Properties and hydration mechanism of autoclaved aerated concrete containing coal gangue and fly ash

Abstract

A new type of autoclaved aerated concrete (ACC) was prepared using coal waste as the main raw materials. The calcination temperatures of coal cangue (CG), effect of calcined coal gangue (CCG) content on properties of AAC, and the variation of hydration products and microstructure of ACC under curing conditions were analyzed using X-ray diffraction (XRD), and scanning electron microscope (SEM). And the result shows that the optimal calcination temperature of CG is 600 °C and the content of CCG is 25%, the qualified products of A3.5, B06 level of AAC regulated by "autoclaved aerated concrete block" GB 11968-2006. After static curing, the hydration products in AAC body were ettringite (AFt), tobermorite, C-S-H gels and hydrated garnet; during the autoclaving, AFt was decomposed and more tobermorite formed coupled with C-S-H gels and hydrated garnet. Because the limitations and synchronization of the generation of tobermorite would lead to apparent stratification in the structure of pore wall, the layer composed by tobermorite made the structure of pore into hollow rigid spheres and played a role in being skeletons and proping as"aggregate".