celsius.

vacuum Batuum

vacuum Batuum

What are Main Bitumen Features?

  • Bitumen material is thermoplastic. It softens and becomes liquid by using heat and hardens when it cools. This substance can be spread easily in areas where it is needed, because it is easily liquefied in Pars Bitumen by one of three methods: application of heat – dissolving it in petroleum solvents – dispersing it in water (emulsion).
  • Bitumen is insoluble in water and can act as an effective waterproofing insulator. It also resists most acids, alkalis and salts and does not contaminate water, so it can be used for water flow lines also.
  • Bitumen material gives controllable flexibility to the mineral aggregate mix, which is why most of the total annual production is used in road construction.
  • Bitumen is available almost worldwide with economical cost for the projects.


What are Bitumen Types?

There are different types of bitumen such as, Asphalt Pavement Bitumen, Oxidized Bitumen, Soluble bitumen, Modified Bitumen by polymer, Bitumen emulsions, Permeable grade bitumen, and Soluble bitumen or cutback which are described as below:


Asphalt Pavement Bitumen:

Paving grade bitumen or Asphalt is the most widely used bitumen worldwide and is refined and mixed for use in road construction and has industrial properties in different weather conditions. Asphalt may be considered the parent bitumen from which other forms are produced.

  • Oxidized Bitumen:

From the reaction of oxygen and bitumen, compounds with higher molecular weight are formed; and, the content of asphaltene and maltene increases, this produces a harder mixture called Oxidized Bitumen. In our Company, Pars Bitumen refinery bitumen is refined with further processing. This process creates oxidized bitumen. During this process, maintaining a controlled temperature, pressurized air enters the soft bitumen. This harder mixture has less flexibility and temperature sensitivity.

  • Soluble bitumen:

They consist of bitumen diluted in a solvent (cut or flux) to make them more fluid for use. The fluidity of soluble bitumen (or as defined) depends on the bitumen hardness and the diluent ratio. Cuts are classified according to the time required to process them, or solidify due to evaporation of the diluent. Classifications include rapid cooking (RC), medium cooking (MC) or slow cooking (SC).

  • Modified Bitumen with polymer:

Polymer modified bitumen is a kind of bitumen that by modifying its strength and rheological properties for this purpose, 2 to 8% of polymer may be added to bitumen. The polymer used can be plastic or rubber. These polymers change the strength and viscoelastic properties of bitumen.

  • Permeable grade bitumen:

Infiltration grade bitumen is the same refinery bitumen that is produced in different viscosities. Penetration testing is done to determine the bitumen specifications based on hardness. For this reason, it is called penetrating bitumen. Bitumen penetration grades range from 15 to 450 for road bitumen. But the most used bitumen is with a penetration range of 25 to 200.

  • Bitumen emulsions:

Bitumen emulsions are dispersions of bitumen in water. Hot bitumen, water and emulsifier are finely processed in a colloidal mill that disperses the bitumen in the water into small droplets. These droplets or particles of this material are usually in the size range of 5-10 micrometers but may be even smaller. Emulsifier helps in forming and maintaining the dispersion of bitumen droplets.

This type forms a two-phase system with two immiscible liquids. So that one of them disperses in the form of tiny globules in the other liquid. When its individual globules are dispersed in a continuous form of water, a bitumen emulsion is formed.

Bitumen emulsions have a low viscosity compared to bitumen from production and can be used at ambient temperature. Their application requires controlled breaking and setting. The emulsion should not break before being poured onto the road surface, but once in place it should break quickly so that the road can be put back into service without delay.

Bitumen emulsions usually make up between 30 and 80% of it. If the bitumen begins to separate from the water solution in storage, the emulsion is usually easily restored by using a gentle stirrer to redistribute the droplets.

  • Soluble bitumen or cutback:

Cutback bitumen is a type of bitumen whose viscosity has been temporarily reduced by adding a volatile oil. Finally, the volatiles evaporate and the bitumen regains its initial viscosity.

What are emulsions Types Bitumen?

Bitumen emulsions are divided into three categories:

  • Anion with negatively charged droplets
  • Cation with positively charged droplets
  • Non-ionic with neutral droplets

The development of bitumen emulsions is an area where technological advances are still being made to meet current and emerging engineering demands. The first emulsions were anionic types. They are currently less favored than cationic types because the positive globules of bitumen in cationic emulsions better cover the majority of aggregate types and lead to greater adhesion. Therefore, the use of cationic emulsions is preferred in most applications. They are categorized as the following:

Modified bitumen:

Modified Bitumen is formulated with additives to improve their performance characteristics by changing properties such as durability, wear resistance, elasticity or flexibility. The most important modifiers are polymers.

Industrial bitumen:

This type of material is made by blowing air through hot paving bitumen. The so-called blowing process results in a harder bitumen that softens at a higher temperature than that at which paving bitumen softens. Industrial bitumen also have more rubbery properties and their viscosity from temperature changes is much lower than paved bitumen samples.

