is a PFa block aerated
2 3 The material Aircrete Autoclaved aerated concrete (AAC, Aircrete) Introduction Autoclaved aerated concrete is a versatile lightweight construction material and usually used as blocks. Compared with normal (ie: âdenseâ concrete) aircrete has a low density and excellent insulation properties.ense concrete is typically a mixture of cement and water, often with slag or PFA, and fine and coarse aggregate. It gains strength as the cement hydrates, reaching 50% of its final strength after perhaps about 2 days and most of its final strength after a month.