Near surface embedded-FRCM for flexural strengthening of reinforced concrete beams

Abstract

Fibre reinforced cementitious matrix (FRCM) systems are mostly externally bonded (EB) for the strengthening of reinforced concrete (RC) and masonry structures. In this paper, the relatively new concept of near-surface embedded (NSE) FRCM, has been introduced for the flexural strengthening of beams. The process of the application of NSE-FRCM strengthening technique involves the removal of the concrete layer at beam soffit, being the most deteriorated in actual practices. Experimental evidence of the flexural strengthening efficacy of this technique is provided here. Fourteen RC beams were prepared and tested under four-point loading with the consideration of three test parameters: (a) FRCM material (polyparaphenylene benzobisoxazole (PBO)/carbon/glass); (b) strengthening technique (NSE and EB); and (c) the reinforcement ratio (0.5% representing flexure-deficient beams and 1.28% representing typical under-reinforced beams). The strengthening led to gains in ultimate loads that ranged between 30.1% and 93.3%. The strengthening techniques are compared based on an introduced strengthening efficiency factor.