Polymer modified binders

Polymer Modified Binder is a major advance in bitumen binder technology as these materials meet the increasing volume and traffic load needs of our road networks. As well as natural rubber, polymers such as styrene butadiene styrene (SBS), polybutadiene (PBD) and ethylene vinyl acetate (EVA) are commonly used to modify bitumen.

Chemically modified bitumen

This type has the properties of a hard pavement grade bitumen at high service temperatures combined with the properties of a soft pavement grade bitumen at low temperatures (i.e. it has properties that are multi-grade). Multi-materials provide better resistance to deformation and reduce the damaging effects of high temperatures, while reducing stiffness at low temperatures compared to a similar conventional bitumen surface.

How is Bitumen Tested?

Bitumen specifications


In the Lab of Pars Bitumen, Bitumen is tested by measuring different characteristics or specifications of Bitumen, such as Penetration degree, Viscosity, degree of ignition, weight loss test, plasticity, degree of purity and softness which are clarified as below:

1- Degree of influence:

Penetration degree test is used to determine bitumen hardness. In Pars Bitumen, this test penetrates into bitumen at a temperature of 25 degrees from a standard needle under the effect of a load of 100 grams in 5 seconds. The amount of penetration in tenths of millimeters is called the degree of penetration. The lower the degree of penetration, the harder the bitumen.


The higher the flow rate of bitumen, the more solid properties it exhibits. It is clear that the mental retardation is less at higher temperatures. This characteristic of bitumen is measured with C-bolt Fiorel device or by kinematic method.

3- Degree of ignition:

The degree of ignition is the temperature at which if the bitumen reaches that temperature, the gases emitted from it will ignite as the flame approaches and a flame will appear on its surface. The maximum temperature that bitumen can be heated in the workshop is limited to the degree of ignition.

4- Weight loss:

The weight loss of bitumen at high temperature is due to the evaporation of part of its oils and petroleum compounds. This characteristic is also one of the important properties of bitumen. The weight loss of bitumen is measured in the oven at 163°C and for 5 hours (approximate asphalt curing conditions).

5- Plasticity feature:

  If we pull a sample of bitumen with a cross-sectional area of 1 cm 2 at a speed of 5 cm/min, the length increase of the sample before breaking is called the plasticity property of bitumen.

6- Degree of purity:

  We know that the solvent of bitumen is carbon tetrachloride and carbon sulfur. Therefore, if we dissolve a sample of bitumen in any of these materials, its impurities will remain and from there we can determine the degree of purity of the bitumen. The degree of purity is: (bitumen sample weight) ÷ [(impurity weight) – (bitumen weight)]

7- Degree of softness:

Softness degree is the temperature at which bitumen turns from solid to liquid when bitumen reaches that temperature. The higher the degree of bitumen softness, the less sensitive it is to temperature changes. The degree of softness of ordinary bitumen is about 60 to 70.

What are Bitumen Applications?

Application of Bitumen in Road Construction

More than 80% of the 100 million tons of bitumen consumed annually worldwide is used for pavements in road construction and maintenance. The rest is used for various purposes. The use of bitumen in road maintenance can be up to four times its use in road construction. Understanding how roads are built is essential to understanding the importance of bitumen.

Bitumen plays a major role in meeting waterproofing and durability, as it binds the particles and seals the aggregate and fills the voids between them. By sealing the gaps, it prevents water from penetrating the road and damaging the natural foundation of the road.

The lowest layer of the road is the natural underpass soil. For a new road, the subgrade has been carefully prepared by modern machinery, but for an old road, this layer consists of everything left by traffic. The rest of the road is made up of layers of aggregates and bitumen, each designed to do a specific job.


Aggregate is a term used to describe hard non-metallic minerals such as crushed stone, gravel, sand and gravel. Aggregates must meet engineering specifications that include shape, strength, surface properties, and size. Subgrade is the first layer laid by the road builder and is made up of compacted granular material – rock, gravel or sand. Its task is to contribute to the strength of the road and provide an operational platform to the road construction machinery.

Variable design factors:

The exact layout of a road depends on several variables, such as the weight and volume of traffic it is designed to carry, local weather conditions, and the availability of mineral materials. In most cases, bitumen is preferred because of its waterproof and durable properties and as the cheapest adhesive generally available.

A minor road may use bitumen only for its top two courses at a rate of 7 tons per km. A highway engineer may require three courses of asphalt in which there are belt coats because of the superior load-carrying characteristics of asphalt. In this case, bitumen consumption can be 1000 tons per kilometer. The percentage of bitumen in asphalt is usually between 4-8%.


Mixing of aggregates and bitumen in Pars Bitumen to produce asphalt takes place in a purpose-built plant located off-site or may be done on-site.

