What is Bulking of sand?

The bulking of sand occurs due to the presence of moisture around the sand particles. Moisture creates a fine layer around these particles, increasing the sand’s volume. For moisture content between 5 to 8%, the volume of sand can increase by approximately 20 to 40%. This increase is based on the sand’s grade. Finer sand tends to absorb more moisture, resulting in a higher increase in volume. Conversely, coarser sand absorbs less moisture, resulting in a smaller volume increase.

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The bulking of sand refers to the increase in volume of sand particles due to an increase in moisture content. When water content increases, sand particles tend to pack closer to each other, reducing the amount of bulking in the sand. This phenomenon significantly affects the volumetric proportioning of sand.

Bulking is more pronounced in fine sand than in coarse sand. If proper allowance is not made for the bulking of sand, it can lead to increased concrete costs. The resulting under-sanded mixes can be challenging to work with and place due to their harsh texture.

Note: From the above definition, we learned

The amount of sand significantly impacts the volume ratio in construction. It is more pronounced in fine sand and less pronounced in coarse sand.

Why Bulking of sand is important in concrete construction?

To Ensure Accurate Mix Proportion: When utilizing fine sand in construction, bulking may occur, causing an increase in sand volume. Understanding and accounting for bulking are crucial to obtain precise measurements and determine the correct sand quantity. This ensures an accurate concrete mix.

Structural Integrity: The correct proportion is Very important as per the design consideration. If the sand quantity does not align with the design requirements, neglecting bulking can lead to improper mixing. This can significantly impact the strength and durability of the concrete.

The correct proportion of ingredients including sand is essential for the strength and integrity of the concrete structure. Ignoring bulking can result in improper mixing, which can affect the strength and durability of the concrete.

Quality Assurance: Accurate material proportions help ensure the quality of concrete. Considering bulking helps achieve the desired properties of the final concrete, thereby ensuring its reliability.

Workability: Precise sand quantity leads to better workability of the concrete mix, allowing easy placement, consolidation and finishing during construction.

Construction Cost: Proper mix ratio reduces the risk of excessive material wastage, ensuring optimal resource utilization and cost-effectiveness in construction projects.

Effect on different grades: From low to high grades of concrete (such as M25 and beyond), consideration of bulking is fundamental as it directly affects the accuracy of material proportions in any concrete mix.

What Are the Procedure to calculate heave of sand due to moisture?

step 1:

Sample Preparation: Fill a container with sand until it is about two-thirds full. Level the top of the sand and use a steel ruler to measure the height (H).

Step 2:

Bulking test: Transfer the sand to another container, and fill the first container halfway with water. Return half of the sand and compact it using a 6 mm steel rod. Measure the depth at the centre of the moist sand (h1).

Calculation of bulking percentage: The percentage of sand bulking due to moisture can be calculated using the formula:

Bulking Percentage =(h2/h1​−1) × 100

In the measuring cylinder

Step 3:

Pour the collected wet sand by stirring into the measuring cylinder until it reaches a certain mark (mL). Fill the cylinder with water, making sure the sand is completely submerged. The surface of submerged sand may settle below the original level (at the mark marked ‘y ‘).

Calculation: The percentage of sand clumping due to moisture can be calculated using the formula:

Bulking of sand = (200-160/160) × 100 = 25%

Reporting

Step 4:

Report the percentage of sand piled to the nearest whole number based on the calculated values obtained.

This process helps measure the amount of sand lost due to moisture, allowing for a more accurate estimate of construction materials.