Lightweight aerated concrete based on activated powders of coal gangue and fly ash

Coal gangue (CG) and fly ash (FA) buildup and storage pose significant environmental and human health issues. Thus, enhancing their use in several applications has gained widespread attention. In the same context, this study aims to evaluate the properties, and structural characteristics of a Lightweight Alkali-Activated Material (LAAM) combining CG and FA as aluminosilicate sources, in the presence of other activating additives such as lime and gypsum and metallic zinc powder as an expansion additive. The research explores various mix proportions and activator concentrations to optimize the LAAM performance. The results reveal that the addition of CG significantly affects the compressive strength of LAAM, an optimal CG content of 25% was identified as the optimal formulation in terms of mechanical properties. Increasing the concentration of sodium hydroxide (NaOH) results in higher compressive strength, with 12 M NaOH achieving a compressive strength of 4.58 MPa, meeting industry standards for autoclaved aerated concrete. The microstructural investigations, which included XRD, FT-IR, TG-DTA, and SEM-EDS, revealed that the activated products of the optimal LAAM ratio elaborated in this study are mainly hydrated alkali-aluminosilicate gel (N-A-S-H/C-A-S-H) with less unreacted Portlandite compounds.