It is extremely urgent to implement comprehensive resource utilization within the framework of the dual carbon strategy. To improve the mechanical strength properties of silty clay, three types of industrial waste slag, such as slag, bottom ash and gypsum, are utilized as primary raw materials. A waste slag-based geopolymer is then prepared through synergistic activation in an alkaline quicklime environment to stabilize the silty clay and enhance its engineering characteristics. The deformation characteristics of samples under varying waste residue geopolymer content were analyzed through unconfined compressive strength tests and X-ray diffraction (XRD) microscopic tests. The study compared and examined the influence of curing method, fiber addition, and curing age on sample performance, as well as explored the types of hydration products present. A test of waste residue geopolymer-stabilized silty clay base was constructed for the actual project. The key findings suggest that the optimal dosage of waste slag geopolymer-stabilized silt clay is 15%, with a slag: bottom ash: quicklime: gypsum mix ratio of 8:2:3:2, polypropylene fiber content of 0.2%, and a curing method of 6 d standard curing followed by 1 d of soaking. The mechanical properties of the samples show significant improvement, particularly in the toughness region of the stress-strain curve due to fiber reinforcement. The samples exhibit excellent water stability, and extending the immersion curing age appropriately enhances the sample's strength, with a water stability coefficient reaching up to 200% The fibers, waste residue geopolymer hydration gel and soil particles interlock closely to create a dense three-dimensional network structure, thereby enhancing the mechanical strength of the fiber-hydration gel component-soil particle interface. The curing time significantly impacts the sample, with a strength growth rate ranging from 80% to 188% at 28 d.

The permeability of treated contaminated soil is an important factor to consider when reusing polluted soil in engineering projects. In this study, lime and fly ash were chosen as solidification materials due to their ability to both adsorb and solidify contaminants. The permeability coefficients of petroleum-contaminated soil before and after solidification, as well as the residual petroleum content within the soil, was investigated under varying parameters such as confining pressure, osmotic pressure and contamination intensity. X-ray diffraction and scanning electron microscopy were used to analyze the evolution of permeability and the migration and diffusion patterns of pollutants, providing insights into the engineering reutilization potential of solidified petroleum-contaminated soil. The results showed that the adsorption effect of the solidified product on petroleum molecules weakened the hydrophobicity of the petroleum, increasing the effective permeation pathways in the soil. The permeability coefficient of solidified petroleum-contaminated soil was two orders of magnitude higher compared to unsolidified soil. Both solidified and unsolidified petroleum-contaminated soil exhibited decreased permeability due to the enhanced adsorption and interception capacity of the soil matrix for petroleum, as well as the elevated confining pressure, osmotic pressure, and contamination level, which intensified the interception among soil particles. The solidification process effectively controlled the migration and diffusion of petroleum contaminants under permeation conditions. The residual petroleum content in various locations closely approximated the initial content, reducing the risk of pollution through permeation. Considering the mechanical properties (compressive strength of 1 280.1 kPa, shear strength of 388.88 kPa), permeability (ranging from 4.28x10(-6) cm/s to 7.39x10(-6) cm/s), and migration control characteristics (fluctuation rate from 0.3% to 4.9%) of lime and fly ash, it can be concluded that lime and fly ash solidified petroleum-contaminated soil can be reused in the construction of subgrade materials that require impermeability.