20-11-2012, 05:37 PM
AGGREGATE IMPACT TEST, TEN PERCENT FINES TEST AND AGGREGATE CRUSHING TEST
AGGREGATE IMPACT TEST.pdf (Size: 143.08 KB / Downloads: 446)
OBJECTIVES
To assess the resistance of an aggregate to mechanical degradation by the
Aggregate Impact Test, Ten Percent Fines Test and Aggregate Crushing Test.
BACKGROUND
When a road aggregate has been manufactured to a specified grading it is
stockpiled, 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.
Granular base layers and surfacings are subjected to repeated loadings from truck
tyres and the stress at the contact points of aggregate particles can be quite high.
These crushing tests can reveal aggregate properties subject to mechanical
degradation of this form. The table below indicates some requirements.
PROCEDURE - Aggregate Crushing Value (SS 1974)
1. The apparatus and sample preparation is identical with that described above
for the Ten Percent Fines Test.
2. The cylinder, plunger and sample are placed in the compression test machine.
It is loaded at a uniform rate so that a force of 400 kN is reached in 10
minutes. The load is then released.
3. The percentage fines is then determined as before. The material passing 2.36
mm is weighed (mass B) and expressed as a percentage of the original mass
(mass A) to give the aggregate crushing value (ACV).