Rheological properties and freeze-thaw durability of fiber-reinforced flowable solidified soil incorporating multi-source waste

• The first systematic study‌ on rheological properties of fiber-reinforced flowable solidified soil with multi-source waste. • Extends engineering applicability of fluidized stabilized soil in extreme environments. • Fibers improve the freeze-thaw damage resistance of fluidized stabilized soil. • Multiscale characterization (SEM/CT) elucidates freeze-thaw degradation mechanisms at micro-meso scales. • Numerical modeling validates progressive failure mode evolution in freeze-thaw cycles. Freeze-thaw cycling induces microstructural deterioration in flowable solidified soil (FSS), leading to strength degradation. This study synthesized FSS using a carbide slag/NaOH composite activator to activate slag and fly ash, reinforced with polypropylene fibers. Systematic investigations were conducted on rheological properties and freeze-thaw durability evolution. Key results indicate: (1) Fiber incorporation reduced fluidity while increasing yield stress and plastic viscosity. At 10‰ fiber content, FSS exhibited 15.54% lower flowability, 259.5% higher yield stress, and 68.52% higher plastic viscosity compared to the baseline. (2) Peak stress, deformation modulus, and cohesion increased initially before declining with fiber content, achieving optimal reinforcement at 6‰ owing to uniform fiber dispersion. (3) Progressive attenuation of peak strength, deformation modulus, and cohesion occurred with freeze-thaw cycles. Fiber-reinforced specimens consistently outperformed non-reinforced counterparts under identical cycling conditions. (4) The synergistic effect of fiber-matrix interfacial bonding and 3D fiber networks effectively alleviated microstructural damage during freeze-thaw exposure.