The Autoclaved Aerated Concrete (AAC), Autoclaved aerated concrete (AAC), also known as autoclaved cellular concrete (ACC) or autoclaved lightweight concrete (ALC) was invented in the mid-1920s by the Swedish architect and inventor Johan Axel Eriksson. It is a lightweight, precast building material that simultaneously provides structure, insulation and fire and mold resistance. AAC products include blocks, wall panels, floor and roof panels and lintels.