Civil Engineering Reference
In-Depth Information
Foamglass
Foamglass is usually produced by adding carbon to a conventional mass of glass
and heating it to 700-800°C until it starts bubbling. The product is usually made
in the form of slabs. These are gas- and watertight with high thermal insulation
properties, and they are mainly used as insulation underneath ground floors.
The raw material is usually new glass, but a rougher product can also be made
from recycled glass in the form of blocks or granules.
Blocks of foamglass not only have a high thermal insulation value, but also
have structural properties similar to conventional lightweight expanded clay
blocks. They are also easy to screw and nail into. They are usual cemented
together with a bituminous mass. The granules are based on 95 per cent by
weight recycled glass with added sugar, manganese dioxide and lime. They are
used as light aggregates in concrete or as loose insulation.
Products based on new glass production use high levels of primary energy and
polluting production methods (see 'Ecological aspects of glass production',
p. 105). Products based on recycled glass are environmentally better, despite the
high level of energy use when re-melting the glass.
Within the building these products present no problems. One exception is the use
of bitumen as a jointing material and any metal reinforcement used can increase the
electromagnetic field. These products have no moisture-evening properties.
Extensive use of them in a building can lead to an indoor climate with rapid air mois-
ture changes and, in certain cases, the possibility of damp in adjacent materials.
Components containing bitumen must be disposed of at a special tip. Blocks
and granules can be re-used in building. Foamglass is inert and can be crushed
and used as an insulating layer in road building. There is no other way of recy-
cling this material.
Synthetic mineral wool fibres
Glasswool/fibreglass
Glasswood/fibreglass is made from quartz sand, soda, dolomite, lime and up to
30 per cent recycled glass. The mass is melted and drawn out into thin fibres in a
powerful oil burner. Glue is then added to the loose wool and heated to form
sheets or matting in a kiln. Phenol glue is commonly used in a proportion of about
5.5 per cent of the product's weight. To give a high thermal insulation value the
diameter of the fibre should be as small as possible. The usual size is about 5 μm.
Rockwool
Rockwool is produced in approximately the same way as glasswool, starting
with a mixture of coke, diabase and limestone. Basalt and olivine can also be
used. The quantity of phenol glue is lower - about 2 per cent by weight. The
diameter of the fibres varies from 1-10 μm.
