Key Tests for Aggrgates

Key Tests for Aggregates

The following Key tests to be done on coarse aggregates before using to make the quality concrete are as follows:

  * Aggregates Crushing Value Test
  * Aggregates Impact Value Test
  * Aggregates Abrasion Value Test
  * Water Absorption Test

Aggregates Crushing Value Test:

Object
This method of test covers the procedure for determining the
Aggregate crushing value of coarse aggregate.

Why to be done
The ‘aggregate crushing value’ gives a relative measure of the resistance of an aggregate to crushing under a gradually applied compressive load. With aggregate of ‘aggregate crushing value’ 30 or higher, the result may be anomalous, and in such cases the ‘ten percent fines value’ should be determined instead.

Apparatus
The apparatus for the standard test shall consist of the
Following:

a) A 15-cm diameter open-ended steel cylinder, with plunger and base-plate of the general form. The surfaces in contact with the aggregate shall be machined and case-hardened .

b) A straight metal tamping rod of circular cross-section 16 mm in diameter and 45 to 60 cm long, rounded at one end.

c) A balance of capacity 3 kg, readable and accurate to one gram.

d) IS Sieves of sizes 12.5,10 and 2.36 mm.

e) A compression testing machine capable of applying a load of 46 tonnes and which can be operated to give a uniform rate of loading so that the maximum load is reached in 10 minutes. The machine may be used with or without a spherical seating.

f) For measuring the sample, cylindrical metal measure of sufficient rigidity to retain its form under rough usage and of the following internal dimensions:
Diameter 11.5 cm
Height 18.0 cm

Preparation of Test Sample
The material for the standard test shall consist of aggregate passing a 12.5mm IS Sieve and retained on a 10mm IS Sieve, and shall be thoroughly separated on these sieves before testing. For other sizes, the material shall be separated on the appropriate...