Development of Microstructure of the Fly Ash Aerated Concrete in time

Calcium hydro-silicate components formed during the autoclaving process are highly complex formations which often blend together mutually and form a variety of intermediate products, from completely amorphous, to the good crystalline phases. For fly ash autoclaved aerated concrete, the situation is even more complicated by the fact that high temperature and fluidized fly ash, as basic silica ingredients, have high variability of the chemical and mineralogical composition. This paper presents the results of microstructure monitoring and physical and mechanical tests on samples of fly ash aerated concrete based on high temperature and fluidized fly ashes performed after 2 years of storage in laboratory conditions. The microstructure of aerated concrete is assessed on the basis of SEM images and mineralogical composition according to X-ray analysis. The changes in compressive strength, density and coefficient of thermal conductivity of the fly ash aerated concrete in time are evaluated.