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Investigating the Effect of Nanosilica Functionalized with Silane in Concrete Mortar on the Corrosion Behavior of Reinforcement

Mohebifar, Alireza | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56463 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Dolati, Abolqasem
  7. Abstract:
  8. The aim of this project is to investigate the effect of adding nano-silica on reinforcement corrosion in concrete caused by chloride. Because concrete is a porous composite, which is exposed to a corrosive environment such as the sea, it needs more protection to control the corrosion of steel reinforcement. This has led to the necessity of using nanoparticles in concrete mortar. This research was done by evaluating the effect of adding nanosilica gel as a partial replacement of type 2 Portland cement and hydrophobic nanosilica, respectively, to mortar and concrete surface on the corrosion resistance of reinforcement. In the project, three models of concrete samples with a cement grade of 550 kg/m3 with a water-to-cement ratio of 0.3, respectively, the control sample, the sample containing nanosilica gel (0.75% and 1.5% by weight compared to cement) and the sample containing nanosilica gel with coating Hydrophobic is used. To check the surface of active nanoparticles and determine the structure of concrete and reinforcement conditions, respectively, by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), X-ray Diffraction (XRD) and electrochemical methods at times (1, 7, 14 and 28 days) after concrete casting such as accelerated corrosion, open circuit corrosion potential (Eocp), linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS) were used. According to the results of the Fourier transform infrared spectroscopy method, due to the reaction between the surface of nanosilica and modifying materials, new peaks appeared on the spectrum of modified silica nanoparticles. Also, the morphology of concrete in the surface transition zone (ITZ) with the addition of nanosilica gel in the concrete sample of 1.5% has become more dense than the control sample. In the X-ray diffraction method, the addition of nanosilica gel after 28 days of immersion caused an increase in the peak intensity of hydration products such as gel (C-S-H) in concrete. In addition, by replacing 1.5% by weight of cement with nanosilica gel, corrosion parameters such as circuit corrosion potential It shows a 50% increase, a 95% decrease in the corrosion current density in the polarization method, and an 816% increase in the electrical resistance in the electrochemical impedance method compared to the armature in the control sample. Therefore, according to the standard (ACI 222), due to the use of functionalized nanosilica in concrete mortar, this reduction in corrosion behavior is significant and can be generalized to concrete structures
  9. Keywords:
  10. Hydrophobic Materical ; Corrosion Resistance ; Modified Nanosilica ; Surface Modification ; Nanosilica Gel ; Hydrophobic Nanosilica

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