Testing for silt content in Sand

 

Testing for silt content in Sand

Fine aggregate or Sand is one of the most important construction materials on any construction site. It should be selected very carefully as it contributes to the strength of various important mixtures such as concrete, and mortars. Sand ought to be tested for the presence of soil, silt, moisture, and other harmful materials (salts, coal, mica) that can affect the strength of a structure.

 

  Fine quality construction and has a particle size ranging from about 150 μm to 4.75 mm.

This causes smaller particles to be classified as silt.

The presence of high salt content (> 8%) in the Sand reduces the bonding capacity of the raw material and affects the strength and durability of the work. Silt content testing is recommended for every 20 m3 of Sand.

The Test Procedure

• First, a 50 ml solution of 1% salt and water is prepared in the measuring cylinder. The addition of salt increases the silt disposal time.

• The sample of Sand to be tested is then added to the cylinder until the level reaches 100 ml.

• 50 mL of salt and water solution is again added to the measuring cylinder.

• Close the open end of the measuring cylinder and shake it well.

• After a period of 3-4 hours, you will see a layer of silt settled on the Sand.

• Now pay attention to the volume V1 of the silt layer settled on the Sand.

• Note the volume V2 of the settled Sand.

• Repeat the process a few times to get the average.

   


Percentage of Silt Content = (V1/V2) x 100

V1 – Volume of the silt layer

V2 – Volume of the sand layer

For example, for a given sand sample, if V1 comes out to be 9 and V2 is 130, the % silt content would be 6.9 %.

The permissible value of silt content in Sand is 8%. Hence the sand sample is ok and can be used for construction purposes.

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