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- 2080 Baisakh · 3 marks
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Types of bitumen
Short answer
Bitumen occurs as natural deposits and as petroleum residue. Types include penetration grade (e.g., 60/70), viscosity grade, cutback (RC, MC, SC), emulsion, blown (oxidised), polymer-modified bitumen, and bitumen felt.
Explain in brief about the types of bitumen.
Bitumen is a black, sticky hydrocarbon used as a binder and waterproofing material. Types:
- Natural bitumen: Found in nature as lake asphalt (e.g. Trinidad), rock asphalt, or asphaltic sand mixed with minerals.
- Petroleum (refined) bitumen: The residue left after distilling crude oil.
- Penetration grade (paving) bitumen: 30/40, 60/70, 80/100 grades; used in roads.
- Viscosity grade bitumen: VG-10, 20, 30, 40 as per IS 73.
- Cutback bitumen: Bitumen dissolved in a volatile solvent (petrol, kerosene, diesel) so it can be applied cold; the solvent evaporates leaving bitumen.
- Rapid curing (RC), medium curing (MC) and slow curing (SC) types.
- Used for prime coat, tack coat and surface dressing.
- Bituminous emulsion: Bitumen droplets suspended in water with an emulsifier. Cationic, anionic types; used for surface dressing, tack coat and patching in wet weather.
- Blown (oxidised) bitumen: Air is blown through hot bitumen to make it hard, with higher softening point and low temperature susceptibility. Used for roofing, damp-proofing and pipe coating.
- Modified bitumen: Polymer or rubber added (PMB, CRMB) for better strength in heavy traffic.
- Bitumen felt: Fibre sheets saturated in bitumen, used for roofing and DPC.
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