Civil Engineering Reference
In-Depth Information
Table 13.3:
Lightweight concretes, their properties and areas of use
Type of concrete
Materials
Properties
Areas of use
Aerated concrete
Cement, sand, lime,
fine aggregate,
aluminium powder
Cement, expanded
clay or similar
lightweight aggregate,
sand
Cement, punice, sand
Relatively good thermal
insulation, weak
resistance to frost
Relatively moderate
thermal insulation,
frost resistant
Internal and external
construction
Lightweight aggregate
concrete
Internal and external
construction,
foundations
Punice concrete
Good thermal
insulation
Relatively low thermal
insulation, not frost
resistant
Good thermal
insulation
Internal and external
construction
Internal
construction
Concrete with wood
chip
Cement, impregnated
wood chip
Woodwool cement
Cement, impregnated
woodwool
Light internal and
external construction
Note:
All the different types of lightweight concrete are described in more detail in the next chapter. In many of
the products, cement can be mixed with pozzolana, or be replaced with lime, gypsum or sulphur.
Concrete binders and, to a certain extent, reinforcement, have the most serious
environmental consequences. It is important to try to choose the most appropriate
alternatives, at the same time reducing the proportion of these constituents. Some
regions lack the required mineral aggregate, so the amount of this component must
also be economised.
The composition of concrete
Binders
Air-curing binders and hydraulic cements can be used. Among air-curing
binders, slaked lime and gypsum are the most important ingredients. Hydraulic
cements include lime and pumice mixtures and Portland cement, with pumice
additives if necessary. Sulphur is a binder in a group of its own because it cures
when cooling, having passed through a melting down phase.
During building, contact with lime products can cause serious damage to the
skin and eyes, so these products should be used with care. Portland cement con-
tains chrome which can lead to a skin allergy, even though current products are
usually neutralized, mostly with ferrous sulphate.
Melting sulphur for sulphur blocks is unlikely to produce dangerous levels of
hydrogen sulphide or sulphur dioxide fumes.
Pure mineral binders usually have no effect on the indoor climate. Dust, how-
ever, can fall from untreated concrete surfaces. This can irritate the mucous
