Bitumen emulsion is a dark brown finely dispersed liquid material, produced by special plants from bitumen by milling it with water and a surfactant emulsifier.
Water-bitumen emulsion is made by special devices, with different emulsification methods and product quality. The mill originates from simple grain mills, which evolved from millstones and windmills into mixers and grinders and then into high capacity dispersing and homogenizing devices.
Bitumen emulsions were first used for road construction in the 1920s. The first emulsified bitumen patents belong to a French company. Development and improvement of production equipment led to product quality improvements. In the second half of the 20th century, bitumen emulsion came into wide use to replace organic solutions and eliminate the problems of hot materials. This economical, safe and environmentally friendly material is a leading material in the road construction industry. Several European countries have banned the use of all organic solutions altogether.
Emulsification equipment can be of several types, but the most popular ones are the wet grinding mills. Dispersers, ultrasonic homogenizers and colloid mills are widely used for this purpose. They offer ultrafine grinding of both organic and inorganic materials on the nanometric scale.
A colloid mill is a device which makes a colloidal solution, when two or more materials are not soluble and do not chemically react with each other. Materials mixed in a colloid mill are more reliable and durable, with high strength and toughness. Polymer additives are often used to improve the quality of water-bitumen emulsions.