The SIP process uses a cationic bitumen emulsion. A stable dispersion of bitumen in water in continuous phase. The bitumen globules are positively charged due to the NH3 + group cover which is formed around bitumen droplets and provide stability for emulsion by electrostatic repulsion.
These bitumen droplets have an affinity with the negatively charged aggregate, which is usually available in India. Dispersion is obtained by processing bitumen & water based solution under controlled conditions through a colloidal mill having a high speed rotor in the presence of scientifically selected surfactants/emulsifier. Selection of emulsifier & its quality is significant for emulsion stability, its breaking & curing when applied over aggregates.
The Cationic Bitumen Emulsion is chocolate brown and free flowing at normal temperature. Once it breaks the bitumen breaks out and colour changes to black. An Emulsion is said to break when the organic and the aqueous phase separate into two distinct layers i.e. the dispersion ceases to exist.
Emulsions are classified as Rapid Setting-1(RS-1),Rapid Setting-2(RS-2) ,Medium Setting (MS), Slow Setting-1 (SS-1), Slow Setting-2 (SS-2) . The breaking time varies according to the designation of Emulsion although being largely dependant upon the climatic condition i.e. temperature, humidity, wind velocity etc.