Bituminous materials are the mixture of hydrocarbon of natural or hydrogenous origin or a combination of both found in gaseous, liquid, semi-solid or solid form and completely soluble in carbon disulphide.
Bituminous materials may classified as :
Bitumen :Bitumen is a hydrocarbon of either natural or artificial obtained during fractional distillation of petroleum.
1. Forms of Bitumen :
i) Bitumen Emulsion : It is a liquid product containing bitumen to a great extent in an aqueous medium. The quantity of bitumen may vary from 40%-60% and the remaining portion being water.
ii) Blown Bitumen : It is obtained by passing air under pressure at a higher temperature.
iii) Cut back Bitumen : If the viscosity of bitumen is reduced by volatile dilutent, it is called cut back bitumen.
iv) Plastic Bitumen : It consist of bitumen, thinner and suitable inert.
v) Straight Run Bitumen : Bitumen being distilled to a definite viscosity or penetration without further treatment.
2. Types of Cut back Bitumen :
i) Rapid Curing (RC) Cutback Bitumen : In RC cutback, the bitumen is fluxed with a petroleum distillate such as Naptha or gasoline.
ii) Medium Curing (MC) Cutback Bitumen : In MC cutback, the bitumen is fluxed with kerosene or light diesel oil.
iii) Slow Curing (SC) Cutback Bitumen : In SC cutback, the bitumen is blended with high boiling point gas oil.
Tar : It is a viscous liquid obtained when natural organic materials such as wood and coal are destructively distillated in the absence of air. For road construction tar prepared from coal is widely used as it is superior to wood tar.
The production of tar can be classified into the following three stages :
i ) Carbonization of coal to procure crude tar.
ii) Distillation of crude.
iii) Blending of distillation residue to get desired road tar.
Grades of Tar :
i) RT – 1 : It is used for surface painting under exceptionally cold weather as this has very low viscosity.
ii) RT – 2 : It is recommended for surface painting under normal indian climatic conditions.
iii) RT – 3 : It is used for surface pointing, renewal coats for light carpets and premixing chips for top course.
iv) RT – 4 : It is used for premixing Tar Macadam in base course.
v) RT – 5 : It is used for grouting purposes.
Note : RT – 4
(Road Tar) – (Larger the number, more the viscosity).
Tags : types of cutback bitumen, bitumen, tar, grade of tar, cutback, forms of bitumen, bituminous materials.