Los Angeles Abrasion test procedure for aggregates to be used in construction of roads
Objective:
To determine the Los Angeles abrasion value of aggregates.
To find out the suitability of aggregates for its use in road construction.
Apparatus / Equipment's Required:
- 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.
- Steel spherical balls 48 mm in diameter and weighing 390 grams to 445 grams. The weight and number of balls per charge of aggregate depends upon the grading of aggregate sample.
- Sieves of size 80 mm to 4.75 mm and 1.70 mm
- Balance of capacity 10 kg.
- Drying Oven
- Steel Tray
Theory:
The aggregate used in surface course of the highway pavements are subjected to wearing due to movement of traffic. When vehicles move on the road, the soil particles present between the pneumatic tyres and road surface cause abrasion of road aggregates. The steel reamed wheels of animal driven vehicles also cause considerable abrasion of the road surface. Therefore, the road aggregates should be hard enough to resist abrasion. Resistance to abrasion of aggregate is determined in laboratory by Los Angeles test machine. The principle of Los Angeles abrasion test is to produce abrasive action by use of standard steel balls which when mixed with aggregates and rotated in a drum for specific number of revolutions also causes impact on aggregates. The
percentage wear of the aggregates due to rubbing with steel balls is determined and is known as Los Angeles Abrasion Value.
Pprocedure:
- Aggregate sample weighing 5 kg (for Grade A, B, C & D) and 10 kg (for Grade E, F & G) is put in the machine along with the abrasive charge as per given in table.
- The machine is rotated at a speed of 30 to 33 R.P.M. for the specified number of revolutions (500 for grade A, B, C, D and 1000 for E, F, G)
- Now the sample is taken out of the machine and sieved through 1.7 mm I.S. Sieve and the weight of aggregate passing through 1.7 mm sieve is determined.
Observations & Calculations:
Type of aggregate
1 Grading
2 Number of spheres used
3 Weight of charge
4 Number of revolution
Results
Los Angeles Abrasion Value = …………………%
Precautions:
The cover should be fixed tightly before rotating the machine
All material should be discharged from the cylinder after the conduct of test.
Interpretation of Results
Los Angeles abrasion test is commonly used to evaluate the hardness of the aggregates. The test has more acceptability because the resistance to abrasion and impact is determined simultaneously. Depending upon the numerical; value, the suitability of aggregates for different road constructions can be judged as per the Indian Road Congress specifications given below;
Test procedure is attached below in Document format.
Objective:
To determine the Los Angeles abrasion value of aggregates.
To find out the suitability of aggregates for its use in road construction.
Apparatus / Equipment's Required:
- 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.
- Steel spherical balls 48 mm in diameter and weighing 390 grams to 445 grams. The weight and number of balls per charge of aggregate depends upon the grading of aggregate sample.
- Sieves of size 80 mm to 4.75 mm and 1.70 mm
- Balance of capacity 10 kg.
- Drying Oven
- Steel Tray
Theory:
The aggregate used in surface course of the highway pavements are subjected to wearing due to movement of traffic. When vehicles move on the road, the soil particles present between the pneumatic tyres and road surface cause abrasion of road aggregates. The steel reamed wheels of animal driven vehicles also cause considerable abrasion of the road surface. Therefore, the road aggregates should be hard enough to resist abrasion. Resistance to abrasion of aggregate is determined in laboratory by Los Angeles test machine. The principle of Los Angeles abrasion test is to produce abrasive action by use of standard steel balls which when mixed with aggregates and rotated in a drum for specific number of revolutions also causes impact on aggregates. The
percentage wear of the aggregates due to rubbing with steel balls is determined and is known as Los Angeles Abrasion Value.
Pprocedure:
- Aggregate sample weighing 5 kg (for Grade A, B, C & D) and 10 kg (for Grade E, F & G) is put in the machine along with the abrasive charge as per given in table.
- The machine is rotated at a speed of 30 to 33 R.P.M. for the specified number of revolutions (500 for grade A, B, C, D and 1000 for E, F, G)
- Now the sample is taken out of the machine and sieved through 1.7 mm I.S. Sieve and the weight of aggregate passing through 1.7 mm sieve is determined.
| Grading | No of Spheres | No of Revolutions | Weight of Sample (g) | Weight of Charges (g) |
|---|---|---|---|---|
A | 12 | 500 | 5000 | 5000 +/- 25 |
B | 11 | 500 | 5000 | 4584 +/- 25 |
C | 8 | 500 | 5000 | 3330 +/- 20 |
D | 6 | 500 | 5000 | 2500 +/- 15 |
E | 12 | 1000 | 10000 | 5000 +/- 25 |
F | 12 | 1000 | 10000 | 5000 +/- 25 |
G | 12 | 1000 | 10000 | 5000 +/- 25 |
Observations & Calculations:
Type of aggregate
1 Grading
2 Number of spheres used
3 Weight of charge
4 Number of revolution
Results
Los Angeles Abrasion Value = …………………%
Precautions:
The cover should be fixed tightly before rotating the machine
All material should be discharged from the cylinder after the conduct of test.
Interpretation of Results
Los Angeles abrasion test is commonly used to evaluate the hardness of the aggregates. The test has more acceptability because the resistance to abrasion and impact is determined simultaneously. Depending upon the numerical; value, the suitability of aggregates for different road constructions can be judged as per the Indian Road Congress specifications given below;
| Types of Pavement Layer | Max permissible abrasion value in % |
|---|---|
WBM Sub Base & Base Course | 40 |
WBM Surfacing course | 40 |
Dense Graded Bituminous Macadam (DBM) | 35 |
Semi Dense Bituminous Concrete | 35 |
Bituminous Concrete | 30 |
Cement Concrete Surface Course | 30 |
Test procedure is attached below in Document format.
