---
title: "Types of bitumen"
subject: "Civil Engineering Materials"
chapter: 10
key: "semester_3/civil_engineering_materials:types-of-bitumen"
source: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/types-of-bitumen
site: BCT Engineering
---

# Types of bitumen

Civil Engineering Materials · Chapter 10: Asphalt, Bitumen, Tar and Miscellaneous Materials

- Asked in: 2080 Baisakh, 3 marks; 2068 Baisakh, 5 marks (asked 2 times)
- Video: [grades of bitumen|uses and applications of different grades of bitumen|Types of bitumen](https://www.youtube.com/watch?v=_9jEiDRJvjo) — Civillogy (Study of Civil Engineering)
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/types-of-bitumen
- Whole chapter: https://www.bctengineer.com/md/semester_3/civil_engineering_materials/chapter-10

## Question

Explain in brief about the 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.

## Answer

Bitumen is a black, sticky hydrocarbon used as a binder and waterproofing material. Types:

1. **Natural bitumen:** Found in nature as lake asphalt (e.g. Trinidad), rock asphalt, or asphaltic sand mixed with minerals.
2. **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.
3. **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.
4. **Bituminous emulsion:** Bitumen droplets suspended in water with an emulsifier. Cationic, anionic types; used for surface dressing, tack coat and patching in wet weather.
5. **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.
6. **Modified bitumen:** Polymer or rubber added (PMB, CRMB) for better strength in heavy traffic.
7. **Bitumen felt:** Fibre sheets saturated in bitumen, used for roofing and DPC.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What is cutback bitumen?
   A. Bitumen in water
   B. Bitumen dissolved in a volatile solvent so it can be applied cold
   C. Air-blown bitumen
   D. Bitumen with rubber
   Answer: B. Solvent evaporates leaving bitumen; used for prime coat, tack coat and surface dressing. (Key point: Cutback bitumen)

2. Bituminous emulsion consists of what?
   A. Bitumen in petrol
   B. Bitumen droplets in water with an emulsifier
   C. Bitumen and cement
   D. Bitumen and sand
   Answer: B. Droplets suspended in water, usable in wet weather. (Key point: Emulsion)

3. How is blown (oxidised) bitumen made and what is it like?
   A. Air blown through hot bitumen; harder with higher softening point
   B. Water added; softer
   C. Polymer added; elastic
   D. Fibre soaked
   Answer: A. Blowing air hardens it and lowers temperature susceptibility. (Key point: Blown bitumen)

4. Viscosity grade bitumen is designated how?
   A. 30/40
   B. VG-10, 20, 30, 40 (IS 73)
   C. RC, MC, SC
   D. PMB
   Answer: B. VG grades follow IS 73; 30/40 etc. are penetration grades. (Key point: Viscosity grade)