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.
This paper present the development on compressive strength of fly ash geopolymer paste under effectiveness of nano-silica and micro steel fiber. Twelve geopolymer paste mixes under two series, the first series with replacement (0% to 1.4%) by increment (0.2%) of binder by nano-silica and using the optimum concentration of nano silica in second series with addition (0.5% to 2%) by increment (0.5%) of micro steel fiber. The mixes were using fly ash as binder with Sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) solutions as the alkali activators. (Na2SiO3 to NaOH) ratio was (2.0) with molarity of sodium hydroxide (10 M), and the specimens cured under room temperature (35 ± 2)°c. Results Show that the compressive strength of fly ash geopolymer paste can be improved as high as 76.5MPa at 28 days by add 0.8% nano silica and 1% micro steel fiber which were the optimum proportion that caused noteworthy improvement of compressive strength.
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