Abstract: In recent years, extreme rainfall in the northwest region has led to frequent instability and landslides of loess subgrade slopes. To address these engineering accidents, a high-strength steel slag-coal gangue geopolymer (SC-GP) was developed to solidify loess, using steel slag (SS) and coal gangue (CG) as raw materials and water glass and desulfurization gypsum (DG) as activators. First, the optimal mix ratio of SC-GP was determined through unconfined compressive strength (UCS) tests after 28 days of curing. Then, solidified loess samples with different curing ages and SC-GP contents were prepared based on the optimal mix ratio of SC-GP. Macro- and micro-scale analyses were employed to investigate the influence of curing age and SC-GP content on the mechanical properties of the solidified loess, utilizing UCS, direct shear, disintegration, X-ray diffraction (XRD), scanning electron microscope (SEM), and mercury intrusion porosimetry (MIP) tests. The results indicate that the optimal mix ratio of SC-GP is SS: CG: DG at 40:54:6, with a water glass modulus of 1.2 and a water glass content of 22%. SC-GP significantly enhances the mechanical properties of loess and effectively reduces the disintegration rate of solidified loess in water. After 28 days of curing, the UCS and cohesion of solidified loess with 20% SC-GP content are 359.09 kPa and 112.76 kPa, respectively, which are 3.45 and 2.3 times higher than those of remolded loess. Moreover, the solidified loess hardly disintegrates within 300 minutes in water, with a disintegration rate of less than 1%. Microscopic studies reveal numerous C-S-H (calcium silicate hydrated) and C-A-S-H (calcium aluminate silicate hydrated) gelling materials. The volume of large pores in the solidified loess decreased, while the volume of small pores increased relatively.

Key words: geopolymer, solidified loess, mechanical properties, microscopic mechanism, gelling materials, pore volume