Autoclaved
Aerated Concrete (AAC) is an ultra-light concrete masonry product.
It can weigh as little as 1/5 as much as ordinary concrete due to its
distinct
cellular structure featuring millions of tiny pockets of trapped
air. This cellular structure gives AAC a number of exceptional physical
characteristics.
This is not a "new" innovation.
Autoclaved Aerated Concrete has been around for over 80 years. Invented
in 1923, AAC has
been used extensively in Europe and Asia. It comprises over 40% of
all construction in the United Kingdom and 60% in Germany. More AAC
is produced
worldwide than any other building material with the exception of regular
concrete. It has only recently been introduced in the United States.
AAC
consists of basic materials that are widely available. These include
sand, cement, lime, gypsum, water and an expansion agent. Silica
sand, the raw material used in the greatest volume in AAC, is one of
the world's
most abundant natural resources. The finished product is up to five
times the volume of the raw materials used, with an air content of
between
70% to 80% (depending on the required strength and density.) Due
to this large increase in volume, AAC is very resource efficient.
Benefits
AAC is highly fire-resistant, unlike most houses
that are conventionally framed with wood.
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AAC is non-combustible. It has one of the highest
hourly fire resistance ratings per inch of any building material currently
used in homebuilding.
A 4” thick non-load-bearing AAC wall provides
a U.L. classified 4-hour fire rating. This far exceeds the requirements
of the Standard Building Code, and provides a significant level of
protection against loss of life and property. This makes it an ideal
choice for fire protection around steel columns and steel beams and
in the construction of shaft walls, stairwells, corridors, egresses
and firewalls.
This AAC house survived a devastating fire
in California while neighboring homes were destroyed.
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U.S. fire departments responded to 396,000 house
fires in 2005, accounting for 3,030 deaths, nearly one every two hours.
Most
were
from
toxic
fumes
generated
from
traditional
materials burning, not flames.
Since
AAC is an
inorganic
material
that does not burn, it does not release these toxic gases in the
event of a fire. The melting point of AAC is over 2900º F. This
is more than twice the typical temperature in a building fire of 1200º F.
AAC is very environmentally friendly. The process
of manufacturing AAC uses only natural materials and produces no pollutants
or by-products.
AAC is totally free of toxic or harmful substances. The fact that AAC
is an inherently "green" building material results in a healthier
home for your family. Low energy is required in production, low raw
material consumption, ease of use in construction, high energy efficiency,
better indoor air quality and recyclability add up to make AAC a very
environmentally friendly building material and system.
Energy
Efficient
It is widely recognized that AAC buildings are very energy
efficient. This efficiency is due to
a combination of high R-value, thermal
mass and air-tightness. AAC is the only product currently available
that meets Germany's stringent energy codes without added insulation.
It is
well documented that the R-value of a mass product need not be
as high as that of light frame construction, to perform thermally
efficient. A recent study in the U.S. shows that an 8" AAC wall performs
much better than a conventional wood stud wall system with R-30
insulation.
The fire
and mold resistant qualities of AAC are far superior to typical
wood construction.
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Concerns of mold growing in our homes and commercial buildings are
at an all time high. Fears of illnesses related to mold growth have
even prompted some people to abandon their homes. Mold contaminated
residences and buildings have become legal and insurance nightmares.
Mold spores are everywhere but they require certain conditions to
thrive: a warm temperature, sustained moisture and organic nutrients.
The typical nutrient source for mold is moisture-damaged building materials
such as wood.
AAC is a breathable, concrete product made with clean, inorganic materials
and does not offer the nutrients needed for mold growth.
Tests conducted by an independent laboratory on AAC block against
the three fungi most commonly involved in indoor air quality studies
showed AAC to be fungal resistant and repressive in allowing mold to
multiply. Additionally, AAC materials are resistant to termites and
other insect pests.
No structure is mold-proof, but choosing appropriate building materials
with proper ventilation and good maintenance practices can greatly
ease the threat of mold problems in your home.
Acoustical Benefits
AAC’s
exceptional sound insulation properties exceed
all other solid materials of the same weight per surface area.
The solid
wall construction
of a building made of AAC provides excellent
sound abatement, greatly reducing
outside environmental noise, providing a
quieter, more comfortable interior for the occupants. Its noise reduction
co-efficient is more than twice
that of a standard concrete block wall and
over 7 times
that
of ordinary
concrete. Theater room walls and master bedrooms become sound proof
"get-aways"!
Production Process
The production process emits no pollutants and creates
no toxic waste products. All waste produced during manufacturing is reused.
Production of AAC requires relatively little energy for the volume of
material produced.
The
ingredients of AAC are mixed to form a slurry that is poured into
large metal molds. The reaction between the expansion agent and other
components
used in AAC causes the slurry to expand in the mold and form
a "cake." After
several hours, the mold is stripped away and the "cake" is
wire-cut into aerated concrete elements of high dimensional accuracy.
These elements are then put into an autoclave vessel where
they are steam cured under pressure. After autoclaving, AAC can
be shipped
and used immediately.
Air Quality and Durability
In the U.S., it is estimated that 80 to 90 percent
of an average person's time is spent indoors; at home, work and in
other buildings.
It is widely known that some of the poorest quality air we breathe
is in our homes and the buildings we work in. AAC is an inorganic material
that contains no toxic substances. It does not slowly decompose and
off-gas.
Since AAC is both a structural and insulation material, it allows
for the elimination of other materials that can contribute to poor
indoor
air quality. With the mineral based plaster coatings commonly used
on the interior of AAC, complete elimination of toxic materials from
the
walls is possible.
Durability, and its environmental impact, is an important
factor when considering use of a building material. A structure that
does not need major repairs and renovation every twenty years or
so, as many wood 
products require, can save money, inconvenience, energy
and other resources. This is a tremendous advantage to the homeowner,
creating a better investment and value up-front and long-term. AAC
has
proven to be a very durable material.
There are numerous AAC structures worldwide, many
over 50 years old and in excellent condition. AAC will not rot, warp,
rust,
corrode or
otherwise decompose. AAC provides a very low maintenance home, saving
considerable time and money in upkeep over the life of the structure.
Although damage to an AAC wall is unlikely, repairs are simple using
AAC repair mortar.
Design
Flexibility
The design flexibility offered by AAC
provide the builder and architect with unlimited possibilities. The
material
can
be carved,
shaped,
sawed
and sculpted, unlike most other materials.
The choice of finishes and their application is improved.
Brick, stone, stucco and siding all benefit from easier installation
and improved durability. More common coatings, such as a hardcoat
stucco finish, along with interior plaster, aid in creating a more
environmentally
friendly structure.
The stucco finish used on AAC is very durable and
requires very little maintenance. These finishes can be integrally
colored with mineral pigments, eliminating the need for frequent painting.
Interior
plaster applied to AAC is durable, yet easy to repair. Veneered
plaster can be left unpainted, providing a pleasing appearance.
The
AAC homeowner will see a significant reduction of maintenance, insurance
and energy costs as well as an increase in overall comfort
and safety.
As a construction material, AAC provides significant
environmental and other benefits for the builder and the homeowner.
The short and long-term
effects of using AAC compared to many other materials result in lower
energy consumption, reduced operating costs, greater safety and comfort
and a healthier and more trouble-free home. These features provide
a better investment for the homeowner and for our environment.
