Shear behavior of RC beams strengthened with FRP grid reinforced engineered cementitious composites

Prefabricated carbon fibre-reinforced polymer (CFRP) grid-reinforced engineered cementitious composite (ECC) plates were used for the shear strengthening of reinforced concrete (RC) beams. In this strengthening system, ECC acted as the matrix material, CFRP grids were used as the reinforcement, and epoxy was used as the bonding agent between the CFRP-ECC plate and the concrete substrate. In total, four RC beams were tested, among which one was un-strengthened as the reference beam and three were shear strengthened with three different schemes: ECC, polymer-modified mortar and CFRP grid reinforced-ECC plate. It was found that the use of highly ductile ECC as the matrix of the strengthening layer could alleviate significantly the local interfacial bond stresses and avoid the debonding of the strengthening layer, which is a dominant failure observed in the traditional externally bonded FRP strengthening system. Instead, the failure mode was dominated by the side concrete cover separation, leading to a significant increase of the shear capacity of the RC beam by 124%. The experimental results have proven the high efficiency of the proposed shear strengthening method.