Determining the Moisture Content of Soil and Rock by Mass (Conventional Oven Method) - Soil Properties: Testing, Measurement, and Evaluation - page 43

The actual step-by-step procedure is as follows (ASTM D 2216-05 [1]):

(1) Determine and record the mass of the clean and dry specimen
container and its lid, if used, along with its identification number.

(2) Select representative test specimens in accordance with “Test
Specimen Selection.”

(3) Place the moist test specimen in the container and, if used, set
the lid securely in position. Determine the mass of the container
and moist material using a balance (see No. 2 under the Section
“Test Specimen” and Table 4-1) selected on the basis of the speci-
men mass. Record this value.

Note 2 —To assist in the oven-drying of large test specimens,
they should be placed in containers having a large surface
area (such as pans) and the material broken up into smaller
aggregations.

(4) Remove the lid (if used) and place the container with moist ma-
terial in the drying oven. Dry the specimen to a constant mass.
Maintain the drying oven at 110 5°C unless otherwise specified.
The time required to obtain constant mass will vary depending on
the type of material, size of specimen, oven type and capacity, and
other factors. The influence of these factors generally can be estab-
lished by good judgment and experience with the materials being
tested and the apparatus being used.

(4.1) In most cases, drying a test specimen overnight (about 12 to
16 h) is sufficient, especially for forced draft ovens. In cases where
there is doubt concerning the adequacy of drying to a constant dry
mass, check for additional loss in mass with additional oven drying
over an adequate time period, for minimum time period of two
hours, however, increasing drying time with increasing specimen
mass. A rapid check to see if a relatively large specimen ( than

about 100 g of material) is dry; place a small strip of torn paper on
top of the material while it is in the oven or just upon removal from
the oven, if the paper strip curls the material is not dry. Specimens
of sand may often be dried to constant mass in a period of about 4 h,
when a forced-draft oven is used.

(4.2) Since some dry materials may absorb moisture from drying
specimens, dried specimens shall be removed before placing moist
specimens in the same oven; unless they are being dried overnight.

(5) After the material has dried to constant mass, remove the con-
tainer from the oven (and replace the lid if used). Allow the mate-
rial and container to cool to room temperature or until the
container can be handled comfortably with bare hands and the op-
eration of the balance will not be affected by convection currents