JOB 7 - STANDARD TEST METHOD FOR THE DETERMINATION OF IMPACT VALUE OF COARSE AGGREGATE PDF

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STANDARD TEST METHOD FOR THE DETERMINATION OF IMPACT VALUE OF COARSE AGGREGATE...

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PLAIN AND REINFORCED CONCRETE-1

JOB NO. 7

DESIGN EXERCISE NO#7 STANDARD TEST METHOD FOR THE DETERMINATION OF IMPACT VALUE OF COARSE AGGREGATE. Code: BS 812 SCOPE & SIGNIFICANCE:i.

ii.

The aggregate impact gives a relative measure of the toughness or the resistance of aggregate sudden shock or impact is not proportional to the resistance to a slowl applied compressive load. The aggregates should therefore have sufficient toughness to resist their disintegration due to impact. This characteristic is measured by impact value test.

APPARATUS:     

Coarse aggregate Impact testing machine Trowel Balance Tamping rod Sieves

RELATED THEORY:IMPACT VALUE: The aggregate impact value is a measure of resistance to sudden impact or shock, which may differ from its resistance to gradually applied compressive load. Aggregate impact value (%)

Toughness Properties

35

Weal for pavement surface course

February 21, 2018

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PLAIN AND REINFORCED CONCRETE-1

JOB NO. 7

IMPACT TESTING MACHINE: The instrument consists of a circular base with two vertical guides. The hammer of weight 13.75 ±0.25 kg can be raised to fall freely down the vertical guides. The height of fall can be adjusted through 380 ± 5mm. The hammer is provided with a locking arrangement. The hammer falls freely to the base and is removable for emptying. Supplied complete with metal measures 75mm dia x 50mm high (for specimen preperation) and tamping rod 230mm long x 10mm dia.

Figure 1: IMPACT VALUE PROCEDURE:i.

Pour the aggregates to fill about just 1/3 rd depth of measuring cylinder.

ii.

Compact the material by giving 25 gentle blows with the rounded end of the tamping rod.

iii.

Add two more layers in similar manner, so that cylinder is full.

iv.

Strike off the surplus aggregates.

v.

Determine the net weight of the aggregates to the nearest gram(W1).

February 21, 2018

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PLAIN AND REINFORCED CONCRETE-1

JOB NO. 7

vi.

Bring the impact machine to rest without wedging or packing up on the level plate, block or floor, so that it is rigid and the hammer guide columns are vertical.

vii.

Fix the cup firmly in position on the base of machine and place whole of the test sample in it and compact by giving 25 gentle strokes with tamping rod.

viii.

Raise the hammer until its lower face is 380 mm above the surface of aggregate sample in the cup and allow it to fall freely on the aggregate sample. Give 15 such blows at an interval of not less than one second between successive falls.

ix.

Remove the crushed aggregate from the cup and sieve it through mm IS sieves until no further significant amount passes in one minute. Weigh the fraction passing the sieve to an accuracy of 1 gm as W2. Also, weigh the fraction retained in the sieve.

February 21, 2018

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PLAIN AND REINFORCED CONCRETE-1

JOB NO. 7

OBSERVATIONS AND CALCULATIONS: OBSERVATIONS

1

Total weight of dry sample (W1 gm)

Weight of portion passing

mm sieve (W2 gm)

Aggregate Impact Value (percent) = W2 / W1 X 100

OBSERVATIONS

2

Total weight of dry sample (W1 gm)

Weight of portion passing

mm sieve (W2 gm)

Aggregate Impact Value (percent) = W2 / W1 X 100

February 21, 2018

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PLAIN AND REINFORCED CONCRETE-1

JOB NO. 7

OBSERVATIONS AND CALCULATIONS: OBSERVATIONS

3

Total weight of dry sample (W1 gm)

Weight of portion passing

mm sieve (W2 gm)

Aggregate Impact Value (percent) = W2 / W1 X 100

OBSERVATIONS

4

Total weight of dry sample (W1 gm)

Weight of portion passing

mm sieve (W2 gm)

Aggregate Impact Value (percent) = W2 / W1 X 100

February 21, 2018

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PLAIN AND REINFORCED CONCRETE-1

JOB NO. 7

RESULTS:

COMMENTS:

February 21, 2018

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