Experiment No.

Department of Civil Engineering

Supreme Knowledge Foundation Group of Institutions Page.-

NAME OF THE EXPERIMENT: BULKING OF FINE AGGREGATES

AIM: To ascertain the bulking phenomena of given sample of sand for varying percentage of

moisture content.

THEORY: The moisture content in the sand will cause the bulking of the volume. Moisture

forms a film around each particle and this film of moisture exerts surface tension which

keeps the neighbouring particles away from it. Therefore, when no point contact is possible

between the particles, this causes bulking of sand. Thus increase in volume of sand due to

presence of moisture is known as bulking of sand. When more water is added sand particles

get submerged and volume again becomes equal to dry volume of sand. Maximum increase

in volume may be 20% to 40% when moisture content is 5% to 10% by weight. Fine sands

show greater percentage of bulking than coarse sands with equal percentage of moisture.

APPARATUS USED: Sample of moist sand, graduated cylinder, clean water, stirrer, tray and

scoop.

PROCEDURE: 1) Take 1000 ml measuring cylinder.

2) Fill it with loose dry sand up to 500ml without tamping at any stage of

filling.

3) Then pour that sand on a pan and mix it thoroughly with water whose

volume is equal to 2% of that of dry loose sand.

4) Fill the wet loose sand in the container, consolidate by shaking and find

the volume of the sand which is in excess of the dry volume of the sand.

5) Level the surface and read the volume in ml (Y1).

6) Repeat the procedure for moisture content of 4%, 6%, 8%, etc. and note

down the corresponding volume of sand (Y2, Y3..).

7) Continue the procedure till the sand gets completely saturated i.e. till it

reaches the original volume of 500ml.

OBSERVATIONS:

Sl. No

Volume of dry loose sand Y1

(ml)

% moisture content added

Volume of wet loose sand Y2

(ml)

% Bulking

=

100%

1 500 2%

2 4%

3 6%

4 8%

5 10%

6 12%

Experiment No.

Department of Civil Engineering

Supreme Knowledge Foundation Group of Institutions Page.-

GRAPH: Draw a graph between % moisture content on X-axis and % bulking on Y-axis. The

points on the graph should be linked as a smooth curve. Then from the graph, maximum

percentage of bulking and the corresponding moisture content is determined.

PRECAUTIONS: 1) While mixing water with sand grains, mixing should be uniform.

2) The sample should not be compressed while being filled in jar.

3) The sample must be slowly and gradually poured into measuring

jar from its top.

4) Increase in volume of sand due to bulking should be measured

accurately.

RESULT: The maximum bulking of the given sand is ________________ at _______________% of

moisture content.

CONCLUSIONS: The bulking of the volume depends on the extent of surface tension and

consequently how far the adjacent particles are kept away which in turn depends upon the

percentage of moisture content and the particle size of the fine aggregate. It is interesting to

note that the bulking increases with the increase in moisture content up to a certain limit

and beyond that the further increase in the moisture content results in the decrease in the

volume and at a moisture content representing saturation point, the fine aggregate shows

no bulking. Due to the bulking, fine aggregate shows completely idealistic volume.

Therefore, it is absolutely necessary that consideration must be given to the effect of

bulking in proportioning the concrete by volume. If the effect of bulking is overlooked, in

case of volume batching, the resulting concrete is likely to be under-sanded and harsh. It

will also affect the yield of concrete for the given cement content.