Effect of in-situ mechanochemical activation on the macroscopic properties and microstructure of graphite tailings-based autoclaved aerated concrete

Graphite tailings (GTs) are hindered from direct AAC application by inherently poor hydrothermal reactivity. This study introduces an alkali-mechanical synergistic, in-situ mechanochemical activation strategy whereby GTs are co-ground with NaOH to boost reactivity for AAC synthesis. Systematic investigation reveals that within a reasonable activation time range, this strategy optimizes pore architecture, and concurrently enhances compressive strength while reducing bulk density. The 30 min co-ground specimen (A30) delivered optimal properties: 3.89 MPa compressive strength and 626 kg/m³ bulk density, fully complying with the A3.5 B06 grade criteria of GB/T 11,968–2020. Microstructural analyses verify that the activation accelerates silicon dissolution and intensifies hydrothermal reactions, augmenting tobermorite abundance and crystallinity while fostering a morphological evolution from acicular and fibrous crystals toward plate-like structures. These findings establish a transferable paradigm for GTs valorization and furnish critical theoretical underpinnings for scaling comparable siliceous wastes in sustainable construction materials.