Flakiness Index and Elongation Index Test Procedure [Update-2019]

Flakiness index and Elongation index test required to find out the shape of aggregate. We described the procedure of Combined Flakiness index and Elongation index test of aggregate as per IS code with formula and calculation. Flakiness and Elongation index test called shape test too.

 

Flakiness Index and Elongation Index

What is Flakiness Index?

Flakiness index is a percentage of the weight of those aggregates, whose are smaller in thickness then 0.6 times of their mean dimensions in size. These aggregates are flaky aggregates.

 

What is Elongation Index?

Elongation index is a percentage of the weight of those aggregates, whose are greater in length 1.8 times of their mean dimensions in size.

 

Flakiness Index and Elongation Index IS Codes

IS code – IS 2386 part-1.

 

Why Flakiness and Elongation Index Test required?

Flaky and Elongated aggregates have very less physical strength. So the percentage of flaky and elongated aggregates must be in limit.

 

Reasons to avoid flaky and elongated aggregates

  1. It decreases the compressive strength of concrete.
  2. It decreases the load capacity of any pavement.
  3. It decreases the flow of concrete.
  4. It decreases the durability of concrete structures, pavements, roadwork or any type of construction work.
  5. It decreases compaction in any type of concrete work or road work.

 

Flaky meaning

Flaky means, something breaking or separating into flakes.

 

Flakiness Index and Elongation Index Test Apparatus and Tools required

  1. Flakiness gauge ( flakiness index apparatus )
  1. Elongation gauge ( elongation index apparatus )
  1. Weighing balance with least count 0.5 gram.
  1. IS sieves 63, 50, 40, 31.5, 25, 20, 16, 12.5, 10, 6.3 mm ( depend on material )

 

Procedure of Flakiness Index and Elongation Index test

Flakiness Test Procedure as per IS Code

We are describing flakiness and elongation index test procedure for wet mix macadam here.

  1. Take sieves 40, 31.5, 25, 20, 16, 12.5, 10, 6.3 mm.
  1. Take WMM dry sample, if not dry, put it in oven for 24 hours.
  1. After dry WMM mix start sieving by 40 mm sieve, whatever material passing through 40 mm, sieve it by 31.5 mm.
  1. Take retained material from 31.5 mm, these aggregates passed through 40 mm and retained on 31.5 mm sieve. These aggregate shall be minimum 200 pieces in number.
  1. Similarly, take 200 pieces aggregates from 31.5 mm passing and 25 mm retained.
  1. Continue it up to 6.3 mm.

Now we have

Passing through

Retained onMinimum rqd pcs.
40.0 mm31.5 mm200
31.5 mm25.0 mm200
25.0 mm20.0 mm200
20.0 mm16.0 mm200
16.0 mm12.5 mm200
12.5 mm10.0 mm200
10.0 mm6.3 mm200

 

  1. After taking minimum 200 pieces from each sieve size, take weight separately and write down it.

Flakiness Index and Elongation Index

  1. Take flaky gauge and check 40 mm – 31.5 mm first in the given gap in flaky gauge ( where written 40-31.5 ) as we have shown in our practical video.
  1. Passed aggregates from flaky aggregate shall be weighed and kept separately, these are flaky aggregates.

 

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Elongation Index Procedure as per IS Code

  1. Aggregates which not passed through flaky gauge shall be taken for elongation test.

Flakiness Index and Elongation Index Test

  1. Like flaky index test we can test elongation, but for elongation index sample weight shall be considered retained weight from the flaky gauge of a particular sieve.
  1. Then retained weight from flaky gauge shall be tested in elongation gauge gap ( written 40-31.5 on gauge scale )
  1. Retained aggregates on elongation gauge shall be considered as elongated aggregate and shall be weighed separately. write down this weight.
  1. Same procedure shall be repeated for flaky and elongation 31.5 – 25 mm, 25 – 20 mm, 20 – 16 mm, 16 – 12.5 mm, 12.5 – 10 mm, 10 – 6.3 mm.

 

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Flakiness and Elongation Index Limits IS Code

PavementMaximum LimitsSpecifications
Concrete35MORTH 5th, section 1700
Water bound macadam35MORTH 5th, section 400
Wet Mix Macadam35MORTH 5th, section 400
Crusher Run Macadam 35MORTH 5th, section 400
Bituminous Macadam35MORTH 5th, section 500
Dense Bituminous macadam35MORTH 5th, section 500
Bituminous Concrete35MORTH 5th, section 500

 

Flakiness and Elongation index test Video for Report and Calculation

Watch video for actual report –

 

Viva Questions on Flakiness and Elongation Index Test

Q.1  What sieves shall be used for flakiness and elongation test of concrete, if msa is 20mm?

Ans. There is no elongation test required for concrete in MORTH 5th revision, section 1700.

         For flakiness these sieves are required 25mm, 20mm, 16mm, 12.5mm, 10.0mm, 6.3mm.

 

Q.2  How many minimum aggregate pieces required for flakiness and elongation test?

Ans. Minimum 200 aggregate pieces required for flakiness and elongation test.

 

Q.3  Which sample shall be taken for elongation test?

Ans. After the flakiness test, non-flaky aggregates shall be taken for the elongation test.

 

Any other question? Just ask in comment. We are waiting.

 

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Read More:

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Aggregate 10 % Fines Value Test Procedure | Ten Percent Fines Value Test

Loose and Compacted Bulk Density Test Procedure of Aggregate

Specific Gravity Test of  Fine Aggregate Procedure by Pycnometer

 

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