Fine Aggregate/Coarse Sand

Fine aggregate/ coarse sand consists of:

1. Natural sand.
2. Crushed stone sand.
3. Crushed gravel stone dust.

Quality of Coarse Sand

Actual specification for the quality of coarse sand can be obtained by laboratory test but in general we
can judge the quality of coarse sand in the field through the following ways.

1. Observe whether there are any lumps of earth or clay balls, grass and decayed
vegetation etc. in coarse sand to check silt contents.
2. Take some samples of coarse sand in hand and observe, The particles of sand should
be coarser, Silt contents should be less.
3. One can simply check the quality of sand by taking some sand in the hand and then
dropping it down. If some finest material sticks with hand, the sand has some silt
contents and finer sand.
4. Check silts contents with the help of water. Take empty glass and put some sand and
water in the glass and stir it well. After some time the silt layer will be framed between
sand and water which shows the quantity of the silt contents present in the sand.
5. It should be hard, durable, chemically inert, clean and free from organic matter, not
containing any appreciable amount of clay balls or pellets and other harmful impurities i.
e. alkaline, salt, mica, decayed vegetation, lumps etc.

Sand obtained from quarry site.

The three types of materials/ coarse sand is found at ‘Quarry Site’. Each material has different impact
on the strength of the building.

1. Screened and washed material: This type of material is the best for use in construction
work and gives full strength of mortar.
2. Screened but unwashed material: This type of material is cheap having more silt. This is
generally 10% cheap.
3. Unscreened, unwashed material: This type of material is cheaper having more silt/clay
and un-graded material. This is generally 20% cheap.

Precautions while Purchasing & Measuring

Precautions while Purchasing

1. The supplier/truck owner carries sub standard material of below two cheap qualities of
‘Coarse Sand’ at the cheap rate and he tells you that carried material is the best material
because you may not know much about the quality of material.
2. Check the quality of material. Never accept fine and silty material because this material
is harmful as stated above.

Rate
 1.  House owner should collect rates from more than 3 or 4 suppliers. He should also
collect the rates from few truck owners who stand their trucks with full of material at the
early hours of the day on prescribed place in every city/town.

Precautions while Measurement

1. Where the supplier or truck owner suspects that the house owner may measure the truck
in day time, he applies following methods to fool the owner. He stops the truck at some
distances from the site and gets the material loosen by spade and sprinkle water on sand
in the truck. Due to spading and the water sprinkled over sand, the sand becomes bulky
and it gives more height. Hence he charges on more quantity. 
2. He also tries to make the house owner fool in calculation, for example if the
measurement is 3 feet 6 Inches, he calculates it as 3.6 but actually it is 3.5 feet. 
3. He also tries to measure the height at the backside where the height is raised with the
help of spade.
4. When one takes supply of material, he should measure the height of material in the truck.
If the material is pressed by your feet when you climb on the material in the truck, you
should think that the material has been made loose with spade by truck driver; you
should reject the material. If the material is not pressed by your feet, it is O.K.
5. You should take the height with the help of iron rod by inserting it into the sand, but care
should be taken if the truck driver takes measurement of the height, he can take the
other height from low place and takes average of 2 or 3 points in heights. Take the length
and width of truck after unloading of the material.
6. Never compromise on the measurement of the material at the ground after unloading as
this will give more quantity.
7. Try to get the material in cash terms and payment made by you after measurement of the
height, length and breadth as the truck driver/owner charges less rates on cash payment,
direct from house owner as compared to the supply taken from suppliers.

Technical Details of fine Aggregate/Sand

1. Specific Gravity= 2.6 to 2.8.

2. Weight per Cubic meter.
 Dry Sand=1600
 Damp Sand=1840
 Wet Sand=1920
3. Angle of repose=30 to 35 Deg.
4. Co efficient of thermal Expansion= Varies from 5.4x10^-6 -12.6x10^-6 /c
5. Finess modulus= Varies From 2.0 - 3.5
6. Silt contents should not be more than 4%
7. If the moisture content is about 4% by weight of dry sand, the increase in volume may be
of the order 20-30%
8. If the moisture content is more than 20%, its volume becomes same as that of dry sand.
9. Finess modulus= 3.768
10. Coefficient of curvature Cc=1.22
11. Uniformly Coefficient Cu=2

Effects on Quality of Mortar and Concrete due to

1. Silt:
 If there is more silt in coarse sand, the strength of cement mortar is reduced
from 1 % to 30%.
2. Bulking:
  If sand is measured by volume and no allowance is made for bulking ,the
mix will be richer than that specified,because for given mass ,moist sand
occupies a considerable larger volume than the same mass of the dry
sand .this results in mix deficient in sand increasing the chance of
segregation and honeycombing of the concrete.
 If no allowance is made for bulking the concrete strength may vary as much
as 25%.

