Autoclaved Aerated Concrete (AAC) is not worth it in my opinion to go through expensive shipping costs and what not for it. I have gotten AAC into the US to experiment with and here are some pros and cons:
Pros:
Easy to carve
Soaks water easily
Well-known material throughout antkeepers
Extremely lightweight
Cons:
Drys out via evaporation extremely rapidly due to porous structure of the material
Very soft and many ants can chew through it
Prone to molding due to moist environment and porous structure
Not durable (if you drop your formicarium it will likely crack or shatter)
Messy to carve
Possibly dangerous to inhale dust from carving or drilling AAC
Not easy to clean
Scratches many things including plastics on your outworld sitting next to it and the wooden shelf it may be sitting on
Overall, I think you may get the point. The main issue with it is that while it may retain water, the duration of which is retains the water consistently is very short, and not suitable for most "insert water into chamber on the side full of cotton" setups, or any similar.
Edited by Kevin, January 3 2018 - 3:17 PM.