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Silt Content Test For Sand
Sand, also known as fine aggregate, is a vital construction material and is widely used in construction work. Sand plays an essential role in concrete and mortar; hence it is necessary always to choose the right quality sand for the construction work.
Always check sand for the silt, clay, gravel, moisture, and other harmful materials (coal, Salt, Mica) that can affect structural member strength and generate avoidable rework.
Good quality sand contains particle size between 150 microns to 4.75mm. Particles below 150 microns are termed as silt. It is preferable to perform a silt content test for sand every 20 cubic meters.
Why we measure Silt Content in Sand?
The excessive amount of silt in the sand can be harmful to the strength and durability of the concrete. It is the simple test to find out the silt content in sand.
Fine material less than 150 Micron size found in the sand is called Silt. Excessive quantities of silt in the sand not only reduce bonding between cement and aggregate but also increase water demand, thereby reducing the strength of concrete.
Also, Read – Soundness Test of Cement by Le-chatelier Apparatus
To find out silt content in sand.
- Graduated Measuring Cylindrical Jar
- Pinch of salt
- Sand Specimen
- 100 ml of the measuring jar is filled with sand.
- Water is then poured till it reaches 150 ml of the jar.
- Then a pinch of salt is added.
- The jar has to be shaken vigorously by closing the mouth of the jar with pam and turning it up and down repeatedly.
- The mixture is then allowed to settle down by keeping the jar on a stable and flat surface for about 3 to 4 hour.
- The silt in the sand will settle at the top of the sand in the jar.
- Then note down the volume of silt layer as V1 in ml.
- The note down the volume of the sand layer as V2 in ml.
- Repeat the procedure by taking two more samples and record their value in the observation sheet.
- The average of three readings is taken as the final result.
Percentage of Silt = Volume of silt / Total volume of sample × 100
% of Silt = V1/V2 × 100
|Height of Silt V1
|Height of Sand V2
|% of Silt
Note – The silt content should not be more than 6% by volume with respect to the total volume of the sand.
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