LAUSR

Abstract Autoclaved aerated concrete (AAC) microstructure consists of tobermorite, which is formed in the strongly alkaline and hydrothermal environment of the CaO – SiO2 – Al2O3 – H2O system and is the main contributor to the strength of AAC. This paper addresses the influence of fluidized bed combustion fly ash (FBC ash) on the formation of tobermorite, and the properties and structure of autoclaved composite. To give the best account of the influence of individual input materials, tests are conducted on samples without aluminum powder, therefore the samples did not have a porous structure. Quartz sand, high temperature fly ash and lime were used as input materials, FBC ash was used as an admixture (10, 30 and 50%). The main components were mixed to achieve a molar ratio of 0.73 for CaO/SiO2. The hydrothermal reaction was carried out in saturated water vapor at 190 °C for 16 h. The main mineralogical phases and microstructure were examined using X-ray diffraction analysis and Scanning Electron Microscope. It was found that fluidized bed combustion fly ash has significant influence on the formation and crystallization of tobermorite and increases compressive strength of the samples of up to 2.5 times after 30 and 50% additions of FBC ash.