A new test method to determine the gaseous oxygen diffusion coefficient of cement pastes as a function of hydration duration, microstructure, and relative humidity

Boumaaza, Mouna; Huet, Bruno; Pham, Gabriel; Turcry, Ph; Aït‐Mokhtar, Abdelkarim; Gehlen, Christoph

doi:10.1617/s11527-018-1178-z

Cited by 33 publications

(26 citation statements)

References 37 publications

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“…Although this gives a deep insight into the moisture distribution in amorphous materials, it does not contain direct information about diffusive moisture transport within the pore network. For the pore widths discussed here, molecular diffusion and Knudsen diffusion coexist, and both have to be taken into account [ 18 , 32 , 80 , 81 , 82 , 83 ]. Molecular diffusion deals with the molecule-molecule interaction in gases and can be described mathematically by Fick’s law [ 84 ].…”

Section: Discussionmentioning

confidence: 99%

About the Dominance of Mesopores in Physisorption in Amorphous Materials

2021

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Amorphous, porous materials represent by far the largest proportion of natural and men-made materials. Their pore networks consists of a wide range of pore sizes, including meso- and macropores. Within such a pore network, material moisture plays a crucial role in almost all transport processes. In the hygroscopic range, the pores are partially saturated and liquid water is only located at the pore fringe due to physisorption. Therefore, material parameters such as porosity or median pore diameter are inadequate to predict material moisture and moisture transport. To quantify the spatial distribution of material moisture, Hillerborg’s adsorption theory is used to predict the water layer thickness for different pore geometries. This is done for all pore sizes, including those in the lower nanometre range. Based on this approach, it is shown that the material moisture is almost completely located in mesopores, although the pore network is highly dominated by macropores. Thus, mesopores are mainly responsible for the moisture storage capacity, while macropores determine the moisture transport capacity, of an amorphous material. Finally, an electrical analogical circuit is used as a model to predict the diffusion coefficient based on the pore-size distribution, including physisorption.

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Section: Discussionmentioning

confidence: 99%

About the Dominance of Mesopores in Physisorption in Amorphous Materials

2021

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“…That prepared sample was placed into a chamber with oxygen detector. The diffusion set-up was based on the design described in [11]. One side of the sample was exposed into the air and other side was purged with nitrogen.…”

Section: Methodsmentioning

confidence: 99%

Changes of microstructure and diffusivity in blended cement pastes exposed to natural carbonation

et al. 2018

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This study compares the phase assemblage and pore structure variation of Portland cement and blended cements, containing limestone and burnt oil shale, during carbonation. Hardened cement paste was exposed to natural carbonation (400 ppm of CO2) at a relative humidity of 70 % for one year. Samples were prepared and cured at 95 % RH for 28 days. Reference mixes were exposed to CO2-free atmosphere to decouple the effect of ongoing hydration and drying from that of carbonation. The phase assemblage was investigated using XRD-Rietveld refinement and thermogravimetric analyses. The porosity and pore structure was assessed based on the results from mercury intrusion porosimetry. Additionally preliminary results of gas diffusion experiment of carbonated and non-carbonated samples are presented.

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“…The results imply that binder systems even with a similar porosity could exhibit contrasting carbonation performance due to the difference in the tortuosity of the system. The pore structure or the tortuosity varies significantly between 3.93×10 -9 3.59×10 -8 LC3 1.36×10 -8 7.05×10 -8 S30FA15 4.44×10 -9 1.34×10 -7 W/B: 0.5 to 0.6 (Boumaaza et al 2018) 1×10 -7 to 1×10 -11 W/B: 0.45 (Villain et al 2007) 4.00×10 -8 binder systems depending on the composition. Therefore, using the same value for different binders could result in inappropriate estimation of carbonation depth.…”

Section: Co 2 Diffusion Coefficientmentioning

confidence: 99%

Understanding the Process of Carbonation in Concrete using Numerical Modeling

Shah

Bishnoi

2021

ACT

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The objective of the study is to develop a model that will help in understanding the process of carbonation. This study investigates the influence of different physical, chemical and environmental parameters on the carbonation process in concrete. The model incorporates the influence of change in porosity on carbonation and the variations in the internal relative humidity of concrete due to drying on the rate of carbonation. The pore saturation and porosity were found to control the rate of carbonation in concrete. The model demonstrates the preconditioning duration and amount of water released on carbonation have an insignificant effect on the extent of carbonation in the long-term. Increased tortuosity and higher alkalinity could help in improving the carbonation resistance of system.

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A new test method to determine the gaseous oxygen diffusion coefficient of cement pastes as a function of hydration duration, microstructure, and relative humidity

Cited by 33 publications

References 37 publications

About the Dominance of Mesopores in Physisorption in Amorphous Materials

About the Dominance of Mesopores in Physisorption in Amorphous Materials

Changes of microstructure and diffusivity in blended cement pastes exposed to natural carbonation

Understanding the Process of Carbonation in Concrete using Numerical Modeling

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