Artificial of expanded clay aggregates differ from natural

Artificial aggregates can also be used in concrete
production. Utilization of waste material such as using recycled concrete or
brick as aggregates is becoming general, and fly ash is used to replace fine
particles. Also the by-product of the iron industry blast-furnace slag has been
widely used in concrete production. Expanded clay aggregates are used to
produce expanded clay light-weight concrete, also expanded shales, slates,
perlites and slags are used. Properties of expanded clay aggregates differ from
natural aggregates, grains absorb water and they crush easily for example
during mixing. Also proportioning of expanded clay light-weight concrete is
very different from normal concrete. Pelletized, air-cooled and granulated
blast furnace slag can also be used, but the use is limited. (Suomen
Betoniyhdistys, 2005a, 32.)

Perlite is one of the artificial lightweight
aggregate. It is an amorphous volcanic glass which is formed by the hydration
of the extrusive igneous rock and has relatively high water content. The process
of hydration is occur naturally and it will expand greatly when it is heated
sufficiently. When it is crushed and heated to temperature above 15000 F, it
will expand to form lightweight, glass-like particle structure, and
noncombustible structure. The weight of perlite is about 1/10 weight of gravel
and sand with white or grey in color. It is used in lightweight fire retardant
for plaster , floor fills, roof, curtain walls , and precast panel, and
insulating concrete.

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Vermiculite is a silicate and hydrous mineral that
expand greatly when subjected to heat. It is formed by hydrothermal and
weathering alteration. The vermiculite concrete is about 15 % of the weight of
the structural grade concrete. It also has good insulating properties and has
fireproofing characteristics. The vermiculite concrete also being used as
precast concrete units like structural slabs with core type, channel slab,
double tees, and pre-stressed single. The cast-in place vermiculite concrete
provides a smooth surface of built up roofing membrane.

Norlite is a porous ceramic material that is formed by
expanding the selected shale in a rotary kiln. The product of the process is
produce a consistent and high quality of ceramic aggregate which has properties
of a strong, durable, physically stable, lightweight, environmentally inert,
and good thermal insulation. It is also absorptive aggregates, non-toxic and it
will not degrade over time. Norlite has the advantages of reducing dead loads,
improving fire rating, and lower the thermal conductivity of element in
building.

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