Influence of carbonation on the microstructure and the gas diffusivity of hardened cement pastes

Boumaaza, Mouna; Turcry, Ph; Huet, Bruno; Aït‐Mokhtar, Abdelkarim

doi:10.1016/j.conbuildmat.2020.119227

Cited by 35 publications

(25 citation statements)

References 43 publications

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“…In addition, blended cements often contain a higher amount of AFt and AFm phases exhibiting substantial volume decrease at carbonation [74]. Several researchers [73,[75][76][77][78][79][80] measured a significant increase in transport properties due to carbonation in blended cement pastes, such as diffusion and permeation coefficients. Auroy et al [77] studied the impact of carbonation on unsaturated water transport in concrete.…”

Section: Assessing the Durability Performance Of Different Bindersmentioning

confidence: 99%

Corrosion of steel in carbonated concrete: mechanisms, practical experience, and research priorities – a critical review by RILEM TC 281-CCC

et al. 2020

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Carbonation of concrete is generally assumed to lead to reinforcing steel corrosion. This mindset has long dictated the research priorities surrounding the developments towards new, low-emission binders. Here, by reviewing documented practical experience and scientific literature, we show that this widely held view is too simplistic. In fact, there are many cases from engineering practice where carbonation of the cementitious matrix surrounding the steel did not lead to noticeable corrosion or to corrosion-related damage at the level of a structure. The influencing factors that can, however, lead to considerable corrosion damage are identified as the moisture state, the microstructure of the carbonated concrete, various species that may be present – even in minor amounts – in the concrete pore solution, and the cover depth. The circumstance that a reduced pH alone is not sufficient to lead to significant steel corrosion in concrete seriously challenges the established approach of assessing the durability performance based on carbonation testing and modeling. At the same time, this circumstance offers great opportunities for reducing the environmental impact of concrete structures with low-emission binders. To realize these opportunities, the focus in research and engineering should shift from studying carbonation to studying corrosion of steel in carbonated concrete.

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Section: Assessing the Durability Performance Of Different Bindersmentioning

confidence: 99%

Corrosion of steel in carbonated concrete: mechanisms, practical experience, and research priorities – a critical review by RILEM TC 281-CCC

et al. 2020

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“…A CEM I 52.5 N cement [8] with a specific gravity of 3.13 g cm À3 and Blaine fineness of 410 kg m À2 was used in the test mix. SF is a powdered concrete admixture with highly effective fines to produce high-performance concrete.…”

Section: Methodsmentioning

confidence: 99%

Compressive, flexural and splitting strength of fly ash and silica fume concrete

Shmlls

Bozsaky

Horváth

2022

Pollack

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Cement replacement materials are commonly used in concrete technology. Several researchers have examined high-performance concrete after adding mineral admixtures to it, but further studies are still needed to provide the optimum dosage of these materials for instance fly ash and silica fume. This study compares three types of concrete and the mechanical properties (compressive strength, flexural strength, and splitting tensile) of these types at the age of 28 and 90 days. The test results designate that adding the mineral admixtures commonly affects the mechanical properties of all the tested types. However, silica fume is more operative than fly ash. Furthermore, adding the fly ash and silica fume in the same concrete type slightly improves the mechanical properties.

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“…[ 26 ] In cement‐based materials, gas diffusion coefficients at dry state of

10^{- 6}

m 2 s −1 are reduced to

10^{- 13}

m 2 s −1 at high saturation levels above 80%. [ 13,30 ] Odeh et al computed the effective pore radius due to water adsorption and its effect on Knudsen diffusion. However, only the average pore radius of the concrete was used, and the pore distribution was not considered.…”

Section: Introductionmentioning

confidence: 99%

Quantification of the Knudsen Effect on the Effective Gas Diffusion Coefficient in Partially Saturated Pore Distributions

Strangfeld

2021

Adv Eng Mater

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The effective gas diffusion coefficient describes the process of gas diffusion in porous materials. Several materials have a significant number of micropores in the lower nanometre range leading to a reduction of gas diffusion (Knudsen effect). In the case of partial pore saturation during adsorption, the available pore space is further reduced, as is the gas diffusion. In this study, the influence of partially saturated pores on the Knudsen effect and on the gas diffusion is quantified. Three different pore geometries are investigated (slit, cylindrical and spherical pores) and three different types of pore size distribution, including a broad equal distribution, three narrow normal distributions and two measured distributions of concrete. Besides the intensive computation of the exact pore saturation, a simplified model with low computational requirements is suggested. This study shows that the influence of the water layer thickness on the effective diffusion becomes significant for pore radii below 50 nm and the assumed pore geometry is important. At the end, the overall effect is quantified for an amorphous material with most pore radii below 30 nm. At a moisture level of 50% relative humidity, the effective diffusion is reduced by 35% due to partial saturation.

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Influence of carbonation on the microstructure and the gas diffusivity of hardened cement pastes

Cited by 35 publications

References 43 publications

Corrosion of steel in carbonated concrete: mechanisms, practical experience, and research priorities – a critical review by RILEM TC 281-CCC

Corrosion of steel in carbonated concrete: mechanisms, practical experience, and research priorities – a critical review by RILEM TC 281-CCC

Compressive, flexural and splitting strength of fly ash and silica fume concrete

Quantification of the Knudsen Effect on the Effective Gas Diffusion Coefficient in Partially Saturated Pore Distributions

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