General Definition of Cationic Bitumen Emulsion
The term Cationic Bitumen Emulsion is derived from the migration of particles of bitumen under an electric field also. The droplets migrate toward the cathode (negative electrode), and hence the emulsion is called cationic. The cationic emulsifying agent functions similarly to the anionic; the negative portion of the head floats around in the water leaving a positively charged head. This imparts a positive charge to all the droplets. Since positives repel each other, all the droplets repel each other and remain as distinct bitumen drops in suspension. A typical cationic emulsifying agent is shown below along with a diagram showing the orientation of the agent at the bitumen-water interface and the positive charge imparted to each drop.
A stable dispersion of bitumen in water in the 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, it’s breaking & curing when applied over aggregates.
The term cationic is derived from the migration of particles of bitumen under an electric field also. The droplets migrate toward the cathode (negative electrode), and hence the emulsion is called cationic. The cationic emulsifying agent functions similarly to the anionic; the negative portion of the head floats around in the water leaving a positively charged head. This imparts a positive charge to all the droplets. Since positives repel each other, all the droplets repel each other and remain as distinct bitumen drops in suspension. A typical cationic emulsifying agent is shown below showing the orientation of the agent at the bitumen-water interface and the positive charge imparted to each drop.
Chemical surface-active agents, serving as emulsifiers, are classified by the electrochemical charge that is attained when they dissociate in a water solution. In the case of cationic emulsions, the chemical charge is positive. The chemical type and quantity of surface-active agents used in the manufacturing process govern the process in which the resulting asphalt emulsion can be used.
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Advantages of Cationic Asphalt Emulsion
- Bitumen Emulsion does not require petroleum solvent to make them liquid as in cut back and also it is not required to be heated like normal Bitumen. Thus saving imported petroleum oil or firewood.
- Toxic fumes (Hydrocarbon emission) normally emitted from heated bitumen & cutbacks not present when Cationic Bitumen Emulsion is used, as no heating is required for its application.
- Cold application of Bitumen Emulsion ensures safety to the workforce, it is a user-friendly product.
- Being cold applied, the work progresses much faster.
Application of Cationic Asphalt
Emulsions were first developed in the early 1900s. It was not until the 1920s however, that emulsions, as we know them today came to the fore due to its ecofriendly behavior & other advantages, the use of Cationic Bitumen Emulsion has had a steady rise in demand worldwide.
Cationic Bitumen Emulsion has been recommended to use in several applications of Road Work like Tack Coat, Prime Coat, Surface Dressing work, 20 mm Premix Carpet, Sealing of cracks with fog seal, slurry seal, micro-surfacing, etc.
