Civil Engineering Reference
In-Depth Information
(neoprene) and silicone rubber. The products include different additives such as
fire retardants, stabilizers and pigments.
Insulation materials
Different insulation materials are produced from polystyrene, polyurethane and
urea formaldehyde. Foamed polyvinyl chloride and polyethylene were once
used. The materials are foamed up using chlorofluorocarbons, pentane or carbon
dioxide, and fire retardants and stabilizers are added.
Climatic products in plastic are based entirely on oil, which is an extremely
limited resource with an extraction that is both polluting and carries a
potential risk. Refining the products requires a great deal of energy com-
pared to other materials. In all phases from production to use in the indoor
climate and waste, the majority of plastic products can cause considerable
pollution (see 'Pollution related to the most important building plastics',
p. 149).
Sheeting and paper sheeting have very important roles in water- and vapour-
proofing. Durability is therefore a decisive factor. According to existing docu-
mentation it is unlikely that plastic products have these qualities. In terms of pol-
lution, products made of polyethylene and polypropylene produce lower levels.
Goods made of PVC usually contain cadmium as a stabilizer against sunlight
and other climatic influences, and as waste, cadmium has a high pollution poten-
tial (see 'Cadmium', p. 80).
Mastics must be applied when still soft. During the hardening process, the
indoor climate can be badly affected by emissions of aromatic, aliphatic and chlo-
rinated hydrocarbons. Chemical and physical breakdown of the material also
occurs. At the Royal Theatre in Copenhagen, an unpleasant smell occurred after
the use of a mastic. It could best be described as garlic or rotten eggs, and came
from the sulphur compounds released on oxidation with the air (Gustafsson,
1990). There have also been many cases of serious mould growth on polymer
mastics in bathrooms.
Mastics break down when exposed to weather and wind, becoming powdery.
They then fall into or out of the joint. This process progresses much more quick-
ly than was assumed during the 1960s when building methods with precast con-
crete elements began, and today a large number of buildings have considerable
problems and high maintenance costs as a result. The decayed remains of the
mastic also represent a toxic risk both inside the building and in the surrounding
soil.
Sealing strips of plastic are already hardened by the manufacturer and are a
lower pollution risk in the indoor environment. Their durability is much shorter
than the products they are built in to, and they can be difficult to replace after a
few years.
