Civil Engineering Reference
In-Depth Information
about 1000°C (Brien, 1978). The light clinker expands even more. The spaces
within the mould are filled and the material becomes a solid block. Once the
moulds have cooled down, the result is a homogeneous and highly-insulating
thermal block which can be used immediately. The density of the blocks can vary
from 200 kg/m
3
to 1200 kg/m
3
depending on the firing temperature. All blocks
are load-bearing, but have different bearing capacities. Holes can be sawn and
drilled into these blocks, just as in other light clay blocks. At the moment, these
blocks are not produced commercially.
Fired clay products and reduced energy consumption
The energy consumption in the manufacture of fired clay products is very high
and thereby also energy polluting.
The brick industry uses large amounts of oil-fired energy to dry the unfired
bricks. The required temperature is relatively low, which means that solar ener-
gy could be used as an energy source.
The consumption of energy in the kilns can be reduced considerably by the use
of bricks with different firing temperatures in building. Many bricklayers will
remember the routine of using low- and medium-fired bricks in internal partition
walls and well-fired bricks outside. Today, only vitrified and well-fired bricks are
available, and these are used inside and out. The use of energy increases by about
0.2 MJ/kg for very 100°C increase in the firing temperature: the brick industry
could reduce its total energy consumption by approximately 20 per cent by going
back to old methods. This system could go a step further by introducing unfired
earth bricks in internal or rendered non-load-bearing walls. There is no technical
barrier to the use of this technique, even in large buildings. Unfired brick also has
exceptionally good moisture-regulating qualities.
Because of the high temperatures needed for firing clay the use of heat
exchangers would be a potential source of energy-saving. One problem that has
arisen is the fast erosion of ducts and equipment, mainly because of aggressive
sulphur gases. By adding lime, the sulphur can be released in the kiln.
Energy consumption is also related to transport needs. Fired clay products are
heavy, and industries producing them are relatively centralized. It is therefore
worth considering whether it is ecologically correct to use brick in an area with
no local brick factory. This is especially relevant for areas that cannot be reached
by water.
Simple technology and the relatively widespread availability of clay gives
brick and clay tile production many potential advantages for local manufacture.
Also in the case of light expanded clay products, it should be possible to have
competitive manufacturing works at local or regional level, especially in the case
of a mobile manufacturing plant.
