Whether you are a highway engineer or a homeowner constructing a private driveway or adjoining road, it’s very important to check the quality of aggregates used to enhance durability. Roads are often exposed to crushing, degradation, and disintegration due to the movement of vehicles, leading to aggregate wear. Poor-quality aggregates can impair the stability of the pavement structure. When aggregates don’t have sufficient resistance to abrasion, it can result in early pavement failure, reduced skid resistance, and excessive dust formation.
Read this blog to learn about the Los Angeles Abrasion Test, its step-by-step procedure, and the IS codes that guide the testing process to ensure durable and high-quality roads.
What is the Los Angeles Test?
The Los Angeles abrasion test is conducted on aggregates to evaluate their toughness and resistance to various forms of abrasion. The main principle of the LA abrasion test involves creating an abrasive action between mixed aggregates using standard steel balls. When the drum, filled with aggregates and steel balls, is rotated for a specified duration and number of revolutions, it produces an impact and grinding effect on the aggregates, similar to real-life abrasion.
After the test, the loss in weight of the aggregates due to abrasion is measured and expressed as a percentage, which is called the Los Angeles Abrasion Value (LAAV). Based on this test result, the engineer can decide whether this aggregate is suitable for road construction or not.
What are the Los Angeles Abrasion Test Apparatus?
The Los Angeles abrasion test apparatus commonly involves the following:
- Los Angeles Abrasion Test Machine: The LA abrasion machine has a circular rotating drum of length 520 mm and an internal diameter of 700 mm installed on a horizontal axis.
- Abrasive Charge: It involves placing cast iron spherical balls, 48 mm in diameter and weighing 340-445 gm, in the cylinder along with the aggregates based on the selected grading. The number of abrasive spheres mainly depends on the grading of the sample, as shown in the table based on IS 2386 (Part IV).
| Grading | No of Sphere balls | Charge Weight (gm.) |
| A | 12 | 5000 ± 25 |
| B | 11 | 4584 ± 25 |
| C | 8 | 3330 ± 20 |
| D | 6 | 2500 ± 15 |
| E | 12 | 5000 ± 25 |
| F | 12 | 5000 ± 25 |
| G | 12 | 5000 ± 25 |
- Sieves of Standard Size: The sieves required for the LAA test of aggregates are 80, 63, 50, 40, 25, 20, 12.5, 10, 6.3, 4.75, and 1.7 mm.
- Weighing Balance: It must have a capacity of 5 kg to 10 kg.
- Drying Oven
- Other Necessary Tools: trays and cups
Stepwise Los Angeles Abrasion Test Procedure
The LA abrasion test procedure involves the following common steps:
Prepare the Apparatus Setup: Clean and dry the entire apparatus setup for the ease of conducting the test.
Oven-dry the Aggregate Sample: Wash and oven-dry the aggregate sample at a temperature between 105°C and 110°C.
Weigh and Grade: Choose the aggregate size that aligns with the IS: 2386 gradings as closely as possible. For grades A, B, C, and D, separately and accurately weigh out exactly 5 kg of aggregate, consisting of individual size fractions in the proportions specified for the selected grading. For grades E, F, and G, the total sample weight should be exactly 10 kg again, using the correct proportions of size fractions for the applicable grading.
The following table indicates the Gradation of aggregate:
| Sieve Size (mm) | Weight in gm. of the sample used for Grade | |||||||
| Passing mm | Retained on mm | A | B | C | D | E | F | G |
| 80 | 63 | 2500 | ||||||
| 63 | 50 | 2500 | ||||||
| 50 | 40 | 5000 | 5000 | |||||
| 40 | 25 | 1250 | 5000 | 5000 | ||||
| 25 | 20 | 1250 | 5000 | |||||
| 20 | 12.5 | 1250 | 2500 | |||||
| 12.5 | 10 | 1250 | 2500 | |||||
| 10 | 6.3 | 2500 | ||||||
| 6.3 | 4.75 | 2500 | ||||||
| 4.75 | 2.36 | 5000 | ||||||
Load Test Machine: Place the chosen aggregates and abrasive charge balls (sizes determined by the grading of the aggregates) into the LA abrasion machine’s cylinder. Cover the opening/lid tightly in place.
Rotation of Machine: Rotate the machine at a constant speed of 20–33 revolutions/minute. For grades A, B, C, and D, rotate for 500 revolutions, and for grades E, F, and G, rotate for 1000 revolutions.
Stop the Machine: After completing the specified number of revolutions, stop the machine and transfer the aggregate sample to a tray.
