Experimental and analytical study on the behavior of RC beams with externally bonded carbon-FRCM composites

Abstract

This paper presents both experimental and analytical study results for predicting the flexural capacity of reinforced concrete (RC) beams with externally bonded carbon fabric reinforced cementitious matrix (carbon-FRCM). Firstly, the available prediction approaches for FRCM-strengthened RC in flexure were summarized. The prediction formulas were deficient in the fabric slippage failure. Nine carbon-FRCM specimens with different layers of carbon fabric (CF) were tested under uniaxial tensile loading. Four RC beams were strengthened in flexure with carbon-FRCM having different layers of CF, which were tested under four-point bending. From the tensile test results, the apparent strain of CF was derived from the global strain of carbon-FRCM, and the two-layer carbon-FRCM was an optimized selection in the design of multilayer carbon-FRCM. From the bending test results, the utilization efficiency of CF was slightly higher in the fabric slippage failure than that in the peeling-off of concrete cover, and the failure mode was differentiated as the layers of CF increased. Additionally, a new procedure of prediction formulas in flexure for carbon-FRCM-strengthened beams was proposed, using the apparent strain of CF to assess the strengthening performance of beams at different load-carrying scenarios. The prediction of the proposed formulas agreed well with the experimental results.