Masonry Magazine June 2008 Page. 35
History of AAC
AAC WAS FIRST PRODUCED commercially in Sweden in 1923. Since that time, its production and use have spread to more than 40 countries on all continents, including North America, Central and South America, Europe, the Middle East, the Far East and Australia. This wide experience has produced many case studies of use in different climates and under different building codes.
In the United States, modern uses of AAC began in 1990 for residential and commercial projects in the Southeastern states. U.S. production of plain and reinforced AAC started in 1995 in the Southeast and has since spread to other parts of the country. A nationwide group of AAC manufacturers was formed in 1998 as the Autoclaved Aerated Concrete Products Association (AACPA, www.aacpa.org). Design and construction provisions for AAC masonry are given in the MSJC Code and Specification. The AACPA includes one manufacturer in Monterrey, Mexico, and many technical materials are available in Spanish. AAC is approved for use in Seismic Design Categories A, B and C by the 2007 Supplement to the International Building Code, and in other geographic locations with the approval of the local building official.
AAC can be used to make unreinforced, masonry-type units, as well as factory-reinforced floor panels, roof panels, wall panels, lintels, beams and other special shapes. This article addresses primarily masonry-type units only.
Materials used in AAC
MATERIALS FOR AAC vary with manufacturer and location, and are specified in ASTM C1386. They include some or all of the following: fine silica sand; Class F fly ash; hydraulic cements; calcined lime; gypsum; expansive agents such as finely ground aluminum powder or paste; and mixing water. AAC masonry units have no internal reinforcement, but can be reinforced at the jobsite with deformed reinforcement placed in vertical cells or horizontal bond beams.