Aggregate abrasion value test

Resistance to wear offered by aggregate is termed as “aggregate abrasion value”. Los Angeles abrasion test on aggregates is the measure of aggregate toughness and abrasion resistance such as crushing, degradation and disintegration.

AIM:

To determine the abrasion value of coarse aggregate.

Apparatus:

• Los Angeles Machine.
• Abrasive charge:

1.   48mm in diameter and each.

2.   weight between 390 to 445 g.

• IS Sieves: 1.70, 2.36, 4.75, 6.3, 10, 12.5, 20, 25, 40, 50, 63, 80 mm
• Balance.
• Drying oven.
• Tray.

FIGURE:

Procedure:

The test sample consists of clean aggregates dried in oven at 105° – 110°C. The sample should conform to any of the gradings shown in table 1.

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		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:

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 =


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