Civil Engineering Reference
In-Depth Information
Figure 14.5: A wooden gutter, well worn after decades of service.
Materials such as cement, magnesite and lime are bad insulators, but they have
potential as binders for different mineral aggregates, to make them into blocks,
slabs etc. In the same way expanded clay pellets, pumice, wood shavings and
woodwool can be bound.
Aluminium powder added to a cement mixture acts like yeast and forms gas
within the concrete. This becomes a lightweight concrete with good insulation
value. It is also possible to foam up a relatively normal mixture of concrete to a
foam using air pressure and nitrogen.
Quartz sand is the main constituent of glass and has a very low thermal insu-
lation value, but glass can be foamed-up to produce a highly insulating and sta-
ble foamglass. The mineral wool glasswool also originates from quartz sand. The
sand is melted and drawn out to thin fibres in the form of thick matting or loose
wool, which also has good insulation value. A similar material, rockwool, is
based on the rock species diabase and lime, treated in almost the same way.
All these mineral materials, except for those containing a lot of gypsum or
lime, have poor moisture-regulating properties. Cement products take up and
release moisture very slowly. Drying out a concrete building can take years, and
during that period damage can occur to organic material touching the concrete.
