Civil Engineering Reference
In-Depth Information
Table 14.6:
The insulation factors of sawdust and wood shavings
Material
Weight
Insulation factor
(kg/m
3
)
(W/m°C)
Compacted sawdust
200
0.081
Compacted sawdust
120
0.071
Sawdust/sand (2:1)
750
0.100
Wood shavings (3-5 cm)
80
0.120
Compressed wood shavings
130
0.080
Well compressed wood shavings
150
0.070
Very well compressed wood shavings
180
0.060
(Source: Granum, 1951).
Cork oak
Cork oak cannot grow in northern or central Europe and therefore must be
imported from southern Europe, mainly Portugal and Spain. The bark has prob-
ably developed to withstand the frequent forest fires that occur around the
Mediterranean. The trees are ripe for peeling after 25 years and can then be
peeled every 8 to 15 years. The material is used as thin boarding or crumbled for
thermal insulation. Cork is built up of dead cell combinations of cork cambium
and resins. It is usual to expand the cork to increase its thermal insulation value.
It is then pressed at a temperature of 250-300°C. The cork's own glue compo-
nents are released and bind the board together. Today it is usual to bind the
boards with a bituminous material, gelatine and another glue in a cold process.
In addition to its use as a loose material for filling walls, cork can be used in con-
crete for cork concrete blocks. Cork products are resistant to fungus and not eas-
ily penetrated by liquids. The material is easily flammable and burns with great
intensity and heavy smoke. The waste of products glued with bitumen has to be
specially treated.
Woodwool cement
Woodwool cement is usually produced as boards in thicknesses of
2.5-15 cm, but can also be produced as structural blocks. The board is used
for sound insulation, and thermal insulation. Reinforcing the thickest
boards with round wooden battens produces a material with good structur-
al properties.
Woodwool cement is resistant to rot. It has a weak alkaline content of about pH
8.5; mould needs a pH of 2.5-6 to develop. Woodwool can therefore be used as
