Bitumen emulsions are used for road surface treatment, soil reinforcement, and ground stabilization as well as for the construction of roads and highways. Bitumen emulsion usually consists of bitumen (50-70%) and water (30-50%). A special component known as an emulsifier (acidol, naphtha soap, sulphate soap) is added to bitumen emulsion to make it stable. The emulsifier is more expensive than bitumen though only 0.6-1.6% of emulsifier is required for bitumen emulsion preparation.
Bitumen emulsions were first introduced in the 1920s by French scientists. Bitumen emulsion has made it possible to avoid many of the difficulties that emerge when applying hot bitumen. Some of them include high viscosity of bitumen that results in excessive bitumen consumption, air pollution and extra time and energy to warm up the bitumen.
Bitumen is emulsified in a colloid mill. It is the colloid mill that blends the water and bitumen phases and determines the quality of the final product. It should be noted that colloid mills have replaced propeller type mixers commonly used in earlier emulsification production processes.
The following is a common procedure of road surface treatment when using bitumen emulsions:
- to remove dirt and dust from the surface and repair potholes (if necessary);
- to moisten the surface if it is hot outside;
- to spread 30% of the regular amount of the emulsion along the surface;
- to spread 70% of the regular amount of crushed stones along the surface;
- to spread the rest of the emulsion (70%);
- to spread the rest of the crushed stones (30%);
- to compact the surface; and
- to form the final surface.
The temperature and the concentration of emulsion do not need to be set according to weather conditions. For example, if the ambient temperature is -20ºC, the temperature of the bitumen emulsion should be heated to between +40 and +50ºC and its concentration between 55-60% of the normal volumes.
Here is the list of benefits of bitumen emulsion that have distinguished it from other construction materials:
- reduction in power consumption (by 20-40%) since there is no need to warm up the bitumen;
- reduction in bitumen consumption (by 30-40%) due to low viscosity and wettability of the mineral material;
- road construction jobs performed on moistened road pavements or mineral materials with natural moisture;
- extended road construction season (from early spring till late autumn, at more than +5ºC);
- improved adhesion to mineral materials due to emulsifier;
- improved work safety;
- reduced risk of fire since water; and
- reduction of hazardous wastes emitted into the atmosphere.
Bitumen emulsion is usually classified according to the charge of the bitumen particles. Emulsions with negatively charged particles are called anionic. In practical terms however, it is troublesome to use them since some filling materials are also negatively charged. It is therefore, very difficult to homogenize filling material and bitumen emulsions that have the same negative charge of particles.
Having done a great deal of work, researchers finally invented emulsions with positively charged particles that are called cationic bitumen emulsions. Such emulsions are used more often when performing road construction projects because they are easy to combine with filling materials.
In practical terms, not only bitumen emulsions but also bitumen pastes and mastics may be used for road pavement. It is the proportion of components that distinguishes bitumen pastes from bitumen emulsion: 40-55% of bitumen, 8-15% of emulsifier and 30-50% of water.
Bitumen mastic is the mixture that consists of bitumen pastes and finely dispersed mineral filling materials (the size of the grains is no more than 1.25 mm).
GlobeCore has developed, and is still producing equipment, designed for production of high-quality bitumen emulsions (cationic and anionic), bitumen pastes and mastics. The colloid mill, as the one of the basic parts of bitumen emulsion equipment, provides for production of highly-stable bitumen emulsions that can be stored for a long period of time and ensures high quality of of completed road construction projects.