Shear Behaviour of RC Beams Strengthened using CFRP Grid-ECC/PMM Matrix Composites: An Experimental and Numerical Investigation

In recent advancements, a novel strengthening approach employing engineered cementitious composites (ECC) and fibre-reinforced polymer (FRP) materials has emerged. This method integrates ECC as the matrix, carbon fibre-reinforced polymer (CFRP) grid as the internal strengthening component, and epoxy resin for bonding the overlay to the concrete substrate. This study conducted tests on four reinforced concrete (RC) beams under a four-point load configuration. One beam served as an un-strengthened control specimen, while three were subjected to different shear strengthening methods: polymer-modified mortar (PMM), ECC, and CFRP grid-reinforced ECC matrix composites layer (FGREM). The investigation covered failure modes, load-deformation relationships, and load-strain relationships. Finite element (FE) analysis was employed to reproduce the test results. Key findings include the ability of ECC as a matrix to substantially reduce concentrated interfacial bond stresses, preventing debonding failure. The FGREM-strengthened specimen exhibited a failure mode characterized by side concrete cover separation, resulting in a notable 124% enhancement in shear resistance. The proposed FE model, incorporating interfacial behaviour, accurately simulated the performance of all specimens.