STANDARD
- IS: 2386 (Part 1)1963.
DEFINITION
- The Flakiness Index of aggregates is the percentage by weight of particles whose least dimension (thickness) is less than 0.6 times their mean dimension.
- The Elongation Index of aggregates is the percentage by weight of particles whose greatest dimension (length) is greater than 1.8 times their mean dimension.
APPARTUS
- Standard thickness gauge.
- Standard length gauge.
- IS sieves 63mm, 50mm, 40mm, 25mm, 20mm, 16mm, 12.50mm 10mm and 6.30mm.
- Balance of capacity 15kg and sensitivity 1gram.
- Thermostatically controlled oven with capacity up to 250 °C.
PROCEDURE
- Take representative sample of aggregates from the stockpile.
- Dry the whole sample in the oven to a constant weight at a temperature of 105° C to 110°C and cool at room temperature.
- Sieve the whole sample through the sieves mentioned in the columns (1) and (2) of the Table: 1
FLAKINESS INDEX
- Take minimum of 200 pieces from each fraction and weigh (A).
- Separate flaky material from each fraction by gauging through the standard thickness gauge.
Weigh the flaky material passing though the specified gauge from each fraction c1+c2+c3+c4+c5+ …………….= C.
CALCULATIONS
- Flakiness index, % = ( C/A ) X 100
ELONGATION INDEX
- Take minimum of 200 pieces from each fraction and weigh (F).
- Separate the elongated material from each fraction by gauging through the standard length gauge.
- Weigh the elongated material passing through the specified gauge from each fraction E1+E2+E3+E4+E5+…………….= E.
CALCULATIONS
- Elongation Index, (%) = (E / F) x 100.
Table: 1
|
Passing |
Retained on IS sieve, mm |
Thickness gauge (0.6 times mean sieve) mm |
Length gauge |
|
1 |
2 |
3 |
4 |
|
63.00 |
50.00 |
33.90 |
– |
REPORT
- Report the result obtained to the nearest second decimal
COMBINED FLAKINESS AND ELONGATION INDEX (Requirement as per MOST)
- Take minimum of 200 pieces from each fraction and weigh (A).
- Separate flaky material from each fraction by gauging through the standard thickness gauge.
- Weigh the material retained and passed through the specified gauge from each fraction b1+b2+b3+b4+b5…………..= B and c1+c2+c3+c4+c5+ = C respectively.
- Take the material retained on the thickness gauge (Non flaky material) and separate the elongated material from each fraction by gauging through the standard length gauge.
- Weigh the material retained on the length gauge from each fraction d1+d2+d3÷d4+d5+…..= D.
CALCULATIONS
- Flakiness index (Fl), % =(C / A) x 100
- Elongation index (El), % (D / B) x 100
- Combined flakiness and Elongation Index = FI + El.
REPORT
- Report the result obtained to the nearest second decimal.
PRECAUTIONS
- Take care while taking sample.
- Do not collect selected pieces.
- Collect pieces by only random sampling.
DETERMINATION OF FLAKINESS & ELONGATION INDICES
IS 2386 (Part 1)1963
| IS Sieve size in mm | Total Wt. of agg. Retained on sieves (A) (g) | Wt. of agg. on thickness gauge (B) (g) | Wt.of agg. Passing through thickness gauge ( C ) ( g ) | Wt. of agg. retained on length gauge after ret. On thickness gauge
( D ) (g ) |
|
|
Passing |
Retained |
||||
| 1. Flakiness Index ( C/A ) × 100 = % | |||||
| 2. Elongation Index ( D/B ) × 100 = % | |||||
| 3. Combined F1 & E1 ( 1+2 ) = % | |||||
| Specified Limits: | For road works 30% ( Max.) & For concrete work 25% ( Max. ) | ||||
| Remarks:
|
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