Sustainable up-cycling of lithium alumino-silicate (LAS) glass-ceramic supported by alkali activation

Lithium alumino-silicate (LAS) glass-ceramics are commonly used in household applications, particularly in cooktops. However, managing their end-of-life remains a substantial technological challenge. This study presents an innovative, energy-efficient upcycling strategy for LAS glass-ceramic waste that avoids remelting by leveraging previous research on mild alkali activation of glass powders. Fine LAS powders were treated with a diluted alkaline solution (3 M NaOH) for 3 hours and hardened at 75 °C for 72 hours. Unlike conventional alkali-activated systems, this method fosters interparticle bonding through surface activation without extensive dissolution of the crystalline phase, preserving the material's intrinsic properties. The formation of strong interparticle bonds, maintaining the integrity of the β-eucryptite phase, was confirmed through stability tests after boiling-water immersion and analyzed via SEM, FTIR, and XRD. Both unfired and fired (700 °C) materials demonstrated a favorable combination of compressive strength and density comparable to commercial lightweight construction materials. Additionally, incorporating sodium perborate and sodium dodecyl sulfate enabled the production of highly porous foams with low thermal conductivity (λ = 0.114 ± 0.001 W·m -1 ·K -1 ). This method is the first demonstration of mild alkali activation applied to highly crystalline LAS glass-ceramics for creating structural and insulating components, paving new paths for the circular valorization of cooktop waste.