Now, we are going to discuss Silt content test for Sand and how to do the test at the field.
Sand is the inevitable material used in construction because it was using as an ingredient in concrete, plastering and flooring etc.,
Life of the structure depended on the good quality of material which has used for construction.
Purpose of Silt Content Test
The silt is a very fine particle which is less than the size of 150 Microns. Silt content is shrinking and expand due to the weather condition so it will affect the strength of the structure.
Impacts of Silt
- Crack shall be formed on concrete. (You may see some cracks in the wall)
- Silt content is contains evaporated matters and salts. (You may see mortar shall be peeled while plastering)
- It absorbs more water. (Expand & shrink due to the weather condition.
- It will affect bonding between cement and aggregates.
Allowable silt content is 6% or 7%.
So the Silt content test for sand is essential to find out the percentage of silt.
Don’t forget to read Types of Cement!.
Silt Content Test for Sand
Now, do the below-mentioned procedure to do the silt content test at the field.
- Measuring cylinder – 250ml
- Sand – Specimen
- Salt Solution
- The measuring cylinder should be free from moisture and dry.
- Fill the water up to 50 ml with 1% salt solution.
- Then fill the sand into the cylinder up to the level of 100 ml.
- Again add salt solution up to the level of 150 ml.
- Finally, 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.
Why is salt added with sand?
To increase the settlement time of silt which is reduce the testing time. First, Sand will settle then silt content settle at the end.
How to calculate the percentage of Silt?
- V1 = Volume of Silt layer (Silt settled over the sand layer).
- V2 = Volume of the Sand layer (which is settled under the silt).
Percentage of Silt = (V1/V2) x 100
Let us see a small example.
V1 = 15 ml and V2 = 135 ml
Then, % of Silt content = (15/135) x 100
% of Silt = 11%
Silt Test Lab Report
You may interest to learn Slump test of Concrete.
You may interest to learn Bulking Test for Sand.