Determination of Water Content of Soil

Test Method Title

Standard Test Method for Determination of Water (Moisture) Content of Soil by the Microwave Oven Method

Reference Number

ASTM D4643

Material

Soil

Test Property

Moisture content, Water content

Description of Test

A moist soil specimen is placed in a suitable container and its mass is determined. It is then placed in a microwave oven, subjected to an interval of drying, and removed from the oven and its new mass is determined. This procedure is repeated until the mass becomes nearly constant. This method is used for occasions when a more expedient method is desirable for water content determinations. This method may not be appropriate when highly accurate results are required. The principal objection to the use of the microwave oven for water content determination has been the possibility of overheating the soil and obtaining erroneous results. The behavior of a soil, when subjected to microwave energy, is dependent on its mineralogical compositions, and as a result no one procedure is applicable for all types of soil. This test method is best suited for minus #4 sized material. Larger size particles can be tested; however, care must be taken because of the increased chance of particle shattering.