Microstructure and Hydration Mechanism of Autoclaved Aerated Concrete from Fly Ash

Abstract

Autoclaved aerated concrete(AAC) with excellent mechanical properties were prepared by the grade II fly ash (FA) as siliceous materials, which was supported by the thermal power plant. The composition, morphology and thermal properties of the hydration products with different stages of AAC were detected by using X-Ray diffraction (XRD), scanning electron microscope (SEM), flourier transform-infrared spectroscopy (FT-IR), and thermogravimetric/differential scanning calorimeter (TG-DSC). Results shows that the main hydration products including ettringite (AFt), low crystallinity of C-S-H gels and Ca(OH)(2) were generated in the hardening body. After heat preservation 0 hour, the new hydration products tobermorite were detected. After heat preservation 8 houra, the major hydrated products were tobermorite and C-S-H gels in the final AAC samples. XRD diffraction peaks of the original mineral composition in FA were reduced, which indicated that the mineral composition of FA was decomposed, and the reaction between active components of SiO2, Al2O3, and Ca(OH)(2) caused the formation of tobermorite under conditions of high temperature and pressure and hot alkaline activation.