This study investigates the strengthening of pre-damaged reinforced concrete slabs using thin layers of carbon-reinforced concrete. The motivation was to evaluate the potential of carbon reinforcement to enhance the structural behavior of flexural elements in existing structures under realistic loading conditions, including pre-damage and strengthening under sustained load. Seven large-scale one-way slab specimens, three meters in length, were tested in four different strengthening configurations and compared to one unstrengthened reference slab. The configurations varied in geometric reinforcement ratio, number of carbon grid layers, and bond properties of plain and ribbed steel reinforcement. Four-point bending tests with quasi-static load cycles were conducted to examine load-bearing capacity, deflections, and crack development. The strengthened slabs exhibited an increase in load-bearing capacity by a factor of four to five, reaching ultimate bending moments of more than 30 kNm. This was accompanied by large ultimate deflections of 60 – 110 mm, indicating pronounced global ductility and a stable post-yield behavior. At service load levels, finely distributed cracks with small openings of less than 0.3 mm were observed, confirming the ability of the carbon reinforcement to govern crack formation. The production in different concrete batches had no significant effect on structural response, demonstrating good transferability of the results. The total flexural stiffness could be decomposed into contributions from steel and carbon reinforcement, revealing consistent and predictable structural behavior. Overall, thin-layer carbon-reinforced concrete proved effective in improving structural performance and enhancing serviceability, providing a viable strengthening approach for existing reinforced concrete members with limited depth and low reinforcement ratios.