An innovative sustainable rehabilitation solution that involves the use of carbon fabric reinforcement and a geopolymeric matrix synthesized in the laboratory was developed. The effectiveness of the newly proposed carbon fabric-reinforced geopolymer matrix (C-FRGM) repair solution to upgrade the shear capacity of reinforced concrete (RC) beams with corroded stirrups was examined and compared to that of the carbon fabric-reinforced cementitious matrix (C-FRCM) composites. Four structural tests were conducted on RC beam specimens. One control specimen served as a benchmark. The stirrups in the test region of three specimens were subjected to accelerated corrosion that corresponded to a measured stirrup cross-sectional loss of 50%. One corroded specimen was tested to failure without repair. Two corroded specimens were repaired with C-FRCM and C-FRGM composites then tested to failure. The unrepaired specimen with 50% stirrup corrosion exhibited a shear strength reduction of 34% relative to that of the control. Both C-FRCM and C-FRGM repair options designed and implemented in this study successfully restored the original shear capacity of the control specimen. The shear capacity of the beam repaired with C-FRGM was 88% of that of its counterpart repaired with C-FRCM. Such research findings confirmed the feasibility of using a geopolymeric matrix rather than a commercial cementitious mortar to develop a sustainable composite-based solution for rehabilitation of RC beams with corroded stirrups.