Silt Content Test of Sand (Fine Aggregates)

AIM

To find-out the silt content in sand (fine aggregates)

Apparatus

Measuring cylinder
1. Measuring cylinder – 250ml
2. Sand  – Specimen
3. Water
4. Salt Solution

Procedure

• The measuring cylinder should be free from moisture and dry.
• Fill the water up to 50 ml with 1% salt solution.
• Then add sand to it until the level reaches 100 ml.
• Again add salt solution up to the level of 150 ml.
• Close the mouth of the cylinder and shake well then keep the cylinder on a flat surface.
• The silt content shall be settled over the sand layer after 2 hours.
• Now note down the silt layer alone volume as V1 ml (settled over the sand)
• Then note down the sand volume (below the silt) as V2 ml
• Repeat the procedure two more times to get the average.

How to calculate the percentage of Silt?

1. V1 = Volume of Silt layer (Silt settled over the sand layer).
2. V2 = Volume of the Sand layer (which is settled under the silt).

Percentage of Silt = (V1/V2) x 100

The permissible Silt content in sand percentage is only 6%.

Report/Observation Table

 S.NO DESCRIPTION SAMPLE NO SAMPLE 1 SAMPLE 2 SAMPLE 3 1 Volume of Sample (V1) ml 2 Volume of Silt (V2) ml 3 Percentage of Silt (V2/V1) x 100 Average

Technical Discussion

Effect of Silt fines on concrete properties:
• Increase in water/cement ratio result to a decrease in the compressive strength of concrete
• The increase in sand fines content has also been found to decrease the compressive and tensile strengths of concrete
• Inadequate sand fine content also has adverse effect of the strength of concrete due to poor adhesion
• The decrease in slump value as a result of increase in fines percentage in sand can be attributed to the fact that finer particles have larger surface area which absorbs more water in concrete mix.