المستخلص
This work considered the first experimental and theoretical study on strengthened of reinforced concrete (RC) beams in shear by near surface mounted (NSM) – steel bar with geopolymer adhesive. Totally thirteen of RC beams with dimensions of 150mm width, 250mm height, and 1200mm length with clear span 1100mm, one of which considered control beam (unstrengthened), while other RC beams were strengthened in shear by NSM – steel bars with geopolymer adhesive and epoxy. The parameter include: the spacing between NSM – steel bars (50, 100, and 160mm), the diameter of NSM – steel bar (6, 8, and 10mm), and the inclination angle of NSM – steel bars (90°and 45°). The theoretical study includes suggested equation used for predicted shear strength of RC beams strengthened in shear by NSM – steel bars with (epoxy and geopolymer) adhesive.
Based on experimental results, it was found that the ultimate load capacity of the RC beams strengthened in shear by different spacing of NSM – steel bars (50, 100, and 160mm) with (geopolymer and epoxy) adhesive increased up to (89 and 117%), respectively, while the first crack load increased up to (37 and 22%), respectively, and the modes failure were shear failure for all specimens expect the specimen that strengthened with epoxy adhesive by 100 mm NSM – spacing which convert the failure from shear to flexural failure. The ultimate load capacity when using different diameter of NSM – steel bars (6, 8, and 10mm) with (geopolymer and epoxy) increased up to (79 and 117%), respectively, while the first crack load increased up to (27 and 17%), respectively. The ultimate load capacity when using different inclination of NSM – steel bars (90°and 45°) with (geopolymer and epoxy) increased up to (118 and 117%), respectively, while the first crack load increased up to (47 and 44%), respectively, all specimens strengthened by NSM – steel bar with 45° inclination angle failed as flexural failure. Furthermore, the results showed that the cost of geopolymer adhesive equal to 47% of the cost of epoxy adhesive.
The results showed that the geopolymer adhesive is cheaper cost than epoxy adhesive, environmentally friendly, safe, sustainable material, and produced results are close compared with epoxy, as such, it can be used as replacement of epoxy adhesive in strengthened the RC beams in shear by NSM – steel bars.
Based on theoretical results, it was found that the ratio of experimental ultimate shear load to theoretical calculation of RC beams strengthened with different spacing of NSM – steel bars (50, 100, and 160mm) range from (0.8 to 1.2), while it was found in range (0.9 to 1.2) of RC beams strengthened with different diameter of NSM – steel bars (6, 8, and 10mm)
