Bitumen is actually the liquid binder that holds asphalt together. The term bitumen is often mistakenly used to describe asphalt.
A bitumen-sealed road has a layer of bitumen sprayed and then covered with an aggregate. This is then repeated to give a two-coat seal.
Asphalt is produced in a plant that heats, dries and mixes aggregate, bitumen and sand into a composite mix. It is then applied through a paving machine on site as a solid material at a nominated or required thickness, relative to the end use. Asphalt results in a smoother and more durable asphalt road surface than a bitumen-sealed road.
Bitumen is known for being strongly adhesive and resistant to damage from water and oil spills. This makes bitumen the ideal binder for asphalt because asphalt is commonly used as a surface for roads, and driveways.
Bitumen can be produced to different specifications depending on how it’s going to be used but in all cases, bitumen is created by distilling crude oil. This process removes the lighter liquid and leaves a thick sticky substance that, in the case of asphalt, will hold heavy aggregate like stones and gravel with sand.Bitumen is a common binder used in road construction.
It is principally obtained as a residual product in petroleum refineries after higher fractions like gas, petrol, kerosene and diesel, etc., are removed. Indian Standard Institution defines Bitumen as a black or dark brown non-crystalline soil or viscous material having adhesive properties derived from petroleum crude either by natural or by refinery processes
Bitumen is Further classified into various Grades:
The most commonly used in Nepal are:
- Bitumen VG-10
- Bitumen VG-30