What is bitumen?
Bitumen is a product that is created during the gentle processing of crude oil. However, it also occurs in natural asphalt or in natural bitumen deposits (natural bitumen). The most well-known deposit is Pitch Lake on the island of Trinidad. There, liquid bitumen bubbles out of the subsoil.
The main component of bitumen is long-chain hydrocarbons. Additionally, sulfur, oxygen, nitrogen and traces of metals can be found in the building material.
What properties does bitumen have?
The building material is hardly volatile, sticky and has a sealing effect.
It is a thermoplastic material, which is why it behaves elastoviscously depending on the temperature. When it cools down, it becomes brittle, and when it is heated, it goes through all states from solid to viscous to thin. As the temperature rises, it slowly begins to decompose.
It also becomes brittle and cracked when it is exposed to the weather for a long time and the oxidation processes damage the material. The addition of plastics weakens the temperature-dependent properties.
The properties of bitumen mean that hot asphalt can be easily poured, spread and smoothed at road construction sites. The mixture then hardens quickly. However, it should be noted that this property of normal bitumen is a disadvantage on hot days, as the asphalt surface can become out of shape. However, in terms of recycling, this is an immense advantage, as the material only needs to be heated and is then ready for reprocessing.
Bitumen is not soluble in water, which is why solvents such as toluene, trichloroethylene, tetrachloroethylene (perchloroethylene) or dichloromethane (methylene chloride) are used.
Where is the binder used?
Since the building material is water-repellent, it is used to protect sensitive materials and components against water. Specific areas of application are listed below:
- Road construction (as a binding agent in asphalt and especially in mastic asphalt)
- Sealing work
- Building construction (bituminous bonding layer connects bridge decking to steel plate and protects against corrosion)
- Bitumen roofing membranes (for roof waterproofing)
- External basement insulation (using bitumen thick coating)
- Backing of carpet tiles
What types of bitumen are there and what are their functions?
Depending on the application, the binding agent must have different properties. In very cold regions it must not be too brittle and in very hot regions it must not be too liquid. It must meet the requirements of our road traffic in both winter and summer and also have a good cost-benefit ratio. This is why there are various types of bitumen.
- Polymer-modified bitumen (PmB): For greater durability on heavily frequented roads
- Road construction bitumen: Denotes hard bitumen
- Oxidized bitumen
- Bitumen emulsion: Is a stable solution of bitumen in water
- Flux bitumen: For use in particularly cold countries. The addition of flux oils ensures a lower viscosity
The building material cannot be extracted or processed at room temperature. Bitumen can be processed by heating it to a liquid state. In addition, bitumen emulsions, foamed bitumen (addition of water and ambient air to bitumen), flux bitumen or cutback bitumen (addition of solvents) can enable processing.
The application of needle penetration gives the bitumen its specific name. The deeper the needle can penetrate into the bitumen, the softer it is. Soft bitumens are therefore given high values and hard bitumens are given low values.
Why does bitumen testing technology exist?
In order to determine the properties of different types of bitumen or to identify the bitumen, it must be examined using special test methods. The tests are specified in the standards for road bitumen.
What testing procedures and examination aspects are there for the building material?
The following tests are carried out on bitumen:
- Determination of the softening point using a ring and ball apparatus
- Breaking point according to Fraaß
- Needle penetration with the penetrometer
- Determination of ductility with the ductilometer
- Rheology
- Aging simulations
