Pore-scale modeling of chloride ion diffusion in cement microstructures

Yang, Yuankai; Wang, Moran

doi:10.1016/j.cemconcomp.2017.09.014

Cited by 57 publications

(53 citation statements)

References 59 publications

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“…The microstructure images of the two types of crushed bricks are shown in Figure 3a-3d. Figure 3a and 3b show that GFFA-containing bricks had many pores, suggesting the insufficient development of hydration products in the bricks [27]. The FBFA-containing bricks formed a denser structure with many tabular crystalline elements, shown in Figure 3c and 3d.…”

Section: Sem Observationmentioning

confidence: 97%

Microstructure and Strength of Alkali-Activated Bricks Containing Municipal Solid Waste Incineration (MSWI) Fly Ash Developed as Construction Materials

Zhao

Qiu

et al. 2019

Sustainability

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Alkali-activated materials (AAM) are widely applied in the field of building materials and civil engineering to substitute cement materials. This study used two types of municipal solid waste incineration fly ash (MSWI-FA): grate-firing fly ash (GFFA) and fluidized bed fly ash (FBFA) as brick raw materials. Various weight ratio of 20%, 30%, and 40% GFFA and FBFA were added to coal fly ash (CFA), GGBFs (Ground Granulated Blast-Furnace Slag), and an alkali-activating reagent to produce alkali-activated bricks. Microstructure and crystalline phase composition were observed to analyze their compressive strength, and a leaching test was used to prove the material’s safety for the environment. It can be seen from the results of this study that the alkali-activated bricks containing FBFA had higher compressive strength than those containing GFFA in the same amount. Considering the engineering properties, the alkali-activated bricks containing FBFA are more suitable to be used as building materials. The difference in the compressive strength resulted from the large amount of calcium compounds and chloride salts present in the GFFA. From SEM analysis, it was observed that there was a large number of pores in the microstructure. It was also found from the results of XRD that the bricks containing GFFA contained a large amount of chloride salt. From the results of the two leaching tests, it was found that the amounts of six heavy metals detected in the leachates of the bricks in this study met the corresponding regulation standards. This described MSWI-FA is suitable for use as alkali-activated material, and its products have potential to be commercially used in the future.

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Section: Sem Observationmentioning

confidence: 97%

Microstructure and Strength of Alkali-Activated Bricks Containing Municipal Solid Waste Incineration (MSWI) Fly Ash Developed as Construction Materials

Zhao

Qiu

et al. 2019

Sustainability

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“…Figuring out chloride ion diffusion mechanism in cement-based materials is of vital importance to improve the durability of RC structures in marine environments [13,14]. Many researchers have also investigated the chloride diffusion process in cement-based materials on a micro scale [15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Influence of Pore Size and Fatigue Loading on NaCl Transport Properties in C-S-H Nanopores: A Molecular Dynamics Simulation

Cao

Fang

et al. 2020

Materials

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The transport properties of chloride ions in cement-based materials are one of the major deterioration mechanisms for reinforced concrete (RC) structures. This paper investigates the influence of pore size and fatigue loading on the transport properties of NaCl in C-S-H nanopores using molecular dynamics (MD) simulations. Molecular models of C-S-H, NaCl solution, and C-S-H nanopores with different pore diameters are established on a microscopic scale. The distribution of the chloride ion diffusion rate and the diffusion coefficient of each particle are obtained by statistically calculating the variation of atomic displacement with time. The results indicate that the chloride ion diffusion rate perpendicular to C-S-H nanopores under fatigue loading is 4 times faster than that without fatigue loading. Moreover, the diffusion coefficient of water molecules and chloride ions in C-S-H nanopores increases under fatigue loading compared with those without fatigue loading. The diffusion coefficient of water molecules in C-S-H nanopores with a pore size of 3 nm obtained from the MD simulation is 1.794 × 10−9 m2/s, which is slightly lower than that obtained from the experiment.

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“…It was argued that there must be surface charge inhomogeneity at both microscopic (pore‐scale) and macroscopic (field‐scale) scale to explain the deposition rate (Kretzschmar et al, ; Ryan & Elimelech, ; L. F. Song et al, ). On the other hand, better understanding of the ionic transport through complex geometries with inhomogeneously charged surfaces could improve our knowledge of the geological measurements (i.e., streaming potential [Andre Revil & Leroy, ; Revil, Pezard, & Glover, ; Revil, Schwaeger, et al, ]), solute transport for concrete pores (Appelo, ; Yang & Wang, ), diffusion (Yang & Wang, ) and dispersion in porous media (Muniruzzaman et al, ; Rolle et al, ), reactive transport (Alt‐Epping et al, ; Muniruzzaman & Rolle, ; Steefel & Maher, ; Zhang & Wan, ), salt removal and electro‐diffusion of shale layer [Andre Revil & Leroy, ], and underground water quality (Muniruzzaman & Rolle, ).…”

Section: Introductionmentioning

confidence: 99%

Pore‐scale Study of Ion Transport Mechanisms in Inhomogeneously Charged Nanoporous Rocks: Impacts of Interface Properties on Macroscopic Transport

Alizadeh

Wang

2019

JGR Solid Earth

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The electrokinetic transport mechanisms of multispecies ions through 3‐D nanoporous rocks with chemical reaction at the solid‐aqueous solution interfaces are investigated. We systematically study the multiphysics transport phenomena by considering either inhomogeneous (local surface charge based on local pH and ion concentrations) or prescribed homogeneous surface charge at solid‐aqueous solution interface while the pores are screened via electric double layers. We develop a lattice Boltzmann numerical framework to solve the set of governing equations (Poisson‐Nernst‐Planck plus Navier–Stokes). Our modeling results reveal that the averaged local electric potential of the nanoporous rock is significantly underestimated (about 83%) when a homogeneous surface charge is prescribed based on the bulk solution properties. It is shown that increasing the porosity of the nanoporous media considerably increases the absolute values and inhomogeneity of the surface charge, which means that while the electric double layers screened the pores, increasing the porosity enhances the ion selectivity of the porous medium. When the scenario with inhomogeneous charge is taken into account, the predicted electroosmotic permeability and tortuosity are higher in comparison with the prescribed homogeneous case. Moreover, we have studied the electrostatic tortuosity, coupling coefficient, and the effective excess charge density of the nanoporous rocks. The results demonstrate that ignoring the inhomogeneity of surface charges may cause erroneous prediction of the ion transport through porous rocks with chemically active surfaces.

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Pore-scale modeling of chloride ion diffusion in cement microstructures

Cited by 57 publications

References 59 publications

Microstructure and Strength of Alkali-Activated Bricks Containing Municipal Solid Waste Incineration (MSWI) Fly Ash Developed as Construction Materials

Microstructure and Strength of Alkali-Activated Bricks Containing Municipal Solid Waste Incineration (MSWI) Fly Ash Developed as Construction Materials

Influence of Pore Size and Fatigue Loading on NaCl Transport Properties in C-S-H Nanopores: A Molecular Dynamics Simulation

Pore‐scale Study of Ion Transport Mechanisms in Inhomogeneously Charged Nanoporous Rocks: Impacts of Interface Properties on Macroscopic Transport

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