Crushing Value Test (IS: 2386 (Part
IV))
The material for
the test should consist of aggregate passing 12.5 mm sieve and retained on 10
mm sieve. For other sizes, the materials are separated on the appropriate
sieves given in Table .
Table 10 Details of Aggregate Crushing Test for Non-standard
Sizes of Aggregate
Note: About 6500 g of natural aggregate is required to provide
samples for the 150 mm cylinder, or about 1000 g for the 75 mm cylinder.
The aggregate is
tested in a surface-dry condition. The weight of material comprising the test
sample is determined (weight A).
The cylinder of the
test apparatus is positioned on the base-plate and the test sample is added in
thirds, each being subjected to 25 strokes from the tamping rod. The surface of
the aggregate is carefully levelled and the plunger is inserted so that it
rests horizontally on this surface.
The apparatus, with
the test sample and plunger in position is then placed between the platens of
the testing machine and loaded at an uniform rate as possible, so that the
total load is reached in 10 minutes. The total load should be 400 kN.
The load is released
and the whole of the material is removed from the cylinder and sieved on a 2.36
mm sieve for the standard test, or on the appropriate sieve given in Table 6.5.
The fraction passing the sieve is weighed.
The ratio of the weight of fines formed to the total sample
weight in each test is expressed as a percentage, recorded to the first decimal
place:
Aggregate crushing value = B/A ¥ 100
Where
B = weight of fraction passing the appropriate sieve
A = weight of surface-dry sample
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