Los Angeles Abrasion Test – Procedure, Calculation, Apparatus & Limits (IS 2386 Part IV)
The Los Angeles Abrasion Test is one of the most important tests
used to evaluate the toughness and abrasion resistance of coarse aggregates
used in road construction and concrete works.
This test determines how aggregates behave when subjected to
wear, impact and grinding action.
Aggregates with high abrasion resistance ensure
longer pavement life, better durability and reduced maintenance costs.
The test is conducted according to
IS 2386 (Part IV) – Methods of Test for Aggregates
and is also specified in
MoRTH Specifications for Road and Bridge Works (5th Revision, 2013).
Importance of Los Angeles Abrasion Test in Highway Engineering
Aggregates are the primary load-bearing material in flexible pavements.
When traffic loads move over pavement surfaces,
aggregates are continuously subjected to:
- Abrasion due to tyre friction
- Impact from moving vehicles
- Grinding action between aggregate particles
If aggregates are weak, they will break into smaller particles,
causing:
- Pavement rutting
- Loss of surface texture
- Premature road failure
The Los Angeles Abrasion Test helps engineers
select durable aggregates suitable for highway construction.
Objective of the Test
The main objectives of the Los Angeles Abrasion Test are:
- To determine the abrasion resistance of aggregates
- To measure the toughness of aggregates
- To evaluate the quality of aggregates for road works
- To ensure aggregates meet MoRTH specifications
Relevant Standards
- IS 2386 (Part IV) – 1963
Methods of test for aggregates for concrete.
- MoRTH Specifications (2013)
Specifications for road and bridge works.
- ASTM C131 / ASTM C535
International standards for abrasion testing.
Apparatus Required for Los Angeles Abrasion Test
-
Los Angeles Abrasion Machine
- Hollow steel drum
- Internal diameter: 700 mm
- Length: 500 mm
- Rotational speed: 30–33 rpm
-
Steel Abrasive Balls
- Diameter: 48 ± 2 mm
- Weight: 390 – 445 g each
- Hardness: 400 – 450 HB
- IS Standard Sieves
- Weighing Balance (accuracy 1 g)
- Drying Oven (105 – 110°C)
- Tray and sieve brush
Sample Preparation
Proper sample preparation is essential for accurate test results.
The following steps should be followed:
- Collect representative aggregate samples.
- Wash aggregates to remove dust and impurities.
- Dry the aggregates in an oven at 105–110°C.
- Allow the sample to cool to room temperature.
- Weigh the required sample weight (usually 5000 g).
Grading of Aggregates for the Test
| Grading | Aggregate Size (mm) | Sample Weight (g) | No. of Revolutions | Typical Use |
|---|
| A | 63 – 50 | 5000 | 500 | Granular Sub Base |
| B | 50 – 40 | 5000 | 500 | WMM Base |
| C | 40 – 25 | 5000 | 500 | Dense Bituminous Macadam |
| D | 25 – 20 | 5000 | 500 | Bituminous Macadam |
| E | 20 – 12.5 | 5000 | 1000 | Bituminous Concrete |
Test Procedure
PROCEDURE – LOS ANGELES ABRASION TEST
-
Clean aggregates dried in an oven at 105–110°C shall be used for testing.
-
The grading used in the test should be nearest to the grading to be used in the construction.
-
Aggregates weighing 5 kg for grading A, B, C or D and 10 kg for grading E, F or G may be taken as test specimen and placed in the cylinder.
-
Choose the abrasion charge depending on the grading of the aggregate and place in the cylinder of the machine.
-
Fix the cover dust tight and rotate the machine at a speed of 30 to 33 revolutions per minute.
-
The machine shall be rotated for 500 revolutions for grading A, B, C and D, and for grading E, F and G it shall be rotated for 1000 revolutions.
-
After the desired number of revolutions, stop the machine and discharge the material from the machine taking care to take out entire stone dust.
-
Using a sieve of size 1.70 mm IS Sieve, the material is first separated into two parts and the finer portion is taken out and sieved further on a 1.70 mm IS Sieve.
-
The portion of material coarser than 1.70 mm size is washed and dried in an oven at 105–110°C to constant weight and weighed correct to one gram.
Calculation of Los Angeles Abrasion Value
The Los Angeles abrasion value is calculated using the following formula:
Los Angeles Abrasion Value (%) = ((A − B) / A) × 100
Where:
- A = Original weight of sample (g)
- B = Weight retained on 1.70 mm sieve after test (g)
Example Calculation
Initial weight of sample = 5000 g
Weight retained after test = 3600 g
Abrasion Value = ((5000 − 3600) / 5000) × 100
Abrasion Value = 28%
Permissible Limits as per MoRTH
| Layer | Maximum LA Abrasion Value |
|---|
| Granular Sub Base | 45% |
| Base Course | 40% |
| Bituminous Layers | 35% |
| Wearing Course | 30% |
Advantages of the Test
- Simple and widely used method
- Provides reliable measure of aggregate toughness
- Essential for pavement design
- Helps maintain highway quality control
Limitations of the Test
- Does not fully simulate field traffic conditions
- Results may vary for soft aggregates
- Not suitable for very small aggregates
Frequently Asked Questions (FAQ)
What is the Los Angeles Abrasion Test?
It is a laboratory test used to determine the resistance of aggregates
to abrasion and impact.
What is the maximum permissible abrasion value?
For wearing courses in highways,
the maximum value is typically 30%.
Which IS code specifies the test?
The test is specified in
IS 2386 (Part IV).
What does a lower abrasion value indicate?
Lower abrasion value means
stronger and more durable aggregates.
