AAC Building Systems:

Autoclaved Aerated Concrete (AAC) was developed in Europe in 1923. Commercial production of the material began in 1930. In 1995, more than 41 million cubic yards were produced by over 50 factories worldwide. More than 98 million cubic yards were produced worldwide by over 100 factories in 2004, and with current construction boom in the Middle East, the production output continues to increase each year.  AAC is used in a wide range of building construction with residential, commercial and industrial buildings being common applications. The system consists of small masonry-like units, larger "jumbo" units, panels, and a variety of specially manufactured shapes and pre-assembled wall sections.

Several important factors contribute to AAC's worldwide acceptance. It is a versatile, easy to use, durable, and energy efficient system. AAC is the only viable, single component structural insulation system available. The walls, floors and roof of a building can be constructed with the system. Using one material to build the entire structural and insulation part of a building offers many advantages, allowing excellent design flexibility, quick construction and reduced waste.

AAC is well known as an environmentally friendly construction material. Compared to the energy consumed in production of many other basic building materials, only a fraction is required to produce AAC. Raw material consumption is very low for the amount of finished product produced. In the manufacturing process, no pollutants or toxic by-products are produced. AAC is also completely recyclable.

Due to AAC's excellent insulation qualities, energy consumption for the heating and cooling of buildings is greatly reduced compared to most conventional wall and roof systems. In the finished structure, no pollutants or toxic substances are released that could affect indoor air quality, even in the event of fire.  Fires are unheard of, since the building material does not act as fuel, unlike a wood frame, sheetrock, and current insulating materials.

Raw Materials:

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.

Production:

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 (rise) in the mold and form a "cake." After several hours, the mould 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 (a vessel in which they are steam cured under pressure.) After autoclaving, AAC can be shipped and used immediately.  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. 

Use in Construction:

Ease of use of a building material is important in many ways. Construction time, manpower, waste, and energy consumed by equipment used during construction are affected. Large, precisely dimensioned elements of AAC allow rapid construction. Their greater dimensional accuracy requires less on-site adjustment. The combination of large size and dimensional accuracy allows greatly increased productivity. Due to the light weight of AAC, reduced equipment demands are realized. This allows a reduction of pollutants by emissions and power usage of equipment during construction.

Construction waste continues to be a serious problem for builders. Before completion of a building project, waste is either burned, buried, recycled, or shipped to a landfill. Many areas do not allow burying or burning due to the environmental problems created. A very small amount of recycling is currently possible due to the lack of infrastructure to support it. Landfills are becoming the more common method of disposal, which presents other environmental problems. Two features of AAC help to greatly reduce waste. First, since it is both a structural and an insulation material, it simplifies construction, eliminating a number of different materials and their associated waste. Second, due to the ease of workability, and dimensional accuracy, very little waste occurs during construction. The woodworking properties of AAC allow even cut pieces to typically be reused.  

The Finished Building:

An AAC building can be very cost effective. In the U.S., costs are generally within 5% of wood framed assemblies, additional savings are recognized by eliminating sheet-rock, insulation, and base stucco coat. Operating cost savings for the building owner prove to be substantial, with life cycle break-even within a relatively short period of time. The AAC building owner sees a significant reduction of maintenance, insurance and energy (heating and cooling) costs, as well as an increase in overall comfort and safety.