Application of thermomechanics equations in describing chloride extraction from concrete

Ali, Abdul Rahman; Zybura, A.

doi:10.1007/s11242-007-9138-z

Cited by 4 publications

(3 citation statements)

References 21 publications

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“…However, a multi-component medium theory has analytically described the diffusion processes of chlorides in concrete, taking into account Cl -ions, accompanying Na + ions and chemically bounded chlorides (Zybura 2007) and ion migration in concrete cover under the influence of an electric field during electrochemical chloride extraction process (Ali, Zybura 2008).…”

Section: -mentioning

confidence: 99%

Modelling the Carbonated Concrete Realkalization

Jaśniok

Zybura

2009

Journal of Civil Engineering and Management

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Abstract. The presented model of carbonated concrete realkalization is compiled on the basis of the multi-component medium theory equations. The process equations have been obtained from an analysis of the partial equations of mass, electric charge, momentum, energy, and entropy inequality. The experimental testing reported is related to a theoretical model which determines changes of ion concentrations in the pore solution of the cover, as a result of the realkalization. On the basis of the test results, the process equations have been simplified and formally transformed into the form of an equation for the OH -ions flow, coupled with the Na + ions transport. By solving the converse problem of this equation, the determinant OH -ions electro-diffusion coefficient is calculated and then, after taking the experimental test results into account, its numerical values, the range of stable solutions and the influence of the process non-stationariness are determined.

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Section: -mentioning

confidence: 99%

Modelling the Carbonated Concrete Realkalization

Jaśniok

Zybura

2009

Journal of Civil Engineering and Management

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“…Thus, the competence for assessing the corrosion risk properly and taking proper repair actions if necessary, is extremely important [6][7][8][9][10]. The application of the polarization techniques [11] and particularly the method of impedance spectroscopy for assessing the corrosion rate of the reinforcement in the reinforced concrete structures encounters considerable difficulties [12].…”

Section: Introductionmentioning

confidence: 99%

Investigation and Modelling of the Impact of Reinforcement Diameter in Concrete on Shapes of Impedance Spectra

Jaśniok

2013

Procedia Engineering

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The impedance test results of the steel reinforcement of various diameters, which was passivated and corroded in concrete specimens, were analysed. The impedance plots clearly indicated the tendencies for spectra shapes of steel rebars to change depending on their diameters. A 3-dimensional model of steel-concrete system was developed to explain the observed effect. This system was composed of the identical electrical equivalent circuits connected in parallel. Each equivalent scheme was characteristic for a theoretical conductive path during the measurement, which was defined between a counter-electrode and the reinforcement. This model was used with the rectangular counter electrode to simulate the formation of impedance spectra characteristic for a single reinforcing bar with the concrete cover of any thickness, a variable diameter and a variable polarization area. The simulation modelling the impact of various reinforcement diameters verified the tendencies for impedance spectra of steel in concrete to change their shapes. The improved of fitting quality of the model spectra to the experimental ones were obtained by considering in that model the moisture content in concrete. IntroductionThe corrosive degradation of reinforced concrete structures [1-3] presents a real threat to their safe use and the reliability [4], [5]. Thus, the competence for assessing the corrosion risk properly and taking proper repair actions if necessary, is extremely important [6-10]. The application of the polarization techniques [11] and particularly the method of impedance spectroscopy for assessing the corrosion rate of the reinforcement in the reinforced concrete structures encounters considerable difficulties [12]. These problems are related to complex measurement conditions and the complicated testing system. The studies are carried out using the potentiostat in a three-electrode system, in which the structure reinforcement (made of long steel bars) serves as the working electrode, and the electrode of known and satisfactory reversible potential serves as the reference electrode. The counter-electrode is applied to the surface of the reinforced concrete element to make the reinforcement polarization possible. The counter-electrode along with the reference electrode in a single enclosure formed the so called measuring head. The use of the head created a situation considerably different from the laboratory conditions form the measurement in an electrochemical vessel in which the large counter electrode uniformly polarizes the small tested electrode of a simple geometry. Regarding the measurements on the reinforcement in the reinforced concrete elements, the area of the tested electrode was significantly larger than that of the counter electrode applied to concrete. This resulted in the very non-uniform polarization of steel rebars. Moreover, the polarization area of the reinforcement required for assessing the rate of the electrochemical processes was unknown. The additional counter electrode in a form of a guard ring reducing the...

