This paper presents an experimental investigation of the shear improvement of defected reinforced concrete (RC) beams using sustainable aluminum boxes filled with high performance concretes (HPCs). The study compares the performance of eleven RC beams with different configurations of aluminum boxes, filling materials, and inclination angles. Additionally, it examines the effect of reinforcing the ultra-high-performance concrete (UHPC) used to fill these boxes with glass fiber reinforced polymer (GFRP) bars. The results show that the proposed technique can effectively restore and enhance the load-deflection behavior, ultimate capacity, stiffness, and energy absorption of the beams. Inclining aluminum boxes within beams at a 45-degree angle and filling them with strain-hardening cementitious composites (SHCCs) partially restores performance. A beam with three boxes showed significant improvements over the defected beam, achieving 65 % higher stiffness, 44 % higher cracking load, and 33 % higher ultimate load. The optimal configuration was found to be 60-degree inclined aluminum boxes filled with UHPC and embedded GFRP bars. This configuration achieved a near-identical performance to the nondefected control beam and surpassed it in some respects. Furthermore, a two-pronged approach was employed. Firstly, finite element models (FEMs) were developed and carefully validated against experimental results. These validated models then became the foundation for a parametric study, allowing researchers to investigate the influence of various parameters on the beam’s performance. The parametric study indicates that with a fixed thickness of the aluminum boxes used, beams strengthened with boxes filled with UHPC have higher shear capacity compared to those strengthened with boxes filled with SHCC. Secondly, a theoretical formula was proposed to predict the total shear capacity of the strengthened beams. This formula exhibited excellent agreement with both the experimental data and the finite element (FE) results, solidifying its potential as a practical tool for engineers in design and analysis.