How to Test Moisture Content of Soil

Moisture content (or water content) of soils measurement, both in the natural state and under defined test conditions could offer us an extremely useful information of classifying cohesive soils and of assessing their engineering properties. The moisture content of a soil is the characteristic which is most frequently determined, and applies to all types of soil.

The standard method for determining moisture content of soils is the oven-drying method, and it is the procedure recommended for soil laboratory testing. The technical standards that commonly used for testing in construction are BS1337: Part 2 1990 and ASTM D2216. It depends on contract specification upon the method to be used and I normally used the British Standards, but the procedures are mostly similar for both standards.

Water content of soil is defined as:

Test Method as accordance to BS1337: Part 2 1990;

Test Apparatus

Apparatus: Sample container, Electronic Balance and Oven-Dry

Basically only three apparatus required:

• Sample container(s) for putting soil samples.
• Electronic balance (readable until 0.01g) for sample weighing.
• Thermostatically controlled drying oven, maintained temperature at 105 to 110^oC.

Test Procedures

1. Weigh the container (an empty one) and record the weight – label as M1.
2. Select the soil sample for testing and put it in the container.
3. Weigh the soil together with the container, and record the weight again – label as M2.
4. Then put it in the oven and turn it on for drying for 24 hours to obtain a constant weight of dry soil sample.
5. Lastly weigh the dry samples (plus container) and record the last reading – label as M3.

The Calculations

• Mass of empty container           = M1
• Mass of wet soil + container     = M2
• Mass of dry soil + container     = M3
• Mass of moisture loss in soil     = M2 – M3
• Mass of dry soil                              = M3 – M1

Moisture content,

The Result Sheet
An example of test results:

Example of calculation, taking the container no. A1:
w = [(52.68 - 47.17) / (47.17 - 15.53)] x 100 % = 17.41 %
Average = (17.42 + 18.59 + 17.68) / 3 = 17.89 % of moisture content
Reported moisture content = 18 %

Things to Remember

• The soil samples took from the selected burrow pits or location should be test for its moisture content.
• Make sure to use dry container before putting the sample and enough for testing.
• Make sure the balance have an adequate battery for a long run (if lots of soil sample to be test).
• The oven-dry and the balance calibration certificate still valid (haven’t due yet) for an accurate results.

An Additional Info
The approximate mass of soil sample required for each main sample:

• Homogeneous clays and silts = 30 g (weigh to 0.01 g)
• Medium-grained soils = 300 g (weigh to 0.1 g)
• Coarse-grained (stony) soils = 3,000 g or 3 kg (weigh to 1 g)

Typical values of water content in a Saturated State:

• Loose uniform sand = 25 to 30 %
• Dense uniform sand = 12 to 16 %
• Loose angular-grained silty sand = 25 %
• Dense angular-grained silty sand = 15 %
• Stiff clay = 20 %
• Soft clay = 30 to 50 %
• Soft organic clay = 80 to 130 %
• Glacial till = 10 %

And that’s all about testing of soil moisture content pretty simple test that we could run. This is the first test that shall be conduct first upon the ‘fresh’ soil samples obtained from the site. There are other kinds of test but this is the most popular ones. Happy testing…

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• Phase Relationships of Soil
• Particle Distribution for Soil Test
• 7 Info You Should Know About Soil.
• Introductory to Laboratory Testing of Soil

Tagged as: Soil and Testing

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