The performance of autoclaved aerated concrete prepared by arenaceous rock coal gangue powder instead of fly ash: The effect of Ca/Si ratio

The use of uncalcined arenaceous rock coal gangue powder (ACP) instead of fly ash as a siliceous raw material to produce autoclaved aerated concrete (AAC) is a potential method for achieving low energy consumption and high-efficiency utilisation of ACP. The effects and mechanism of the Ca/Si ratio (C/S) on the slurry and physical and mechanical properties of ACP-based AAC (AAAC) and fly ash-based AAC (FAAC) were studied. The results show that the compressive strength of FAAC decreases first and then increases with C/S, while the compressive strength of AAAC increases with C/S increasing. When the C/S is 0.73-0.93, the compressive strength of AAAC was 89.3-165.6 % lower than that of FAAC, and the thermal conductivity was 3.1-10.9 % higher. This is mainly related to the morphology, distribution characteristics and pore structure of tobermorite crystals in different AAC, and the morphology and quantity of tobermorite crystals are mainly affected by the amount of active Si4+ 4 + dissolved in the siliceous raw material.