Flexural behavior of RC beams strengthened with CFRP sheets and ECC material

Premature debonding is a common failure mode of externally bonded fiber reinforced polymer (EB-FRP) strengthened reinforced concrete (RC) members, which leads to inefficient use of FRP. In this paper, engineered cementitious composite (ECC) with multiple fine cracks was introduced as a transition layer in FRP-concrete interface to delay CFRP sheet debonding. Four strengthened beams with CFRP sheet and ECC layer and one reference RC beam were tested under four-point bending. The effects of the type of strengthened scheme and CFRP sheet layers were investigated. The results showed that the beams strengthened with CFRP sheet and ECC layer had a significant improvement in crack load (71.8-105.1%), yield load (39.5-86.1%) and ultimate load (59.5-84.6%) relative to the reference beam. The introduction of the ECC layer could effectively delay CFRP debonding and had positive effect on the crack resistance. Fracture of CFRP sheet occurred when the beam was strengthened with one CFRP sheet layer. These findings are expected to provide better understanding on the FRPECC repair system.