Bulking of Sand: Test and Limit As Per IS Code

Bulking of sand refers to the increase in volume of sand due to the presence of moisture. When dry sand comes into contact with water, a thin film of water forms around the sand particles, causing them to separate. This results in an expansion of the sand volume, known as bulking.

The bulking of sand phenomenon is significant in construction, especially in activities like concrete mix proportioning. Engineers and builders need to account for the bulking factor when determining the correct amount of sand to be used in construction materials.

What Is Bulking of Sand?

Bulking of Sand occurs when sand comes in contact with moisture, which forms a thin layer of water around the sand particle and this thin layer of water exert an outward force on each other which cause the sand particle to move away from each other and ultimately increase the volume of sand.

This phenomenon of the increasing volume of sand due to moisture in the sand is called “Sand Bulking “

Excessive moisture or bulking affects the water-cement ratio and ultimately reduces the strength and durability of concrete. bulking of sand is code: IS 2386-3 if the sand contains 4% moisture, then it will increase sand volume by 25%.

Bulked sand consumes more volume & hence if volumetric measuring is done while proportioning for concrete, bulking correction is necessary.

Moisture Content in Sand	Increase in Volume of Sand
2%	15%
3%	20%
4%	25%
5%	30%

Bulking depends on sand particles’ size. As the smaller the particle size of sand, the volume of bulking increases. Generally, Medium and coarse sand have lower bulking sand.

High bulking result in low quality concrete mix and ultimately reduce the strength of concrete.

Bulking of Sand Test Procedure

The sand is filled, in the loose condition in a box of measured height (H) in cm. The box is then filled with water and rodding is done to make the sand settle and consolidate.

Care should be taken that the sand does not overflow during the flooding and compaction. The sand is then leveled in the box and the drop in height is measured (h) in cm.

Bulking of sand is calculated as,

Bulking of Sand in % = h/H x 100%

Dry sand occupies the same volumes as fully saturated sand. The bulking may differ from load to load and day to day depending on the surface moisture content and fineness of sand.

Therefore, it becomes essential to make bulking corrections by checking the actual bulking of sand proposed to be used by volumetric batching for mortar or concrete.

Sample Calculation

H = 10 cm (Height of Bulked Sand in Container)

h= 2 cm (Height Difference of Saturated Sand & Bulked Sand in Container)

Bulking of Sand (%) = (h/H) x 100

= (2 / 10) x 100

= 20 %

Principle of Bulking of Sand

Bulking of a sand test depends on the fact that the dry volume of sand and saturated volume of sand has almost the same volume.

Therefore in this test sand is filled in a container and water is added to it up to its saturation point. As the sand is saturated in water its volume is reduced and shows the actual volume of sand or dry volume of sand.

By measuring the difference between the volume of sand and saturated volume of sand we can calculate the bulking of sand value.

Significance 

In simple words, it is often said that sand bulking is just the looseness of soil without compacting. Generally, water available in any sand reduces the pores in the sand and compacts the sand.

Sand is employed in concrete for the reduction of segregation and to fill out the pores between cement and coarse aggregates.

for instance, we’d like 1 m3 of sand in concrete, we’d like to understand the approximate sand bulkage value.

If the given sample features a bulkage of 25% then we’d like to require 25% more sand or 1.25 times of the sand while volume batching to urge 1 m3 of sand for concrete.

If we don’t take this extra amount of sand considering the bulkage value, the entire volume is going to be lessened to 75% after adding water. we all know that the standard of concrete depends tons on the right proportioning of the contents.

Generally, we consider the wet volume of concrete is 1.5 times the quantity of dry concrete, during this case, we are typically using approximately 30% of sand bulkage and 20% of wastage.

If we don’t consider the bulkage of sand, the entire quantity is going to be lessened and can impact the general concrete quality.

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