To determine the aggregate crushing value of coarse aggregates as per IS: 2386 (Part IV) – 1963.
i) Cylindrical measure and plunger
ii) Compression testing machine
iii) IS Sieves of sizes – 12.5mm, 10mm and 2.36mm
i) The aggregates passing through 12.5mm and retained on 10mm IS Sieve are oven-dried at a temperature of 100 to 110oC for 3 to 4hrs.
ii) The cylinder of the apparatus is filled in 3 layers, each layer tamped with 25 strokes of a tamping rod.
iii) The weight of aggregates is measured (Weight ‘A’).
iv) The surface of the aggregates is then levelled and the plunger inserted. The apparatus is then placed in the compression testing machine and loaded at a uniform rate
so as to achieve 40t load in 10 minutes. After this, the load is released.
v) The sample is then sieved through a 2.36mm IS Sieve and the fraction passing through the sieve is weighed (Weight ‘B’).
vi) Two tests should be conducted.
Aggregate crushing value = B/A x 100%
The result should be recorded to the first decimal place and the mean of the two results reported.
APPLICATION/LIMITS OF AGGREGATE CRUSHING VALUE:
The aggregate crushing value for cement concrete pavement shall not exceed 30%
The aggregate crushing value for wearing surfaces shall not exceed 45%
PURPOSE OF TEST:
The strength of coarse aggregate is assessed by aggregate crushing test, the aggregate value provide the relative measure of resistance to crushing under gradually applied compressive load.
Lesser the aggregate crushing value greater will be the “resistance to crushing under gradually applied compressive load”.
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