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4.0 ACCURACY
When testing soils, it is recommended that the procedures in ASTM D4944, Standard Test Method for
Field Determination of Water (Moisture) Content of Soil by the Calcium Carbide Gas Pressure Tester
Method be followed. This will ensure accurate and reliable results. For optimum accuracy with most
materials, the Aqua-Check results should be correlated with oven-dry tests for each material as shown
in this summary. This simple procedure is outlined in detail in D4944.
1. Select several samples of the material to be tested having a wide range of water content.
2. Carefully divide each sample into two representative specimens.
3. Taking care to not lose moisture during handling, run a test on one specimen in the Aqua-Check, and
record the gauge reading. Oven dry the other specimen according to the procedure and calculate the
percent moisture.
4. Plot the oven-dry moisture on a graph vs. the gauge readings and draw a best-fit curve through the
points. A wide scatter in the points may indicate operation errors or that the material is not suitable
for this comparison.
5. When testing, find the point on the graph where the gauge reading intersects the correlation curve
and record that value as the corrected percent.
Exceptionally cool or warm ambient temperatures may cause fluctuations in test results. Repeated testing
or hot weather may heat up the vessel body, and show test results that are artificially high. Allow the
vessel to cool down before further testing. In cold weather, it may help to run two or three tests in rapid
succession to warm up the vessel.
The maximum recommended particle size is 0.75in (20mm). Some test methods may have a smaller size
limit.
Gilson Aqua-Check Moisture Tester, MA-26X
Typical Calibration Curve
Calcium Carbide Tester
Gauge Reading, Calcium Carbide Tester
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