ANGULARITY NUMBER OF COARSE AGGREGATE (IS:2386-Part 1-1963)

Objective

For determination of angularity number of coarse aggregates. 

Reference Standards

IS: 2386 (Part I) – 1963 – Method of test for aggregates for concrete (Part I) Particle size and shape.

Equipment & Apparatus

  • Balance (0-10kg)
  • Sieves (20,16,12.5,10,6.3,4.75mm)
  • Metal cylinder
  • Tamping rod
  • Scoop 

Test Sample Preparation

The test sample consist of aggregate retained between the appropriate pair of IS sieves from the following sets

PASSING

RETAINED

20 mm

16 mm

16 mm

12.5 mm

12.5 mm

10 mm

10 mm

6.3 mm

6.3 mm

4.75 mm

The aggregate to be tested is dried for at least 24 hours in a well ventilated oven maintained at a temperature of 100 to 1100C. 

Procedure

  1. The aggregate is compacted in three layers, each layer being given 100 blows using the standard tamping rod at a rate of 2 blows/second by lifting the rod 5 cm above the surface of the aggregate and then allowing it to fall freely.
  2. The blows are uniformly distributed over the surface of the aggregate.
  3. After compacting the third layer, the cylinder is filled to overflowing and excess material is removed off with temping rod as a straight edge.     
  4. The aggregate with cylinder is then weighed. Three separate determinations are made and mean weight of the aggregate in the cylinder is calculated. 

Calculation

Aggregate angularity number 1

Where,

W = mean weight of the aggregate filling cylinder.

C = Weight of water required to completely fill the cylinder (i.e. Volume of cylinder)

Gs = Specific Gravity of the aggregate 

Reports

The mean value of three determinations, expressed to the nearest whole number is reported. 

Safety & Precautions

  • Use safety shoes, mask & aprons at the time of test.
  • Thoroughly clean & dry the container before testing.
  • Special care should be taken that no outer air enters when using the balance.
  • After test sieve should be clean by  a soft brush.
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