The bulk density of AAC – Influencing factors and their magnitude

The bulk density of AAC determines many of its properties like compressive strength, thermal conductivity, sound insulation, and so on. It is described by the solid mass divided by the volume. The volume again is determined by the volume of the slurry in the mixer plus the rising volume. The rising volume is mainly caused by the hydrogen generation of the aluminum reaction. In practice, the rising volume is controlled by dosing of the aluminum, based on experience. This article shows that the rising volume cannot be calculated resp. controlled by the aluminum reaction only. Other influence parameters like casting temperature, final temperature and air pressure must be considered. The magnitude of this influence parameters is described, and some practical consequences are shown.