Durability of autoclaved aerated concrete

Field inspections and further tests have been carried out in order to identify damages and degradation factors for the external wall components made of autoclaved aerated concrete. Within this project 24 industrial buildings in the area of Orebro and Kumla in Sweden have been inspected to get information about all damage types and to rate the status of the AAC-plaster system. The buildings had one of three different types of surface treatments. They were built over three decades beginning in the 1960's. The inspected external AAC-walls were either untreated or if treated, organically or inorganically based thin plaster systems were applied. In-situ measurements of the moisture content within the first 15 mm below the surface were carried out by a conductance type electric moisture meter. The evaluation of damages was performed with regard to differences in plaster system, plaster thickness and colour, AAC's density, location and orientation of the walls. To detect possible changes in properties of the AAC, capillary water absorption tests and water vapour diffusion tests were performed at core samples from three buildings of different age and surface treatment. Of main interest have been moisture-related damages in organic and inorganic based plaster systems. The level of moisture content is directly related to damage and is also connected to the degree of damage. AAC-walls treated with organic plaster systems showed most moisture-related damage. Where organic plaster systems were used, the level of degradation of the AAC was in general conspicuously higher than that at the walls which were coated with inorganic plaster systems. Damage causes and possible degradation systems are provided for the different plaster systems.