Angularity Number Test of Aggregate

It is a non- destructive quality test for aggregate. It is the test about the shape of the aggregate. It gives the qualitative representation of the shape of the aggregate. It is measured in terms of percentage of voids in excess of voids in perfectly rounded aggregate(33%). The more angular the aggregate is, the more is the Angularity number.The normal aggregate suitable for making concrete have angularity number lying between 0 and 10. The rounded aggregate has Angularity Number zero.
When rounded aggregate is filled in a vessel, it leaves about 33% void in it. If a well compacted Aggregate in the same vessel of rounded aggregate leaves 43% voids then its Angularity Number is 10. This test is not applied for the aggregates which gets crushed during compaction of this test.

Apparatus required:

• Metal cylinder of 3 litre capacity.
• Metal scoop
• Tamping rod.  

Procedure: 

• The test sample of the aggregate is sieved and specified size ranges such as 16-20 mm, are used for the test.
• The sample is then filled in the metal cylinder in three layers. Each layer is tamped 100 times with tamping rod before the next layer is put.
• The weight of the aggregate filled in the cylinder is determined. And then after emptying it, it is filled with water and weight of the water is also determined.

Then use the following formula to find the Angularity number:
Angularity Number= 67 - W*100/w*G
W=Aggregate weight filled in the cylinder.
w=Weight of the water filled in the cylinder.
G= Sp. gr. of aggregate.




 Fig. Metal scoop.