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Submitted
February 10, 2025
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May 15, 2025
Published
June 1, 2026
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Abstract

This research investigates the effectiveness of geopolymer adhesive (GPA) as an alternative to epoxy in the near-surface-mounted (NSM) technique for the shear strengthening of reinforced concrete (RC) beams. Five reinforced concrete beam specimens with dimensions of 1200 mm in length, 120 mm in width, and 160 mm in height were tested under three-point loading conditions. The specimens included one reference beam specimen and four strengthened beam specimens. The present paper investigated parameters regarding the types of paste adhesive (epoxy or geopolymer) and the types of strengthening bar materials. Major performance indicators include the load that leads to the first appearance of flexural cracks, ultimate load-carrying capacity, deflection, and crack pattern. According to the results, the epoxy adhesive can increase load capacity to 60.1% compared to the reference beam specimen. While Geopolymer adhesive can be increase load capacity to 47.7% compared to the reference beam. Compared with unstrengthened RC beam specimens, the first crack load on strengthened specimens increased by up to 15.3% and 12.12% when using geopolymer and epoxy adhesive. Using epoxy adhesive shows a greater increase in deflection, reaching up to 96%, while using geopolymer leads to a deflection increase of up to 50%. The steel bar with geopolymer exhibits the lowest increase in deflection at 46.43%, indicating enhanced stiffness and better crack control. The feasibility of geopolymer adhesive in structural strengthening applications can be established due to its adequate bonding strength, excellent thermal resistance, and environmental sustainability.

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