To determine the Bulking of Sand

To determine the Bulking of Sand.

IMPORTANCE OF BULKING OF SAND:

INTRODUCTION

The volume of fine aggregate is affected largely by its moisture content. When the fine aggregate is most each particle gets coated with a film of water the particles are kept separated and hence the volume increases. This apparent increase in the volume of sand disturbs the volume batching, which in terms disturbs the proposed mix design. This test is intended to determine the amount of bulking and different moisture contents so that the volume can be adjusted accordingly.

MATERIALS REQUIRED:

• Matching cylinder, bowl.

APPARATUS REQUIRED:

• Meter Scale

THEORY:

Bulking of sand: It is defined as the increase in the volume of the sand when the sand catches a small amount of water. Sand when wet or moist shows more volume than in dry form. Thus, if a certain volume of dry sand is made moist by adding water, it will show an increase in volume. This is the fact that water forms a film around each sand particle, thereby causing an increase in volume. This phenomenon is called the “Bulking of Sand”. It is of importance because certain fixed proportions of dry sand are to be mixed for making mortars of different specifications necessary allowance is, therefore, to be kept for wet sand.
However, the increase in volume for a certain percentage of moisture varies with the grade gain size of sand, in general. It is found that 5 to 8 percent moisture causes 20 to 40 percent volume increase. As the volume of sand increases with the increase in moisture, a stage comes when with any further increase in moisture content the volume suddenly falls back to its original volume in dry form.

Procedure.

1. Take a dry sample of fine aggregate (sand) which is put into a measuring cylinder.
2. The reading of dry sand in the measuring cylinder is then that sample of sand is taken in a bowl add a few drops of water and mix them then this wet sand is again.
3. Put into the matching cylinder and you will observe there is an increase in the volume of sand.
4. Now we have to determine the bulking % of sand there is

The volume of dry sand in matching cylinder =V1=

Mixing of the water volume of sand=

Bulking %=((Bulking volume – Dry volume) / Dry Volume ) * 100

Bulking %=

Pre-Cautions:

1. Water filled in the measuring cylinder should be able to submerge the whole sand.
2. Sand should be stirred well so that all the voids are expelled.
3. The experiment should be performed away from shocks and vibrations.
4. Readings should be carefully taken.

Results:

Bulking % of sand is =

Review Questions

1. What is the bulking of sand?
2. State the limits of the bulking of sand.