Abrasion Test of Aggregate

Abrasion test of aggregate is carried out to find out hardness of aggregates. And it is mostly used when aggregates used to be in road construction.

Abrasion test is carried out with help of Los Angeles machine and that’s why it can be also called Los Angeles Abrasion test.

IS Code: IS 2386 part-IV

Los Angeles Abrasion test

It is carried out to find out hardness of aggregates.

Mostly carried out to find out suitability of aggregates for different types of pavements.

This is very important to find out wear and tear of aggregates in road construction.

Principle of Los Angeles Abrasion test:

Tio find out the percentage of wear due to rubbing action of aggregates and steel balls.

Determination of Los Angeles Abrasion:

The Los Angeles abrasion test is done for following purposes:

1. To find out the Los Angeles abrasion value.
2. To determine the suitability of aggregates for use in road construction.

 

IS code:

IS 2386 part-IV

Apparatus:

1. Los Angeles Machine
2. Abrasive charge: Cast iron or steel balls, approximately 48mm in diameter and each weighing between 390 to 445 g; six to twelve balls are required.
3. Sieve: 1.70, 2.36, 4.75, 6.3, 10, 12.5, 20, 25, 40, 50, 63, 80 mm IS Sieves.
4. Balance of capacity 5 kg or 10 kg
5. Drying oven
6. Miscellaneous like tray

 

Procedure for Los Angeles Test

The test sample should be of clean and aggregates dried in oven at 105° – 110°C.

1. Select the grading to be used in the test such that it conforms to the grading to be used in construction, to the maximum extent possible.
2. Take 5 kg of sample for gradings A, B, C & D and 10 kg for gradings E, F & G.
3. Choose the abrasive charge as per Table 2 depending on grading of aggregates.
4. Place the aggregates and abrasive charge on the cylinder and fix the cover.
5. Rotate the machine at a speed of 30 to 33 revolutions per minute. The number of revolutions is 500 for gradings A, B, C & D and 1000 for gradings E, F & G. The machine should be balanced and driven such that there is uniform peripheral speed.
6. The machine is stopped after the desired number of revolutions and material is discharged to a tray.
7. The entire stone dust is sieved on 1.70 mm IS sieve.
8. The material coarser than 1.7mm size is weighed correct to one gram.

Table 1: Grading of Test Samples – *Tolerance of ± 12 percent permitted.

Sieve size (square hole)	Weight of test sample in gm
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

Table 2: Selection of Abrasive Charge

Grading	No of Steel balls	Weight of charge in 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

 

 

Observations of Los Angeles Test

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 = (W₁ – W₂ ) / W₁ X 100 Results 

Los Angeles Abrasion Value =

 

Los Angeles Test Values for road Pavements:

Depending upon the Los Angeles abrasion value the suitability if aggregates for different types of pavements is decided. And standards as er IRC specification for the same are mentioned as below,

Sl. 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