Carbonation of autoclaved aerated concrete containing fly ash.

Abstract: Due to the process of carbonation, the durability of autoclaved aerated concrete (AAC) may be affected. An adequate test method to assess the durability of AAC products in a short period currently does not exist. Hence, the German Institute for Building Technology (DIBt) has defined a limit value for drying shrinkage in order to prevent massive strength decrease of AAC products. In order to understand the deterioration mechanisms more in detail, investigations on the development of the compressive strength and the structural transformation of AAC have been carried out. Specimens taken from two different AAC products on the basis of quartz sand as well as fly ash were stored in different climate conditions. Shrinkage behavior was determined in normal climate (NC) of 20°C and 45% relative humidity. The compressive strength was determined at the beginning and additionally after about 180, 360, and 540 days. Phase analyses by X‐ray diffraction (XRD) were applied to correlate the structural transformation with compressive strength as well as shrinkage behavior in dependence of the silicate‐bearing raw materials. [ABSTRACT FROM AUTHOR]