WHY USE BITUMEN EMULSIONS?
Standard flexible road structures consists of layers of
manufactured materials laid onto an roadbed soil. The upper portion of the
roadbed soil is commonly exposed to harsh environmental and heavy traffic
leading to distortion and subsequent cracking of the upper surface layers.
It is not economically viable to excavate the complete structure and
therefor emulsion mixes are used successfully to follow roadbed soil
movement without cracking. It has been proven that emulsion mixes have
membrane-like mechanical properties rather than the slab-like properties
of standard hot bituminous mixtures. Furthermore, emulsion mixes are not
as susceptible to thermal cracking as regular standard hot bituminous
An emulsion is a mixture of two immiscible liquids, one of which is dispersed in the other in the form of very fine particles. The process of emulsification is accomplished by use of an emulsifier and a stabilizer.
Emulsion mixes are used as a base layer in a pavement structure as well as a surfacing course. They are obtained by dispersing a cationic bitumen emulsion in an aggregate and can be produced in cold mix plants as well as with mix-pavers. The application rates vary from 50 mm to 200 mm in thickness.
The binder within an emulsion stabilized granular material selectively coats smaller particles. The stiffness of emulsion mixtures is lower than Hot Mix Asphalt. Unlike Hot Mix Asphalt, the manufacturing of emulsion mixes does not require heat.
The surface of emulsion mixes is relatively fragile when compared to the surface of Hot Mix Asphalt. Unsealed emulsion mixes do not provide waterproofing and the cohesion at the surface may not be sufficient to withstand surface tangent stresses. By sealing the surface emulsion mixes, waterproofing is achieved and the inherent performance of emulsion mixes is not compromised by premature stripping, oxidation and raveling.
Are used for cold weather construction as well as maintenance under all weather conditions. The petroleum distillate generally used for obtaining cut back bitumen is kerosene.