What is the water content of soil?

The water content of the soil mass is defined as the ratio of the weight of the water present in a given soil mass to the weight of dry soil.

In other words Water content = (weight of water in mass of soil) / (weight of dry soil)

The amount of water is usually expressed in percentage (%).

soil water content
soil water content

How much sample is needed for the test?

The minimum amount of sample required for testing depends mainly on the maximum particle size present in that soil mass. The table below can be used as a reference to determine the minimum weight of a moist soil sample required.

Maximum particle size in soil (mm) Minimum weight of soil sample (g)
0.425 20
2.0 50
4.75 100
10.0 500
19.0 2500

necessary equipment

  • Moisture cans (should be made of heat-resistant material)
  • oven with temperature. Control (105 .)0C to 1100C)
  • Desiccator (used for cooling)
  • Balance (readability of 0.01 g for samples with a mass of 200 g or less and 0.1 g for samples with a mass greater than 200 g.

Standard Testing Procedures to Follow

  1. Determine Weight (g) of Empty Moisture Can Plus Cap (W.)1), and also record the CAN number.
  2. Keep the required amount of moist soil in the can with its cap on to avoid moisture loss.
  3. Determine the combined weight of the can and moist soil (W.)2,
  4. Remove the cap from the top of the can and place it on the bottom of the can.
  5. Put the can with the moist soil sample in the oven for 24 hours.
  6. After the clay mass is completely dry, remove it from the oven and let it cool to room temperature inside the desiccator. Determine the combined weight of the can and its cap along with the dry soil sample (W.)3,

Calculations Involved

Calculate Moisture Weight = W2W3

Calculate mass of dry soil = W3W1

Calculate the quantity (%) of water as given below

W (%) = [(W2-W3)/(W3-W1)]*100

How to report exam result?

At least three samples of the same sample should be tested. The average value of 3 observations should be reported. The water content of the soil is described as two important figures.

Er. Mukesh Kumar

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Er. Mukesh Kumar is Editor in Chief and Co-Funder at Civil Engineering Website. Mukesh Kumar is a Bachelor in Civil Engineering From MIT. He has work experience in Highway Construction, Bridge Construction, Railway Steel Girder work, Under box culvert construction, Retaining wall construction. He was a lecturer in a Engineering college for more than 6 years.