Los Angeles Abrasion test is used to determine aggregates’ level of abrasion resistance and toughness. Los Angeles abrasion test of aggregate assesses the deterioration of aggregate standard gradings when subjected to abrasion and impact in a rotating steel drum containing an abrasive charge of steel balls. LA abrasion test on aggregates is the measure of aggregate toughness and abrasion resistance such as crushing, degradation and disintegration. Basically, finding the percentage wear as a result of relative rubbing between the aggregate and steel balls used as an abrasive charge is the primary objective of the Los Angeles abrasion test.
- Significance of Los Angeles Abrasion Test of aggregates
- Types of aggregate tests
- Los Angeles Abrasion tests on aggregates
Significance of Los Angeles Abrasion Test of aggregates
Aggregate is a fundamental and necessary component of concrete, flexible pavements, and other similar structures. More than 70% to 80% of the volume of concrete is aggregate. Quality matters when it comes to aggregates because they are the main component of concrete, flexible pavements, etc. Various tests are conducted to determine the following properties of Aggregates.
- Water Absorption etc.
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Types of aggregate tests
The following are the various aggregate tests used to determine aggregate suitability:
- Crushing strength test
- Los Angeles Abrasion test
- Impact test
- Water absorption test
- Flakiness index test
- Elongation index test
- Bulk-specific gravity test
- Polishing test
- Soundness test on aggregate
This article is about Los Angeles Abrasion tests on aggregates
Los Angeles Abrasion tests on aggregates
The aggregate toughness and abrasion resistance such as crushing, degradation, and disintegration are evaluated by the Los Angeles abrasion test. Generally, this test is performed in accordance with AASHTO T 96 or ASTM C 131.
The Los Angeles Abrasion test determines the aggregate’s wearing resistance and hardness. Abrasion is indeed the wearing action on aggregate caused by vehicle movement. In order to resist abrasion, the aggregate should have an adequate abrasion value. The abrasion test value can ensure the quality and suitability of aggregates. Furthermore, aggregate with high abrasion resistance has a long life span.
Codes and standards for Los Angeles Abrasion test of aggregates
There are 3 tests commonly used to test aggregates for their abrasion resistance. (a) Deval Attrition Test (b) Dorry Abrasion Test (c) Los Angeles Abrasion Tests. However, Los Angeles abrasion test values are more realistic and correct.
Working principle of LA Abrasion test
The principle of this test is to produce abrasive action using steel balls mixed with aggregates. Accordingly, the aggregate and steel balls are rotated in a drum for a specific number of rotations. The percentage of wear due to relative rubbing action between the aggregate and steel balls is recorded. This value is the Los Angeles Abrasion value.
The test procedure for the Los Angeles Abrasion test of aggregate
The Los Angeles abrasion testing machine consists of a hollow steel cylinder, closed at both ends, having an inside diameter of 700 mm and an inside length of 500 mm. The abrasive charge shall consist of cast iron spheres or steel spheres approximately 48 mm in. diameter and each weighing between 390 and 445 g. The number of balls to be placed shall be as per IS 2386.
The test sample shall consist of clean aggregate which has been dried in an oven at 105 to 110°C to substantially constant weight. They shall conform to one of the gradings shown in Table II.
- Firstly, place the specimen inside the horizontal drum.
- Then, put the steel balls and rotate the cylinder for a total of 500-1000 revolutions at the speed of 30-33 rpm about its horizontal axis. For gradings A, B, C and D, the machine shall be rotated for 500 revolutions. However, for gradings E, F and G, it shall be rotated for 1000 revolutions.
- After completing the specific rotations, collect the specimens from the cylinder.
- Then sieve on a 1.7 mm IS sieve and weigh the specimen.
- Lastly, calculate the abrasion value using the formula below.
The formula for LA Abrasion Test
The original weight of aggregate sample = W1 g
Weight of aggregate sample retained = W2 g
Weight passing 1.7mm IS sieve = W1 – W2 g
Abrasion value = [(weight of sample taken – weight of sample retained on IS sieve) / weight of sample taken ] x 100
The difference between the original weight and the final weight (sieved through 1.7mm) is expressed as % of the original weight of the sample aggregate. Similarly, this value is called as Los Angeles abrasion value.