Civil Engineering Reference
In-Depth Information
is rubbed between the fingers, it leaves a
thick fatty, layer on the skin, a bit like but-
ter. If the peat contains a lot of fibre, it feels
rough. If it contains too little fibre, it feels
smooth, like soap. The peat is cut out in
cubes of 12
12 cm, often going
down several layers before water fills the
hole.
This special peat must not dry out and
should be used as quickly as possible,
but its properties can be preserved for up
to a week in damp weather by covering it
over with leaves and pine needles. It
must be used in frost-free situations.
Extraction is simple, but somewhat
heavy. The use of energy is minimal and
its durability high. At the silver mines of
Kongsberg in central Norway, dams of
this peat are still watertight after being in
use for 100 years.
12
Figure 14.20: Log wall sealed with moss.
Peat matting
This consists of peat fibres sewn into paper.
Peat boards
Peat boards are made in thicknesses of 20-170 mm. Their thermal insulation is
very good and can compete with mineral wool or cellulose fibre. The most wide-
spread method of production begins with the peat being taken to a drying plant
where it is mixed and placed in warm water. It is then removed from the water,
which is allowed to run off, leaving a moisture content of about 87-90 per cent.
The mass is then put into a mould in a drying kiln to dry up to 4-5 per cent. To
achieve different densities, different pressures can be applied. The whole process
takes about 30 hours.
A dry production method can also be used. The peat is pressed into moulds so
that the damp is driven out of it. By warming it to 120-150°C with no air, its own
binders and impregnating substances are released. This is equivalent to its char-
ring temperature, so the boards become fire resistant. There is also no need for
added binders. The material has a strong resistance to fungus and insect attack.
Its absorption of water is very low, and its stable moisture content is around 10
per cent. As the contents of the board are stable, there is no chance of it settling.
This dry method of pressing came into use between 1935 and 1940 in the former
Soviet Union. The method requires a relatively large amount of energy for the
drying and setting processes, but this can be reduced to a certain extent by using
solar energy for the warming process.
