【国外标准】 Standard Specification for Precast Autoclaved Aerated Concrete (AAC) Wall Construction Units (Withdrawn 2013)

This specification covers solid nonload-bearing and load-bearing precast concrete wall units made from autoclaved aerated concrete. Precast autoclaved aerated concrete (AAC) 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 shall be protected against direct exposure to moisture using a coating material. The raw materials used in the production of precast autoclaved aerated concrete are portland cement, quartz sand, water, lime, gypsum or anhydrite, and an agent resulting in macroscopic voids. The quartz sand used as a raw material may be replaced by a siliceous fine aggregate other than sand, and usually is ground to a fine powder before use. Fly ash may be used as a sand replacement. The batched raw materials are mixed thoroughly together to form a slurry. The slurry is cast into steel molds. Due to the chemical reactions that take place within the slurry, the volume expands. After setting, and before hardening, the mass is machine cut into units of various sizes. The units then are steam-cured under pressure in autoclaves where the material is transformed into a hard calcium silicate. The units shall be subjected to the following tests: compressive strength test, moisture content test, bulk density test, and shrinkage test.1.1 This specification covers solid nonload-bearing and load-bearing precast concrete wall units made from autoclaved aerated concrete. Precast autoclaved aerated concrete (AAC) 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 AAC manufacturer.1.2 The raw materials used in the production of precast autoclaved aerated concrete are portland cement, quartz sand, water, lime, gypsum or anhydrite, and an agent resulting in macroscopic voids. The quartz sand used as a raw material may be replaced by a siliceous fine aggregate other than sand, and usually is ground to a fine powder before use. Fly ash may be used as a sand replacement. The batched raw materials are mixed thoroughly together to form a slurry. The slurry is cast into steel molds. Due to the chemical reactions that take place within the slurry, the volume expands. After setting, and before hardening, the mass is machine cut into units of various sizes. The units then are steam-cured under pressure in autoclaves where the material is transformed into a hard calcium silicate.1.3 The values stated in inch-pound units are to be regarded as the standard. The values given in parentheses are for information only.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. See Section 8, Section 9, and Section 10.