Building Materials, Third Edition

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e˜—2g—X2The abrasive charge consists of cast iron spheres or steel spheres approximately
48 mm in diameter and each weighing between 390 and 445 g.
The abrasive charge, depending upon the grading of the test sample should be as given in
Table 6.8.

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The test sample consists of clean aggregate dried in an oven at 105 -110°C to substantially
constant weight.
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The test sample and the abrasive charge is placed in the Los Angeles abrasion testing
machine and the machine is rotated at a speed of 20 to 33 rev/min. For gradings A, B, C and D,
the machine is rotated for 500 revolutions; for gradings E, F and G, it is rotated for 1000
revolutions. The machine is so driven and so counter-balanced as to maintain a substantially
uniform peripheral speed. If an angle is used as the shelf, the machine is rotated in such a
direction that the charge is caught on the outside surface of the angle. At the completion of the
test, the material is discharged from the machine and a preliminary separation of the sample
made on a sieve coarser than the 1.70 mm. The finer portion is then sieved on a 1.70 mm sieve.
The material coarser than the 1.70 mm sieve is washed, dried in an oven at 105 -110°C to a
substantially constant weight, and accurately weighed to the nearest gram. The difference
between the original and the final weights of the test sample expressed as a percentage of the
original weight of the test sample gives the percentage of wear.

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The sample of fine aggregate for the test is passed through 10-mm IS sieve and should be of
such size that it yields not less than 100 g of each of the sizes as below.

Passing IS sieve Retained on IS sieve

600 micron 300 micron

1.18 mm 600 micron

2.36 mm 1.18 mm

4.75 mm 2.36 mm

10 mm 4.75 mm