Bitumen Definition

Bitumen is a black to dark brown hydrocarbon substance that dissolves completely in carbon disulfide and carbon tetrachloride. Bitumen is solid at ambient temperature. But as the temperature increases, it turns into a paste and then becomes liquid. The important use of bitumen is due to the presence of two important properties of this substance; Being impermeable to water and being sticky

Bitumen Types

Bitumen extracted from oil or special minerals is called pure bitumen, which is classified according to its origin. Pure bitumens are also subjected to other processes in order to find the desired properties for different applications and form different types of bitumen (including blown bitumen, soluble bitumen, emulsion bitumen, polymer bitumen, etc.).

قیر نفتی و قیر طبیعی

Bitumen is usually obtained from the distillation of crude oil. Such bitumen is called petroleum bitumen or distillate bitumen. [3] Petroleum bitumen is the product of two stages of crude oil distillation in the distillation tower. 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 atmospheric pressure. 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 and it is more durable than petroleum bitumen. Such bitumen may exist in pure form in nature (lake bitumen) such as Behbahan bitumen lake in Iran and Trinidadian bitumen lake in America, or it is extracted from mines (Uintaite) is also known.

قیر دمیده

Blown bitumen is obtained by blowing hot air into pure bitumen in the last step of the refining process. In this process, hot air with a temperature of 200 to 300 degrees Celsius is blown into the chamber containing bitumen through perforated pipes. As a result of this process, the hydrogen atoms in the bitumen hydrocarbon molecules combine with the oxygen in the air and the polymerization process takes place with the formation of water. Compared to pure bitumen, blown bitumen has a lower degree of penetration, a higher degree of softness and less sensitivity to temperature changes. This type of bitumen is mostly used in making roofing sheets, car batteries and plating. The sign means blown bitumen with 80 degree of softness and 25 degree of penetration

قیر مخلوط یا محلول

The sale of mixed bitumen refers to a mixture of bitumen and a suitable solvent (for example, kerosene or gasoline). This bitumen is liquid at room temperature or turns into liquid with a little heat. Mixed bitumen is used in all types of covering asphalt and macadamia. The speed of setting or hardening of this type of bitumen depends on the type of solution. For example, due to the high rate of evaporation of gasoline, bitumen dissolved in gasoline hardens faster. This bitumen is called quick-acting bitumen (RC). Also, bitumen dissolved in oil is called retarding bitumen (MC) and bitumen dissolved in gas oil or fuel oil is called retarding oil (SC). Soluble bitumens are graded according to their viscosity

قیر امولسیون

Emulsion bitumen is obtained by mixing bitumen, water and an emulsifier. The amount of emulsifier is very small, around 0.3 to 0.5% of bitumen weight. The amount of water used in this type of bitumen is about 30 to 50% of the bitumen weight. The emulsifier is usually an alkaline salt of organic acids or an ammonium salt that charges the bitumen particles. In this way, bitumen particles repel each other due to the induced charge and float in water as spheres with a diameter of one hundredth to one thousandth of a millimeter. The use of this type of bitumen reduces environmental pollution and because oil or flammable solvents are not used, the risk of ignition during bitumen transportation is reduced. Emulsified bitumen is used for cold asphalt in wet environments or for insulation, in which case water must be added to it again and its content is about 65%.

کاربرد

Bitumen is usually used in two areas: road construction and insulation. About 90% of the produced bitumen is used in the field of road construction, and insulation uses only 10% of the bitumen consumption.

Insulation: Bitumen is usually used to insulate roofs and bathroom floors. Usually, in order to stabilize bitumen, it is used together with a sack, which is called Qirguni. Sack fibers have the role of reinforcing the bitumen and stabilize the bitumen in place. Also, products such as bituminous cardboard or bituminous felt, which are offered with brand names such as Izogam, etc. Blockage or macadam is used in order to prevent the penetration of ground moisture to the floor of the building.

مشخات قیر

1- Penetration degree: Penetration degree test is used to determine bitumen hardness. In this test, it 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.

2- Viscosity: The higher the viscosity 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- Ignition degree: The ignition degree is the temperature at which if the bitumen reaches that temperature, the gases emitted from it will ignite when 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 feature 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 (asphalt curing conditions).

5- Ductility: If we pull a sample of bitumen with a cross section of 1 square centimeter at a speed of 5 cm/min, the amount of increase in length of the sample before breaking is called the ductility property of bitumen.

6- Degree of purity: We know that tar’s solvent 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) (bitumen purchase)

7-Softness degree: Softness degree is the temperature at which bitumen turns from solid state to liquid state 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.

Tests to determine the properties of bitumen for bitumen sales

The following tests determine the properties of natural bitumen:

  1- Softening Point measurement
  2- Penetration measurement
  3- Ductility measurement
  4- Fraass Breaking Point measurement
  5- Investigating the effect of heat and air on bitumen Thin Film Over Test
  6- Viscosity measurement
  7- Measuring the weight of Specific Gravity
  8- Measuring the solubility or degree of purity of bitumen Solubility
  9- Flash point measurement
10- Measurement of durability of asphalt mixtures by Marshall method
11- Sieve Analysis of mineral materials
12- Extraction and testing of bitumen in asphalt mixtures Extraction