Sand silt Content Test (IS 2386 Part II)

Sand silt Content Test (IS 2386 Part II)

Purpose :

In order to find out the proportion of silt (fine dust and clay crown) in natural sand. This may cause concrete to be weakened by excessive silt which causes weakening in the attaching of cement and the aggregates.

Apparatus :

• Measuring cylinder /graduate jar 250 ml
• Water (clean tap water)
• A 1 percent salt (common salt) or sodium chloride solution (to facilitate sedimentation)
• fine aggregate ( Dry Sand sample)
• Stopwatch or a timer

Test Procedure :

• Sample up:

            dry sand up to mark 100ml in the measuring cylinder.

• Add salt solution:

            To the 150 ml line, add 1% solution of salt water.

• Shake Well:

            Put the lid on the top and shake the cylinder hard with about 2 minutes to make sure that the silt is well mixed.

• Let them settle:

            Leave the cylinder at rest with 2 hours. In the process, the silt will rest over the sand cover.

• Determine the Depth of the Layer of Silt:

            At the end of 2 hours,

            Hs: Silt layer:

            H: Sand layer:

Calculation :

Silt content (%) = ( H s / H ) X 100

Where:

Hs = Silt height layer (in mm)

H = Sand layer height (in mm)

Acceptable Limits:

Max. Silt Content

• PCC 5%
• Reinforced Cement Concrete (RCC) 3%

Where the silt percentage is above the limit, the sand is supposed to be washed or replaced.

Example:

Height of sand layer = 100mm

The height of the silt layer = 3 mm

Silt content=(3/100)×100=3%

Result: suitable for RCC

notes;

• Dry sand should always be tested to prevent mistakes.
• Accept silt quicker by applying salt solution.
• Conduct the test every stockpile or batch or once at least.