--- title: "Types of bitumen and bituminous materials" subject: "Transportation Engineering I" chapter: 6 key: "semester_6/transportation_engineering_i:bitumen-types" source: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/bitumen-types site: BCT Engineering --- # Types of bitumen and bituminous materials Transportation Engineering I · Chapter 6: Highway Materials - Asked in: 2074 Bhadra; 2072 Ashwin; 2067 Mangsir (old course), 4 marks; 2065 Chaitra (old course), 4 marks; 2063 Kartik (old course), 2+2+2+2 marks; 2062 Jestha (old course), 4 marks (asked 6 times) - Video: [Everything You Need to Know About Bitumen: Types, Uses, and Properties Explained!](https://www.youtube.com/watch?v=qxyI_0fCcWw) — Aashmi Classes (Dr.Sovan) - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/bitumen-types - Whole chapter: https://www.bctengineer.com/md/semester_6/transportation_engineering_i/chapter-6 ## Question What are the different types of bitumen / bituminous materials used in road construction (natural bitumen, petroleum bitumen, cutback bitumen, bitumen emulsion, tar)? Explain them briefly with their importance. ## Short answer Main types: petroleum bitumen (penetration/viscosity grades) for hot mixes; cutback bitumen (RC, MC, SC) dissolved in solvent for cold application; bitumen emulsion (cationic RS, MS, SS) in water for tack coats and surface dressing; natural bitumen from lakes; and coal tar (rarely used). Each provides different application and performance properties. ## Answer Bituminous materials are used as the binder in road construction. The main types are as follows. #### 1. Natural bitumen Found in nature, in lakes and as rock asphalt (Trinidad lake asphalt, Dead Sea, Gilsonite). It occurs mixed with mineral matter and is used as a modifier or for waterproofing. It is not common in Nepal. #### 2. Petroleum bitumen (straight-run bitumen) The residue left after distilling crude petroleum. It is the most common binder in Nepal (imported from India). Grades: penetration grades 30/40, 60/70, 80/100 and viscosity grades VG-10, 20, 30, 40. Used for bituminous macadam, DBM, bituminous concrete, seal coats and tack coats. Variants: **blown (oxidised) bitumen** for roofing and waterproofing, and **modified bitumen** (PMB/CRMB) for heavy traffic. #### 3. Cutback bitumen Bitumen dissolved in a volatile solvent (petroleum distillate) to reduce its viscosity so that it can be used cold: - **Rapid curing (RC)** - gasoline/naphtha solvent, - **Medium curing (MC)** - kerosene, - **Slow curing (SC)** - diesel/heavy oil. Used for prime coat, tack coat, surface dressing and patching, where heating is difficult, or in cold weather. The solvent evaporates after laying. #### 4. Bitumen emulsion Fine droplets of bitumen dispersed in water with an emulsifier. **Cationic** (positively charged) types are used with most aggregates. Types by setting speed: rapid (RS), medium (MS) and slow setting (SS). No heating is needed; used for tack coat, surface dressing, slurry seal, cold mix and in wet conditions; it is environmentally friendly and safe. #### 5. Tar Obtained by destructive distillation of coal, wood or similar organic matter (coal tar). Road tar grades are RT-1 to RT-5 (RT-1 and RT-2 for surface painting, RT-3 for surface painting/renewal coats and light premixing, RT-4 for premix tar macadam, RT-5 for grouting). It has good adhesion with aggregate, but it is more temperature susceptible, ages quickly and is carcinogenic, so it is now rarely used. | Binder | Form | Main use | |---|---|---| | Petroleum bitumen | Solid/semi-solid | Hot mixes | | Cutback | Liquid, volatile | Prime/tack coat, patch | | Emulsion | Water dispersion | Cold works, seal coat | | Tar | Dark viscous | Surface dressing (older practice) | ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. How is petroleum bitumen obtained? A. As residue after distilling crude petroleum B. By distilling coal C. By dissolving in solvent D. From lake asphalt Answer: A. Straight-run bitumen is the residue from crude distillation and is the most common binder. (Key point: Petroleum bitumen) 2. What is cutback bitumen and why is it used? A. Bitumen dispersed in water B. Bitumen dissolved in volatile solvent to reduce viscosity so it can be used cold C. Coal tar D. Oxidised bitumen Answer: B. The solvent lowers viscosity and evaporates after application; RC, MC and SC are the types. (Key point: Cutback) 3. Which statement is correct? A. Emulsion is bitumen droplets in water with emulsifier and needs no heating; tar is from destructive distillation of coal and is carcinogenic B. Tar is a residue of petroleum C. Emulsion requires heating to 150 degrees C D. Tar has low temperature susceptibility Answer: A. Emulsions are cold-applied and safe; tar is coal-derived, ages quickly and is rarely used. (Key point: Emulsion and tar) ## Related in Transportation Engineering I - [Macadam road construction method](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Amacadam-construction) — Transportation Engineering I, chapter 1 - [Tests on bituminous binders](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Abitumen-tests-list) — Transportation Engineering I, chapter 6, asked 8× - [Define bitumen premixes](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Adefine-bitumen-premixes) — Transportation Engineering I, chapter 6, asked 5× - [Desirable properties of road aggregates](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Aaggregate-desirable-properties) — Transportation Engineering I, chapter 6, asked 5× - [Viscosity test of bitumen](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Aviscosity-test) — Transportation Engineering I, chapter 6, asked 2× - [Materials in pavement layers](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Apavement-layer-materials) — Transportation Engineering I, chapter 6 ## Related in other subjects - [Road construction equipment, paver and bitumen sprayer](https://www.bctengineer.com/question.md?key=semester_8%2Fconstruction_management%3Aroad-equipment-paver-sprayer) — Construction Management, chapter 4 - [Road construction activities; plants for bituminous and CC](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Aroad-construction-activities-plants-bituminous-cc) — Transportation Engineering II, chapter 3 - [Bitumen versus tar](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Abitumen-vs-tar) — Civil Engineering Materials, chapter 10, asked 2× - [Compare asphalt, bitumen and tar](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Aasphalt-bitumen-tar-comparison) — Civil Engineering Materials, chapter 10, asked 2×