Coarse Aggregate/Jelly

The aggregate which is retained over I.S Sieve 4.75 MM is termed as Coarse aggregate/Jelly

Technical Details of Coarse Aggregate/Jelly

1. Finess modulus = 3.768

2. Coefficient of curvature, Cc = 1.22                                      
3. Uniformly Coefficient, Cu = 2 

Lab Test

Bulking of fine aggregate

Aim: To determine the percentage of bulky of fine aggregate.

Apparatus: Cylindrical measuring jar,bowl,glass rod etc.

Theory: The Volume of fine aggregate such as sand particles depends largely upon its moisture
containment. If fine are met each particles gets a coat of water which is due to surface tension keeps
them apart , and thus cause to increase in volume called bulking. Bulking increases gradually with
moisture content . The increase being about 25% by volume as about 4% moisture content by weight
then decreases to zero.

Procedure:

1. Weigh out 500gm of sand, fill it in 1000 ml measuring jar note down the volume.
2. Transfer the sand to the basin and mix very well with 2% of moisture content by weight.
3. Fill the moisture to 1000 ml jar ,level the top surface with the glass rod note down the
increase in volume.
 4. Similarly repeat the procedure by adding 2% of moisture content by weight up to the
decrease in volume.
5. Determine the percentage of bulky of fine aggregate.
6. Draw the variation for percentage of water added and increase or decrease.

Observation:

Sl No. Volume of Sand (cc) % of water Increase/Decrease in water % Bulky

1 500 0 680 36%
2 500 2 830 66%
3 500 3 860 72%
4 500 4 910 82%
5 500 5 930 86%
6 500 6 910 82%
7 500 7 860 72%

Calculation:
Bulking of sand= (H2-H1)/H1 =((930-500)/500)= 86%                         

Result: The Percentage of bulky for fine aggregate is 86%.

Sieve Analysis

Aim: To determine the fineness modulus of the course aggregates.

Apparatus: set of Is sieves,sample,balance with weights etc.

Theory: The object of finding the fineness modulus is to grade the given aggregate for obtain most
economical and workable mix with minimum quantity of cement.

The aggregate fraction from 80mm-4.75mm are termed as coarse aggregates and those fractions
from 4.75mm-150mm are termed as fine aggregates .The size of 4.7mm is a common fraction
appearing both in coarse and fine aggregates.

Procedure:

Coarse aggregates:

1. Take about 5kg of road aggregates.

2. Put the aggregates in IS sieves i.e..
80mm,40mm,20mm,10mm,4.75mm,2.36mm,1.18mm,600mm,150m, pan
3. Hold whole assembly in hand and shake it well or sieve for about 10min
4. Stop the sieving process and weight the mass retained on each sieve after cleaning the
sieve with wire brush.
5. Calculate the cumulative % retained on each sieve and fineness modules.

Observation:
 IS sieve size in Weight ratained in Cumulative wt retained Cumulative % wt %
Sl No
mm gms in gms retained fineness

1 40 0 0 0 0
2 20 4106 4106 82.12 17.88
3 12.5 690 4796 95.92 4.08
4 10 146 4942 98.84 1.16
5 4.75 54 4996 99.92 0.08
      Total 376.8  

Calculation:
Fineness modulus = sum finer / 100 = 376.8 / 100 = 3.768
D10 = 16mm D30 = 25mm D60 = 32mm
Cc = (D30 * D30) / (D60 * D10) = (25 * 25) / (32 * 16) = 1.2207 Well graded
Cu = D60 / D10 = 32 / 16 = 2

Result:

1. Fineness modulus of coarse aggregate = 3.768

2. Coefficient of curvature, Cc = 1.22
3. Uniformly Coefficient, Cu = 2

Aggregate Impact Test

Aim: To determine the strength offered by the coarse aggregate under impact loads

