PURPOSE: To readily obtain a lightweight aerated concrete having uniform foams by blending a concrete raw material with lightweight aerated concrete powder and a polyalkylarylsulfonic acid-based surfactant and curing the blend in a specific state.

CONSTITUTION: A water slurried raw material consisting essentially of calcareous raw material and siliceous raw material is blended with a blowing agent, fed to a mold, semihardened, cut into a proper size and cured at high temperature under high pressure to produce a lightweight aerated concrete. The production is carried out in the following way. Namely, the raw materials are mixed with ≤30wt.% based on total solid content of lightweight aerated concrete powder and 0.01-1.0wt.% based on total solid content of a polyalkylarylsulfonic acid-based surfactant. By the above-mentioned production, even if the lightweight aerated concrete (ALC) powder is recovered and used, the slurry viscosity can be maintained constant without increasing an amount of water mixed. Consequently, ALC powder can be added up to 30wt.% based on total solid content while maintaining performance of product with a fixed amount of mixed water.