Silt content in sand refers to the proportion of fine particles of silt (typically smaller than 75 microns) present in a sample of sand.
Silt is a type of sedimentary material that can be found in natural sand deposits, and it can affect the quality of sand used in construction.
High levels of silt content in the sand can reduce its strength, cohesion, and permeability, making it less suitable for use in certain types of construction projects. Testing for silt content in the sand is important to ensure that it meets industry standards and requirements, and to prevent potential issues that may arise during construction.
The permissible silt content in the sand must not exceed the values as specified in the IS standards. This methodology is only applicable to natural sand; it should not be used for crushed rock sand.
A good quality generally has a particle size between 150 microns to 4.75 mm sieve size and if the particle size in the sand is less than this size, it is known as silt in the sand.
If silt content in sand exceeds more than 8% that may result in a reduction in the binding capacity of mixed materials, and also affect the strength and durability of the final product.
IS Code for Silt Content Test of Sand: IS 2386-2 (1963)
Silt Content In Sand Limit
Silt content in the sand must not exceed 8% as per IS 2386-2. If the silt content on sand exceeds 8 % that may result in a reduction in the binding capacity of mixed materials, which also affects the strength and durability of the final product.
Silt Content Test
- 250 ml glass measuring cylinder
Silt Content Test of Sand Procedure
- The measuring cylinder is filled with the salt-water solution (the concentration of the solution will be a teaspoon full of common salt for every 570 ml) up to the 50 ml mark on the cylinder.
- Add sand until the level of the sand is reached the 100 ml mark.
- Add further salt-water solution till the 150 ml mark is reached.
- Place the palm on the mouth of the glass cylinder and shake it vigorously.
- Place the measuring cylinder on a hard leveled surface and tap it all around so that the sand is leveled.
- Wait for three hours for the silt to settle on top of the sand.
- Measure the thickness of the silt layer and the height of the sand.
DETERMINATION OF SILT CONTENT
|Sr. No:||Description||Sample – 1||Sample – 2|
|1||The thickness of the Sand Layer|
|2||Height of Sand + Silt|
If silt content is exceeding 3% by weight, then the washing of sand is necessary. After performing a few tests, a co-relation can be developed for silt layer thicknesses at various intervals of time. The silt content after a time interval of 10 minutes can be fixed as inspection criteria.
If the following observations are taken from the silt content of the sand test,
- Silt Layer Thickness = 1 cm
- Sand + Silt Layer Height or Thickness = 10 cm
- Silt Content of Sand = (1 cm / 10 cm) x 100 %
- Silt Content of Sand = 1%
So, from the above Test and calculations, we can say that this sand has a 1% silt content.
The silt content limit in the sand as per IS code is 8%, so this sand we can use this for construction purposes.
Watch Video: Silt Content of Sand Determination
In conclusion, the determination of silt content in sand is a vital test for assessing sand quality in construction projects, excessive silt content can negatively impact the strength, workability and durability of concrete and mortar.
The test procedure involves collecting a representative sample, drying, washing sieving, and weighing the silt particles, the silt content is calculated as a percentage, the Indian Standards Institute(ISI) recommends the use of IS: 2386(part1)-1953 code for conducting the test.
Adhering to this code ensures standardized testing and accurate results.
By controlling the silt content within permissible limits, engineers can ensure the overall quality and performance of concrete and mortar structures, the silt content test, supported by the IS code recommendation, enables informed decision- making and helps maintain the integrity of construction projects.
What is the silt content in sand?
The silt content in sand refers to the percentage of fine particles, particularly silt-sized particles, present in a given sample of sand. Silt particles are smaller than sand particles and larger than clay particles.
Why is it important to determine the silt content in sand?
Determining the silt content in sand is crucial because excessive silt content can adversely affect the properties and performance of sand in construction applications. High silt content can reduce the strength, increase shrinkage, and impair the workability of concrete and mortar.
What is the recommended standard for conducting the silt content test?
In India, the Indian Standard (IS) code IS:2386 (Part 1) – 1963 provides guidelines for the determination of silt content in aggregates, including sand. This code specifies the procedure for conducting the silt content test.
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