Flexural behavior of RC beams strengthened with prestressed and non-prestressed BFRP grids

Abstract This study was aimed to investigate the flexural behavior of reinforced concrete (RC) beams strengthened with a thin composite layer consisting of a basalt fiber-reinforced polymer (BFRP) grid and polymer cement mortar (PCM). Ten RC beams were tested in the four-point flexural experiments, and following variable parameters were examined: (1) the FRP grid type, (2) amount of FRP grid, (3) types of bonding materials, (4) prestress, and (5) number of prestress release. The experimental results demonstrated that the BFRP grid effectively improved the serviceability and ultimate behavior of RC beams. The prestressed BFRP grid further improved the cracking load, yield load, and flexural stiffness of the RC beams owing to its higher strength utilization efficiency. Moreover, the failure mode of the prestressed beams changed from “concrete cover separation” to “concrete crushing” or “BFRP grid rupture” when the number of prestress release increased. Based on the strain compatibility and classical flexural theory of RC members, the prediction of the ultimate load of the FRP grid-strengthened beams exhibited a good agreement with the experimental results.