Applied as a binder in road construction, bitumen is required to behave as a liquid during its application. Other than heating, there are at least two other ways with which bitumen can be made to behave as a liquid at lower ambient temperatures. One option is to dilute bitumen with petroleum solvents like kerosene and naphtha until it becomes fluid enough for application; the final strength of the material develops when the solvent evaporates. Another option is to emulsify bitumen wherein it is liquefied by dispersing in water.

Bitumen emulsions are used widely in road construction, mostly in maintenance and repair works in the form of slurry seals and surface dressing, and in structural pavements in the form of prime and tack coats, cold mixes, recycled asphalt mixes and more.In road construction applications, bitumen emulsions provide a safer and more environment-friendly system than hot bitumen by avoiding the risks of fire and burns; using less energy in processes; and reducing emissions.

What are bituminous emulsions?

Bitumen emulsions are usually dispersions of minute droplets of bitumen in water. The droplets normally range from 0.1 to 20 microns in diameter. The bitumen content in bitumen emulsions are varied to suit different requirements and typically varies between 30 per cent and 70 per cent.

Bitumen emulsions are usually made using a colloid mill. In the colloid mill, hot bitumen is sheared rapidly in water containing an emulsifying chemical agent (emulsifier). This results in the production of very small particles of bitumen dispersed in water (continuous phase). The bitumen particles in suspension do not readily coalesce owing to the presence of the emulsifier, which will get concentrated on the surface of the bitumen particles...

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