Building with earth - Gernot MINKE (1)

5.6
5.7
Tools
5.9
5.10
In former times, earth was rammed manually,
using rams with conical, wedge-shaped
or flat bases (5.7).
If conical or wedge-shaped rams are used,
the different layers are better mixed and,
provided there is sufficient moisture, a better
bond is obtained. However, this takes
more time than ramming with flat-based
rams. Walls rammed with flat-based rams
show less lateral shear resistance and therefore
should only be loaded vertically.
The base of the ram should not be too
sharp, so that the formwork, if made of timber,
is not damaged. The base should be
no smaller than 60 cm 2 , and no larger than
200 cm 2 . The weight of the ram should
be between 5 and 9 kg. It is preferable to
use a two-headed ram with a round head
on one side and a square one on the other.
This allows the ram to be used with the
round side for general work, and with the
square edge to compact corners effectively.
Such a ram is used even today in Ecuador
(5.8).
Electric and pneumatic rams were used as
early as the second quarter of the 20th century
in Germany, France and Australia. The
electrical ram shown in 5.9, built by the Ger-
54
5.8
man firm Wacker, was often used in former
times for rammed earth work, and has been
written about extensively. It has a hammerlike
action with a lift of 33 mm, and a frequency
of 540 strokes per minute. The ram
is very effective; its only disadvantage being
difficult in handling, since it weighs 24 kg. It
is no longer manufactured.
In Australia in the 1950s, a pneumatic ram
was used (5.10). This acts like a jackhammer,
has a frequency of 160 strokes per minute,
and weighs 11 kg.
Rammed earthworks
5.6 The circular barn,
Bollbrügge, Germany
(1831)
5.7 Rams used for
manual compacting
5.8 Two-head ram
used in Ecuador
5.13