The size of the autoclaved fly ash bricks is identical to that of ordinary solid clay bricks, measuring 240mm x 115mm x 53mm, thus autoclaved bricks can be directly used as a substitute for solid clay bricks.

Fly ash bricks are available in two types: autoclaved fly ash bricks and steam-cured fly ash bricks. Autoclaved fly ash bricks are those made by curing with high-pressure steam. Steam-cured fly ash bricks are those cured under normal pressure with steam. Both types have similar raw materials and production processes, but differ in curing techniques and performance characteristics. Autoclaved fly ash bricks are cured under saturated steam pressure (with steam temperature above 174.5℃ and working pressure above 0.8MPa), allowing the active components in the bricks to undergo sufficient hydrothermal reactions, resulting in high strength and stable performance. Conversely, steam-cured fly ash bricks may experience cracking and other issues commonly found in masonry walls.

Vapor-activated fly ash bricks generally have high compressive strength, reaching 20MPa or 15MPa, at least 10MPa, and can withstand 15 freeze-thaw cycles. Additionally, fly ash bricks are a potentially active hydraulic material that can continue to undergo hydration reactions in a humid environment, making the brick's internal structure denser and beneficial for strength enhancement.