Theory:

Aggregate crushing value is measured which relatively gives idea of his resistance to crushing under the compressive load applied gradually. Lower the crushing value stronger the aggregate again crushing. Therefore good quality concrete, aggregate having comparatively lower crushing value is to be preparable. Aggregate crushing value (ACV) should not be exceed 30 % for concrete used for wearing surface such as road, runways and aggregate crushing value should not exceed 45 % for other than wearing surfaces such as road, runways and used for any concrete work.

Application:

The purpose of the test is to have an idea of compressive strength relatively i.e. its resistance relatively under compressive strength applying gradually and then to decide its suitability to use in cement.

Item Required:

1.     Aggregate sample balance of capacity 5 kg.
2.     Steel cylinder, steel conger, compressive testing machine, I.S. sieve 12.5 mm, 10 mm and 2.36 mm, side tamping rod.

Procedure:

1.     Sample of aggregate is prepared by sieve the aggregate. The sample is passed through 12.5 mm sieve and retained at 10 mm sieve. 
2.     Sample is dryed in an oven at temperature between 1000c to 1100c for four hours. Then along it to cooled.
3.     Filled the cylindrical lable in layer each layer was tamp by tamping rod the top was of with the rods. The weight of the sample was noted (W).
4.     The cylindrical steel cup is fixed to base plate and tamp it with 25 strokes.
5.     The plunger is placed on the aggregate. The whole assembly is placed between plates of compressive testing machine.
6.     The load is applied to the sample of aggregate through the plunger at the rate of per minute up to 40 Tone.
7.     The load is released and sieve the material the cylinder through 2.36 mm sieve weight the fraction passed through 2.36 mm sieve (W1).

Precaution:

1.     The aggregate sample should be sieved and weight correctly.
2.     Each time layer should be tamped 25 time with the help of tamping rod.
3.     The cylinder at the test apparatus with aggregate is carefully levelled and plunger inserted horizontally.
4.     The plunger should not touch cylinder.
5.     The load should applied uniformly into a total load at 40 Tone in 10 min time.

Result:

The aggregate crushing value at the given sample is 19 %

Diagram:



Sample Calculation:

1.     w1/w X 100 = 390 / 2000 X 100
                      = 0.195 X 100
                      = 1.95 %

2.     w1/w X 100 = 370 / 2000 X 100
                      =  0.185 X 100
                      = 18.5 %

Mean value % percent = 19.5 + 18.5 / 2
                                         = 19 %

Observation Table :

Sr. No.
Weight of aggregate
Weight of crushed aggregate
% percent of value
Load applied
1
200 gm
390 gm
19.5 %
40 tones
2
200 gm
370 gm
18.5 %
40 tones

Observation:

Weight of dry sample = 200 gm

Weight of fraction passing through 2.36 mm sieve (w1) = 390 gm

Result:

The aggregate crushing value of the given sample is 19 %.