Civil Engineering Reference
In-Depth Information
9
Fossil oils
The most useful type of oil is oil extracted from the Earth. Oil can also be extract-
ed from coal or from oliferous slate or clay. Natural gas is a form of gaseous oil
and has approximately the same properties.
Refined oil is the starting point for many products used in the building indus-
try. Tar and asphalt by-products of oil can be used directly, mostly for making
roofs, joints etc. watertight. Other refined products provide raw materials for a
whole spectrum of products: solvents for painting, glue, waxes, oils, and also
plastics. Plastic has developed greatly over the past 40 years. By 1971 an average
apartment contained about 1 ton of plastic. A modern Swedish apartment con-
tains approximately 3 tons of plastic in everything from the covering for electric
cables to floor coverings and window frames. The building industry uses 25 per
cent of all plastic produced.
Distillates from coal tar, natural oil and natural gas are formed by hydrocar-
bons. These are chemical compounds containing only carbon and hydrogen.
The explanation of how oil has been formed has changed somewhat over the
centuries. Oil was once considered to come from the corpses of those who died
during the great flood described in the Bible; theories later claimed that it came
from rain from outer space. Today, most researchers agree that the oil within the
Earth is formed from animal and plant remains that have sunk in shallow stretch-
es of sea in prehistoric times, and have later been exposed to certain pressure and
temperature conditions.
It is estimated that 6000 years ago oil from the Earth was used for building in
the form of asphalt. Noah used the material to make his ark watertight, and the
Babylonians jointed their clay block houses with bitumen from asphalt lakes.
Wider use of oil did not really start until the nineteenth century, when the indus-
try began with the huge exploitation of reserves on the American continent. The
main use of oil was as a fuel, and later for waterproofing. It was not until the
twentieth century that is was first used for the commercial production of plastics.
