Types of bitumen
– Bitumen (Gilsonite):
Some types of bitumen are found in nature due to the gradual transfer of crude oil near the earth’s surface and the evaporation of its volatiles over many years. Such bitumen is called natural bitumen.
Such bitumen may exist in pure form in nature (lake bitumen), such as Behbahan Lake Bitumen in Iran and Trinidad Lake Bitumen in the United States, or it may be extracted from mines (mineral bitumen). Natural bitumen is also known as Uintaite. Examples of natural bitumen are rock bitumen and lake bitumen.
Bitumen is usually obtained by distilling crude oil. Such bitumen is called petroleum bitumen or distilled bitumen. Petroleum bitumen is the product of two stages of crude oil distillation in the distillation tower.
In the first stage of distillation, light materials such as gasoline and propane are separated from crude oil. This process takes place at a pressure close to one atmosphere (units). In the second stage, heavy compounds such as diesel and kerosene are extracted. This process takes place at a pressure close to vacuum.
Until the end of the nineteenth century, the bitumen used in road construction and street construction was a variety of mineral bitumen, bitumen stone, bitumen mastic and stone powder, which is considered as mineral or natural bitumen.
In the early twentieth century, petroleum bitumen from crude oil refining came on the market and replaced mineral and natural bitumen in asphalt pavements and other industrial uses.