Simulation of Chloride Movement in Hardened Concrete

Maruya, Tsuyoshi; Matsuoka, Yasunori; Tangtermsirikul, Somnuk

doi:10.2208/jscej.1992.442_81

Cited by 17 publications

(12 citation statements)

References 5 publications

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“…3,[13][14][15][16][17][18][19] This correlation can be used to calculate D eff if the Clconcentration at any time is known as a function of depth. The solution to Fick's second law for a semiinfinite slab is:…”

Section: Determination Of D Effmentioning

confidence: 99%

Predicting Chloride Profiles in Concrete

Berke

Hicks

1994

CORROSION

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concentration in the vicinity of steel reinforcing reaches a critical value, corrosion commences. The corrosion rate increases as Clconcentration increases. A concentration of 0.6 kg/m 3 to 0.9 kg/m 3 (1 Ib/yd 3 to 1.5 Ib/yd 3 ) is sufficient to initiate corrosion. Major damage can be expected when the concentration reaches 6 kg/m 3 (10 Ib/yd 3 ). 1-3 Use of a high-quality mix (low water-to-cement [W/C] ratio and high cement factor) and provision of adequate concrete cover over reinforcing steel are the first approaches to increase longevity of concrete. [4][5][6] Clingress into concrete can be modeled by a diffusion process. 1,7-20 Furthermore, the diffusion coefficient (D eff ) can be calculated from the rapid Clpermeability 20 measured according to ASTM C 1202 21 (the ASTM equivalent of AASHTO T277). 22 The AASHTO method essentially determines the electric conductivity of the pore solution. Because conductivity of the pore solution depends on mobility of the ions in the solution, the conductivity is related directly to D eff . 17 Consequently, this noninvasive electrochemical procedure can be used to estimate D eff . This eliminates the need for time-consuming determinations of local Clconcentrations in concrete samples.One problem with this procedure is that the presence of certain admixtures that contain ionic salts increases rapid Clpermeability values, although no change occurs in concrete permeability. Calcium nitrite (Ca[NO 2 ] 2 ), a widely used corrosion inhibitor, is one of these ionic admixtures.Two equations relating rapid Clpermeability to D eff were presented, one for concrete with and the other for concrete without admixed Ca(NO 2 ) 2 . ABSTRACTLaboratory studies were undertaken to compare chloride (Cl -) profile data to predictions obtained using ASTM C 1202 of Cldiffusion into concrete. The effective diffusion coefficients (D eff ) derived can be used to determine long-term Clprofiles of concrete structures. Equations relating D eff with resistivity and permeability of concrete were developed. One-and twodimensional models were used to determine Clprofiles of Clions entering concrete in structures such as square piles and decks.

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Section: Determination Of D Effmentioning

confidence: 99%

Predicting Chloride Profiles in Concrete

Berke

Hicks

1994

CORROSION

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“…These findings prove the applicability of Equation (1) to the evaluation of over-time change of D a . When the boundary condition is given as a constant value of flux, a solution equation with T in a similar form to Equation (2) C' b (kg/kg-cement) and free Cl − concentration c f is generally expressed as an adsorption isotherm, and applicability of linear adsorption equations as well as Freundlich (Tang 1993;Bigas 1995), Langmuir (Pereira 1984;Tang 1993;Bigas 1995) and other nonlinear adsorption equations (Maruya 1992;Hirao 2005) has been conventionally examined. Regarding the regression of the relationship between the C' b and the c f , the nonlinear adsorption equations are more precise than the linear one in some cases.…”

Section: Type Of Cement Exposure Environmentmentioning

confidence: 99%

Time Dependency of Cl Diffusion Coefficients in Concretes with Varied Phase Compositions and Pore Structures under Different Environmental Conditions

Hosokawa

Yamada²,

Takahashi

2012

ACT

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There have been many reports showing measured diffusion coefficients have a time dependency, but very few studies considering the mechanisms of that time dependency. The aim of this study is to investigate the variation of time dependency of diffusivity due to the type of cement and environmental condition using four parameters: the linear chloride binding capacity, unit cement content, porosity and pore structure factors. Concrete specimens with different phase compositions and pore structures were prepared using various cement-based materials and different mix proportions, and their apparent and effective diffusion coefficients D a and D e were measured to know how they are influenced by the phase composition, pore structure and environmental conditions such as exposure temperature and marine tidal or splash zone environment. This paper verifies the applicability of analytical solutions of diffusion equations to the evaluation of D a with variations in surface chloride ion (Cl − ) concentration depending on the immersion time. Over-time changes of D a and D e are then discussed from the viewpoint of variations in influential factors depending on the mix proportions and environmental conditions. For the present study, specific focus is placed on the factors influencing D a including linear binding of Cl − , cement content and pore structure factors as well as tortuosity and constrictivity as typical pore structure parameters.

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“…The total chloride profile obtained from the experiment was further compared with the calculation result by a well-known error function method shown by Cal-3. The apparent diffusion coefficient of chloride ions for the mortar specimen was assumed to be 5.0×10 -12 m 2 /s, based on the research of Maruya et al (1992), although the water to cement ratio of his mortar specimen was 50%. By comparing the calculated chloride profiles with Cal-1, Cal-2, and Cal-3, it can be inferred that consideration of coexisting ions in a multicomponent concentrated solution is necessary for an accurate understanding of ion transport in concrete.…”

Section: Profile Of Total Chloride Concentrationmentioning

confidence: 99%

Simultaneous Transport of Chloride and Calcium Ions in Hydrated Cement Systems

Sugiyama

Ritthichauy

Tsuji

2003

ACT

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This paper presents a new method for numerically calculating the concentration profiles of both solid calcium and total chloride ions (Cl -) in concrete in contact with 3% (0.5 mol/l) sodium chloride (NaCl) solution. Since the diffusion of ions present in the pore solution is a primary controlling factor, the application of mutual diffusion coefficients of corresponding ions that are influenced by the concentration of other coexisting ions is proposed. The method of calculation is based on the generalized form of Fick's First Law suggested by Onsager, which is composed of the Onsager phenomenological coefficient and the thermodynamic force between ions, which occurs according to the gradient of electrochemical potential in a multicomponent concentrated solution for the pore solution. In addition, the chemical equilibrium for Ca(OH) 2 dissolution and C-S-H decalcification are also modeled and coupled with diffusion. Increased porosity due to dissolved Ca 2+ and a chloride binding isotherm are taken into consideration. The concentration profiles of solid calcium and the presence of Friedel's salt in mortar specimens are experimentally identified by the X-ray diffraction method (XRD) and the thermal analysis (TG/DTA) as well as the total chloride profile using an acid extraction method after three years of exposure to 0.5 mol/l NaCl solution. This experimental result verifies the calculation result.

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Simulation of Chloride Movement in Hardened Concrete

Cited by 17 publications

References 5 publications

Predicting Chloride Profiles in Concrete

Predicting Chloride Profiles in Concrete

Time Dependency of Cl Diffusion Coefficients in Concretes with Varied Phase Compositions and Pore Structures under Different Environmental Conditions

Simultaneous Transport of Chloride and Calcium Ions in Hydrated Cement Systems

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