Environmental priorities,
the pursuit of high performance materials and new production techniques are
combining to stimulate imaginative, resourceful and extraordinary building
materials and methods. From super lightweight carbon reinforced concrete to
glue-laminated timber produced from undersized reclaimed branches, material
hybrids are, as was the case in the early twentieth century, reforming
production and altering the way we build and perceive the limits of traditional
building materials. This union of tradition and technology is behind a fresh
look into rammed earth as a prefabricated mega-building-block for buildings.
Rammed earth is a
traditional building material made of a dampened mixture of clay, straw, lime,
gravel and stabilizers such as cement or asphalt emulsions. The mixture is
compressed with a flat-headed rammer, a type of large mallet or sledgehammer,
into timber formwork. Austrian company Lehm
Ton Erde transferred this labour intensive process into a factory setting
for an ornithological visitors centre in Sempach Switzerland. Designed by
architectural firm MLZD the building was
the first to use prefabricated rammed earth panels. The panels were produced
in climate-controlled conditions using techniques similar to precast
concrete. The fundamental difference is that the rammed earth formwork is
vertical whereas concrete panels are usually cast horizontally.
Each panel
consists of equivalent layers of compressed dampened loam. The earth mixture is
transported and dumped into the vertical formwork by an automated loader. A
linear pneumatic rammer followed by steel rollers then moves across each
thickness ensuring an identical quality and constitution for each subsequent
layer of loam. The production of large rammed earth blocks in the factory
reduces construction time and also allows for greater quality control. Each
mega block is bound on site by a loam mortar, similar to standard brick
construction. The loam binder is also used for repairing any damage from shipping
or handling.
The ornithological
visitors centre in Sempach Switzerland is a hybrid system of vertical rammed
earth building blocks which support simple timber framed floors and roofs. The
on-site version of the same technology is as old as civic building culture and
outdates more standardized mud brick building. The certified «MInergie-P-Eco»
(eco-label) the rammed earth massive panels participate in creating a
low-energy building and a low-energy embodied building material.
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| Delivery and stacking of rammed earth panels |
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