Building with earth - Gernot MINKE (1)

8.15
Preparing the mix
Tests with 30 different mixtures, including
some containing straw, sawdust and pine
needles, showed that shrinkage reduction
and increase of output was negligible, indicating
that the additional labour and effort
involved in introducing these additives was
not worthwhile. However, the addition of
whey increased output slightly, and gave
better water resistance and surface hardness.
Casein powder and water can be substituted
for whey. The mix for this technique
must have higher clay content than that for
rammed earth blocks. A clay content of
15% was found advantageous. Loam elements
with lower clay contents showed
cracks at the corners. The content has to be
optimised so that the finished profile is dry
enough to be handled, yet wet enough to
adhere when being stacked into the wall.
8.16
Laying the elements
In the first test building made at the University
of Kassel, Germany, in 1982 (8.17
and 8.18), 2-m-long extruded profiles were
transported on a board and flicked over
onto the wall. The joints were finished by
pressing them with bare hands or with
a modelling stick. Since the weight of the
upper layers cannot be allowed to squeeze
out the lower material, only three to five
layers are possible in a day.
As these profiles showed shrinkage of
about 3%, it was necessary to refill the
shrinkage cracks that appeared. Since this
was laborious, at the next application of this
technique in a residential house at Kassel,
Germany, in 1984, only 70-cm-long profiles
were used. The results showed that at this
length, and with pre-designed contraction
8.17
joints spaced at 70 cm, no shrinkage occurs
in the elements themselves. The extruder
was positioned at the centre of the house
to minimise transportation distances.
8.15 Vertical extruder
for extruded loam profiles
(Heuser)
8.16 Horizontal
extruder for extruded
loam profiles (Heuser)
8.17 to 8.18 Walls of
extruded loam profiles,
test house, University
of Kassel, 1982
8.19 Extrusion of loam
profiles
8.18
8.20 to 8.22 Stacking
extruded loam profiles
in a plastic state
8.23 Smoothening
the surface with a wet
sponge
8.24 Sculptured interior
wall made of
extruded loam profiles
8.26 Filling a contraction
joint with slightly
moist loam
76
Direct forming