Sieve the Rotated Sample: Use a 1.7 mm IS sieve to separate the finer particles from the coarser ones in the complete aggregate sample. Wash the retained material and dry in an oven at 105–110°C to a constant weight. Weigh the left material larger than 1.7 mm in size.
Calculation for the Los Angeles Abrasion Test
The Aggregate Abrasion Value can be calculated using the formula
Aggregate Abrasion Value = ((A-B)/A) X 100
where,
A = weight in grams of oven-dried sample before putting into the LA abrasion machine.
B = weight in grams of fraction left on 1.70 mm IS Sieves after washing and oven-drying to constant weight
Results of the Los Angeles Abrasion Test
The Los Angeles abrasion value is an indication of the aggregate’s resistance power against wear and tear caused by traffic and other loads. The lower the LA abrasion value, the more durable and tough the aggregate is.
- For high-quality pavements (like cement concrete or bituminous concrete), the LA abrasion value should be less than 30%.
- For base or sub-base layers (like water-bound macadam or bituminous macadam), values up to 50% are acceptable.
The following table indicates the maximum allowable Los Angeles abrasion values of aggregates for different road construction methods:
| Sl. No. | Types of Pavement Layer | Los Angeles Abrasion Value, Maximum % |
| 1 | Water Bound Macadam (WBM), sub-base course | 60 % |
| 2 | (i) WBM, base course with bituminous surfacing (ii) Bituminous Macadam (BM) base course (iii) Built-up spray-grout base course | 50 % |
| 3 | (i) WBM, surfacing course (ii) Bituminous Macadam binder course (iii) Bituminous Penetration Macadam | 40 % |
| 4 | Aggregates used for surface course, such as bituminous carpet, bituminous surface dressing (single or double coat), cement concrete surface course | 35 % |
| 5 | Aggregates used for bituminous concrete, cement concrete pavement as surface coarse material | 30 % |
IS Code for the Los Angeles Abrasion Test
IS 2386 (Part IV) 1963 provides updated guidelines for conducting the Los Angeles Abrasion Test on Aggregate, which is used to measure the resisting power of aggregate against wear and tear. The standard outlines the apparatus dimensions, testing procedure, sample handling, and calculation methods to ensure accuracy and consistency. It is primarily applicable to aggregates that will be used in various road construction methods. Also, IS 383-1970 provides a specification for coarse aggregates.
Advantages of the Los Angeles Abrasion Test
The following are the benefits of conducting the Los Angeles Abrasion Test on Aggregate:
- This test is straightforward and simple to perform, requiring minimal equipment and expertise.
- This is the widely accepted standard test to assess aggregate resistance to abrasion and impact. Performing this test helps to ensure that it meets the required standards and specifications for maintaining the strength and durability of roads.
- This test is essential for evaluating the abrasion resistance of aggregates, which plays a crucial role in ensuring the performance and durability of dense-graded aggregate systems used in road surfaces.
Limitations of the Los Angeles Abrasion Test
- The combination of abrasion and impact in the test may not separate wear mechanisms clearly.
- Test conditions do not perfectly replicate all field conditions and stresses.
- Results depend on the condition of the apparatus, the preparation of the sample, and the lab operator’s skill, causing some variability.
- It only tests aggregates, not finished concrete or asphalt, so it does not cover all material durability facets.
In conclusion, the Los Angeles (LA) Abrasion Test is a simple yet effective method for evaluating the toughness and durability of aggregates. By checking the LA abrasion value using this test, the engineer can ensure that the aggregates used in concrete or pavement construction adhere to the required strength and quality standards. This will also improve the performance of the structure. Although this test has some limitations, it remains one of the most often used test methods for aggregate quality assessment.
The difference between a building that lasts for decades and one that wears out early depends on basic quality checks done during the initial stages of construction. This is where Brick & Bolt stands out, as it carries out careful material testing, including checking the quality of aggregates, in every project from the very beginning.
Frequently Asked Questions
What is a good LA abrasion value?
A good Los Angeles abrasion value is typically less than 30%, indicating high durability suitable for high-quality pavement surfaces.
What is the meaning of the abrasion value found from the Los Angeles test?
The abrasion value is the percentage loss in weight of aggregates after the test, representing their resistance to wear and tear.
What is the Los Angeles abrasion value apparatus?
The apparatus consists of a rotating steel drum, cast iron or steel spherical balls as an abrasive charge, sieves, an oven, and a weighing balance.
What sieve is used in the Los Angeles abrasion test?
In the Los Angeles Abrasion Test, sieves of 80, 63, 50, 40, 25, 20, 12.5, 10, 6.3, 4.75, and 1.7 mm are used for grading aggregates before testing. After the test, the 1.7 mm IS sieve is used to separate fine particles and calculate the abrasion value.