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Aerated Concrete

Aerated Concrete Also Known As Autoclaved Aerated Concrete




Photo © Safecrete.com

Aerated Concrete is a type of precast concrete composed of all natural raw materials producing great benefits and better energy efficient performance. As early as 1914, the Swedes discovered a mixture of cement, lime, water and sand, just like regular concrete but adding aluminum powder. This last material gives the Autoclaved Aerated Precast Concrete expansion properties.

Aerated Concrete: How It Is Manufactured?

Aerated Concrete is a pre-cast concrete that is formed by distributing air bubbles throughout the material to generate the low-density lightweight material in an autoclave oven.

It produces a soft material that can be easily cut with a regular saw blade and drilled easily, in both residential and commercial buildings. The manufactured units shall be subjected to the following tests: compressive strength test, moisture content test, bulk density test, and shrinkage test. The result is a non-organic, non-toxic, airtight material that can be used for wall, floor, and roof panels, blocks, and lintels which according to the manufacturers generate no pollutants or hazardous waste during the manufacturing process.

Aerated Concrete: Properties

Aerated concrete blocks are solid and relatively lightweight that are glued together with an adhesive and reinforced with steel for additional strength. AAC has incredibly high insulation values and provides an excellent soundproofing barrier. Autoclaved aerated concrete blocks are used mostly in above-grade construction. AAC’s low density ranges between 30-pound to 40-pound per cubic foot (pcf), compared to approximately 105 pcf for light-weight concrete block and approximately 125 pcf for normal-weight concrete block. The Autoclaved Aerated concrete typical design strength is about 580 psi compared to approximately 1900 psi for concrete masonry units. The precast autoclaved aerated concrete wall units are large-size solid rectangular prisms, which are to be laid using thin-bed mortar. Installed units shall be protected against direct exposure to moisture using a coating material.

Aerated Concrete Benefits

Some of the benefits that you will get when using autoclaved aerated concrete are:

  • Excellent thermal protection, approximately 1.25 per inch. The thermal conductivity of AAC is 6 to 7.5% that of conventional concrete, making it energy-efficient.

  • AAC will have lower energy costs because it has a greater thermal resistance.

  • Excellent soundproofing material and acoustic insulation.

  • Aerated concrete provides fire and termite resistance.

  • AAC is manufactured in a variety of form and sizes.

  • AAC blocks store and release energy over time.

  • The aerated concrete is recyclable.

  • Route chases can be cut to install electrical and plumbing rough-in.

  • Extremely lightweight precast blocks, stacked like conventional CMU.

  • Shipping and handling more economical than regular concrete or CMU.

  • Aerated concrete reinforcement bars can be placed in panel joints for continuity and diaphragm performance.

  • AAC can be used as wall and roof panels.

  • Panels are available in thicknesses of between 8 inches to 12 inches, 24-inches in width, and lengths up to 20 feet.

  • Blocks come 24”, 32”, and 48” inches long, between four to 16 inches thick, and eight inches high.

Autoclaved Aerated Pre-Cast Concrete Drawbacks

Aerated concrete as any other material has also some disadvantages:

  • Consistency in quality and color may be difficult to obtain.

  • Unfinished exterior walls should be covered with an exterior cladding to protect them from wear and tear.

  • If installed in high humidity environments, interior finishes with low vapor permeability, and exterior finishes with a high permeability are recommended.

Aerated Concrete Costs

Autoclaved aerated concrete walls installed as CMU can cost approximately $3.50 in 8” x 8” x 24”, depending on the complexity of the project. Labor cost might be lower because it is easier to install and easier to handle.

Aerated Concrete Code Acceptance

Aerated concrete has been accepted by many building codes and international standards such as:

  • ASTM C1386 (Precast Autoclaved Aerated Concrete Wall Construction Units)

  • ASTM C 1452 (Standard Specification for Reinforced Autoclaved Aerated Concrete Elements)

  • ACI 523.5R, which is a guide for using autoclaved aerated concrete panels

Aerated Concrete Installation

Aerated concrete can be easily installed with a thin-set mortar.

Aerated concrete can be easily finished by paint, plaster, cladding, or siding materials. Autoclaved aerated concrete can be finished on interior surfaces by plastering, tiles, painted, sheet rocked or just left exposed.

Concrete Comparison

PropertiesAerated ConcreteTraditional Concrete
Density (PCF)25-5080-150
Compressive Strength (PSI)360 - 10901000 - 10000
Fire Rating (hrs)≤ 8 ≤ 6
Thermal Conductivity (Btuin/ft2-hr-F) 0.75 - 1.20 6.0 - 10
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