Apparatus:Impact testing machine IS sieve sizes of 2.36mm , 12.5mm , 10mm, balance, tamping
rod

Theory:The aggregate Impact value gives a relative measure of the resistance of all aggregate  to
sudden shock or impact which in some aggregate differ from its resistance to slow a compressive load
with respect to concrete aggregate toughness is usually considered the resistance of the material to
failure by impact several attempts to develop a method for aggregate impact  value have been
made .The most successful is the one in which a sample of std aggregate kept in a mould is subjected
to 15 blows of a metal hammer of weight 14 kg falling from a height of 38 cm. the quantity of finer
material results from powdering of aggregate.

Procedure:-

1. The given aggregate sample is sieved through 12.5mm sieve and retained on 10mm IS
sieve is taken out
2. The aggregate retained on 10mm IS sieve is taken and filled the cylinder on 3 equal
layers giving 25 strokes on each layer by standard tamping rod and the sample surface
is leveled off. Then the hammer is allowed to fall free on the aggregate from a height
such that the lower end face of hammer is 38 cms above the upper surface of aggregate.
3. The Crushed aggregate is then removed from the cup and sieved through 2.36 mm sieve
4. The ratio of the weight of aggregate passing through 2.36 mm is sieve to the total weight
of the aggregate in the cylinder gives the impact value of the aggregates.
Observation:

Sl No Description Weigjt
1 Empty weight of mould W1 in gm 2000
2 Weight mould +Aggregates W2 in gms 2500
3 Weight of portion passing through 2.36 12
4 Crushing value =(W3/(W2-W1))x100 2.40%
Calculation: 

Impact Value=(W3/(W2-W1))x100= (12/(2500-2000))x100= 2.4%

Result:

The aggregate impact value of a given coarse aggregate is 2.4%

Conclusion:

If the impact value is less than 10% it is considered as very strong

10% - 20% Strong

20% -30% is satisfactory

Above30% Suitable for pavement construction.

Crushing Strength

Aim: To find the crushing strength of given coarse aggregates

Apparatus: Compressing testing machine , Plunger , cylinder mould , IS sieve , weighting balance

Theory: The aggregate crushing value gives a relative measure of the resistance of an aggregate to
crushing under a gradually applied compressive load with aggregates of aggregates crushing value 30
higher the result may be in such cases the 10% fine value should be determined and used instead.
The standard aggregates crushing test is made on aggregates passing a 12.5mmIS sieve and retained
on 10mm IS sieve, if required or if the standard size is not available other size up to 25mm may be
tested.

Procedure:

1. The given aggregate sample is sieved through 12.5mm sieve and retained on 10mm IS
sieve.
2. The aggregate retained on 10mm IS sieve is taken and filled the cylinder on 3 equal
layers giving 25 strokes on each layer by standard tamping rod.
3. Leveled of the surface and top of the cylinder is covered by the plunger.
4. The whole assembly is kept under compressive testing machine.
5. The load is applied at the rate of 4 tones/min up to 40tonnes.
6. The cylinder is taken out from the plunger and the crushed aggregates to be 2.36mm
ARE SIEVE.
 7. The weight of the crushed aggregates passing through 2.36mm IS sieve is noted down.
8. The ratio of the weight of the aggregates passing through 2.36mm sieve to total weight of
aggregates in the cylinder gives the crushing strength of aggregates. ie., crushing value
= W3 / (W2-W1)

Observation:

Sl No. Description Weight

1 Empty weight of crushing mould in gm 7200
2 Weight mould + Aggregates in gms 9700
3 Weight of portion passing through 2.36 713
4 Crushing value = W3 / (W2-W1*100) 28.52

Calculation:
Time taken t=5 min
Crushing value = W3 / (W2-W1*100) = 713 / (9700-7200*100) = 28.52%

Result:
The crushing strength of a given coarse aggregate = 28.52%

Conclusion:
The required crushing value for coarse aggregate for cement concrete pavement should not exceed
30% for granite.

Elongation Index

Aim: To determine the Elongation index of the given sample of coarse aggregates.

Apparatus: IS sieve sizes of 63mm, 50mm, 40mm, 25mm, 20mm, 16mm, 10mm, 6.3mm, Pan,
coarse aggregate sample, Balance.

