CO2 mineralization-assisted stabilization of loess with fly ash, MgO and Ca(OH)2: Static and dynamic performance, multiscale pore evolution, and carbon balance

Carbonation-based loess stabilization has mainly focused on static strength, leaving the links among CO 2 mineralization, dynamic properties, microstructure, and carbon balance unclear. This study developed a fly ash-MgO-Ca(OH) 2 ternary system and integrated static and dynamic tests with X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS), mercury intrusion porosimetry (MIP), and micro-computed tomography (micro-CT). MgO-rich mixtures showed rapid early strengthening, with the maximum dynamic shear modulus increasing by 142.0-195.7% after 12 h, whereas Ca(OH) 2 -rich mixtures developed more gradually. XRD, XRF, and SEM–EDS confirmed carbonate formation, particle coating, and contact cementation. For P25F6M4A0, MIP porosity decreased from 27.90% to 19.44% at 12 h but rebounded to 25.00% at 24 h; micro-CT connected porosity similarly changed from 5.68% to 1.06% and then 3.54%. The empirical interpolation model achieved R 2 = 0.8863 on the internally held-out P20 dataset. Apparent carbonation efficiencies reached 73.2-91.5%, 75.0-86.1%, and 79.2% for F6M4A0, F6M2A2, and F6M0A4, respectively. In the preliminary binder-level carbon balance, the mineralized CO 2 offset 60.3-69.5% of the estimated binder-production emissions. These results provide a composition-specific basis for balancing mechanical performance and net binder-level carbon emissions in stabilized loess.