Minerals - The Ecology of Building Materials - page 71

Table 6.1: Metals, their ores and their use in building - continued

Metal Ore Use in building

Metal alloys:
Steel

Constituents:
Iron (85-98%)
Manganese (0.1-0.5%)
Nickel (1-10%)
Silicon (0.5-1.0%)

Structure for floors, walls and roofs; roof
covering; reinforcement in concrete; wall
cladding; guttering; door and window furniture;
nails and bolts (galvanized or zinced)

Bronze Copper (more than 75%)

Tin (less than 25%)

Roof covering

ores (see Table 6.1). The most common ore from which aluminium is extracted is
bauxite, which contains iron as well as aluminium oxides.
In earlier times metals were worth a great deal because they were often inac-
cessible and required complicated working techniques. At first they were used
for weapons and tools. During the industrial revolution great changes occurred
in production techniques, and metals became more essential in the building
industry, which mainly uses steel and aluminium, followed by copper and zinc.
The areas of use are spread over a wide spectrum, from roof-laying and window
frames to structures, nails, impregnation materials and colours in plastic, ceram-
ics and paints.
In general metals can be replaced with other materials such as timber, cement
products, etc. The exceptions are mechanical jointing elements such as nails and
bolts.
During the extraction of ore, the mountains of slag and dust produced from
breaking up and grinding cause environmental problems. Extraction can also cre-
ate huge scars in the landscape which require filling and planting to restore after-
wards. This is especially the case with shallow opencast mines. Even after much
work it can be difficult or even impossible to rehabilitate or re-establish the local
flora and fauna and an acceptable water table level. All industries that deal with
metal extraction or smelting are environmental polluters. This is partly through
the usual energy pollution from burning fossil fuels and partly through material
pollution from the smelting process. Amongst other things the ores often contain
sulphur, and during smelting huge amounts of sulphur dioxide are released. It is
usual for this to be extracted and used in the production of sulphuric acid.
The consumption of energy for the extraction of metals from ore is far too high.
All metals can in principle be recycled and through recycling of steel, copper,
zinc and lead from waste the energy consumption can be reduced by 20-40 per
cent and for aluminium by 40-70 per cent. The metal industry has good poten-
tial as far as excess heat is concerned, which can be recycled and distributed as
district heating or for heating industrial premises.