Lesson 4/Learning Event 1
Experienced engineers can judge moisture content by field examination. The best and most accurate
method uses an oven with temperature control. If time is not a consideration, the soil may be air-dried
in the sun. Under expedient conditions, the soil sample may be dried in a frying pan or container heated
by an external source. Because organic material may be burned off by high temperatures an error may
result.
Another expedient method is to saturate the soil sample in alcohol and to burn the alcohol off. However,
this procedure must be done carefully and repeated several times to achieve the best results. Also, the
speedy moisture tester, a component of the soil test set, can be used. The speedy moisture test is the
preferred method for field determination. It is the test most often used in the field.
TEST PROCEDURE FOR THE OVEN OR ALCOHOL METHOD
Record identifying information of the sample on a data sheet (DD Form 1205).
Weigh and record the weights of the containers to be used in the test.
Place the sample in a container, weigh it, and record the total weight of the container (tare) and
wet soil. If the weight of the sample is less than 100 grams, weigh it to the nearest 0.1 grams,
otherwise the weight should be to the nearest 1.0 gram.
Place the open container and sample in an oven heated to 110, ƒ5,C and dry until the sample
weight becomes constant. This will require 8 to 12 hours.
Remove the container from the oven and place it in the desiccator to cool. If the container is too
large for the desiccator, allow the sample to cool to room temperature in the open air.
After the sample has cooled, weigh it and the container and record the weight (tare and dry soil)
on the data sheet.
Calculations. The moisture content (in percent) is equal to:
EXAMPLE:
A pan weighing 44 grams was used to contain a sample of soil for determination of its moisture content.
The total weight, including the pan, was 189.39
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