Civil Engineering Reference
In-Depth Information
There are many examples of bronze being used in building relatively early,
especially as a roof material. The roof on the Pantheon in Rome was covered in
bronze sheeting. This was subsequently removed and transported to
Constantinople. Copper has always been an exclusive material. It is found main-
ly in churches and larger buildings.
The most important alloy, brass, consists of 55 per cent copper and 5-45 per
cent zinc, occasionally combined with other metals. It is commonly used in light
fittings and a variety of timber impregnation treatments.
Copper ore is extracted from quarries and mines in the Congo, Zimbabwe,
Canada, USA and Chile and entails a heavy assault on the natural environment.
The natural reserves are very limited. Large quantities of sulphur dioxide are
emitted during traditional copper smelting. Modern plants resolve this problem
by dissolving the ore in sulphuric acid, then extracting pure copper by electroly-
sis. Copper is poisonous and can be washed out of waste. It can accumulate in
animals and plants living in water, but unlike many other heavy metals it does
not accumulate in the food chain. Copper has a very high durability but is expen-
sive. Most copper in Western Europe is recycled. Some, however, is re-used local-
ly, such as thick copper sheeting.
Zinc
Zinc is the fourth most common building metal in Scandinavia. It probably came
into use around 500 BC. It has commonly been used as roofing material and later
to galvanize steel to increase corrosion resistance. It is also used as a pigment in
paint and a poison against mould in impregnation treatments. Zinc is part of
brass alloy. Extraction of zinc causes the release of small amounts of cadmium.
Zinc is susceptible to aggressive fumes. In ordinary air conditions one can
assume a life span of 100 years for normal coating but only a few years in sea air,
damp town air or industrial air. There are very restricted reserves of zinc. It was
estimated at 21 years in 1992, and ought to be greatly restricted in its use. When
zinc is broken down, the zinc particles are absorbed in earth and water. In high-
er concentrations, zinc is considered poisonous to organisms living in water. It
can be recycled.
Secondary building metals
The following metals collectively represent a very small percentage of the use of
metal in the building industry.
Lead
Lead has been in use for 4000-5000 years. It is not found freely in the natural envi-
ronment but has to be extracted, usually from the mineral galena - lead sulphide
