The first vital factor for grading bitumen emulsion is the viscosity value. The viscosity of bitumen emulsion is determined by its bitumen content. An emulsion with small droplet size and a narrow distribution will give a higher viscosity.
To indicate the bitumen resistance to breaking, a ductility test is done. This testing system measures the extent to which a sample of bitumen can stretch before breaking. A bitumen emulsion that its ductility is more than 40 cm makes the surface of a road safe and strong to heavy traffic and do not break easily.
The softness level of bitumen is indicated by entering a standard needle into it. The harder the bitumen, the better it is for using in hot temperatures. The standard range of penetration can vary among different grades of bitumen emulsion.
This parameter evaluates the stability of bitumen emulsion during the storage. known also as sedimentation, storage stability shows if the bitumen emulsion droplets settle after manufacturing or not.
For testing the sedimentation of bitumen emulsion, a sample of bitumen is stored in a cylinder in the room temperature. After 24 hours, two sample will be taken, one from the top of the cylinder and the other from the bottom. The weight of two samples will be compared at the next stage. The difference between two samples’ weight should not exceed 1 unit.
Two main factors that affect the storage stability of bitumen emulsion are viscosity level and the droplet size. A bitumen with smaller droplets has less risk of settlement.