Measurement of toughness and resistance like degradation, crushing, and disintegration is the right definition of the Abrasion test.
This test is suggested by AASHTO T 96 or ASTM C 131 Resistance to degradation of small coarse aggregates by Abrasion and impact on the Los Angeles Machine.
Aggregates are used for the surface course of road pavements and are subject to wear and tear due to traffic movement. (ASTM c131 Los Angeles abrasion test)
Therefore, aggregates used in road construction must be hard enough to resist Abrasion. The resistance offered by the aggregate to Abrasion is determined in the laboratory by the Los Angeles testing machine.
The Los Angeles abrasion test’s working principle is to produce abrasive action using standard steel balls, which, when mixed with aggregates and spun in a drum for a specified time for a specific number of revolutions, also impact the aggregates.
The percentage of wear of sample aggregates due to friction with steel balls is determined and is known as the Los Angeles Abrasion Value.
Test to Determine the Abrasion Value
The abrasion test on aggregates in Los Angeles is carried out with the following objectives:
- To discover the value of Abrasion in Los Angeles aggregate.
- Find the suitability of aggregates for use in road construction projects.
Apparatus Used For Abrasion Test
The device is standardized according to IS: 2386 (Part IV) – 1963 consists of:
- Los Angeles abrasion machine
- Abrasive load spheres: Spheres of cast iron or steel, approximately 48 mm in diameter and each weighing between 390 and 445 g; six to twelve balls are needed
- Sieve: 1.70 mm, 2.36 mm, 4.75 mm, 6.3 mm, 10 mm, 12.5 mm, 20 mm, 25 mm, 40 mm, 50 mm, 63 mm, 80 mm IS sieves.
- The 5 kg or 10 kg capacity balance is used.
- Drying the oven.
- Miscellaneous like a tray
Procedure For Abrasion Test
- Select the grading to be utilized in the test such that it conforms to the grading to be utilized in construction, to the maximum extent possible.
- Require 5 kg of sample for gradings A, B, C, and; D, and 10 kg for gradings E, F & G.
- Pick the abrasive charge according to Table 1, depending on the grading of aggregates.
- Place the aggregates and abrasive charge to the cylinder and fix the cover.
- Rotate the machine at a speed of 30 to 33 revolutions per minute. The number of revolutions is 500 to get gradings A, B, C, and D, and 1000 for gradings E, F, and G. The machine ought to be balanced and driven such that there’s uniform peripheral speed.
- The machine is stopped after the desired number of revolutions and material is discharged to a tray.
- The entire stone dust is sieved on 1.70 mm IS sieve.
- The material coarser than 1.7mm size is weighed correct to one gram.
|Grading||No of Steel balls||Weight of charge in gm.|
|A||12||5000 ± 25|
|C||8||3330 ± 20|
|D||6||2500 ± 15|
|E||12||5000 ± 25|
|F||12||5000 ± 25|
|G||12||5000 ± 25|
Table-1 Selection of Abrasive
|Source||Tested as per|
|Weight of sample taken (gms)||Confirmation as per|
|Sieve size (square hole)
|Weight of test sample in gm
Retained on (mm)
|80.0 mm||63.0 mm|
|63.0 mm||50.0 mm|
|50.0 mm||40.0 mm|
|40.0 mm||25.0 mm|
|25.0 mm||20.0 mm|
|20.0 mm||12.5 mm|
|12.3 mm||10.0 mm|
|10.0 mm||6.3 mm|
|6.3 mm||4.75 mm|
|4.75 mm||2.36 mm|
|Remarks ( If Any) –|
Table-2 Format of Abrasion Test Report
Principle of Abrasion Test
Steel ball bearings in the hardness test To produce the abrasive action using standard steel balls that, when mixed with the aggregate and rotated in a drum for a specific number of revolutions, impact the aggregate.
The wear per age due to friction with steel balls is determined and is known as the abrasion value. Prepare the sample by the portion of an aggregate sample retained in the 1.70 mm (# 12) sieve and place in a large rotating drum that contains a shelf plate attached to the outer wall.
Standard Test Methods of Abrasion Test
The standard test method for Abrasion test are as follows.
- AASHTO T 96 and ASTM C 131: Resistance to degradation of coarse aggregate of small size by Abrasion and impact on the Los Angeles machine
- ASTM C 535: Resistance to degradation of large coarse aggregates by Abrasion and impact on the Los Angeles machine.
Uses Of The Abrasion Test
For an aggregate to perform satisfactorily on the pavement, it must be difficult enough to resist the abrasive effect of traffic for a long period of time.
Soft aggregates will be quickly crushed into powder, while hard aggregates are quite resistant to crushing.
The test will also determine the quality of the aggregate.
The L.A. abrasion test is widely used as an indicator of the quality or relative competence of mineral aggregates.
How Does the La-Abrasion Test Works?
- A sample is prepared by separating the required masses into individual size fractions.
- The sample of specific size aggregates and the abrasive load are placed on the L.A. Abrasion Machine and spun at 30-33rpm.
- The sample is removed and washed over a No. 12 sieve (1.70 mm) and placed in an oven to dry.
- The percentage loss or the difference between the original mass and the final mass.
- A. abrasion loss value of 40 indicates that 40% of the original mass of the sample passed through the sieve.
Important of Abrasion Test
- The abrasion test determines the relative quality, strength, and durability of mineral aggregates subject to impact and Abrasion.
- The values derived from L.A. Abrasion tests provide information on the performance of aggregate in use. This test provides insight into how asphalt and concrete aggregates resist wear and tear over time.
- It is also a good indicator of change in properties in an aggregate source as part of a quality assurance or control program.
IS Recommended Los Angeles abrasion test Values for Pavements:
A Los Angeles test is performed to find the hardness of aggregates. On the basis of this value, the suitability of aggregates for different road constructions can be judged as per IRC specifications as given.
|SI. No.||Type of Pavement||Max. permissible abrasion value in %|
|1||Water bound macadam sub base course||60|
|2||WBM base course with bituminous surfacing||50|
|3||Bituminous bound macadam||50|
|4||WBM surfacing course||40|
|5||Bituminous penetration macadam||40|
|6||Bituminous surface dressing, cement concrete surface course||35|
|7||Bituminous concrete surface course||30|
Conclusion of Abrasion Test
It is important to remember that, regardless of the method chosen, abrasion testing is a necessary procedure as part of a quality control process to assess how materials will react to wear over time.