Measuring flask

How to perform a silt content test of sand?

In this test we find out the silt content of sand by volume method. This test does not require any equipment or nor to be perform in laboratory. Simply this test can be performed anywhere as at working site or home.

Simple funda of this test is if we find more silt content, then sand is not acceptable and could be worst for the construction. The less silt content is required and consider the good sand for the construction.

Only one tool required to perform this test is “measuring flask”. If this also not available then transparent glass also can be use.

Measuring flask could be 250 ml or 500ml. Let’s take 250ml and 500ml measuring flask or jar.

First step is taking the sample ensure that minimum 5 places sampling using and mixing up it.

As per IS code 2386 part 3, 50 ml normal water taken into 250ml measuring flask and take 1% NaCl (salt) consider nearly half gram and make a solution of it and mixed it well. Take this solution into 500ml measuring flask.

Now fill the sand up to 100ml in the flask, so we have surface reading occur 100ml in the flask of sand and solutions, because 50ml solution were already there in the flask.

Now again take 50ml solution of water and salt as earlier practiced in 250ml jar and mixed it well. Place this second solution in the 500ml measuring flask and reading will occur 150ml.

Now lock the measuring flask from up side with hand and mixed it well in upside down moment. Make sure any amount of water could not be out from the flask.

Take flask stable for 3 to 4 hours and let make settlement of it.

After the settlement of sand take a note to observe the reading. We will take V1 as sand content in the flask can be shown in the reading. The division of reading is 5ml.

Here V1 comes 95ml and V2 is 10ml (V2 is silt shown in the flask reading)

Now puts the values of V1 and V2 in the formula below.

Percentage of silt= (V2/V1)*100

                               =(10/95)*100

                               =10.52%

Same as take sample 2 and sample 3, then take average of all these three samples and that will be below 8% by volume method, then a sand will be considered as acceptable. If the average is above 8% then silt content in the sand is more and not suitable for the construction.  (Mentioned in CPWD page 17)

In sieve analysis of sand particles less than 150 micron consider as silt. And more silt content in means absorption of water in sand by volume will be increased, so it affects the workability of concrete. Also, Higher silt content is cause of cracks in concrete. It decreases the bonding of concrete ingredient and decreased the strength of concrete. 

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Post Author: hemantduva

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