Civil Engineering Reference
In-Depth Information
Table 6.4:
Base materials
Material
Main constituents
Areas of use
Cements:
Lime
Structural concrete; concrete roof tiles; render;
Quartz
mortar; fillers; foamed up as a thermal insulation
Gypsum
Sulphur
Magnesium oxide
Fossil meal
Ground bricks
Fly ash
Clay
Blast furnace slag
Glass:
Quartz
Openings for light in doors and windows;
Lime
glasswool or foamglass as thermal insulation;
Dolomite
external cladding
Calcium silicate
Soda
Potash
Sodium water glass:
Soda
Surface treatment on timber as a fire retardant
Quartz
Potassium water glass:
Potash
Silicate paint
Quartz
The main material in a snail's shell and in coral is lime. The formation of these struc-
tures happens electrolytically by negatively charged organisms, such as snails, precipi-
tating natural lime and magnesium in salt water.
These processes can be performed artificially using electrolysis. The method is effec-
tively the same as that used in galvanizing. A good conductor, usually a metal mesh
which can also be used for reinforcement in the structure to be repaired, is dropped in
the sea and given a negative charge. This is the cathode. A positively charged conduc-
tor, an anode, of carbon or graphite is put into the sea close by. As the magnesium and
calcium minerals are positively charged from the beginning, they are precipitated on the
metallic mesh. When the coating is thick enough, the mesh is retrieved and transported
to the building site. The mesh or cathode can have any form and the possibilities are infi-
nite.
There are many experiments nowadays around such sea-water based industries,
even using solar panels as sources of energy. There is evidence that this is an envi-
ronmentally acceptable method for the production of lime-based structures (Ortega,
1989).
In the continued working of raw materials, high process temperatures and
fossil fuels are often used. Depending on the temperature level there is also a
