Carbon Fiber-Reinforced Polymer Strengthening of Reinforced Concrete Beams: A Review of Flexural, Shear, and Impact-Related Techniques, Performance, and Failure Mechanisms

Due to the high tensile strength-to-weight ratio, corrosion resistance, and relative ease of installation, Carbon Fiber–Reinforced Polymer (CFRP) composites are commonly utilized to strengthen deficient reinforced concrete (RC) beams. Therefore, several CFRP techniques for flexural and shear strengthening such as externally bonded reinforcement, near-surface-mounted systems, embedded and through-section reinforcement, prestressed systems, and side-, U-, and O-jacketing configurations, were compared in this review. The study investigates how the CFRP technique performance is impacted by CFRP properties and layout, bonded area, number of layers, fiber orientation, anchorage details, substrate condition, and installation quality rather than treating these techniques as interchangeable. According to the results, CFRP strengthening commonly increased load-carrying capacity and stiffness while improving crack control. However, these advantages and improvements fluctuate significantly, and strength enhancement does not guarantee higher ductility. Underperformance is mostly caused by major constraints, including early debonding, CFRP rupture, adhesive deterioration, inadequate anchorage, and site-related construction constraints. Moreover, while the externally bonded systems remain the most accessible and widely used option, near-surface-mounted and embedded techniques offer superior protection for reinforcement and demonstrate higher resistance to debonding. The results indicate that enclosed wrapping typically provides the greatest structural benefit regarding shear strengthening, although spatial constraints around existing beams often make U-wrapping the more viable alternative. However, long-term durability, high-temperature and fire resilience, standardized anchorage design, full-scale field validation, hybrid strengthening approaches, and practical design models are considered substantial knowledge gaps. As a result, this review offers a robust framework for optimal design of CFRP strengthening systems for RC beams based on establishing a correlation between installation choices and both structural behavior and failure modes.