Red clay bricks are made from a combination of clay (alumina), sand, lime, iron oxide, and magnesia, and are widely available throughout the country. AAC blocks are made from a mixture of fly ash, cement, lime, gypsum, and aeration agents and need development and production from specialized factories.
While red clay bricks are widely available, they do not provide superior compressive strength in comparison to AAC blocks, which are crafted to become more resilient to compression load. Red bricks have a compressive strength of 2.5 to 3.5 N/mm2, whereas AAC blocks have a compressive strength of 3 to 4.5 N/mm2.
Source: https://coneccconcrete.com/blog/Are-aac-blocks-strong
