What is the allowable Silt Percentage in Sand?

The excessive presence of silt in the sand reduces the bonding between cement and aggregates. It increases water demand for concrete. This reduces the strength of the concrete.

 

It also modifies the setting times of concrete. It can cause cracks in hardened concrete. Hence, silt content is undesirable in the sand. Here is a simple method to find out the silt content in sand.

 

The permissible limit of silt content

The silt content should be less than 8 % by volume.

 

What to do if silt content is more than the allowable limit?

The sand having silt content more than 8 %, should not be used in concrete. However, the sand can be used after washing. It brings the sand content below the permissible limit.

 

Frequency of Testing of silt content

The silt content should be tested daily and once for each truck at the time of unloading at sites.