When purchasing for Autoclaved Aerated Concrete (AAC) production, the most critical factor is the active aluminum content, which should ideally be above 90%. You must also specify the particle size distribution (fineness), as this directly affects the gas evolution rate and the pore structure of the concrete. Common grades include 600-mesh or 800-mesh powders. Additionally, verify the gas evolution speed (usually measured at 2, 4, 16, and 30 minutes) to ensure it matches your slurry's setting time to prevent hydrogen leakage or structural collapse.