This study investigates the performance of slag-based materials enhanced with Recycled Concrete Fines (RCF) as a sustainable construction solution. The primary goal was to assess the mechanical properties, durability, and environmental advantages of these materials at varying RCF replacement levels (5%, 10%, and 20%) compared to a control group with no RCF. Compressive and flexural strength tests revealed that a 5% RCF replacement provided optimal results, increasing compressive strength to 44.5 MPa—a 5% improvement over the control—while maintaining good flexural strength. It was also discovered that higher RCF content (10% and 20%) caused strength reductions due to increased water demand and porosity. Durability tests, including freeze-thaw resistance and sulfate exposure, further demonstrated the benefits of 5% RCF, which improved material longevity under harsh environmental conditions. Scanning Electron Microscopy (SEM) revealed that 5% RCF contributed to a denser microstructure by filling voids and reducing porosity. In contrast, higher RCF levels led to micro-cracks and compromised the matrix's integrity. The Life-Cycle Assessment (LCA) highlighted significant environmental benefits, showing up to a 12% reduction in carbon emissions and substantial waste diversion, with approximately 200 kg of construction debris repurposed per cubic meter of concrete. Economically, RCF inclusion reduced material costs by 8%, making it not only environmentally beneficial but also cost-effective. These findings position slag-RCF composites as a promising material for sustainable construction, with clear environmental and economic advantages. However, further research is recommended to optimize RCF content and explore the long-term durability of these materials in diverse real-world environments. footprint.