Clay and silt is present in the aggregates
in the form of coating or loose form it prevented the development of good bond
between the cement paste and aggregates. Clay is the material of size below
0.002mm and silt varies between 0.002 to 0.061mm on account of their finess and
if present in large quantity more water needed in preparing concrete mix of
required workability. It reduces the strength. In case the silt exceed 3% by
volume it is recommended to wash the sand.
Purpose:
It is necessary to determine the silt and
clay present in sand because it is exceed 3% by volume sand is needed to be
washed and to find suitability of sand to use in concrete mix.
Items Required For Finding Silt Contain In
Sand:
1. 250 ML measuring cylinder
2. Sample of sand
3. Water
Procedure:
In a 250 ml measuring cylinder, pour the
damp sand until it reached the 200 ml mark. Then fill the cylinder with water
and stir the sand well. It will seen that the sand suface is now below its
original level and the silt and clay level form above the sand. Note down the
sand level as v1 smilarly note down the level of silt & clay as v2.
Percentage of silt contain shall be calculated from the formula as below.
Percentage of silt contain = v2/v1 × 100
Where v1 = Volume of sand.
v2 = Volume of silt contain.
