Abstract: In order to improve the resource utilization rate of copper tailings,a study was conducted to replace 50% of
river sand with copper tailings as a siliceous material for preparing autoclaved aerated concrete (AAC). The effects of the calcium-
silicon ratio (Ca/ Si) on the physical and mechanical properties and microstructure of AAC were analyzed. The research
included the impact on dry density,compressive strength,and thermal conductivity,combined with microscopic characterization
techniques such as XRD,FTIR,and SEM. The results showed that when the Ca/ Si ratio was 0. 75,the AAC exhibited optimal
comprehensive performance,with a dry density of 605. 7 kg/ m3,compressive strength of 3. 6 MPa,and thermal conductivity of
0. 151 W/ (m·K),meeting the A3. 5 B06 grade requirements specified in the Test Methods for the Performance of Autoclaved
Aerated Concrete(GB/ T 11969—2020). Microscopic analysis revealed that the crystal morphology of tobermorite evolved from
willow-leaf,platelet,plate,needle shapes as the Ca/ Si ratio increased. When the Ca/ Si ratio was 0. 75,the platelet tobermorite
content was highest,corresponding to the optimal mechanical performance. This study provides a theoretical basis and technical
support for the efficient utilization of copper tailings in green building materials.

Key words: copper tailings,autoclaved aerated concrete,siliceous material,calcium-silica ratio,compressive strength,hydration
product