Theory: An aggregate having least dimension less than 3/5th of its mean dimension is termed flaky.
where the mean dimension is the average of the sieve size through which the particles pass and the
sieve size on which these are retained .on the other hand the particles having the largest
dimension(length) greater than 9/5 times the mean size are termed elongated.
The presence of excess of flaky and elongated particles in concrete aggregate decreases the
workability appreciably for a given water-cement ratio thus requiring large amounts of sand, cement
and water .The flaky and elongated particles and to orient in one plane and cause lamination which
adversely affect the durability of the concrete. the percentage of flaky and elongated particles should
be limited to 10 to 15.

Procedure:

1. The set of sieve are arranged in decreasing order of their size I.e. 63mm sieve at top.
2. The sample of aggregate are sieved through these sieve.
3. Then Weight of aggregate retained on each sieve is noted with the help of balance.
4. In that retained aggregate the weight of the aggregate retained on gauge length (1.8 X
mean size) is noted down.
5. The aggregate smaller than 6.3mm are not considered.
6. Then total of weight of aggregate retained on each sieve is calculated.
7. Similarly total of weight of aggregate retained on gauge length is also calculated.
 8. Using formula elongation index is calculated.

Observation:

Weight
Sl Passing thru IS Retained on Weight of aggregate Elongation
aggregate in
No. sieve size in mm sieve size in mm retained on gage length Index
sieve
1 50 40 380 - -
2 50 25 1330 244 -
3 25 20 480 380 -
4 20 16 1316 33 -
5 16 10 460 104 18.76%
6 10 8.3 110 26 -
7 8.3 - 320 38 -
8 - Total 4396 825 -

Calculation:
E.I = (Wt of retained in gauge length * 100) / Total weight of aggregate
E.I = (825 * 100) / 4396 = 18.76%

Result:
Elongation index of Coarse aggregates=18.76%

Conclusion:
Since EI>15%, aggregate are unfit to use for pavement construction.

Flakiness index

Aim: To determine the flakiness index of the given sample of coarse aggregates.

Apparatus:IS sieve sizes of 63mm,50mm,40mm,25mm,20mm,16mm,10mm,6.3mm,Pan,corase

aggregate sample.

Theory: An aggregate having least dimension less than 3/5th of its mean dimension is termed flaky.
where the mean dimension is the average of the sieve size through which the particles pass and the
sieve size on which these are retained .on the other hand the particles having the largest
dimension(length) greater than 9/5 times the mean size are termed
elongated.                                                                                                                                      
        The presence of excess of flaky and elongated particles in concrete aggregate decreases the
workability appreciably for a given water-cement ratio thus requiring large amounts of sand,cemet
and water .The flaky and elongated particles tend to orient in one plane and cause lamination which
adversely affect the durability of the concrete. The percentage of flaky and elongated particles should
be limited to 10 to 15.

Procedure:

1. The set of sieve are arranged in decreasing order of their size I.e. 63mm sieve at top.
2. The sample of aggregate are sieved through these sieve.
3. Then Weight of aggregate retained on each sieve is taken with the help of balance.
 4. In that retained aggregate the weight of the aggregate passing through thickness gauge
(0.6Xmean size) is noted down.
5. The aggregate passing through 6.3 IS sieve are not considered.
6. Then total of weight of aggregate retained on each sieve is calculated.
7. Similarly total of weight of aggregate passing through thickness gauges is calculated.
8. Using formula flakiness index is calculated.

Observation:

Passing through Retained on weight weight of aggregate

Sl Thickness
IS sieve size in sieve size in aggregate in Passing through the slot
No gauge size mm
mm mm sieve in gm
1 63 50 440 33.90  
2 50 40 380 27.00  
3 40 25 1130 19.50 54
4 25 20 480 13.50 18
5 20 12.5 136 9.75 274
6 12.2 10 460 6.75 154
7 10 4.75 110 4.43 195
8 4.75 Pan 320 0 46
9   Total 3456   741

Calculation: 

F.I= (Sum (W1)/Sum (W)) x100= (741/3456)x100     =20.26%

Result:

Flakiness of Coarse aggregates=20.26%

Conclusion:

Since FI>15%, aggregate are unfit to use for pavement construction.