ATT-15, Part I
1.0 Scope
ATT-15/96, MOISTURE CONTENT, Oven Method
Part I, Soil and Gravel
1.0
SCOPE
This method describes the procedures for determining the moisture content of soils
and aggregates using a field laboratory oven.
2.0
EQUIPMENT
oven
electronic balance
plastic pails
plastic bags with twist ties
drying pans
bread pans or pie plates
wash basin
teri-cord gloves
Data Sheet: Moisture Content, MAT 6-24
3.0
PROCEDURE
3.1
Soil
1.
Obtain approximately 1 kg of representative soil and seal it in a pail or plastic
bag.
2.
Complete the Heading and Sample Identification portions of the data sheet.
An example is illustrated in Figure 1.
3.
Label a bread pan or pie plate and record as Container No.
4.
Weigh the pan and record as Tare (line "C").
5.
Dump the contents of the pail or plastic bag into a wash basin.
6.
Break up the soil in the wash basin so that there are no lumps larger than 15
mm in diameter.
7.
Place in the bread pan or pie plate approximately 400 g of soil obtained
randomly throughout the wash basin.
8.
Spread the sample evenly over the bottom of the pan.
9.
Weigh the pan and its contents immediately and record as Wt. of Wet
Sample + Tare (line "A").
10.
Place the container and sample in the oven set at 110oC ± 5oC.
11.
Dry the sample to a constant weight. To verify, after a couple of hours of
drying, weigh the sample. Replace the sample in the oven for approximately
one hour and re-weigh. Continue drying and weighing each hour until two
consecutive weights are the same.
ATT-15, Part I
3.2 Aggregate
FIGURE 1
12.
Weigh the hot sample. Record as Wt. of Dry Sample + Tare (line "B").
13.
Calculate the Weight of Water removed (line "D") as follows:
Wt. of Water (g) = Wt. of Wet Sample and Tare - Wt. of Dry Sample and Tare
14.
Determine the Weight of Dry Sample (line "E") as follows:
Wt. of Dry Soil (g) = Wt. of Dry Sample and Tare - Wt. of Tare
15.
Calculate the Moisture Content in percent (line "E") of the sample using the
formula:
Moisture Content (%) '
Wt. of Water
× 100%
Wt. of Dry Soil
3.2
Aggregate
1.
Complete the Heading and Sample Identification portions of the data sheet.
2.
Label a drying pan and record as Container No. as shown in Figure 2.
3.
Weigh the pan and record as Tare (line "C").
4.
Obtain a representative sample of aggregate as directed in ATT-38,
SAMPLING, Gravel and Sand.
5.
At the field laboratory, empty the contents of the paid into a mixing pan and
mix thoroughly.
6.
Place approximately 3 000 g of the aggregate in the tared drying pan and
weigh.
ATT-15, Part I
4.0 Hints and Precautions
FIGURE 2
7.
Record as Wt. of Wet Sample + Tare (line "A").
8.
Place the drying pan and contents into the oven set at 110oC ± 5oC and dry
the sample to a constant weight.
9.
Calculate moisture content of the aggregate (line "E") by repeating steps 11
to 15 of Section 3.1.
4.0
HINTS AND PRECAUTIONS
1.
Ensure that soil samples are between 350 to 400 g. Larger samples take too
long to dry, while smaller samples lead to inaccurate results.
2.
Ensure that the oven temperature is maintained at 110oC ± 5oC. Do not allow
the oven door to stay open for too long, as it takes a while for the oven to
regain the drying temperature.
3.
Do not put moist samples in the oven on a shelf below dry samples. Moist
samples should be placed on the top shelf and all partially dried samples
placed on the lower shelf.
4.
Do not over-load the oven, as this will create a much longer drying time.
5.
Do not allow dried samples to pick up moisture after they are removed from
the oven. Weigh them immediately after drying.
6.
Keep the laboratory benches clean so that spilled samples can be readily
noticed and retrieved.
7.
Use gloves or tongs when handling hot samples.