--- title: "Ductility test of bitumen" subject: "Transportation Engineering I" chapter: 6 key: "semester_6/transportation_engineering_i:ductility-test" source: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/ductility-test site: BCT Engineering --- # Ductility test of bitumen Transportation Engineering I · Chapter 6: Highway Materials - Asked in: 2081 Ashwin, 6 marks; 2079 Chaitra, 4 marks; 2076 Baisakh; 2076 Bhadra; 2074 Bhadra; 2072 Ashwin; 2072 Magh (asked 7 times) - Video: [DUCTILITY TESTING OF BITUMEN AS PER IS 1208 Part 1- 1978 I Ductility Test Of Bitumen हिन्दी मे](https://www.youtube.com/watch?v=LzgAjlnk7mc) — HIGHWAY GUIDE - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/ductility-test - Whole chapter: https://www.bctengineer.com/md/semester_6/transportation_engineering_i/chapter-6 ## Question Explain the concept of ductility test of bitumen with the test procedure, neat sketch, its significance and engineering application. ## Short answer A standard bitumen briquette is pulled in a water bath at 27°C at 50 mm/min until the thread breaks; the distance in cm is its ductility. High ductility indicates cohesion and flexibility, reducing low-temperature cracking. Minimum requirement is 75 cm for 60/70 and 80/100 penetration grades. ## Answer #### Concept **Ductility** of bitumen is the distance, in cm, to which a standard briquette of bitumen can be drawn out before the thread breaks, under specified conditions (27 degrees C in IS:1208, 25 degrees C in ASTM; rate of pull 50 mm/min). It shows the **cohesion, elasticity and flexibility** of the binder. #### Apparatus - Standard briquette mould (brass, 75 mm long, with a minimum cross-section of 10 mm x 10 mm at the neck). - Ductility machine with a water bath at 27 (or 25) degrees C, in which one clip is fixed and the other moves at 50 +/- 2.5 mm/min. - Thermometer, knife, and glycerine-dextrin release agent. ```text fixed end moving end [clip]=====\ /=====[clip] | | \___thread___/ | | water bath 27 C, pulled at 50 mm/min ``` #### Procedure 1. Heat the bitumen to 75-100 degrees C above its softening point so that it is fluid, and pour it into the mould (coated with the glycerine-dextrin release agent) placed on a brass plate; slightly overfill it. 2. Cool in air for 30-40 minutes, then trim the excess with a hot knife so that it is level with the mould. 3. Place the specimen, with the mould and plate, in the water bath at the test temperature for 85-95 minutes. 4. Remove it from the plate, take off the side pieces of the mould, and fix the rings to the clips of the machine; the water in the bath, at the test temperature, should cover the specimen by at least 25 mm. 5. Pull at **50 mm/min**; the distance from the start to the breaking point is the **ductility value** (cm). Report the average of three tests. #### Significance and engineering application - A high ductility means that the binder can stretch without cracking, so the pavement stays flexible under temperature changes and traffic. - Bitumen with low ductility cracks, especially in cold weather and after ageing; ductility also indicates the adhesive strength with the aggregates. - Minimum values: **75 cm for 60/70 and 80/100 penetration grades** (50 cm for 30/40) under IS:73:1992, and 40 cm for VG-30 after thin-film oven ageing (IS:73:2013); a general minimum of 50 cm is often quoted in textbooks. - Used in specifying and controlling the quality of bitumen for surface dressing, bituminous concrete and DBM, and to reject bitumen with low ductility. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Under which standard conditions is ductility measured? A. 25 degrees C at 50 mm/min B. 60 degrees C at 5 mm/min C. 100 degrees C at 50 mm/min D. 0 degrees C at 500 mm/min Answer: A. The briquette is pulled in a 25 degrees C water bath at 50 mm/min. (Key point: Test conditions) 2. What does a high ductility value show? A. Bitumen can stretch without cracking, so the pavement stays flexible B. Bitumen is very hard C. Bitumen has high flash point D. Bitumen is impure Answer: A. High ductility means good cohesion and flexibility, resisting cracking. (Key point: Meaning of result) 3. What is the minimum ductility for 60/70 and 80/100 penetration grade bitumen? A. 10 cm B. 50 cm C. 100 cm D. 5 cm Answer: B. The minimum is 50 cm per IS:73 / NRS 2070. 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