Water Content of Soil by Oven Drying Method

The Oven Drying Method is a standard laboratory technique used to determine the water content of soil. This involves heating a moist soil sample in an oven at 105°C–110°C for 24 hours until all moisture evaporates. By comparing the weight of the wet and dry soil, the moisture content is calculated. This method provides highly accurate results and is essential for soil analysis in geotechnical and construction engineering projects.

OBJECTIVE – Water Content of Soil by Oven Drying Method

To determine the water content (moisture content) of a given soil sample using the Oven Drying Method as per IS: 2720 (Part II) – 1973.

NEED AND SCOPE OF THE EXPERIMENT

Need:

Accurate water content determination is crucial in all phases of geotechnical engineering such as: Compaction, Shear strength, Consolidation,Bearing capacity analysis.

Scope:

• The oven drying method provides a standard and most reliable technique for water content determination.
• Applicable for both field and laboratory testing of coarse-grained and fine-grained soils.
• It serves as a reference method for validating rapid field moisture tests.

DEFINITION

Water Content (w): The ratio of the weight of water to the weight of dry soil, expressed as a percentage.

w = (Ww/Wd)×100

Where:

Ww​ = Weight of water = W2−W3

Wd​ = Weight of dry soil = W3−W1

W1​ = Weight of empty container

W2 = Weight of container + moist soil

W3​ = Weight of container + dry soil

APPARATUS REQUIRED

1. Oven – Maintains a temperature of 105°C to 110°C
2. Non-corrodible airtight containers – With lid and marked ID
3. Balance – Accuracy of 0.01g
4. Desiccator – To cool the dry sample
5. Tongs or gloves – For handling hot containers
6. Sample soil – Collected as per IS code

PROCEDURE

Weigh the Empty Container (W₁):
Take a clean, dry, labeled container and weigh it with the lid.

Add Moist Soil Sample (W₂):
Put a representative moist soil sample (20–30g for fine soil) into the container and weigh again.

Add Moist Soil Sample (W₂):
Put a representative moist soil sample (20–30g for fine soil) into the container and weigh again.

Dry the Soil in Oven:
Place the container (with lid removed) in an oven at 105°C–110°C for 24 hours.

Cool in Desiccator:
Remove the container from the oven, place the lid, and let it cool in a desiccator for 30–45 minutes.

Weigh the Dry Sample (W₃):
After cooling, weigh the container with dried soil and lid.

Repeatability Check:
Conduct the test on 3 specimens, and ensure variation is within ±1%.

• Also Read: Specific Gravity of Cement by Specific Gravity Bottle

OBSERVATIONS AND RECORDING

S. No.	Description	Weight (g)
1	Weight of empty container (W₁)	…
2	Weight of container + wet soil (W₂)	…
3	Weight of container + dry soil (W₃)	…
4	Water content (%)	… %

Water Content (w)= [(W2​−W3​)/(W3​−W1​)]​×100

RESULT

The water content of the given soil sample is: w = …………… %

GENERAL REMARKS

The Oven Drying Method is considered the most accurate for determining water content but is time-consuming.

Not suitable for soils with organic matter or gypsum, as oxidation or loss of crystal water may occur.

For coarse-grained soil, oven drying is quicker, while for fine clayey soils, ensure sufficient drying to constant weight.

In case of field limitations, Rapid Moisture Meter can be used, but must be validated with oven-dried results.

• Also Read: Water Content Determination of Soil by Different Methods