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چكيده انگليسي :

Improving Resistance of Buried Reinforced Concrete against Stray Current Abbas Aghajani aghajani@cc iut ac ir September 12 2013 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Mohammad Ali Golozar golozar@cc iut ac ir Supervisor Ahmad Saatchi asaatchi@cc iut ac ir Keyvan Raeissi k raessi@cc iut ac ir Advisor Mustafa Urgen urgen@itu edu tr Department Graduate Coordinator Keyvan Raessi Abstract The aim of this research is to investigate effects of stray current on concrete durability and its microstructural changes The structural changes can be studied by changes in the permeability volume of capillary pore resistivity electrical charge in Rapid Chloride Penetration RCP test chloride diffusion and changes in Electrochemical Impedance Spectroscopy EIS spectra of concrete They are related to concrete durability in environmental conditions and so can act as an effective agent in rebar corrosion In this study water saturated concrete samples with different mix design were exposed to 220 and 380 AC voltage and 50 DC voltage Effects of applied voltages on concrete microstructure of concrete were investigated using several techniques including resistivity EIS RCP chloride diffusion depth of chloride penetration and SEM In addition for validation of laboratory data field tests were done on some concrete power poles which had been failed by leakage of high voltage power from surface of insulators in rainy conditions Based on the results obtained high voltage AC stray current can reduce concrete durability in a short time by increasing its capillary pore size creating new network of pores creating micro cracks and extensive concrete microstructural changes such as changes in volume and size of capillary pores AC current in concrete can flow through two different paths including solid paths and capacitor paths capillary pore paths At high voltage in water saturated concrete passing current through the pores is the main reason for generation of thermal and shrinkage stresses and mass transfer These phenomena would reduce concrete durability Compared with AC current DC current can only pass through solid phase and not capacitor paths Therefore under DC stray current thermal stresses are less important and thus have less destructive effects compare with AC stray current in water saturated concrete Reducing water to cement ratio and adding pozzolanic materials such as silica fume to concrete mix design would reduce the volume of capillary pores increase concrete density reduce permeability reduce calcium hydroxide phase The impedance of capacitor paths would also increase due to reducing the volume of capillary pores Therefore destructive effects of AC stray current on water saturated concrete would reduce Also with decreasing permeability transfer of calcium hydroxide by diffusion mechanism due to DC stray current and thus its degradation effects would decrease Furthermore adding non metallic fiber such as polypropylene PP to concrete mix design reduce the cracks propagation in concrete due to AC stray current Keywords Stray current Concrete Structure Durability Professor Department of Materials Engineering Isfahan University of Technology Isfahan Iran Professor Department of Materials Engineering Isfahan University of Technology Isfahan Iran Associate Professor Materials Engineering Isfahan University of Technology Isfahan Iran Professor Department of Metallurgical and Materials Engineering Istanbul Technical University Istanbul Turkey PDF created with pdfFactory trial version www pdffactory com

آقاجاني كوپائي، عباس

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