Lightweight concretes can either be lightweight aggregate
concrete, foamed concrete or autoclaved aerated concrete (AAC).
Such lightweight concrete blocks are often used in house
Lightweight aggregate concrete
Lightweight aggregate concrete can be produced using a variety
of lightweight aggregates. Lightweight aggregates originate from
- Natural materials, like volcanic pumice.
- The thermal treatment of natural raw materials like clay, slate
or shale i.e. Leca.
- Manufacture from industrial by-products such as fly ash, i.e.
- Processing of industrial by-products like FBA or slag.
The required properties of the lightweight concrete will have a
bearing on the best type of lightweight aggregate to use. If little
structural requirement, but high thermal insulation properties, are
needed then a light, weak aggregate can be used. This will result
in relatively low strength concrete.
Lightweight aggregate concretes can, however, be used for
structural applications, with strengths equivalent to normal weight
The benefits of using lightweight aggregate concrete include:
- Reduction in dead loads making savings in foundations and
- Improved thermal properties.
- Improved fire resistance.
- Savings in transporting and handling precast units on
- Reduction in formwork and propping.
Foamed concrete is a highly workable, low-density material which
can incorporate up to 50 per cent entrained air. It is
generally self-levelling, self-compacting and may be pumped. Foamed
concrete is ideal for filling redundant voids such as disused fuel
tanks, sewer systems, pipelines, and culverts - particularly where
access is difficult. It is a recognised medium for the
reinstatement of temporary road trenches. Good thermal insulation
properties make foamed concrete also suitable for sub-screeds and
filling under-floor voids.
Autoclaved aerated concrete (AAC)
AAC was first commercially produced in 1923 in Sweden. Since
then, AAC construction systems such as masonry units, reinforced
floor/roof and wall panels and lintels have been used on all
continents and every climatic condition. AAC can also be sawn by
hand, sculpted and penetrated by nails, screws and fixings.
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Aircrete Products Association