Building with earth - Gernot MINKE (1)

is to throw the dry material over a sieve.
More effective is an apparatus with a cylindrical
sieve that is inclined and turned by
hand or engine (3.11).
Mechanical slurrying
3.10
3.11
3.9 Crusher (Ceratec)
3.10 Crusher (Royer)
3.11 Sieving device
3.12 Rakes for preparing
loam slurries
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3.9
a machine (3.8). This has steel angles fixed
onto a horizontal plate, which rotates at a
rate of 1440 rotations per minute. It requires
an electric engine of 4 kW. The machine
does not work if the lumps are wet. Another
example can be seen in 3.9, manufactured
by Ceratec, Belgium, which is able to crush
up to 20 m 3 of clods in eight hours with
a 3-horse-power engine. In this machine,
the clods are crushed by two counter-rotating
cylinders. The machine shown in 3.10,
manufactured by the firm Royer in France,
can crush up to 30 m 3 of earth clods in
eight hours.
It is always important to get the readymixed
material out of the container fairly
soon. There are different possibilities for
doing so: the machine shown in 3.5 has an
opening at the bottom through which the
mixture can be pushed automatically into
a wheelbarrow, and the container of the
apparatus can be tilted so that it falls into
the flat wheelbarrow below.
Common concrete mixers where only the
drum rotates are unsuitable for preparing
loam mixtures, because in them, the clods
of earth agglomerate instead of breaking
down.
An electric hand mixer of the kind shown in
3.7 is very time-consuming and is recommended
only if small quantities of mud
mortar or plaster are to be prepared.
Sieving
For specific earth construction techniques, it
might be necessary to sieve out larger particles.
The simplest method that can be used
In order to enrich a sandy soil with clay or
prepare a lightweight loam, slurry is usually
required. This can be prepared most easily
from dry loam powder mixed with water.
If clods of clayey soil are to be used, they
have to remain covered with water for
some days in large flat containers. After
that, slurry can be obtained by using special
rakes, as shown in 3.12, or by using electrical
hand mixers, as shown in 3.10. A forced
mixer usually used for mixing and spraying
plaster is more efficient.
Water curing
Water curing is a process by which the wet
loam mixture is allowed to stand for a period
of 12 to 48 hours. Experience shows that
this process enhances the binding force of
the loam. This phenomenon is probably due
to electrochemical attraction between different
clay minerals that forces them into a
more compact and ordered pattern.
Thinning
If it is too rich in clay, loam must be made
lean. Coarse aggregates like sand or gravel
are added, increasing the compressive
strength of the loam. The coarse aggregates
should always be moistened before being
mixed into the rich loam. Besides sand and
pebbles, hair, cow dung, heather, straw,
husk, sawdust and other similar materials
can also be used. These also serve to
reduce the shrinkage; some even serve to
increase the degree of thermal insulation.
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Moisture protection