Effectiveness of FRCM system in strengthening reinforced concrete beams

Abstract

In this paper, experimental work has been reported to investigate the efficiency of fiber-reinforced cementitious matrix (FRCM) in enhancing the flexural capacity and deformational characteristics of reinforced concrete (RC) beams. The aim of the experimental work is to assess the parameters that contribute to such enhancement. Twelve RC beam specimens, 2500 mm long, 150 mm wide and 260 mm deep, were prepared with two different reinforcement ratios of: ρs D12= 0.72% and D16=1.27%, representing under-reinforced beam sections. The strengthened beams utilized two FRCM types; namely carbon and polyparaphenylene benzobisoxazole (PBO) FRCM systems. The RC beam specimens were tested in flexure under four-point loading until failure. Two beams without FRCM strengthening were used as control specimens. Six beams were externally reinforced by one, two and three layers of carbon FRCM system. Four beams were strengthened with one and two layers of PBO FRCM system. From the experimental observations, a reasonable gain in flexural strength was achieved for both the FRCM systems. Results showed that the flexural capacity of carbon FRCM strengthened beams (FRCM stiffness = 1422 MPa) can be increased by 78% and of PBO FRCM counterparts (stiffness = 605 MPa) by 27.5% over that of their control (un-strengthened) specimens.