Preparation and properties of autoclaved aerated concrete using coal gangue and iron ore tailings

• The optimum activation temperature for coal gangue found in this study is 600 °C.
• A new type of autoclaved aerated concrete is developed using the coal gangue and iron ore tailings.

In this paper a new type of autoclaved aerated concrete (ACC) was developed using coal gangue (CGC) and iron ore tailings (ITOs). The material compositions, calcination temperatures of the coal gangue, and the composition of the hydration products were analysed using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscope (SEM). The optimal thermal activation temperatures and the activation mechanisms of the calcined coal gangue were also studied. The results indicated that the optimal calcination temperature of coal gangue was approximately 600 °C. The bulk density and compressive strength of AAC samples were approximately 609 kg m−3 and 3.68 MPa, respectively, which passed the requirements of A3.5, B06 level of AAC sample regulated by GB/T 11969-2008. Before the autoclaving, the hydration products in ACC containing CGC and ITOs were tobermorite, hibschite, ettringite, and C–S–H gel; during the autoclaving, ettringite was decomposed and more tobermorite formed coupled with C–S–H gel and hibschite.