Civil Engineering Reference
In-Depth Information
Brick and other fired clay products
'If brick had been discovered today, it would undoubtedly have been the
sensation of the century.' (Hoffmann).
Clay is formed by the grinding and disintegration of rock. In a dry state clay has
the formula Al
2
O
3
.2SiO
2
.2H
2
O. By adding water clay becomes workable. The
process is reversible.
Clay can be formed and fired up to 1000°C. All water is removed by firing the
clay, so the formula becomes Al
2
O
3
.2SiO
2
, and this change is irreversible. Water
cannot be reintroduced into the clay. It has become a ceramic material, with areas
of use that have been the same for thousands of years, in construction, on floors
and roofs, as water pipes and tanks. When the temperature in specially-built
kilns is increased even more, the clay begins to expand, turning into expanded
clay pellets, which in recent years have become an important insulation material
and a light aggregate in concrete. If expanded clay is poured into moulds and
heated to an even higher temperature, it melts and becomes a highly insulating
material called Zytan.
History
'The Chinese invented the compass, gunpowder and the brick' is an old saying amongst
brick makers. It could well be true, as archaeologists have unearthed Chinese burnt clay
tableaux which can be dated back 6000 years. The first traces of building bricks are from
between 1000 and 2000 years later. In Asia there are remains of 4000-year-old brick
buildings. In Bombay a brick kiln from about the same period has been found. Between
900 BC and AD 600AD the Babylonians and Assyrians developed a very comprehensive
brick-building technique. In Egypt, a pioneering country in many areas, sun-dried bricks
were used, except for the occasional use of stone, possibly because of lack of fuel for fir-
ing. Brick remains have been found deep in the silt of the Nile, which could mean that
there was once brick production even in this area. In Greece, burnt clay probably came
into use during the Golden Age of Athens, around 400 BC. The main product was roofing
tiles, as used in Italy. The Etruscan walls by Arezzo were built a few years into the
Christian epoch and are probably the first brick structures in Italy. The Roman brick indus-
try developed very quickly and produced a whole series of brick elements for both deco-
rative and structural use.
The brick industry in Europe really developed during the eleventh century, and since
then it has been the dominant building material in towns. Since 1920 concrete has
become a major rival, but brick now seems to be enjoying a renaissance, partly because
of its much higher durability.
Brick manufacture
The argillaceous materials used to manufacture bricks must be easily workable
and not contain any large hard components or lumps of lime. The latter can
