Bitumen

a black viscous mixture of hydrocarbons obtained naturally or as a residue from petroleum distillation. It is used for road surfacing and roofing.
Bitumen, also known as asphalt is a substance that forms through the distillation of crude oil. It has waterproofing and adhesive properties. Bitumen production through distillation removes lighter crude oil components, such as gasoline and diesel, leaving the heavier bitumen behind.
There are different types of bitumen available with different properties, specifications and uses based on requirements of consuming industry.
The specification of bitumen also shows variation with the safety, solubility, physical properties, and the durability.
To understand the performance of the bitumen when it is on service, the design of physical properties of the material is highly essential. The standard testing methods are carried out to grade bitumen.
Kind of Bitumen grades
Types of Bitumen and their Properties and Uses:
1. Air Blowing Grade
1.1 Peneteration Grade
1.2 Performance grade (PG)
1.3 Oxidized Bitumen

2 .Cutback Bitumen
2.1 slow curing cutback (SC)
2.2 Medium Curing Cutback (MC)
2.3 Rapid curing cutback (PC)

3. Bitumen Emulsion
3.1 Rapid Setting Emulsion (RS)
3.2 Medium Setting Emulsion
3.3 Slow Setting Emulsion

4. Polymer Modified Bitumen

The Air Blowing Bitumen is produced by process of vacuum Bottom (VB) and air in the reactor or batch. And due to the control of the process conditions, different grades are produced.

The regular distillation process is discontinued at some point while the topped crude is still liquid. The heavy fraction is into a converter and air is blown through it while it is maintained at a high temperature. This process is continued until the asphalt has attained desired properties. Often, such asphalts are called Blown asphalt. However, this is not strictly a true term because not only oxidation but also vaporization, Dehydrogenation, condensation, polymerization and other reactions occur during the air blowing process.

Types of Air Blowing Bitumen:
• Penetration Grades
• Performance Grades (PG)
• Viscosity Grades (VG)

Asphalt Air Blowing Process

The physical properties of asphalts may further be modified by ‘air blowing’. This is an oxidation process which involves the blowing of air through the asphalts, either on a batch or a continuous basis, with the short residue at a temperature of 240°C to 320°C.

Air blowing is an extensively used process to upgrade and achieve specifications of final bitumen product. The air blowing process is accompanied by hardening of bitumen, with corresponding changes in chemical composition thereby yielding product having acceptable consistency and temperature susceptibility.

The blowing process dehydrogenates the short residue, resulting in oxidation and polycondensation, increasing the overall molecular size of the asphaltenes already present in the feed and forming additional asphaltenes from the maltene phase. The reaction is exothermic. Therefore close temperature control of this process is required, which is achieved by regulating the air-to-short residue ratio in the blowing column.

Air-rectified or semi-blown bitumens:

To produce penetration grade bitumens suitable for road construction, bitumens manufactured from some crudes require a limited amount of air blowing. This process is termed semi-blowing or air rectification. Used judiciously, semi-blowing can be applied to reduce the temperature susceptibility of the bitumen, ie increase its penetration index.

Fully blown bitumens:

Fully blown or oxidised bitumens are produced by vigorous air-blowing of short residue or short residue blended with a heavy distillate. The position of the blowing curve is primarily dependent on the viscosity of the feed, ie the softer the feed the higher the curve. The severity of blowing depends on the temperature in the column and to a lesser extent on the residence time. Thus by controlling the viscosity of the feed and the conditions in the column all the blown grades of bitumen can be manufactured.