Bitumen and its sources
Bitumen is a viscous and elastic material It is soluble in organic solvents, such as toluene and carbon disulphide, . It is a complex mixture of hydrocarbon material and dark or black in color we extensively use bitumen in our road construction. The main reason to use bitumen as binding material are its water proofing properties , excellent binding characteristics and low cost.
Sources of Bitumen Binder
- One of the largest sites is on the island of Trinidad, 100 acre of land in west indies, in which more than 10 million tones have been mining.
- Due to the combined action of heat, pressure, and oxidation, the volatile constituents of the oil change into the Lake Asphalt. Then this Lakes asphalt comes out if fissures existed in overlaying rock and finally lake asphalt comes into the surface.
- Lake asphalt material basically comprises a mixture of bitumen, water and very fine mineral matter.
- Trinidad Lake asphalt (modified ) is well known for its consistent properties, stability and durability.
- It is widely used for bridge and airport applications where high stability surfaces are required.
- It is a kind of asphalt that comes from the petroleum flowing from the split crack of the rock .
- Due to combined action of Heat, pressure, Oxidation, catalyst and bacteria, the volatile constituents of the oil change into the Rock Asphalt.
- Rock asphalt does not require chemical processing hence it is a kind of green, energy-saving, environmental new pavement material.
- Gilsonite or Asphaltum is a natural asphalt resinous hydrocarbon.
- Samuel H. Gilson began to promote it as a waterproofing coat, insulation for wire cable, etc. and he formed the first company to mine and market Gilsonite.
- Gilsonite is found below the earth’s surface in vertical veins or seams that are sometimes between 0.5 and 2 metres in width but are usually as wide as 10 metre.
- It is also used in more than 160 products.
- Industries use Gilsonite are Oil and Gas industries, Inks and Paints industries, Foundry Industries, Asphalt industries, in Gilsonite lab, etc
Petroleum Crude :
- Crude oil is a flammable liquid found in nature. It is the main source of bitumen
- It is composed of hydrocarbons made of carbon chains or rings primarily with hydrogen as the other primary constituent.
- In a Refinery process, Crude oil is heated up to 650 Deg to 700 Deg F in a distilling column container so that it changes into vapor form.
- Container contains a set of trays that allow heated vapors to rise and collect at different levels.
- The top of the column container is cooler than the bottom, hence liquids vaporize and rise, they condense again, and collecting them their respective trays.
- As in general phenomena, higher the carbon atoms in a hydrocarbon compound, the denser it is and will have a higher boiling temperature. And the lower carbons means a lighter compound and lower boiling temperatures.
- Hence light products (like Butane) rise to the top of the column, while gasoline, naphtha, kerosene, diesel, and heavy gas oil gather on the trays, leaving straight run residue (bitumen ) at the base of the column.
- Bitumen (High Molecular weight) is mainly used in road construction and insulation, for either paving grade or roofing grade.
Composition of Bitumen
- Asphaltenes (8 to 16 % ): It Causes hardness in Bitumen and leads to early top-down cracks
- Resins ( 24 to 36 % )
- Aromatics ( 42 to 72 %): High aromatics lead to tender mixes and rutting (deformation)
- Saturates ( 4 to 12 %)
- During the process of aging (oxidation) Aromatics converted into resins and that resins converted into Asphaltenes . which makes the bitumen harder and causes Top-down to crack.