Using Recycled Coarse Aggregate in Reinforced Concrete Beams Strengthened for Shear by GFRP bars Using NSM Technique

The NSM technique began to apply as a modern technique to treat defects in structural elements and to increase the shear and flexural strength of structural elements. For this technique to be effective, a series of practical experiments were conducted to characterize the behavior of the element strengthened by the NSM technique for flexure and shear. Shear strengthening with GFRP rods is the focus of this paper for concrete beams that contain 30% coarse aggregate replacement ratio of thermstone (volumetric ratio) obtained from the rubble of demolished buildings. A total of 7 beams were loaded under four-point load test, the parameters examined were the angle of inclination and the distance between the GFRP bars, the presence and absence of stirrups and the thermstone aggregate replacement ratio. The characterization of the tested beams includes failure mode, load-deflection curves, load-strain curves of stirrups, rebars and GFRP rods and the surface concrete strain in the shear zone of beam. The results showed that the use of GFRP rods to strengthen concrete beams was effective, especially in the presence of stirrups, where the gain in shear strength was 29.6% and 22.2% when the distance between the GFRP bars was (200 and 300) mm, respectively with the presence of stirrups. While the gain in shear was just (3.7% and 11.1%) in the absence of stirrups, when the distance between the GFRP bars was (200 and 300) mm, respectively.