what ıs bıtumen emulsıon ?
Bitumen emulsion is a mixture of water & bitumen. Hey wait, we know that bitumen is a oil product and it cannot be mixed with water. That is why we add an emulsifier (a surface active agent) with water before adding bitumen. Addition of emulsifier with water facilitates breaking of bitumen into minute particles and keeps it dispersed in suspension.
Therefore we can say that a bitumen emulsion is a liquid product consisting of three things, (i.e. water + Emulsion + Bitumen) where droplets of bitumen are suspended in water.
What are the types of emulsions ?
- Anionic with negatively charged globules
- Cationic with positively charged globules
- Non-ionic with neutral globules
How is it Manufactured Bitumen Emulsion ?
The production of bitumen emulsion consists of two primary steps.
In the 1st step water is mixed with appropriate emulsifying agent and other chemicals. The type of emulsifier to be used depends upon the ionic nature of the mix.
The 2nd step is the addition of bitumen with the water-emulsifier mix. This is done in a colloidal mill. Depending upon the use, the amount of bitumen to be added with water may range from 40 to 70%. Water-emulsifier mix and bitumen is pumped to a colloidal mill. The colloidal mill breaks the bitumen into tiny droplets. The average diameter of these tiny droplets of bitumen is about 2 micron. Here comes the role of emulsifier. Emulsifier creates a coating of surface charge around the bitumen droplets that helps to keep these tiny particles away from each other. It also helps to keep these particles in a dispersed form.
After completion of the 2nd step, the bitumen emulsion is pumped into storage tank.
ADVANTAGES – WHY TO USE BITUMEN EMULSIONS?
- The strength properties of bitumen are preserved in emulsion mixes since emulsions do not need hot mixing. Generally cold mixing or just slightly warming the ingredients of the emulsion mix are done for construction of pavements.
- Emulsion can be used in wet weather even when it is raining.
- Emulsions possess anti-stripping properties.
- Emulsions with lower viscosity or thinner consistency improve spreadability and allows better coating of the bitumen on the surface of aggregate.
- There is no wastage during laying and storage.
- Since emulsions are water based, there is less effect on the environment.
- It is the least energy intensive of all construction material: there is no need to heat.
LIMITATIONS
- No one type of emulsion is suitable for every work. it depends upon whether the aggregate is acidic or basic in nature..
- The setting time may vary depending on the air temperature, wind velocity and type of emulsion.
- There is a wide range of curing time; a suitable emulsion mix needs to be designed for a particular need, i.e. we need to determine for each case, the optimum quantity of emulsion based on zone, type of emulsion, mix grade and desired mechanical properties
- It has limited storage time (ranging from few days to six months)