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“…Coupled transport of water and salt are widely recognized as a major factor of porous materials damage, therefore a lot of experimental and theoretical studies are devoted to it (Tang and Nilsson 1993;Palliser and McKibbin 1998;Pel et al 2003;Steiger et al 2008;Ali and Zybura 2008). The presence of salt changes the internal structure of a porous material (Lubelli et al 2006) and pore size distribution (Koniorczyk and Gawin 2008).…”

Section: Introductionmentioning

confidence: 99%

Numerical Modeling of Salt Transport and Precipitation in Non-Isothermal Partially Saturated Porous Media Considering Kinetics of Salt Phase Changes

Koniorczyk

Gawin

2010

Transp Porous Med

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Water and salts strongly influence the durability of porous materials. One of the most adverse phenomena which is related to the salt and moisture presence in the pore system of building materials is salt crystallization. The process is associated with the supersaturation ratio. The salt phase change kinetics is taken into account during the modeling of coupled moisture, salt, and heat transport. To solve the set of governing, differential equations the finite element and the finite difference methods are used. Three different rate laws are assumed in modeling the salt phase change. The drying, cooling, and warming of the cement mortar sample, during which the salt phase change occurs, have been simulated using the developed software. The changes of salt concentration in the pore solution and the amount of precipitated salt due to variation of boundary conditions are presented and discussed. The results obtained in the numerical simulation assuming the first, second, and fourth order rate low indicate that the higher order of the rate law the longer time delay between the change of boundary conditions and the salt precipitation. Such an analysis might be very useful during the determination of the material parameters by solving the inverse problem. List of SymbolsA Supersaturation parameter (−) C p Effective specific heat of porous medium (J/(kg K)) D d Tensor of hydrodynamic dispersion (m 2 /s) D g v Effective diffusivity tensor of vapor in the air (m 2 /s) D mol Molecular diffusivity (m 2 /s) g Acceleration of gravity (m/s 2 ) 123 58 M. Koniorczyk, D. Gawin H vap Enthalpy of vaporization per unit mass (J/kg) H prec Enthalpy of crystallization per unit mass (J/kg) I identity matrix (−) J dysp Dispersive flow of salt (kg/(m s)) J a g Diffusive flux of dry air (kg/(m s)) J v g Diffusive flux of water vapor (kg/(m s)) j ws = [ j ws 1 , j ws 2 ] Darcy velocity of water (m/s) j gs Darcy velocity of air (m/s) K Rate constant (rate law) (−) kIntrinsic permeability tensor (m 2 ) kIntrinsic permeability scalar (m 2 ) k rπ Relative permeability of π-phase (π = w, g-liquid, gas) (−) M π Molar mass of π = a, w, g-dry air, water, gas (kg/kmol) m vap Rate of mass due to evaporation (kg/(m 3 s)) m prec Rate of mass due to crystallization (kg/(m 3 s)) N π

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Application of thermomechanics equations in describing chloride extraction from concrete

Cited by 4 publications

References 21 publications

Modelling the Carbonated Concrete Realkalization

Modelling the Carbonated Concrete Realkalization

Investigation and Modelling of the Impact of Reinforcement Diameter in Concrete on Shapes of Impedance Spectra

Numerical Modeling of Salt Transport and Precipitation in Non-Isothermal Partially Saturated Porous Media Considering Kinetics of Salt Phase Changes

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