Civil Engineering Reference
In-Depth Information
than 20 per cent, is used to define the quality of that material, e.g. a 'gravelly
sand'. They can have quite pure mineral content or they can be a mixture of
organic substances such as peat and mud - mostly mould and plant material,
known as humus. Loose material that is well suited for cultivation is not suitable
for building, as it contains organisms and humus acids which have negative
effects on both earth construction and concrete. These materials should be avoid-
ed in building construction.
Loose materials in building
Many parts of Europe do not have access to gravel and sand as a building mate-
rial - not necessarily because the resources are not there, but because extraction
would have too much impact on the local environment. Certain types of clay, e.g.
clay used for ceramic tiles, can also be limited in certain regions. Otherwise,
deposits of argillaceous materials are very large. Their use, however, is very
small - in fact this material is an almost unused resource. It will continue to be
available as a valuable resource in the future.
Extraction of loose materials for use in the building industry requires very low
energy consumption. Drilling into the earth and explosives are unnecessary. It
often takes place in quarries, but if these become too large they can damage
groundwater and local biotopes. The most suitable clay for the production of
bricks and ceramic tiles is usually in the 4-5 m nearest the surface. An annual
production of 15 million bricks requires 30 000 cubic metres of clay, which repre-
sents 0.6 hectares to a depth of 5 m.
A very large amount of water is used in brickworks and also in the production
of expanded clay pellets and ceramic tiles when grinding the clay. The ceramics
industry in Italy has developed an efficient re-circulating system with a simple
filter for the waste sludge. In this way they have reduced the quantity of water
used and kept the sludge effluent to a minimum.
The energy consumption while processing fired clay products is very high. Oil
is the usual source of energy, but wood, peat or a combination of electricity and
coal can also be used. When oil alone is used, large amounts of greenhouse gas
carbon dioxide, acidic sulphur dioxide and nitrogen oxides are released.
Emissions are usually much higher than for the equivalent production of con-
crete.
The brick industry has become increasingly more centralized in Europe. This
has resulted in heavy energy consumption in brick transport and distribution,
with associated energy pollution.
Heated clay emits pollutants such as sulphur and fluorine compounds. These
can be neutralized by adding 15-20 per cent lime to the clay. The red dust
