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Department of civil engineering

Experiment No: 01

DETERMINATION OF BULKING OF FINE AGGREGATES

THEORY:

AGGREGATES

Aggregate forms a very large proportion of concrete and hence it plays a very important role in the

properties of concrete. Aggregate may be considered an inert material which combines with cement

paste by developing a mechanical bond to form a hard mass. Aggregate is cheaper than cement and

hence directly help in achieving economy in concrete manufacture. Aggregate also imparts greater

volumetric stability and durability to concrete as compared to the cement paste alone.

Aggregates can be obtained from natural sources such as river bed, sea shore, etc. or from artificial

sources such as crusher plants: plants producing light weight- aggregates (foamed slag, expanded

shales, sintered materials, etc. ) and plants producing heavy weight aggregates ( scrap iron,

magnetite, barite, etc. )

Concrete properties are greatly influenced by aggregate characteristics given as under:

Size and grading of aggregates

Shape and surface texture

Strength

Specific gravity and bulk density

Water absorption and surface moisture Bulking of sand

Soundness, and durability including alkali-aggregate reactivity

Deleterious substances

The size, shape, surface texture, surface moisture and grading directly influence the water

requirement for the desired workability during plastic stag. Other characteristic s have influence on

the strength and durability during the hardened stage and proportions of concrete. The aggregate

should satisfy the requirements laid in IS: 383-1976 in regard to its properties



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BULKING OF AGGREGATES

The increase in the volume of a given mass of fine aggregate caused by presence of water is known as

bulking. Bulking of fine aggregate is caused by the films of water which push the particles apart.

The extent of bulking depends on:-

a. Percentage of moisture present in the sand

b. Fineness of the sand

The free moisture content in fine aggregate results in bulking of volume.

Free moisture forms a film around each particle. This film of moisture exerts what is known as surface

tension which keeps the neighboring particles away from it. Similarly the force exerted by surface

tension keeps every particle away from each other; therefore no point contact is possible between

the particles. This causes bulking of volume. The extent of surface tension and consequently how far

the adjacent particles are kept away will depend upon the percentage of moisture content and the

particle size of the fine aggregates.

VARIATION OF BULKING OF AGGREGATES WITH MOISTURE CONTENT

The bulking increases with the increases in the moisture content up to a certain limit and beyond that

the further increases in the moisture content result in the decrease in the volume and at a moisture

content representing saturation point . Extremely fine sand and particularly the manufactured fine

aggregates bulk as much as 40 percent.

The fine sand bulks more than the coarse sand.

EFFECT OF BULKING OF AGGREGATES

Due to the bulking, fine aggregate shows completely unrealistic volume. Therefore, it is absolutely

necessary that consideration must be given to the effect of bulking in proportioning the concrete by

volume . If cognizance is not given to the effect of bulking, in case of volume batching, the resultingconcrete is likely to be under-sanded and harse. It will also affect the yield of concrete for given

cement content.



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PROCEDURE:

VOLUME DETERMINATION OF THE CYLINDRICAL MEASURE

1. Measure the height of the mould (h) using scale.

2. Measure the diameter along the two perpendicular directions in theplane of the area of its cross-section.

3. Take the average of the two diameters (d).

4. Calculate the volume of mould (V1) using formula;

V1= π(d/2)2h

BULKING DETERMINATION

1. Take the empty weight of the container.

2. Fill the container with the sample in loose state and take the weight of the container plus loosesample.

3. Take 6kg of dry sand sample and place it in the mixing pan.

4. Add water 2% by weight of the sample and mix the water with the fine aggregate rapidly and

thoroughly to obtain a uniformly mixed appearance.

5. Fill the container with the moist sample in loose state

taking care that the container doesn’t experience any shock or

vibration or impact forces. Strike off the top surface.

6. Weigh the container filled with moist sample.

7. Add further 2% water and repeat step 4-7 until the sample

get fully saturated.

Fig: Mould

Fig: digital electronic

balance



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EXPLANATORY NOTE:

m1 = Weight of mould

V1 = Volume of mould

m2 =Weight of mould including sample

w1 =Weight of sample =m2 – m1

Weight of dry sample= w2 =( m2 – m1)/( 1+m)

If D= Density of sample

Volume of dry sample = w2/D =V2

Increase in volume due to moisture =V i = V1-V2

% of bulking = (Vi-V) x 100/V

TABLE

Moisture

Content

(m)

(1)

Wt of sample

including

mould

(2)

Wt of

sample =

(2)-m1

(3)

Wt of dry

sample =

(3)/(1+m)

(4)

Volume of

dry sample =

(4)/density

(5)

Increase of volume

due to moisture =

m2-(5)

(6)

Percentage of

bulking =

(6)100 / (5)

(7)

0.02 4.580 2.23 2.18 1.44 0.48 33.25

0.04 4.579 2.22 2.14 1.42 0.51 35.93

0.06 4.569 2.21 2.09 1.38 0.54 39.17

0.08 4.620 2.27 2.10 1.39 0.54 38.60

0.20 4.617 2.26 1.89 1.25 0.68 54.20

0.12 4.693 2.34 2.09 1.38 0.54 39.25

0.14 4.800 2.45 2.14 1.42 0.50 35.53

0.16 4.834 2.48 2.14 1.42 0.51 36.02

0.18 4.870 2.52 2.13 1.41 0.51 36.38

0.20 4.954 2.60 2.17 1.43 0.49 34.210.22 4.966 2.61 2.14 1.42 0.51 35.82

0.24 5.128 2.77 2.24 1.48 0.44 29.98

0.26 5.219 2.86 2.27 1.51 0.42 27.88

0.28 5.347 2.99 2.34 1.55 0.38 24.35

0.30 5.545 3.19 2.45 1.63 0.30 18.46

0.32 5.598 3.24 2.46 1.63 0.30 18.31



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GRAPH

STANDARD GRAPH

0.00

10.00

20.00

30.00

40.00

50.00

60.00

2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32

p e r c e n t a g e o f b u l k i n g ( % )

Moisture Content ( %)

Graph: Variation of bulking in fine aggregate with increase in moisture content



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COMPARISON WITH STANDARD RESULTS

The curve peaks close to 50 % in volume and when compared to the standard graph we can say it

reflects the behavior of fine sand. The behavior of both of the graph reinforces the theory thatthe bulking increases with the moisture content up to a certain limit.

SOURCE OF ERROR:

1. Improper mixing of sand sample.

2. Evaporation of moisture from the sand sample due to time lag or atmospheric conditions.

3. Addition of incorrect moisture due to Parallax error.

4. Fault in the measuring instruments. 5. Due to some shock or impact forces experienced by the sample during the time of experiment.

PRECAUTIONS:

1. Mixing of the sand sample with water should be done properly.

2. Measurements should be taken carefully.

3. The time gap between the two successive readings should be minimum.

4. Mixing should not be done with hands.

PRACTICAL APPLICATIONS OF THE EXPERIMENT:

Bulking increases the volume of fine aggregates. Cement, sand and concrete must be added in the

right proportions in construction. So Finding Out the bulking in sand is very important since

resulting concrete could be harsh and undersanded if attention is not given to the effects of

bulking.

ass 01bulking

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