Ceramics-Silikáty

To facilitate the application of alkali-activated concrete (AAC) derived from multi-element aluminium-silicon-based solid wastes in a cold-region infrastructure, the freeze-thaw (F-T) deterioration law of AAC under different erosive environments is thoroughly studied. Through a comprehensive analysis of the apparent morphology, relative dynamic elastic modulus (RDEM), mass loss rate, and compressive strength under aqueous, chloride salt, and sulfate salt freeze-thaw conditions, the paper systematically investigated the frost degradation mechanisms of AAC and predicted its service life. By integrating micro-analytical techniques-nuclear magnetic resonance (NMR), X-ray diffraction (XRD), and scanning electron microscopy (SEM), the impact of the freeze-thaw cycles on the hardened paste microstructure is clarified, and the underlying freeze-thaw damage mechanisms are elucidated. The experimental results demonstrate that the frost resistance hierarchy of alkali-activated concrete across environments follows: water environment ˃ sulfate environment ˃ chloride environment. Freeze-thaw cycling induces pore coarsening and degradation of the originally dense microstructure. In chloride-dominated conditions, Friedel’s salt formed through chemical adsorption, undergoes progressive decomposition, exacerbating the concrete surface deterioration. Under sulfate exposure, crystalline assemblages of gypsum and ettringite with a needle-like morphology emerge post the freeze-thaw cycles, initiating crack propagation that ultimately culminates in matrix failure.