Building with earth - Gernot MINKE (1)

3 Preparing of loam
Soaking, crushing and mixing
3.1
It is not always easy to produce building
material out of a clayey soil, and experience
is required. The right preparation depends
on the type of earth, its consistency and its
expected application.
Moist crumbled earth with less clay and
more sand content can be used immediately
to build a rammed earth wall even as it is
dug out. Clods of earth with high clay content
cannot be used as a building material;
they must either be crushed or dissolved in
water and thinned with sand. This chapter
describes the different possibilities of
preparing earth for specific applications.
There are several methods available for
making workable building material out of
clods of earth. One of the easiest methods
for reducing the size of clods and making
their consistency workable without mechanical
labour is to place the earth clods in
water so that they can become plastic on
their own. The loam-clods are placed in
large flat containers in a layer 15 to 25 cm
high and then covered with water. After
two to four days, a soft mass is obtained
which can be easily moulded and mixed by
hand, feet or machines, together with
aggregates such as sand and gravel.
In cold climates where there is sufficient
frost, a traditional method is to stack the
moistened earth 20 to 40 cm high and
allow it to freeze over winter so that disintegration
occurs due to the expansion of
freezing water.
The easiest way to prepare the right loam
mixture is by mixing the wet loam with a
hoe or moulding it with the feet. Animal
power can also be used. Straw, chaff, coarse
sand and other additives can be mixed during
the same operation.
At the Building Research Laboratory (BRL)
at the University of Kassel in Germany, an
effective mud wheel was built (3.1) in which
two pairs of old truck tyres were filled with
concrete and used to prepare the mixture.
The tyres were mounted on a horizontal
beam fixed to a vertical central post and
powered by a tractor or by animal or manu-
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Preparing of loam