--- title: "Los Angeles abrasion test" subject: "Transportation Engineering I" chapter: 6 key: "semester_6/transportation_engineering_i:la-abrasion" source: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/la-abrasion site: BCT Engineering --- # Los Angeles abrasion test Transportation Engineering I · Chapter 6: Highway Materials - Asked in: 2078 Chaitra, 5 marks; 2078 Poush, 4 marks; 2078 Baisakh, 4 marks; 2073 Magh; 2072 Ashwin; 2070 Magh; 2069 Bhadra; 2067 Mangsir (old course); 2065 Chaitra (old course), 4 marks; 2062 Jestha (old course), 4 marks (asked 10 times) - Video: [Los Angeles Abrasion Test | Transportation Engineering | Elegant Corner | Civil Engineering](https://www.youtube.com/watch?v=qQey8I5y1Iw) — Elegant Corner - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/la-abrasion - Whole chapter: https://www.bctengineer.com/md/semester_6/transportation_engineering_i/chapter-6 ## Question Describe the test procedure for the determination of Los Angeles abrasion value of road aggregates and discuss its significance. ## Short answer Oven-dried aggregate sample is placed in a rotating drum with a specified charge of steel balls and turned at 30–33 rpm for 500 or 1000 revolutions. The material is then sieved on a 1.7 mm sieve; the percentage loss in weight is the LA abrasion value. It indicates aggregate hardness and toughness; typical limits are 30–40%. ## Answer The **Los Angeles abrasion test** measures the resistance of road aggregate to wear through the combined action of abrasion, attrition and impact in a rotating drum. It follows IS:2386 (Part IV) / AASHTO T96 / ASTM C131 and is used in NRS 2070. #### Apparatus - Los Angeles machine: hollow steel cylinder 700 mm in diameter and 500 mm long, closed at both ends, rotating about a horizontal axis, with one internal shelf (steel plate) 90 mm wide. - Abrasive charge: cast iron or steel balls about 48 mm in diameter, each 390-445 g. - IS sieve 1.7 mm, balance (accuracy 1 g), oven, tray. #### Procedure 1. Take a clean, oven-dried (105-110 degrees C) sample of 5 kg (gradings A to D) or 10 kg (gradings E to G), according to the grading of the aggregate in IS:2386. 2. Select the number of balls by the grading: A - 12, B - 11, C - 8, D - 6 balls, and 12 balls for gradings E, F and G. 3. Place the sample and the charge in the drum, fix the cover, and rotate at **30-33 rpm** for **500 revolutions** (gradings A to D) or **1000 revolutions** (E to G). 4. Remove the material, separate the balls, and sieve the aggregate on a **1.7 mm IS sieve**. 5. Wash and oven-dry the retained portion and weigh it. $$ \text{LA abrasion value} = \frac{W_1 - W_2}{W_1}\times 100\% $$ where $W_1$ = original weight and $W_2$ = weight retained on the 1.7 mm sieve after the test. #### Significance - It indicates the **hardness and toughness** of the aggregate and its ability to resist crushing, wear and abrasion under traffic. - A low value means a strong aggregate. Desirable limits (IRC/NRS 2070, MoRTH): **not more than 30%** for wearing course/bituminous concrete, **not more than 35%** for dense bituminous macadam, **40%** for bituminous macadam and WBM base courses (up to 50% for lower layers such as the granular sub-base). - The test is quick and repeatable, and it is widely used for quality control of aggregate sources. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What does the Los Angeles test measure? A. Resistance of aggregate to wear and impact in a rotating drum B. Adhesion of bitumen C. Flakiness of particles D. Water absorption Answer: A. The aggregate is tumbled with steel balls so it is subject to abrasion, attrition and impact. (Key point: What LA test measures) 2. In the LA test, after the drum rotates 500 revolutions (gradings A to D), the sample is sieved on which sieve? A. 2.36 mm B. 1.7 mm C. 12.5 mm D. 10 mm Answer: B. The retained portion on the 1.7 mm IS sieve is washed, dried and weighed. (Key point: Procedure details) 3. How is the LA abrasion value found, and what does a low value mean? A. (W1 - W2)/W1 x 100, strong aggregate B. W2/W1 x 100, weak aggregate C. (W1 - W2)/W1 x 100, weak aggregate D. W1/W2 x 100, strong aggregate Answer: A. The loss in weight divided by the original is the percentage; a low value means hard, tough aggregate. 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