Bulking of sand

BULKING OF SAND

Ref : IS 2386-3: 1963 - Methods of test for aggregates for concrete, Part 3 http://www.iitk.ac.in/ce/test/IS-codes/is.2386.3.1963.pdf

BULKING OF SAND

The increase in the volume of sand due to increase in moisture content is known as bulking of sand. A film of water is created around the sand particles which forces the particles to get a side from each other and thus the volume is increased.

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 cognisance is not given to the effect of bulking, 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 given cement content. To compensate the bulking effect extra sand is added in the concrete so that the ratio of coarse to fine aggregates will not change from the specified value. 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: Beaker, 1000ml measuring jar, brush, scale, mixing tray.

Material: Fine aggregate, water.

Procedure:

1. Put sufficient quantity of dry sand into the beaker until it is about one-thirds full.

2. Level off the top of the sand and measure the height (H₁) by pushing a steel rule vertically down through the sand at the middle to the bottom. Measure weight of the sand.

3. Add 2% of water; mix it thoroughly in the container. Smooth and level the top surface measure the height (H₂) of soil. Find the height percentage increment.

4. Repeat the same procedure with increasing amount of water by 2% until percentage increment of sand height is reduced and attends original level.

5. Plot a graph of percentage increment of sand height against percentage of water.

Observations:

Initial Height of sand in the Jar (H1) : _______ mm

Weight of fine aggregate : ________ g

                                                        Typical Curve Showing Bulking of Sand

Table 1: Observation Sheet

Sl. No.	% of Water	Volume of water (in ml)	Height of sand (H2)	Bulking = {(H2-H1)/H1}x100
1
2
3
4
5