The one thing
that we are without on the planet arda, and which is necessary for making
concrete, is a furnace to heat the limestone. But, if there is clay on
the planet, (which there most likely is),we could use that to make one.
Clay is made up of silica and aluminum, which come from disintegrated
volcanic rock, as well as oxygen and Hydrogen. The furnace will be important
not only for burning the limestone, but also for making glass, so clay
is very necessary.
The best sort of clay to use is a mineral called Montmorillonite (it is
made up of hydrated sodium calcium aluminum silicate). It is found usually
in a more tropical climate in a solid crystal form. It is usually white
or gray and has a very opaque surface. This mineral, which has dissolved
out of volcanic rock, is in the class of Silicates and its subclass is
a phyllosilicate. As a result, it has some important properties that make
it very useful ,for example, it is extremely water absorbent, and can
swell up to fifteen times its original volume when exposed to water. This
characteristic is important, because it means that it can be very malleable
when exposed to water, and can easily be shaped into a furnace.
figure 5: photograph of Montmorillonite clay
Montmorillonite
has three important layers which make it extremely sturdy when dry. It
consists of an aluminum layer sandwiched between two silica layers. These
three layers bond in such a way that they form a strong, hard rock (when
they are not met with water).
Although more sophisticated furnaces, made out of steel or iron, could
be used, a clay furnace is a fairly simple way to heat the cement. As
time goes on, more complex ways of producing concrete could be developed,
but the way I have just explained is the most simple way to make concrete.
figure 6: colored x-ray picture of concrete when it is dried (the large
chunks are pieces of aggregate)