Page 16 - HIGHWAY ENGINEERING LABORATORY_FLIP BUILDER

Page :
WORK INSTRUCTION
Edition :

Checking No.
AGGREGATE IMPACT VALUE (AIV)
CIVIL ENGINEERING (Reference Standard: BS 812: Effective Date:
part 112 1990)
JKA/ DCC30112/ 2021 Amendment Date:

1.0 OBJECTIVE OF EXPERIMENT :

To assess the resistance of an aggregate to mechanical degradation by the Aggregate
Impact Value and to determine percent crush due to impact load

2.0 SUMMARY OF THEORY :

When a road aggregate has been manufactured to a specified grading it is stock piled,
loaded into trucks, transported, tipped, spread and compacted. If the aggregate is
weak, some degradation may take place and result in a change in grading and/or the

production of excessive and undesirable fines. Thus, an aggregate complying with a
specification at the quarry may fail to do so when it is in the pavement.

The standard amount of impact is produced by a known weight, i.e. a steel cylinder,
falling a set height, a prescribed number of times, onto an amount of aggregate of

standard size and weight retained in a mould. Aggregate Impact Values, (AIV’s) below
10 are regarded as strong, and AIV’s above 35 would normally be regarded as too weak
for use in road surfaces. Aggregate Impact Values and Aggregate Crushing Values are

often numerically very similar, and indicate similar aggregate strength properties. Then,
the aggregate impact value gives a relative measure of the resistance of an aggregate
to sudden shock or impact, which in some aggregates differs from its resistance to a
slowly applied compressive load. With aggregate or aggregate impact value higher
than 30 the result maybe anomalous.

3.0 EQUIPMENTS:

Higway Engineering Laboratory page 3