Why We Measure the Silt Content from the Sand?
Silt content is a fine material that’s less than 150 microns. It’s unstable in the presence of water. It’s unstable in the presence of water. If we utilize silty sand for bonding, it will reduce the strength and cause rework.
You could be experienced this while plastering for a roof where the mason tries to plaster the mortar where it gets continually peel off. The excessive quantity of silt, not only reduces the bonding of fine and concrete aggregates but also affects the strength and durability of work.
You may check out this article for silt and clay properties. In the field, we have to conduct a silt test for every 20 Cum of sand. This may vary.
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, ointments, 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 and cause avoidable reorientation. 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 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 Sand.
Induction of Silt Content
The sand caused to a building site or other works may contain an amount of moisture, which will cause it, when loosely filled to a container, to occupy a large volume than it would occupy if dry.
If the sand is measured by loose volume, it’s necessary in such a case to increase the measured volume of the sand, so that the amount of sand put to the concrete might be the amount intended for the nominal mix used (based on dry sand).
It’ll be necessary to increase the volume of sand from the ‘percentage’ bulking. The correction to be made is only a rough approximation since the system of measurement by loose volume is a rough method at best.
However, the correction of the right order can easily be determined and must be applied in order to keep the concrete uniform.
Apparatus for Silt Content in Sand
- A measuring cylinder (250 ml)
Test Procedure of Silt Content in Sand
- 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 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 Sand.
- Now pay attention to the volume V1 of the silt layer settled on the Sand Sand.
- Note the volume V2 of the settled Sand 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.
Observation Table For Silt Content in Sand
|Sr.no||Description||Sample 1||Sample 2||Sample 3|
|1||Volume of silt layer (V1)|
|2||Volume of sample Sand (V2)|
|3||Percentage of silt|