<p>Copper slag is a by-product of copper extraction that has emerged as a sustainable substitute for traditional fine aggregates in reinforced concrete (RC) structures. The rising demand for construction materials, along with the focus on sustainable practices, has driven researchers to explore the use of industrial waste in concrete production. Incorporating copper slag converts waste material into a useful resource and helps reduce environmental harm. This research explores the effects of replacing 50% of fine aggregate with copper slag and 10% of cement with silica fume in RC beams. It aims to increase the percentage of copper slag used to replace fine aggregate beyond the previously identified optimum level in RC beams. Achieving this involves substituting 10% of the cement in the concrete mix with silica fume and replacing 50% of the fine aggregate with copper slag to improve the flexural performance of the RC beams. The results show that the synergistic effect of copper slag and silica fume significantly improves the ultimate load capacity, energy absorption, and stiffness of the RC beam compared to beams with 50% copper slag and conventional concrete. A numerical model is developed to simulate results based on experimental investigations, which are then validated to improve accuracy. Regression analysis is a statistical method used to evaluate and quantify the relationship between variables. It was employed to compare theoretical predictions with actual experimental data. This analysis confirmed a perfect correlation between the theoretical models and the experimental results.</p>