Silt Content Test as per IS Code

Silt Content Test as per IS Code 

Take a little sand and rub the same in hand, if palm remain clean it can be assumed that sand is free of silt that called is silt content test . It is hand test.

Frequency of testing 

Every 20cum or more frequency as decided by engineer in charge 

Permissible limit 

Acceptance standard -maximum permissible limit silt content shall not be "more than 8%" as per is code 383 and as per CPWD specification 

Note: (i) If silt content is more, corrective action taken should be noted in column 10 and silt content referred after such action  and recorded in the register.

            (i) Fine aggregate contenting more silt than allowable percentage shall be washed so that the silt contents are with in prescribed limit for which nothing shall be paid 

Test for silt content 

The method for determining silt contents is as follows:

   A sample of sand to be tested shall be placed with out drying in a 200 ml measuring cylinder the volume of sample shall be such that it fills the cylinder up to 100 ml marks. clear water shall be added up to 150 ml marks. Dissolved a little salt in the water in proportion one tea spoon to half a litter. The maximum shall be shaken vigorously, the last few shakes side wise direction to level of the sand and contents allowed to settle for three hours. 

The height of the silt visible as settled layer above the sand shall be expressed as a percentage of the height of sand bellow 

Measurement percentage of silt content  

Formula : 

  1. volume of silt = (V1-V2)
  2.  Percentage of silt = ((V1-V2)/V2) X100

Where V1= volume of sand +silt ml

              V2= Volume of sand 

Example or maintain of register 

  1. Initial volume of sand (in ml)=200
  2. Volume of sand + silt (in ml) V1= 190
  3. Volume of sand (in ml) V2 = 180
  4. Volume of silt (in ml)= (190-180)=10
  5. Percentage of silt =5.555%
  6. As per IS code maximum permissible limit < 8%
Frequency of silt test per 20 cum Sand 1 test 


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