Repair of thermally shocked reinforced concrete beams using near-surface mounted – Carbon fiber reinforced polymers ropes and strips

Abstract

The use of near-surface mounted (NSM) carbon fiber reinforced polymer (CFRP) ropes and strips is a recent and promising repairing/strengthening technique for improving the mechanical properties and structural performance of damaged reinforced concrete (RC) members. This study aimed to evaluate the behavior of RC beams after being damaged by thermal shock and the efficiency of using NSM-CFRP strips and ropes as repairing techniques. Therefore, eleven RC beams with dimensions of (150 mm in width × 200 mm in depth × 1150 mm in length) were cast. Nine of the specimens were heated to a temperature of 600 °C for three hours, cooled rapidly by being immersed in water for 15 min, and repaired with different configurations of NSM-CFRP strips and ropes and CFRP sheets. All specimens were tested under a four-point loading test. Three main parameters were studied, namely: NSM-CFRP type, configuration, and the number of U-wrapping ropes used. Experimental results showed a significant reduction in the concrete’s compressive strength with a percent of about 49% after being damaged by thermal shock. The thermally shocked RC beam exhibited a significant degradation in the mechanical and structural performance represented by a reduction in the ultimate capacity, stiffness, and toughness of the beam with a percentage of about 14.4%, 39%, and 11.8% if compared with the control beam, respectively. Also, using an efficient repairing technique can improve the properties of these damaged beams, especially when using NSM-CFRP ropes with U-wrapping CFRP sheets which contributed to the increase in the ultimate load capacity, stiffness, and toughness by a percent of about 54.7%, 23.8%, and 32.8% if compared with the thermally shocked beam, respectively.