Sand Quality Assessment: Silt Content Evaluation

Sand, a crucial construction material, significantly influences the strength of structures like concrete, mortar, and plasters. Ensuring the quality of sand is vital, as impurities such as clay, silt, moisture, and other harmful substances can impact structural strength, potentially leading to rework.

Understanding Sand Particle Size

Quality construction sand typically has particle sizes ranging from 150 microns to 4.75mm. Particles smaller than 150 microns are categorized as silt. Excessive silt content (> 8%) diminishes bonding capacity, affecting the strength and durability of the construction. Therefore, it is recommended to perform silt content tests for every 20m3 of sand.

Test Procedure

Objective:

To determine the silt content in sand.

Apparatus:

• Measuring cylinder (250ml)
• Water
• Sand

Procedure:

1. Prepare a 50ml solution of 1% salt and water in the measuring cylinder to enhance silt settlement time.
2. Add the sand sample to the cylinder until the level reaches 100ml.
3. Add 50ml of the salt and water solution to the measuring cylinder.
4. Seal the cylinder and shake it thoroughly.
5. After 3-4 hours, observe the silt layer settled over the sand.
6. Record the volume (V1) of the silt layer and the volume (V2) of the settled sand.
7. Repeat the procedure for accuracy and calculate the average.

Silt Content Calculation

Percentage of Silt Content=(V1V2)×100Percentage of Silt Content=(V2V1​)×100

For example: If, for a given sand sample, V1 is 9 and V2 is 130, the % silt content would be 6.9%.

Observations

S.no	Description	Sample 1	Sample 2	Sample 3
1	Volume of sample Sand (V2)
2	Volume of silt layer (V1)
3	Percentage of silt
	Average

Maintaining a silt content within the permissible limit of 8% ensures that the sand is suitable for construction purposes. This test aids in making informed decisions about the quality of sand used in construction projects.