الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
Reinforcing bars (rebars) are used to reinforce concrete structures and are usually made from carbon steel. Due to the relatively poor corrosion resistance of carbon steel, alternative alloys with better corrosion resistance and mechanical properties have been suggested. Micro-composite Multi structural Formable Steel (MMFX) is among these alloys. However, the high cost of these alternative rebar materials and the lack of reliable information regarding the corrosion behavior of these alloys in concrete have made it difficult to justify their use. The main objective of this study is to provide a quantitative evaluation of the mechanical properties and corrosion behavior of these alloys in simulated pore solutions (chloride and sulphate medium) and compare the results with steel Grade 60. Another objective is to investigate the effect of the presence of corrosion inhibitors such as adenine and diethylbarbituric acid on the two steels.
Steel grades under investigation, conventional Grade 60 and MMFX steel grade, are mechanically tested under tension machine to compare the yield strength, tensile strength, toughness, resilience and elongation percentage. The obtained results showed that MMFX steel’s mechanical properties exceeds that of Grade 60 steel due to the difference in their chemical composition and microstructure which are studied using spark spectrographic, optical microscope and scanning electron microscope (SEM).
Synthetic concrete pore solutions that emulate solutions in both chloride and sulphate ions were used in this study. Evaluation techniques, including Potentiodynamic Polarization and Electrochemical Impedance techniques, were used to characterize the corrosion behaviour (in terms of the corrosion currents and charge transfer resistance) of steels under investigation in solutions contaminated with fixed concentration of chloride ions (0.1M) and sulphate ion (0.1M).
The results showed that micro-composite steels MMFX has much higher corrosion resistance in thesfe solutions compared to steel Grade 60. In both solutions, the measured corrosion current density (Icorr) were determined for Grade 60 and MMFX steels and found to be 0.46 mA and 0.233 mA in Sulphoric acid respectively, and 0.0071 mA and 0.0027 mA in sodium chloride respectively. This means that in sulphoric acid the corrosion rate of steel Grade 60 is about 1.97 times the corrosion rate of MMFX steel. Besides in sodium chloride solution the corrosion rate of steel Grade 60 is about 2.6 times the corrosion rate of MMFX steel.
Thermodynamic studies for MMFX steel in Adenine inhibitor were calculated to investigate the inhibition mechanism and the thermodynamic parameters. In the present investigation, Langmuir, Frumkin, Flory- huggins and Kinetic- thermodynamic model adsorption isotherms are assessed, and it was found that the corrosion performance of MMFX steel was fitted with only Langmuir, Flory- huggins and Kinetic- thermodynamic model adsorption isotherms.