Abstract: In order to investigate the synergistic reinforcement effect of industrial waste residue and recycled fine aggregate on muddy clay foundation,field tests were conducted using quicklime,an industrial waste-based composite curing agent(referred to as composite curing agent),and recycled fine aggregate. The cone penetration resistance,bearing capacity,compressive strength,and compressive modulus of the foundation soil in five test sections were compared and analyzed. Microscopic testing methods such as XRD and SEM were employed to reveal the reinforcement mechanism of muddy clay treated with industrial waste and recycled fine aggregate. The results indicate that after solidification,the specific penetration resistance,bearing capacity,and compressive modulus of the foundation soil increased significantly by 5 to 10 times,with the composite curing agent exhibiting a notably better reinforcement effect than quicklime. The addition of 10% to 30% recycled fine aggregate further enhanced the improvement effect of the composite curing agent,with the degree of enhancement increasing along with the content of recycled fine aggregate. The compressive modulus of the solidified soil showed a strong linear relationship with both the specific penetration resistance and the unconfined compressive strength,allowing for rapid prediction of the compressive modulus based on these indices. When the composite curing agent and recycled fine aggregate were used together to reinforce the muddy clay,direct and indirect hydration products—such as C-S-H gel and AFt crystals—generated by the composite curing agent effectively filled and cemented the soil particles. Meanwhile,the recycled fine aggregate provided a skeletal supporting effect. The synergy between these two materials significantly improved the mechanical properties of the solidified soil. The findings of this study enable the simultaneous resource utilization of industrial solid waste,construction waste,and sludge,offering a theoretical basis for sustainable reinforcement technology of muddy clay foundations.