Which is the hardest type of bitumen

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bitumen (Plural: Bitumina) is according to DIN EN 12597 an "almost non-volatile, sticky and sealing petroleum-based product" that is extremely viscous or almost solid at ambient temperature. It has very good sealing properties. The name bitumen is derived from the Latin "bitumen" = "earth pitch".

From a chemical point of view, bitumen is a mixture of different hydrocarbons. More precisely, it is a system made up of an oily base (Maltene) in which the dark, higher-molecular asphaltenes are dispersed (finely divided). Bitumen should not be confused with tar, which is made from coal and has not been used as a building material in Germany for a long time.

Bitumen also occurs naturally, for example in La Brea asphalt lake on the island of Trinidad; these deposits are called natural bitumen. However, it is mainly produced from petroleum, i.e. industrially it is obtained as a residue from the vacuum distillation of petroleum. Most of the time, the bitumen is further treated by blowing in air (air blowing), which allows its properties to be adjusted. Road construction bitumen is produced with a short blowing time, while oxidation bitumen is obtained with a long reaction time, which is used exclusively as industrial bitumen.

Bitumen is not hazardous to health or water. However, bitumen fumes that are produced during hot processing contain carcinogenic polycyclic aromatic hydrocarbons (PAHs). Bitumen is chemically stable to non-oxidizing acids and bases, but reacts violently with oxygen in the event of a fire. At high temperatures it begins to slowly decompose. It is practically insoluble in water and is therefore used to protect sensitive materials and components from water.

The properties of bitumen can be specifically adjusted using additives. Mixing with polymers produces polymer-modified bitumen (PmB). For example, they have better stability at higher temperatures or better fatigue behavior and are used on particularly stressed surfaces such as highways and airports.

Bitumen cannot be transported at ambient temperatures and must therefore be heated to over 100 ° C. To make it easier to process, flux agents (flux oils) are often added, which reduce the viscosity.

The main area of ​​application of bitumen is asphalt, a mixture of aggregates with bitumen as a binding agent. Industrial bitumen is processed into roofing and waterproofing membranes, asphalt coatings and sealing agents.

Road construction bitumen is classified using the needle penetration test according to DIN EN 1426. Bitumen 50/70, for example, means that the penetration depth of the test needle is between 5 and 7 mm. Common grades are 70/100, 50/70, 30/45 and 20/30. The smaller the numbers, the "harder" the bitumen type.

In 2014, 3.7 million tons of bitumen were produced in Germany. World consumption is around 100 million t; around 85% of this includes the production of asphalt for roads, runways for airfields and paths, 10% for roofs and 5% for other building materials. Bitumen consumption is highly cyclical and depends in particular on the economic situation in road and building construction.

The product portfolio of NordBit (subsidiary of Petronord) includes not only finished products but also bitumen for road construction.

Status: December 2015
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