EXPERIMENT NO – 4
LOS ANGELES ABRASION TEST
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1. Objective:
To determine the Abrasion (Hardness)) value of aggregates by the Los Angeles Abrasion test method
2. Apparatus/Equipments Required:
1. It consists of a hollow cylindrical machine closed at both ends having 70 cm internal diameter and 50 cm long, mounted on supports so that it may rotate about its horizontal axis.
2. Steel spherical balls 4.5 cm diameter and weighing 390grams to 445 grams. The weight and number of balls per charge of aggregate depends upon the grading of aggregate sample.
3. Sieves of size 80 – 4.75 mm and 1.7 mm
4. Balance of capacity 10 kg.
5. Tray
LOS ANGELES ABRASION TESTING MACHINE SET OF SIEVES
3. Theory:
Due to the movements of traffic, the road stones used in the surfacing course are subjected to wearing action at the top. Resistance to wear or hardness is hence an essential property for road aggregates especially when used in wearing course. Thus road stones should be hard enough ton resist the abrasion due to the traffic.
4. Procedure:
1. Aggregate sample weighing 5 kg or 10 kg depending on the grading is put in the machine along with the abrasive charge.
2. The machine is rotated at a speed of 30 to 33 R.P.M. for the specified number of revolutions (500 to 1000) depending on the grading of aggregate.
3. Now the sample is taken out of the machine and sieved through 1.7 mm Sieve and the weight of aggregate passing through 1.7 mm sieve is determined.
5. Observation:
Type of aggregate =
1. Grading =
2. Number of spheres used =
3. Weight of charge =
4. Number of revolution =
Observations / Sample 1 / Sample 2Let the original weight of aggregate = g
Weight of aggregate retained on 1.7 mm IS sieve after the test = g
Loss in weight due to wear = - g
Percentage wear =
Average Value =
6. Calculation
i) The material coarser than 1.70mm Sieve should be washed dried in an oven at a temperature of 100 to 110oC to a constant weight and weighed (Weight ‘B’).
ii) The proportion of loss between weight ‘A’ and weight ‘B’ of the test sample should be expressed as a percentage of the original weight of the test sample. This value should be reported as,
Aggregate abrasion value = (A-B)/B x 100%.
Los Angles abrasion value, % = Percentage wear =
7. Result
For test sample = …………………
Standard value = ………………….
%age error =……………………….
8. Precautions:
9. Remarks:
10. Discussions:
Grading / No of Steel balls / Weight of charge in gmA / 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
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