the Development Of AAC in Europe and US 
Autoclaved Aerated Concrete (AAC) is a fully mature technology. It was developed in Sweden in the early 1900s.It was a mixture of lime and finely divided quartz could be foamed with aluminum powder and then autoclaved at 180°C to produce a lightweight, insulating, sound absorbing building material. The Germans refined the technology and have been producing lime-silica AAC for over 50 years under licensed trademarks such as Hebel and Ytong. Others, most notably the English and Eastern Europeans, substituted Class F fly ash for quartz and have been marketing fly ash derived AAC for almost as long (H&H Celcon, Spirox). Although AAC is used for construction on every continent (>200 plants in 35 countries including Mexico), its use in the United States and Canada has been rather limited. I believe that potential homeowners in the U.S. and Canada make choices based on cost and traditional construction methods. North America has always had an abundant supply of wood, an innovative wood products industry, and a very strong wood lobby, thus wood-stud construction continues to be one of the most economical ways to construct a home. The Pilgrims started in log cabins, and 300 years later, we the people continue to live in wood framed houses. Although AAC has an impressive track record, it is still a relatively new construction material for those of us that live in North America. At this point in time, building a home out of AAC would cost more than a similarly sized wood framed house, but on the other hand the AAC house would be allegern free, maintenance free, water proof and last considerably longer. Last, but also important are urban legends that are hard to shake. For example, because AAC is lightweight and cellular in nature it tends to be subject to edge damage and breakage if handled like concrete block. First time users tend to comment on this characteristic more than any other. Unfortunately, the word gets around and people become hesitant to try the material. However, in the hands of an experienced construction crew, a stucco finished AAC house having a conventional wood truss/shingle roof will actually take less time to build than a conventional wood framed/fiberglass insulated house. AAC block can be assembled with thin set mortar and window and door openings as well as electrical and plumbing recesses fashioned after the fact with hand tools. It is conceivable that lower labor costs could begin to close the affordability gap, as AAC becomes a more widely available lower cost construction material. Efforts are now underway to develop low cost housing from AAC block that could be marketed in kit form. In retrospect such an alternative could have helped the reconstruction efforts now underway in Louisiana and Mississippi.
Aritcle Sources: http://www.personal.psu.edu/gur/