CLAY AS A BINDER
Clays are the main binders of
earth and are made up of very
small mineral particles (<2
microns), leached out during
erosion of rock. The molecular
structure of clays consists of
sheets of silicate and aluminate
ions. Electrostatic forces set up
within such structures produce
Clays have a variety of uses,
especially for ceramics, but it is
their use as binding materials in
the unfired state which is
described in this leaflet.
Although they have the limitation
that they soften when wetted,
Figure 1: House near Rennes in France built at the end
of the 19th Century Photo: CRATerre/EAG.
they are also undoubtedly the
cheapest binders, with very low energy consumption, and are deeply embedded in traditional
building cultures in many parts of the world.
It is estimated that over a third of the world's population are living in houses of earthen
Historical uses of clay as a binder
Throughout history clay has been the most widely used binder in the world, not just for
vernacular building but also for castles, public and religious buildings, and monuments such
as the 35-metre-high minaret of Tarim in Yemen and the thousands of kilometres long great
wall of China.
The world's earthen architectural heritage is rich and diverse, with a wide variety of
techniques providing a fabulous wealth of know-how in an extremely wide range of natural,
historic, cultural and socio-economic environments. There is hardly an inhabited country
which has not developed a tradition in earth, and all the great civilizations in the past built
The development of the technology of building with earth has been continuous and, in
Western countries, was particularly significant during the 18th century under the patronage of
the great French builder François Cointeraux and his enlightened disciples. More recently the
energy crisis and growing concern for the environment has led to a revival of interest in the
technology by many scientists and builders.
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