This Video shows how
Autoclaved Aerated Concrete
(also called Aerated
Autoclaved Concrete, or AAC)
is made.
Although several formulas
are used for manufacturing
Autoclaved Aerated Concrete,
the basic raw materials are
Portland cement, limestone,
aluminum powder, water, and
a large proportion of a
silica-rich material-usually
sand.
Once raw materials are mixed
into a slurry and poured
into greased molds, the
aluminum powder causes a
reaction to create millions
of tiny hydrogen gas
bubbles. These microscopic,
closed cells cause the
material to expand to nearly
twice its original
volume-similar to the rising
of bread dough. This imparts
the lightweight cellular
quality to ACC.
After a setting time ranging
from 30 minutes to 4 hours,
the foam-like material is
hard enough to be wire cut
into the desired shapes and
moved into an autoclave for
curing. The hydrogen in the
cells dissipates, and
becomes replace by air.
During the curing process,
the autoclave uses
high-pressure steam at
temperatures of about 356° F
(180°C) to accelerate the
hydration of the concrete
and create a second chemical
reaction that gives ACC its
strength, rigidity, and
dimensional stability.
Autoclaving can produce in 8
to 14 hours concrete
strengths equal to strengths
obtained in a concrete
moist-cured for 28 days at
70° F (21°C).
ACC, is about one-fourth of
the weight of conventional
concrete, and is available
in blocks, wall and roof
panels, lintels, and floor
slabs. Each of these
products can be manufactured
in a range of sizes
depending on specific
applications, allowing for
maximum efficiency and
flexibility in construction.
ACC is well suited for all
types of structures ranging
from single-family housing
to large industrial
complexes.
ACC is an inert,
nontoxic substance that has an energy-efficient and
pollution-free manufacturing process. Perhaps the
most significant environmental benefit of using ACC
is that fly ash can be used as the silica-rich
component. The electric utility industry generates
more than 50 million tons of fly ash each year-only
a fraction of which can be recycled.
ACC is virtually frost and
sulfate resistant, allowing it to be used around the
world in all climatic zones and for a wide range of
applications.
When AAC is used
on the exterior, it is normally protected by stucco
or other protective coatings. Being a solid
inorganic material, AAC is not penetrated by
termites or vermin and is resistant to rotting and
mold.
