This research explores the use of industrial by-products as stabilizers to enhance the bearing capacity of clayey soils, aiming to offer more sustainable alternatives to conventional lime or cement stabilization methods. Specifically, the feasibility of using ladle furnace slag (LFS) as a binder instead of lime was investigated. This study evaluated its key properties, including plasticity, unconfined compressive strength (UCS), California Bearing Ratio (CBR), and expansive behavior. Additionally, the impact of incorporating fibers sourced from the mechanical recycling of wind turbine blade waste (WTBW) on UCS was examined. The results indicate that the addition of LFS to the soil led to a slight decrease in the plasticity index. Moreover, the CBR of the soil improved significantly, increasing from 5.3% to 74% immediately after mixing with 5% LFS. After 90 days of curing, UCS improvements of 87%, 246%, and 479% were observed for mixes with 5%, 8%, and 16% LFS, respectively, compared to untreated soil. These improvements surpassed those achieved with 2% lime stabilization by 44%. Furthermore, incorporating 1% recycled WTBW fiber into the mix with 8% LFS enhanced UCS by 30% after 90 days of curing compared to the mix without fibers and by 313% relative to untreated soil. These findings suggest that the combined use of LFS and WTBW fibers can effectively improve the mechanical properties of clayey soils, offering a promising and sustainable alternative to traditional soil stabilization methods.