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 sand silt content test for every 20 Cum of 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, 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 SandSand 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 SandSand.
Induction of Silt Content
The sand brought to a building site or other works may contain an amount of moisture, which can influence the silt content of sand, 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.
Object
A measuring cylinder (250 ml)
Water
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 SandSand 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 SandSand.
- Now pay attention to the volume V1 of the silt layer settled on the SandSand.
- Note the volume V2 of the settled SandSand.
- Repeat the process a few times to get the average.
Measurement Cylindrical Jar
Percentage of Silt Content Formula = (V1/V2) x 100
V1 – Volume of the silt layer
V2 – Volume of the sand layer
For instance, using the silt content in sand formula, 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 silt content in sand is 8%. Hence the sand sample is ok and can be used for construction purposes.
Observation table
| 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 | |||
| Average | ||||
Frequently Asked Questions (FAQ) on Measuring Silt Content in Sand
Why is it important to measure the silt content in sand?
Measuring the silt content in sand is crucial because excessive silt can weaken the strength of concrete and mortar, reducing the durability of the structure. Silt is unstable in the presence of water and can cause bonding issues in construction materials.
How does silt content affect construction quality?
High silt content reduces the bonding of fine and concrete aggregates, affecting the strength and durability of the construction. It can lead to issues like peeling off plaster and rework.
What is considered a high silt content in sand?
Silt content exceeding 8% is considered high and can negatively impact the bonding capacity and strength of construction materials.
How often should silt content be tested?
Silt content in sand should be tested for every 20 cubic meters (20 m³) of sand delivered to the construction site.
What equipment is needed to test silt content in sand?
The equipment needed includes a 250 ml measuring cylinder, water, and the sand sample to be tested.
What is the procedure for testing silt content in sand?
- Prepare a 50 ml solution of 1% salt and water in a measuring cylinder.
- Add sand to the cylinder until the level reaches 100 ml.
- Add another 50 ml of the salt and water solution to the cylinder.
- Shake the cylinder well and let it sit for 3-4 hours.
- Measure the volume of the silt layer (V1) and the volume of the sand layer (V2).
- Repeat the process to get an average measurement.
How do you calculate the percentage of silt content in sand?
The percentage of silt content is calculated using the formula: Percentage of Silt Content=(V1V2)×100\text{Percentage of Silt Content} = \left( \frac{V1}{V2} \right) \times 100 where V1 is the volume of the silt layer, and V2 is the volume of the sand layer.
What is the permissible silt content in sand for construction purposes?
The permissible silt content in sand is up to 8%. If the silt content exceeds this limit, the sand is not suitable for construction purposes.
What are the consequences of using sand with high silt content?
Using sand with high silt content can lead to weaker concrete and mortar, resulting in structural issues such as poor bonding, reduced strength, and increased maintenance and rework costs.
