Q. Write short notes on Abrasion Test?
The abrasion test for ballast shall be carried out using Los-Angeles machine.The abrasive charge shall consist of 12 nos. cast iron or steel spheres approx. 48mm dia and each weighing between 390 and 445 gm ensuring total weight of charge as 5,000 ± 25 gm.
The test sample of 10000gm shall consist of clean ballast conforming to the following grading :- Passing 50mm and retained on 40 mm square mesh sieve 5,000 gm and Passing 40 mm and retained on 25mm square mesh sieve 5,000 gm tolerance of ± 2% permitted.
The sample shall be dried in oven at 100 - 110 °C to a constant weight and weighed (Weight 'A')
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 - 33 revolutions/minute for 1000 revolutions. At the completion of test, the material shall be discharged and sieved through 1.70mm IS sieve.
The material coarser than 1.70 mm IS sieve shall be washed, dried in oven at 100-110°C to a constant weight and weighed (weight B).
The proportion of loss between Weight "A" and Weight "B" of the test sample shall be expressed as a percentage of the original weight of the test sample. This value shall be reported as: Aggregate Abrasion Value =((A-B)/A)X100.