AAC was developed over 85 years ago by Swedish architect Johan Axel Ericksson and is now being produced in more than 300 factories around the world. AAC is made from fine ground silica sand, Portland cement, lime, water and aluminum powder as an expansion agent. The production process is very carefully monitored to insure a controlled consistency in the proportions and timing of all ingredients that are used in each batch. The materials are first mixed into a slurry and then poured into large molds where the expansion agent reacts with the alkalis in the cement and lime to produce millions of small hydrogen gas bubbles. The mix expands and rises almost 2 times its initial volume. The hydrogen evaporates and the ‘cake’ sets up and hardens into a stable closed cell matrix which can then be precision wire-cut into blocks or panels. The green aerated concrete is then steam cured in a pressurized autoclave for about 12-14 hours where upon it undergoes a second chemical reaction and transforms into the mineral Tobermorite or calcium silicate hydrate. The finished materials are palletized, wrapped and delivered by truck to the job site.