Civil Engineering Reference
In-Depth Information
Figure 1.5: (a) Multimaterial component; (b) monomaterial component.
Third principle: Use of standardized monomaterial components
Before re-use of the components on the open market it is necessary to check their quali-
ty. This often presents problems. Many building components are composed of different
materials laminated together (see Figure 1.5). Re-use of such products is difficult.
Different rates of decay within the same component may result in one of the materials
being partially broken down while the others are still in good condition. This problem is
especially acute in large, prefabricated building elements where cladding, insulation and
structure are integrated in a single component.
For re-usable structures only so-called primary and secondary monomaterials are
used. A primary monomaterial is a single homogeneous material used in its natural state,
e.g. untreated wood. A secondary monomaterial is a mixed material of homogeneous
nature, e.g. concrete, glass or cellulose fibre. By only using monomaterials it is usually
easy to check the quality for re-use.
Even if re-use products are thoroughly quality controlled, there still may not be a mar-
ket for them. The shape of the components may be so unusual that they would need to
be transported some distance to find a buyer. So this whole strategy can quickly become
an energy problem. Re-usability is therefore determined by the generality of the compo-
nent, i.e. its re-usability in a local market. This means that it has to comply with local stan-
dards, making it easy to use in new structures.
Most components of a building can be adapted for re-use in this way, though some, e.g.
electrical installations, may be less suitable for re-use. In this case, new technology may
meanwhile have taken over, for example in energy-saving, making re-use quite ecologi-
cally unsound.
In all levels of recycling there will be waste. And even when all the recycling is
done, there are still materials left over which need to be taken care of. This can
be a very large amount if the material quality is poor from the beginning, as in
the case of waste paper pulp, which has already gone through several rounds of
recycling. The alternatives for their use are dumping or global recycling. Global
recycling means making compost of the materials, or in some other way reunit-
ing them with nature, making them a potentially new resource. When cellulose,
for example, is composted, it is first covered by earth. A series of complex bio-
logical processes follow in which mould deteriorates the cellulose structure.
