Durability and performance of carbon fibre reinforced polymer-concrete bonding system under tropical climates

Abstract

The existing reinforced concrete structures may require rehabilitation and strengthening to overcome defect and environmental deterioration. Fibre Reinforced Polymer (FRP)-concrete bonding systems can provide solution for the deficiencies, but the durability of the bonded joint needs to be investigated for structural reliability. This research studies the flexural performance of reinforced concrete beams strengthened with Carbon FRP and the interfacial bonding behaviour of CFRP-concrete system under tropical climate exposure. A 300 mm concrete prisms were bonded with CFRP plate and exposed for 3, 6, and 9 months to continuous natural weather, laboratory environment, and wet-dry exposure in 3.5% saltwater solution at room and 40 °C temperature. The prisms were subjected to tension and compression load under bonding test to determine the strain, stress distribution and shear stress transfer behaviour. The flexural performance was studied on 2400 mm length reinforced concrete beams strengthened with CFRP plate and fabric and exposed for six months to similar conditions as the concrete prisms without the higher temperature. The results of the bonding test showed that load transfer was fairly linear and uniform at lower load level and changed to non-linear and nonuniform at higher load level. The force transfers affected and shifted the shear stress distribution along the bonded length. The flexural capacity of the reinforced concrete beams increased between 32% and 37% and for CFRP plate and between 10% and 12% for CFRP fabrics. High interfacial stress developed near the cut-off point and decreased towards the centre of the beam. Plate-end debonding dominated the failure pattern of the beam. The combination of climate effects may have provided better curing of the bonded joints, but longer duration of exposure may be required to weaken the bond strength. Nevertheless, the tropical climate and salt solution did not yield significant bad effect on the CFRP-concrete bonding system.