Evaluation for Ion Transportin Hardened Cementitious Pasteby Oxygen Diffusion and Chloride Diffusion

Kikuchi, Michio; Suda, Yuya; Saeki, Tatsuhiko

doi:10.14250/cement.64.346

Cited by 7 publications

(4 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The ORCD in mortar was higher than that in cement paste. Apparent oxygen diffusion coefficient in mortar was larger than that in cement paste, 20) because pores of mortar, which are formed between cement paste and fine aggregate, are larger than those in cement paste. The larger pores in mortar allowed faster oxygen diffusion than those in cement paste, leading to the higher ORCD in mortar.…”

Section: Oxygen Reduction Reaction On Iron Specimenmentioning

confidence: 87%

Hyperbaric-Oxygen Accelerated Corrosion Test for Iron in Cement Paste and Mortar

2018

View full text Add to dashboard Cite

A novel accelerated corrosion test method which enhances oxygen supply has been proposed for reinforcing steel in concrete in this study. Oxygen reduction current density (ORCD) was measured by means of potentiodynamic polarization test for an iron specimen embedded in cement paste or mortar in a saturated Ca(OH) 2 solution in ambient air. The ORCD decreased with an increase in cover thickness and the current density was reciprocally proportional to the cover thickness from 1 mm to 10 mm, suggesting that diffusion limited oxygen reduction can be accelerated by reducing the cover thickness below 10 mm. The oxygen supply to iron surface in cement paste or mortar was enhanced by pressurized oxygen gas using a newly developed hyperbaric-oxygen accelerated corrosion test container. Iron specimens with 5 mm cement paste and mortar covers showed almost 25 times higher ORCD in 0.5 MPa oxygen gas than that in ambient air, respectively. The iron specimens covered with 5 mm of cement paste or mortar containing chloride ion were immersed in a saline solution and exposed to 0.5 MPa oxygen gas in the container for 30 days. The thickness of the rust layer formed for 30-days was in good agreement with that estimated from the ORCD obtained in 0.5 MPa oxygen gas, indicating that the corrosion was accelerated in proportion to the oxygen (partial) pressure. Furthermore, the rust formed in pressurized oxygen gas showed similar characteristics to that formed in a practical service environment. Thus, the hyperbaric-oxygen is beneficial and effective to validly accelerate the corrosion of reinforcing steel in concrete.

show abstract

Section: Oxygen Reduction Reaction On Iron Specimenmentioning

confidence: 87%

Hyperbaric-Oxygen Accelerated Corrosion Test for Iron in Cement Paste and Mortar

2018

View full text Add to dashboard Cite

show abstract

“…The measurement range of the pore diameter is approximately 4 nm to 120 µm. Kikuchi et al (2010) was measured the oxygen diffusion coefficient of the hardened cement paste, which is capable of grasping the complexity of the pore structure. Therefore, in order to grasp the pore structure of the specimens immersed in sodium sulfate solutions, the oxygen diffusion test was performed.…”

Section: Discussionmentioning

confidence: 99%

“…Because it has been reported that the tortuosity is an index representing the complexity of the pore structure (Saeki et al, 2014), the tortuosity of the oxygen diffusion in the hardened cement paste was calculated in this study. The tortuosity of the oxygen diffusion was calculated using the formula (4), with reference to the past studies (Kikuchi et al, 2010;Saeki et al, 2014)…”

Section: Change In Pore Structure By the Effects Of Sodium Sulfatementioning

confidence: 99%

Evaluation of Pore Structure of Hardened Cement Paste Immersed in Sodium Sulfate Solution

Sakata¹,

Sato²,

Saito³

2020

XV International Conference on Durability of Building Materials and Components. eBook of Proceedings

View full text Add to dashboard Cite

The purpose of the present study is to evaluate pore structure of hardened cement paste immersed in sodium sulfate solutions and to experimentally examine the relation between the change of pore structure and hydration products. Cement paste specimens were immersed in sodium sulfate solutions and ion-exchanged water for two weeks. Since oxygen gas can pass through the pores having micro scale, it is possible to evaluate the effect of the pore structure on the oxygen transport in cement pastes. Thus, the oxygen diffusion coefficient (D O2) of the specimens after immersion were measured, and the pore volume and the pore size distribution were also measured. In addition, the phase compositions of the specimens were acquired. As a result, D O2 of the specimens immersed in the sodium sulfate solutions decreased as compared to the specimens immersed in the ion-exchanged water. The tortuosity of the specimens immersed in the sodium sulfate solutions increased due to decreasing of the pore volume having a diameter larger than 20 nm. There was a correlation between the volume of ettringite and the pore volume having a diameter larger than 20 nm. According to the above results, it was considered that the decreasing of D O2 in the case of sulfate immersion can occur as a result of the complication of the pore structure owing to filling of the pores by ettringite.

show abstract

“…Peng et al (2014) showed that 5.92 µm is a sufficiently high resolution to capture the main flow paths for the rock and that the smaller pores need not always be resolved. For ionic diffusion, however, Kikuchi et al (2010) suggested that Cl − is restricted to pore radii of 6 nm or higher. This work focused on the separate phenomena on permeability and diffusion parameters.…”

Section: Comparison Of the Permeability And Diffusivity Anisotropiesmentioning

confidence: 99%

Effect of Bedding Planes on the Permeability and Diffusivity Anisotropies of Berea Sandstone

et al. 2018

View full text Add to dashboard Cite

Evaluating the anisotropy of transport parameters in rocks is important for various applications, such as reservoir engineering and rock mechanics. Owing to their anisotropic pore structures, the tortuosity, constrictivity, and pore size distribution of rocks are often anisotropic in nature, which in turn affect the permeability and diffusivity. However, it has still not been determined whether the permeability and diffusivity are anisotropic in the same manner. This study used experiments and numerical modeling to examine the effect of the pore structure on the permeability and diffusivity anisotropies of rocks. The experimental results showed a clear difference in the anisotropy ratios of the permeability (k ⊥ /k) and diffusivity (D ⊥ e /D e) for Berea sandstone, which is the de facto standard porous sandstone. The analysis results from micro-focus X-ray computed tomography and simulation with the lattice Boltzmann method supported the experimental difference in anisotropy ratios. In the analysis and simulation, the relation between the minimum cross-sectional porosity area and characteristic pressure gradient was estimated. The analysis results suggest that the minimum cross-sectional porosity areas that influence the permeability anisotropy are too large to physically induce anisotropic NaCl diffusion, and thus, the diffusivity of Berea sandstone is nearly isotropic.

show abstract

Evaluation for Ion Transportin Hardened Cementitious Pasteby Oxygen Diffusion and Chloride Diffusion

Cited by 7 publications

References 0 publications

Hyperbaric-Oxygen Accelerated Corrosion Test for Iron in Cement Paste and Mortar

Hyperbaric-Oxygen Accelerated Corrosion Test for Iron in Cement Paste and Mortar

Evaluation of Pore Structure of Hardened Cement Paste Immersed in Sodium Sulfate Solution

Effect of Bedding Planes on the Permeability and Diffusivity Anisotropies of Berea Sandstone

Contact Info

Product

Resources

About