It's not a noble material.
AAC stands for autoclaved aerated concrete. The mix is heated and expanded with lots of air. It's sort of the stay puffed pastry version of concrete. Used primarily as a light weight building material, for insulation, it's an interesting new medium for sculpture.
You can carve it very quickly, it's soft enough that you can use a bread knife or anything handy to carve, rasp, file it. I hogged out the background with my drill press and a dull bit and then used a small stone comb tool and my steel gouges.
Available in 24 x 12 x 12 inch blocks, I cut each block in half lengthwise for these reliefs. Each new carving took about a day to complete. That's fast.
These new carvings are going to debut at Portland's Yard Garden Patio Show this weekend.