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
- 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.
- The blows are uniformly distributed over the surface of the aggregate.
- After compacting the third layer, the cylinder is filled to overflowing and excess material is removed off with temping rod as a straight edge.
- The aggregate with cylinder is then weighed. Three separate determinations are made and mean weight of the aggregate in the cylinder is calculated.
Calculation
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.
Why it is 67 whynot 65 or70
What is meaning of 67
Maximum voids area present in the condition of angular agg. In the case of angular aggregate the total covered area by agg. is found 67%. And total voids area is found 33%.
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