Los Angeles Abrasion Test Calculator
Ref: IS 2386 (Part 4) – 1963
Aim
To determine the abrasion value of coarse aggregate by using Los-Angeles testing machine with an abrasive charge.
Theory
The principle of Los Angeles abrasion test is to find out the percentage wear due to relative rubbing action between the aggregates and steel balls used as abrasive charge. Along with rubbing action the steel balls also give pounding action to the aggregates.
Apparatus
- Los Angeles Machine
- Abrasive charge consisting of cast iron spheres.
- IS Sieve – 1.7mm
- Aggregates
Los Angeles Machine
1) The machine shall consist of a hollow steel cylinder, closed at both ends.
2) Inside diameter = 700 mm
3) Inside length of 500 mm.
4) The cylinder is rotated about its axis in a horizontal position.
5) An opening is provided for the introduction of the test sample.
6) A removable steel shelf, projecting radially 88 mm into the cylinder and extending its full length, is mounted along one element of the interior surface of the cylinder.
Aggregates
Clean oven dried (105 to 110 degree Celsius) aggregates are used and should conform to one or more of the gradings as given below.
| Sieve Size (Square Hole) | Weight in ‘gm’ of test sample 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 | ||||||
Abrasive Charge Grade
The grading of abrasive charge indicates the number of cast iron spheres to be used in the test as well as the weight of the charge it shall have.
| Grading | Number of Spheres | Weight of charge (gm) |
| A | 12 | 5000 ± 25 |
| B | 11 | 4584 ± 25 |
| C | 8 | 3330 ± 25 |
| D | 6 | 2500 ± 25 |
| E | 12 | 5000 ± 25 |
| F | 12 | 5000 ± 25 |
| G | 12 | 5000 ± 25 |
Procedure
- The test sample and the abrasive charge shall be placed in the Los Angeles abrasion testing machine and the machine rotated at a speed of 20 to 33 rev/min.
- For grading’s A,B,C and D, the machine shall be rotated for 500 revolutions.
- For grading’s E,F and G ,it shall be rotated for 1000 revolutions.
- The machine shall be so driven and so counter balanced as to maintain a uniform peripheral speed.
- At the completion of the test, the material shall be discharged from the machine and a preliminary separation of the sample made on a sieve coarser than 1.70 mm IS sieve.
- The material coarser than 1.70mm is weighed.
Result
W1 = weight of test sample aggregates, before putting in machine.
W2 = weight of aggregates retained on IS sieve 1.7mm.
\text { Los Angeles Abrasion Value }=\frac{W_{1}-W_{2}}{W_{1}} * 100