Geology Reference
In-Depth Information
5
CHAPTER FIVE
CHAPTER FIVE
Determining the
Moisture Content
of Soil (Microwave
Oven Method)
Determining the
Moisture Content
of Soil (Microwave
Oven Method)
(Referenced Document: ASTM D 4643)
Chapter 4 presented the conventional oven method for determining
moisture content of soil. That method has been used for many years in
soils laboratories everywhere. It has one disadvantage, however; the
time required to completely dry a soil sample in a conventional oven can
be rather lengthy, while an assessment of moisture content may be
needed quickly.
Soil can be dried faster in a modern microwave oven, and in 1987,
ASTM published for the first time a standard test method (D 4643-87)
for determining moisture content of soil using a microwave oven. This
method is much quicker than the conventional oven method and has
been found to give reliable results for most soil types. (The method may
not give reliable results for (1) soils containing significant amounts of
mica, gypsum, halloysite, montmorillonite, or other hydrated materials;
(2) highly organic soils; or (3) soils in which the pore water contains dis-
solved solids.)
The microwave oven method generally gives results comparable to
those obtained using conventional ovens, but ASTM states that if there
are questions of accuracy between the two methods, the conventional
oven method shall be the referee method. Furthermore, the microwave
oven method is intended not as a replacement for the conventional oven
method, but rather as a supplement when rapid results are needed to
expedite other phases of testing.
INTRODUCTION
51
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