Influence of deteriorated stirrups on the shear performance of RC beams incorporating fly ash and enhanced with carbon fiber-reinforced polymer strengthening

This study presents findings on the impact of corrosion of stirrups on the shear performance of reinforced concrete (RC) beams incorporating fly ash (FA) and strengthened with carbon fiber-reinforced polymer (CFRP). The study has identified that the optimal replacement proportion of cement with FA is 20%, resulting in improved compressive strength and split tensile strength of the concrete. The stirrups of the RC beam were subjected to controlled exposure periods of 4, 8, and 10 days, achieving targeted mass losses of 5%, 10%, and 15%, respectively by the accelerated corrosion method. The CFRP strengthening significantly improved the shear capacity of the RC beams by 9.1% to 23.1% in comparison to the control RC beam without corrosion. In the corroded beams, CFRP sheets hindered the development and spread of diagonal cracks, postponing the appearance of critical failures. Failure in the specimens initiated with the debonding of the CFRP from the concrete substrate. This subsequently led to the crushing of the concrete, preventing the CFRP from achieving its ultimate strength capacity. Interestingly, CFRP strengthening was proportionally more effective for corroded RC beams at the same corrosion level. The strengthened corroded beam displayed 20% greater deflection at mid-span than the strengthened uncorroded beam. Applying the proposed equation to the beam yielded a calculated shear capacity in close agreement with the experimental findings.