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This search report is an experimental result on load –deflection relationship of various ratios of longitudinal reinforcement for six simply supported reinforced concrete beams. All specimens’ dimensions are (200×300×1750mm) and they were tested under two-point loading. Concrete compressive strength was (37.0-40.7 MPa). The variables studied in this work were tensile steel ratio (0.46-3.0%), bar diameter (12, 16 and 25mm) and number of bars (2 or 3 bars). It is concluded that for low reinforcement values (ρ < 0.013), an increase in ρ is sharply reduced the ductility index μ d . However, this effect decreases with increase in ρ values. All beams exhibit insufficient displacement ductility (less than 3) when reinforced with ρ/ρ b > 0.4. The increase in longitudinal steel ratio using 2 bars is more significant than when using 3 bars in yield and ultimate strengths of specimens as well as the deflection values at yield load, but the deflection values have gradual decrease at the ultimate load as a result of ductility decrease. It was concluded that the increase in longitudinal reinforcement ratio causes an increase in yield and ultimate strength of beams, these increments are compatible with the steel ratio i.e. by increasing the ρ by 50% the strength is increased about this ratio. As well as, the decreasing in ductility compatible with increasing the ρ by 50% the ductility decreased in about 50% on average.

Near surface mounted (NSM) is a promising strengthening technique for improving the flexural, shear and torsional strength of structures. Epoxy is the adhesive material used in this technique, but, the rapid failure happened in the mechanical properties of the epoxy matrix at high temperature, and the dangerous effects of epoxy fumes on the workers made the need of replacing epoxy with a new sustainable adhesive. Geopolymer Paste Adhesive and Modified Geopolymer Paste Adhesive were used in this study as adhesive materials in NSM strengthening technique to be an alternative to epoxy, where the geopolymer is a sustainable, environmentally friendly and less expensive material than epoxy. More importantly, it can better work at high temperatures. The test results showed that the modified geopolymer paste adhesive beat the epoxy adhesive by (4.1)% when adding (1)% micro steel fiber and (9.6)% when adding (0.6)% carbon fiber, while the bond strength reaches to (93)% of epoxy adhesive when adding (0.6)% polypropylene fiber.

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