الفهرس 
The Uses of Nano Silica of Reinforced Concrete Structural ElementsOnly 14 pages are availabe for public view
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Abstract
The use of Nano silica as an additive material in manufacturing concrete is a new technology. Tests have shown that this material enhances the mechanical properties of hardened concrete. The addition of this material increases density, reduces porosity and bleeding, and improves the bond between cement matrix with aggregates. Thus, some concrete with high compressive and flexural strengths can be produced when using Nano-silica. Pertaining to the shear failure of concrete members, it is well known that when principal tensile stresses exceed the tensile strength of concrete, diagonal cracks occur in the shear span. Some of the existing reinforced concrete structures may require strengthening or repairing to increase their structural performance. It has been reinforced using carbon fiber, which has a very high tensile strength, and it is reinforced using an internal epoxy injection, where epoxy is used as a strong material with high compressive strength and high cohesion with concrete. This study presents research on shear behavior where studied variables include making different concrete mixtures using nano-silica (2, 4, 6%) and different cement content to obtain concrete compressive strength of 300, 450, 600 kg / cm2. The comparison between the presence of nano-silica and its absence repair by internally injected epoxy, carbon fiber reinforcement, and without repair. Through this study, it is found that concrete mix with 4% nano silica as additive, showed the best results in terms of ultimate load and ductility, the use of injected kemapoxy103 increased the ultimate load and absorbed energy significant in most case, and the use of CFRP laminates in shear strengthening showed an excellent result in terms of both ultimate load and absorbed energy. from the test results it was inferred that the use of CFRP strips showed a better performance compared to the use of Kemapoxy injection in terms of both ultimate load and absorbed energy. The results showed that strengthening with CFRP increased the ultimate load and absorbed energy up to 10% and 63.8%, respectively, on the other hand the injection of Kemapoxy 103 increased the ultimate load and absorbed energy up to 7.4% and 38.6%, respectively.