1.1 This specification covers solid nonload-bearing and load-bearing precast concrete wall units made from autoclaved aerated concrete (PAAC) is a cementitious product based on calcium silicate hydrates in which low density is attained by the inclusion of an agent resulting in macroscopic voids and is subjected to high-pressure steam curing. The precast autoclaved aerated concrete wall units are large-size solid rectangular prisms, which are to be laid using thin-bed mortar. Installed units covered by this specification shall be protected against direct exposure to moisture using a coating material accepted by the PAAC manufacturer.