Performance of hybrid carbon and basalt FRP sheets in strengthening concrete beams in flexure

This study presents the bending performance of reinforced concrete (RC) beams strengthened with hybrid carbon and basalt fiber reinforced polymer (CFRP/BFRP) composite sheets. The proposed hybrid system is intended to improve the properties of the strengthening composite material, in which high strength CFRP sheets are combined with ductile BFRP sheets via epoxy adhesive. A total of 10 beams were tested, nine of which were strengthened with different combinations of CFRP and BFRP sheets, and the remaining beam was unstrengthened to serve as a control specimen. The test results indicated clear improvements in the load-carrying capacity and ductility of the strengthened specimens. The range of increase in the ultimate capacity of the hybrid-strengthened beams over that of the control beam specimen was between 66 and 75%. In addition, the deflection ductility indices of the hybrid beams presented an improvement up to 108% compared to those strengthened with CFRP laminates only. Finite element (FE) models were also developed to predict the response and load-carrying capacity of the tested specimens. The models precisely predicted the experimentally obtained load-carrying capacity and associated mid-span deflections at yield and ultimate loads, with a deviation that did not exceed 12%.