Corroded RC beams patch repaired and strengthened in flexure with fiber-reinforced polymer laminates

This paper presents the experimental and analytical behavior of four reinforced concrete beams with corroded steel reinforcements with low mass loss (around 7.5%), yet in need of removal of cracked concrete cover, treatment of steel bars, application of cement-based repair patch and of externally bonded EBR or NSM FRP laminates. It comes out the assessment of residual flexural capacity of the as-built corroded beams and the suitable strengthening measures depend largely on the concrete cover crack pattern and width, as accelerated corrosion-related cracks were measured just wider than 0.3 mm (failing to fulfill serviceability limit state requirements marginally). This study also demonstrates that assessment of contribution of corroded steel and treatment in the above cases requires partial uncovering in order to apply inhibitors and better calibrate the actual mass loss with corresponding cover concrete damage. All the above may be fulfilled at the characteristic limit state of initiation of concrete cover separation. The observed failure modes, the recorded force - deflection curves and strains on steel and FRP laminates, validate for the strengthened corroded beams the full force transfer through old concrete - patch interface and through patch and FRP laminate interface, as predicted in the case of non-patched beams. The beam strengthened with two NSM FRP strips of equivalent axial rigidity with EBR FRP laminate presented 18.2% higher load and 41.6% higher deflection than the latter. The P-d behavior of all beams was modeled with advanced 3D Finite Elements (FE) that enabled further analytical investigation of the observed modes of failures and patch repair effects.