Safecrete

In 1914, the Swedes discovered a mixture of cement, lime, water and sand that expands by adding aluminum powder. A material like wood but without the disadvantages of combustibility, decay, and termite damage, the material was further developed to what we know today as autoclaved aerated concrete (also called autoclaved cellular concrete or ACC).

In the product’s manufacture, Portland cement is mixed with lime, silica sand, or recycled fly ash (a byproduct from coal-burning power plants), water, and aluminum powder or paste and poured into a mold. Steel bars or mesh can also be placed into the mold for reinforcing. The reaction between aluminum and concrete causes microscopic hydrogen bubbles to form, expanding the concrete to about five times its original volume. After evaporation of the hydrogen, the now highly closed-cell, aerated concrete is cut to size and form and steam-cured in a pressurized chamber (an autoclave). The result is a non-organic, non-toxic, airtight material that can be used in non- or load-bearing exterior or interior wall, floor, and roof panels, blocks, and lintels. According to the manufacturers, the production process generates no pollutants or hazardous waste.

Building Homes with AAC is convienient because the blocks come in a variety of precast units. Blocks come two-feet long, between three and 12 inches wide, and eight inches high.Building with Floor Panels is easy because they are available in thicknesses between 3 inches and 16 inches, 24-inches wide, and spans of up to 20 feet.

AAC not only features structural capabilities, but also excellent thermal, fire, and acoustical properties. Depending on the density, AAC has a compressive strength of 300 to 900 pounds per square inch, which makes it a structural material for low-rise buildings. With an R-value of 1.25 per inch, AAC significantly outperforms conventional concrete block or poured concrete (having about R-0.1 per inch). Study showed that an 8" AAC wall performs much better than a conventional wood stud wall system with R-30 insulation. AAC 4-inch wall panels have a fire rating of 4 hours (ASTM E-119) and acoustically perform with an STC rating of 41.

Consistency in quality and color may be difficult to obtain in AAC made with fly ash. Untreated exterior walls should be finished when exposed to physical damage, dirt, and water, which can collect in the open pores. If installed in high humidity environments, interior finishes with low vapor permeability, and exterior finishes with a high permeability are recommended.

AAC has incredible thermal mass and because of it's ability to store and release energy over time, AAC is most beneficial in climates where outdoor temperature fluctuates over a 24-hour period from above to below the indoor temperature setpoint. AAC is typically limited to use in warm climates. When combined with additional insulation, it can be an energy-efficient choice for moderate to cold climates.

AAC insulating properties when compared with conventional concrete, make it an energy-efficient choice for warm climates.

AAC is completely recyclable.

The precast material is of uniform dimensions, easing the creation of uniform wall system. Because it does not contain organic matter, it is naturally resistant to fire, termites, and fungal decay. AAC has proven to be very durable.

AAC is a solid building material that can deflect projectile debris in high-wind areas. In the finished structure, no pollutants or toxic substance are released that could affect the indoor air quality, even in the event of fire.

AAC Attributes

AAC is lightweight, about a fifth the weight of concrete. (It will float on water)
AAC can be engineered for earthquake and tornado regions and in hurricane prone areas where it can withstand severe wind loads from storms.
AAC works a lot like wood. It can be cut, drilled, shaped and sanded with hand or power tools. Electric chases are easily sawn or routed in. A variety of fasteners are available to meet pull and shear requirements.
AAC is non-combustible with a UL fire rating of 4 hours for a 4 inch non-load bearing wall. Also, when exposed to fire, AAC gives off no toxic gases. Given the current concern over wild fires in the South West, AAC can be an important choice for the building shell of a home.
AAC has unique thermal properties because of its cellular structure. It combines high heat loss resistance for a masonry material with excellent thermal inertia resulting in an overall 'mass enhanced R-value'. AAC is renowned for its energy efficiency and gentle thermal motion in hot or cold climates, especially in areas that experience large day-night temperature swings.
AAC has exceptional sound absorbing characteristics. Because the material has a porous structure containing 60-70% air, it performs as an acoustic insulator to reduce sound transmission.
AAC is impervious to termites and boring insects and will not rot or decay.
AAC provides a vapor permeable, breathable wall system
The manufacturing of AAC materials is a pollution free process that makes best use of a minimum amount of energy and natural resources, resulting in a premier green building material.

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