--- title: "Penetration test of bitumen" subject: "Transportation Engineering I" chapter: 6 key: "semester_6/transportation_engineering_i:penetration-test" source: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/penetration-test site: BCT Engineering --- # Penetration test of bitumen Transportation Engineering I · Chapter 6: Highway Materials - Asked in: 2073 Magh; 2071 Magh; 2070 Bhadra; 2068 Bhadra (old course), 8 marks; 2067 Mangsir (old course), 2+6 marks; 2066 Magh (old course), 4 marks (asked 6 times) - Video: [PENETRATION VALUE OF BITUMEN](https://www.youtube.com/watch?v=IGlFmQ3u-jE) — 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/penetration-test - Whole chapter: https://www.bctengineer.com/md/semester_6/transportation_engineering_i/chapter-6 ## Question What do you mean by penetration value of bitumen? Describe the step by step procedure for the determination of penetration value of bitumen in the laboratory and its significance. ## Short answer Penetration value measures bitumen hardness as the depth (in 0.1 mm) a standard 100g needle penetrates in 5 seconds at 25°C. The test involves heating bitumen, pouring into a container, cooling, and measuring needle penetration in a water bath. Lower values indicate harder bitumen; grades like 60/70 suit hot climates while 80/100 suits cold regions. ## Answer #### Meaning The **penetration value** of bitumen is the depth, in units of 0.1 mm, to which a standard needle with a total load of 100 g penetrates vertically into a bitumen sample in 5 seconds at 25 degrees C (IS:1203). It is a measure of **hardness/consistency**: a lower value means a harder bitumen. The grade is named by its penetration, such as 60/70 (value 60 to 70). #### Apparatus - Standard needle (1 mm diameter, tapered) and penetrometer with a 50 g weight on the needle assembly (total 100 g). - Container (55 mm diameter, 35 mm deep for penetration below 200), water bath at 25 degrees C (capacity 10 litres, depth 100 mm), a transfer dish, thermometer and stopwatch. #### Procedure 1. Heat the bitumen sample gently to a pouring consistency (75-100 degrees C above the softening point), stir to remove air bubbles, and pour it into the container to a depth at least 15 mm more than the expected penetration. 2. Cool in air at 15-30 degrees C for 1 to 1.5 hours; then place the container in the water bath (at 25 degrees C) for 1 to 1.5 hours. 3. Fill the transfer dish with water from the bath, put the container in it, and place it on the penetrometer stand. 4. Adjust the needle so that its tip just touches the sample surface (use its reflection). Set the dial to zero. 5. Release the needle for **5 seconds**, then read the penetration from the dial in units of 0.1 mm. 6. Take at least three readings at points at least 10 mm apart and at least 10 mm from the edge of the container, cleaning the needle each time. The mean of the three readings, if they agree within the allowed tolerance, is the penetration value. #### Significance - It measures consistency and is used for grading, and so decides the **suitability of bitumen** for the climate: harder grades (30/40, 60/70) for hot climates and heavy traffic; softer grades (80/100) for cold regions. - It is used for quality control and, together with the softening point, for estimating the temperature susceptibility (penetration index). - NRS 2070 and IS:73 specify penetration grades 60/70 and 80/100 for roads in Nepal (80/100 is used in the hills because of the lower temperatures). ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What does a lower penetration value indicate? A. Harder bitumen B. Softer bitumen C. Higher ductility D. Lower flash point Answer: A. Penetration is needle depth in 0.1 mm; less depth means harder bitumen. (Key point: Meaning of penetration) 2. What are the standard conditions of the penetration test? A. 100 g load, 5 seconds, 25 degrees C B. 50 g, 60 s, 60 degrees C C. 200 g, 5 s, 0 degrees C D. 100 g, 30 s, 40 degrees C Answer: A. The total load of 100 g acts for 5 s at 25 degrees C. (Key point: Test conditions) 3. How many readings are taken, and how are they placed? A. At least three, 10 mm apart and 10 mm from the container edge B. One at the centre only C. Five at the same point D. Two at the edge Answer: A. The needle is cleaned each time and the mean of three readings is reported. (Key point: Readings) 4. Which grades suit hot climates and which suit cold regions? A. Harder grades like 60/70 for hot; softer 80/100 for cold B. Soft for hot; hard for cold C. All the same D. 30/40 for cold only Answer: A. Harder bitumen resists softening in heat; softer bitumen resists cracking in cold, so 80/100 is used in hills. (Key point: Significance) ## Related in Transportation Engineering I - [Marshall stability test procedure](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Amarshall-stability-test) — Transportation Engineering I, chapter 6, asked 3× - [Ductility test of bitumen](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Aductility-test) — Transportation Engineering I, chapter 6, asked 7× - [Softening point test of bitumen](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Asoftening-point) — Transportation Engineering I, chapter 6, asked 4× - [Aggregate crushing value test](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Acrushing-value) — Transportation Engineering I, chapter 6, asked 7× - [Aggregate impact value test](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Aimpact-value) — Transportation Engineering I, chapter 6, asked 3× - [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× ## Related in other subjects - [Metacentre and laboratory determination of height](https://www.bctengineer.com/question.md?key=semester_3%2Ffluid_mechanics%3Ametacentre-importance-lab-determination) — Fluid Mechanics, chapter 3, asked 2× - [Procedure: test of significance of mean](https://www.bctengineer.com/question.md?key=semester_5%2Fprobability_and_statistics%3Atest-of-significance-mean-procedure) — Probability and Statistics, chapter 6 - [Standard penetration test and corrections](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Aspt-procedure-corrections) — Foundation Engineering, chapter 2, asked 3× - [Aggregate crushing value determination](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Aaggregate-crushing-value) — Concrete Technology and Masonry Structure, chapter 1