Análisis del comportamiento frente a la corrosión del acero embebido en hormigón en ambiente marino

Resumo

Electrochemical impedance spectroscopy (EIS) was used to study the corrosion behaviour of reinforcing steel embedded in alkaline activated fly ash mortar with chloride pollution. The porous nature of the rust layer was studied using a transmission line model and the parameters of the interfacial oxide/hydroxide film were determined by interpretation of the impedance data using a cylindrical pore. The rust layer generated on the steel surface was studied at the end of the experiment (two years) using scanning electron microscopy and X-ray diffraction. Steel reinforcing bars are often coated with natural oxides (rust) formed during exposure to the atmosphere prior to embedding in concrete and/or during service in reinforced concrete structures. Rust layers growing on steel rebars induce expansive stresses generated by their crystallization pressure and cause cracking and spalling of the cover concrete. This Memory uses thermodynamic data to study the crystallization pressure caused by the formation of iron oxide/hydroxide layers, following the model proposed by Correns and Steinborn based on supersaturation of the pore aqueous solution. Standard free energy and molar volume thermodynamic data have been analyzed for goethite, lepidocrocite, magnetite, hematite and wüstite, which are described in the literature as the most frequently found solid phase constituents of rust. As described above, rust layers growing on steel rebars induce expansive stresses and cause cracking of the concrete cover. The present study uses steel corrosion rate results measured on reinforced concrete buildings of more than 50 years of age located in marine environments and considers the pressure generated by the volume expansion of corrosion product layers to calculate the service life of the RC structures using a numerical simulation, estimating the time to corrosion cracking of the concrete cover. Akaganeite, goethite, lepidocrocite, hematite, magnetite and maghemite were identified by X-ray diffraction as crystalline phase constituents of the rust layers.