Controlled quantities of various aggregates, carefully mixed and graded to meet the required specifications, are heated before being mixed with a measured amount of dry bitumen. All this takes place in a purpose-built factory. The hot mixture is transported to the construction site at a temperature of 160°C while it is still hot.

The above, in simple terms, describes the process by which skill and experience are applied to computer control systems to perform a series of complex operations. Different aggregate sizes dry, gain and retain heat at different rates. Their temperature should be controlled so that the bitumen does not cool down when mixed with materials. The supply of aggregates is continuously measured by gauges attached to the bitumen metering pump to ensure that a constant ratio of aggregate to bitumen is maintained.

The mixing time should not be longer than necessary to evenly distribute the bitumen as a coating for the grain particles, otherwise the bitumen film hardens due to oxidation as it is exposed to air. If the mixing process is too long, the durability of the mixture will be impaired.

Continuous operation of the system is required to produce consistently high quality mixtures. This in turn means that all parts of the operation must be integrated so that the steps of drying, screening, mixing, transporting and loading are carried out. Bitumen materials are supplied daily to carry out the production plans for the next day in the road band plans.

Because bitumen storage capacity is usually limited, deliveries must be made on an “as-needed” basis, often within 30 minutes of the target time based on the moment the aggregates are heated to the appropriate temperature for mixing with the bitumen. Any delay means wasting expensive fuel to keep the whole rock at the right temperature. This precision in delivery demands a high degree of commitment from the supplier in terms of capital equipment, logistics and technical expertise.

Application of bitumen in asphalt

Asphalt mixtures are classified into several types, which may be simply called compacted asphalt or asphalt concrete, a dense and ordered mixture of coarse and fine aggregates, mineral fillers and bitumen, with a carefully controlled content.

Hot rolled asphalt

A sand-based, high-viscosity bitumen material, with approximately 30% selected stone content, is rolled to the surface with larger stones.

Stone Mastic Asphalt

A large stone mix in which the large stones form a load-bearing matrix within the mix to provide a high resistance to deformation up to a substantial interface with the filler mastic bitumen.

Graded open asphalt

A combination of graded aggregate and bitumen manufactured to provide an open texture and air voids to provide ready water drainage through the finished asphalt layer – also known as porous asphalt and drainage asphalt.

Tack Coat

A thin layer of emulsified or sheared bitumen that bonds one layer of road to the layer below it. Current practice favors the use of bitumen emulsion rather than cutting in this application.

Sprayed insulation

Also known as surface dressing and chip seals, this process involves spraying a bituminous coating on the surface of a track or granular coating. Sprayed insulations can be sprayed as an emulsion, cut or as an asphalt grade bitumen. Either a one-layer or two-layer coating of aggregates is applied.

These remedial methods are used to renovate and waterproof old roads that need maintenance, or asphalt pavements without boundaries in new construction. An example of a remedial method is fog insulation, which is a layer of bitumen emulsion applied to an existing surface to seal a crack or to refill worn bitumen as a maintenance method.

Bitumen slurry surface

A major surface maintenance repair where a mixture of fine aggregate, filler and emulsified bitumen is applied to partially correct the road surface to a structurally correct surface. It has the advantage that it can be applied quickly and at relatively low cost by a truck mix plant.

 Application of bitumen in road reconstruction

Road recycling techniques recover materials used in road construction. These materials benefit in terms of reducing the demand for materials and energy. Road surface layers are crushed and reprocessed with different proportions of fresh aggregate, new bitumen or bitumen emulsion and, if necessary, a recycled material. This process may be carried out on site (simultaneously), or the reclaimed material may be transported to the site for mixing.

Industrial applications of bitumen

The use of bitumen in industrial applications is less than 20% of global bitumen consumption. However, it is important for those manufacturers and engineers who rely on its special properties as an economical adhesive and protector. In many parts of the world, bitumen is used to waterproof the roofs of houses.

It is often in the form of strips that are first impregnated with bitumen and then covered on both sides with harder bitumen and a coating of mineral grains. A similar construction method involves sheets of saturated bitumen material on a flat roof with layers of bitumen below, between and above them. Also, bitumen is used in anti-floor and floor tiles.

Other materials, especially felt and paper, are impregnated with bitumen to improve their performance as insulators. Paper packages, printing inks, floor coverings, soundproofing felts hidden in car bodies and underlay compounds, electrical insulation compounds, and battery boxes are some of the hundreds of industrial and household products that may contain industrial-grade bitumen.

What Cautions should be taken during Bitumen Application?

  • High temperature is required and the need for predetermined storage and transportation tanks and equipment
  • Flammable property is needed in certain degrees of cuts
  • Must maintain the health and safety of personnel before any action
  • Personnel training is mandatory

Because of its high viscosity, almost all bitumen products must be heated to liquefy enough for distribution and application. Contact with this substance or the equipment involved in its transportation, storage and use can cause severe skin burns at the temperature recommended for use.