Influence of pH on chloride binding isotherms for cement paste and its components

A non-equilibrium diffusion–reaction model is proposed to describe chloride transport and binding in cementitious materials. A numerical solution for this non-linear transport with reaction problem is obtained using the finite element method. The effective chloride diffusion coefficients and parameters of the chloride binding are determined using the inverse method based on a diffusion–reaction model and experimentally measured chloride concentrations. The investigations are performed for two significantly different cements: ordinary Portland and blast furnace cements. The results are compared with the classical diffusion model and appropriate apparent diffusion coefficients. The role of chloride binding, with respect to the different binding isotherms applied, in the overall transport of chlorides is discussed, along with the applicability of the two models. The proposed work allows the determination of important parameters that influence the longevity of concrete structures. The developed methodology can be extended to include more ions, electrostatic interactions, and activity coefficients for even more accurate estimation of the longevity.

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Prediction of chloride binding isotherms for blended cements

Computers and Concrete ◽

10.12989/cac.2016.17.5.655 ◽

2016 ◽

Vol 17 (5) ◽

pp. 655-672 ◽

Cited By ~ 14

Author(s):

Hailong Ye ◽

Xianyu Jin ◽

Wei Chen ◽

Chuanqing Fu ◽

Nanguo Jin

Keyword(s):

Chloride Binding ◽

Blended Cements ◽

Binding Isotherms

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Chloride-Binding Capacity of Portland Cement Paste Blended with Synthesized CA2 (CaO·2Al2O3)

Advances in Materials Science and Engineering ◽

10.1155/2018/5418930 ◽

2018 ◽

Vol 2018 ◽

pp. 1-11 ◽

Cited By ~ 1

Author(s):

Yunsu Lee ◽

Mingyun Kim ◽

Zhengxin Chen ◽

Hanseung Lee ◽

Seungmin Lim

Keyword(s):

Portland Cement ◽

Cement Paste ◽

Binding Capacity ◽

Water Soluble ◽

Chloride Binding ◽

X Ray Diffraction ◽

Total Chloride ◽

X Ray ◽

Isotherm Equation ◽

Portland Cement Paste

A chloride-binding capacity is the major factor to mitigate the ingress of chloride into concrete. This paper presents the chloride-binding capacity of Portland cement paste containing synthesized CA2 (CaO·2Al2O3). The CA2 was synthesized in the high-temperature furnace and characterized by X-ray diffraction for inspecting the purity. The synthesized CA2 was substituted for Portland cement by 0%, 5%, and 10% by weight, and the NaCl solution was used as an internal chloride, which is assumed as a total chloride. The chloride-binding capacity of cement paste was calculated from a water-soluble chloride extraction method by the application of the Langmuir isotherm equation. And the hydration products were analyzed using X-ray diffraction and thermogravimetric analysis. We demonstrate that the CA2 increases an AFm phase in the Portland cement system, and the incorporation of CA2 consequently enhances the chloride-binding capacity of cement paste samples.

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