How to check bulking of sand- Field Method

[Srinivasan]

AIM: To ascertain the bulking phenomena of given sample of dry sand.

BULKING FACTOR:
The bulking factor is defined as the ratio of the volume of moist sand to volume of the sand when dry.

BULKING PERCENTAGES:
It is defined as the ratio of increase in volume of moist sand to the volume of sand when dry.

PROCEDURE:

• Take about 200gms of dry sand in a 1 liter jar and find its volume (V1)
• Put the above sand in a mixture pan and add 2% water by weight. Mix it thoroughly to get uniform color.
• Fill this moist sand into the 1 liter cylinder and note down the volume (V2)
• The increase in volume is (V2 -V1) and the percentage of bulking is V2 - V1 ´100 V1
• The bulking factor V2,V1
• Repeat the experiment with different percentages of water i.e., 4,6,8,12,16%
• Plot the graph of bulking factor on Y axis v/s moisture content by percentage of dry mass of sand on X-Axis. This is known as bulking curve.

The field test to find out the percentage of bulking is so simple that this could be conducted in a very short time interval and the percentage of bulking so found out could be employed for correcting the volume of fine aggregate to be used. This can be considered as one of the important methods of field control to produce quality concrete. Since volume batching is not adopted for controlled concrete, the determination of the percentage of moisture content is not normally required. The quality of water could be controlled by visual examination of the mix and by experience. The percentage free moisture content is required to be determined and correction made only when weigh batching is adopted for production of quality concrete.