Determination of Bulking of Fine Aggregate

The increase in volume of fine aggregate due to presence of moisture content is known as bulking. Fine sand bulks more as compared to coarse sand. Extremely fine sand particularly the manufactured fine aggregate bulks as much as about 40%.

The moisture present in aggregate forms a film around each particle. These films of moisture exert a force, known as surface tension, on each particle. Due to this surface tension each particles gets away from each other. Because of this no direct contact is possible among individual particles and this causes bulking of the volume.

Note: Fine aggregate do not show any bulking when it is absolutely dry or completely saturated.

AIM:

To determine bulking of a given sample of fine aggregate.

Apparatus:

·         Measuring jar,

·         Taping rod, etc.

FIGURE:

Procedure:

1. Put sufficient quantity of the sand loosely into a container. Level off the top of the sand and pushing a steel rule vertically down through the sand at the middle to the bottom, measure the height. Suppose this is h1 cm.
2. Empty the sand out of the container into another container where none of it will be lost. Half fill the first container with water. Put back about half the sand and rod it with a steel rod, about 6 mm in diameter, so that its volume is reduced to a minimum. Then add the remainder of the sand and rod it in the same way.
3. The percentage of bulking of the sand due to moisture shall be calculated.

CALCULATION:

• Percentage Bulking = [(h1/h2)-1]x100

Conclusion / Result:

• Bulking of a given sample of fine aggregate is found to be ……. %

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